Source file src/cmd/link/internal/ld/data.go

Documentation: cmd/link/internal/ld

     1  // Derived from Inferno utils/6l/obj.c and utils/6l/span.c
     2  // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/obj.c
     3  // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/span.c
     4  //
     5  //	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
     6  //	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
     7  //	Portions Copyright © 1997-1999 Vita Nuova Limited
     8  //	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
     9  //	Portions Copyright © 2004,2006 Bruce Ellis
    10  //	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
    11  //	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
    12  //	Portions Copyright © 2009 The Go Authors. All rights reserved.
    13  //
    14  // Permission is hereby granted, free of charge, to any person obtaining a copy
    15  // of this software and associated documentation files (the "Software"), to deal
    16  // in the Software without restriction, including without limitation the rights
    17  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    18  // copies of the Software, and to permit persons to whom the Software is
    19  // furnished to do so, subject to the following conditions:
    20  //
    21  // The above copyright notice and this permission notice shall be included in
    22  // all copies or substantial portions of the Software.
    23  //
    24  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    25  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    26  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    27  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    28  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    29  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    30  // THE SOFTWARE.
    31  
    32  package ld
    33  
    34  import (
    35  	"bytes"
    36  	"cmd/internal/gcprog"
    37  	"cmd/internal/objabi"
    38  	"cmd/internal/sys"
    39  	"cmd/link/internal/loader"
    40  	"cmd/link/internal/loadpe"
    41  	"cmd/link/internal/sym"
    42  	"compress/zlib"
    43  	"debug/elf"
    44  	"encoding/binary"
    45  	"fmt"
    46  	"internal/abi"
    47  	"log"
    48  	"math/rand"
    49  	"os"
    50  	"sort"
    51  	"strconv"
    52  	"strings"
    53  	"sync"
    54  	"sync/atomic"
    55  )
    56  
    57  // isRuntimeDepPkg reports whether pkg is the runtime package or its dependency.
    58  func isRuntimeDepPkg(pkg string) bool {
    59  	switch pkg {
    60  	case "runtime",
    61  		"sync/atomic",          // runtime may call to sync/atomic, due to go:linkname
    62  		"internal/abi",         // used by reflectcall (and maybe more)
    63  		"internal/bytealg",     // for IndexByte
    64  		"internal/chacha8rand", // for rand
    65  		"internal/cpu":         // for cpu features
    66  		return true
    67  	}
    68  	return strings.HasPrefix(pkg, "runtime/internal/") && !strings.HasSuffix(pkg, "_test")
    69  }
    70  
    71  // Estimate the max size needed to hold any new trampolines created for this function. This
    72  // is used to determine when the section can be split if it becomes too large, to ensure that
    73  // the trampolines are in the same section as the function that uses them.
    74  func maxSizeTrampolines(ctxt *Link, ldr *loader.Loader, s loader.Sym, isTramp bool) uint64 {
    75  	// If thearch.Trampoline is nil, then trampoline support is not available on this arch.
    76  	// A trampoline does not need any dependent trampolines.
    77  	if thearch.Trampoline == nil || isTramp {
    78  		return 0
    79  	}
    80  
    81  	n := uint64(0)
    82  	relocs := ldr.Relocs(s)
    83  	for ri := 0; ri < relocs.Count(); ri++ {
    84  		r := relocs.At(ri)
    85  		if r.Type().IsDirectCallOrJump() {
    86  			n++
    87  		}
    88  	}
    89  
    90  	switch {
    91  	case ctxt.IsARM():
    92  		return n * 20 // Trampolines in ARM range from 3 to 5 instructions.
    93  	case ctxt.IsARM64():
    94  		return n * 12 // Trampolines in ARM64 are 3 instructions.
    95  	case ctxt.IsPPC64():
    96  		return n * 16 // Trampolines in PPC64 are 4 instructions.
    97  	case ctxt.IsRISCV64():
    98  		return n * 8 // Trampolines in RISCV64 are 2 instructions.
    99  	}
   100  	panic("unreachable")
   101  }
   102  
   103  // Detect too-far jumps in function s, and add trampolines if necessary.
   104  // ARM, PPC64, PPC64LE and RISCV64 support trampoline insertion for internal
   105  // and external linking. On PPC64 and PPC64LE the text sections might be split
   106  // but will still insert trampolines where necessary.
   107  func trampoline(ctxt *Link, s loader.Sym) {
   108  	if thearch.Trampoline == nil {
   109  		return // no need or no support of trampolines on this arch
   110  	}
   111  
   112  	ldr := ctxt.loader
   113  	relocs := ldr.Relocs(s)
   114  	for ri := 0; ri < relocs.Count(); ri++ {
   115  		r := relocs.At(ri)
   116  		rt := r.Type()
   117  		if !rt.IsDirectCallOrJump() && !isPLTCall(rt) {
   118  			continue
   119  		}
   120  		rs := r.Sym()
   121  		if !ldr.AttrReachable(rs) || ldr.SymType(rs) == sym.Sxxx {
   122  			continue // something is wrong. skip it here and we'll emit a better error later
   123  		}
   124  
   125  		if ldr.SymValue(rs) == 0 && ldr.SymType(rs) != sym.SDYNIMPORT && ldr.SymType(rs) != sym.SUNDEFEXT {
   126  			// Symbols in the same package are laid out together (if we
   127  			// don't randomize the function order).
   128  			// Except that if SymPkg(s) == "", it is a host object symbol
   129  			// which may call an external symbol via PLT.
   130  			if ldr.SymPkg(s) != "" && ldr.SymPkg(rs) == ldr.SymPkg(s) && *flagRandLayout == 0 {
   131  				// RISC-V is only able to reach +/-1MiB via a JAL instruction.
   132  				// We need to generate a trampoline when an address is
   133  				// currently unknown.
   134  				if !ctxt.Target.IsRISCV64() {
   135  					continue
   136  				}
   137  			}
   138  			// Runtime packages are laid out together.
   139  			if isRuntimeDepPkg(ldr.SymPkg(s)) && isRuntimeDepPkg(ldr.SymPkg(rs)) && *flagRandLayout == 0 {
   140  				continue
   141  			}
   142  		}
   143  		thearch.Trampoline(ctxt, ldr, ri, rs, s)
   144  	}
   145  }
   146  
   147  // whether rt is a (host object) relocation that will be turned into
   148  // a call to PLT.
   149  func isPLTCall(rt objabi.RelocType) bool {
   150  	const pcrel = 1
   151  	switch rt {
   152  	// ARM64
   153  	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_CALL26),
   154  		objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_JUMP26),
   155  		objabi.MachoRelocOffset + MACHO_ARM64_RELOC_BRANCH26*2 + pcrel:
   156  		return true
   157  
   158  	// ARM
   159  	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_CALL),
   160  		objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PC24),
   161  		objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_JUMP24):
   162  		return true
   163  	}
   164  	// TODO: other architectures.
   165  	return false
   166  }
   167  
   168  // FoldSubSymbolOffset computes the offset of symbol s to its top-level outer
   169  // symbol. Returns the top-level symbol and the offset.
   170  // This is used in generating external relocations.
   171  func FoldSubSymbolOffset(ldr *loader.Loader, s loader.Sym) (loader.Sym, int64) {
   172  	outer := ldr.OuterSym(s)
   173  	off := int64(0)
   174  	if outer != 0 {
   175  		off += ldr.SymValue(s) - ldr.SymValue(outer)
   176  		s = outer
   177  	}
   178  	return s, off
   179  }
   180  
   181  // relocsym resolve relocations in "s", updating the symbol's content
   182  // in "P".
   183  // The main loop walks through the list of relocations attached to "s"
   184  // and resolves them where applicable. Relocations are often
   185  // architecture-specific, requiring calls into the 'archreloc' and/or
   186  // 'archrelocvariant' functions for the architecture. When external
   187  // linking is in effect, it may not be  possible to completely resolve
   188  // the address/offset for a symbol, in which case the goal is to lay
   189  // the groundwork for turning a given relocation into an external reloc
   190  // (to be applied by the external linker). For more on how relocations
   191  // work in general, see
   192  //
   193  //	"Linkers and Loaders", by John R. Levine (Morgan Kaufmann, 1999), ch. 7
   194  //
   195  // This is a performance-critical function for the linker; be careful
   196  // to avoid introducing unnecessary allocations in the main loop.
   197  func (st *relocSymState) relocsym(s loader.Sym, P []byte) {
   198  	ldr := st.ldr
   199  	relocs := ldr.Relocs(s)
   200  	if relocs.Count() == 0 {
   201  		return
   202  	}
   203  	target := st.target
   204  	syms := st.syms
   205  	nExtReloc := 0 // number of external relocations
   206  	for ri := 0; ri < relocs.Count(); ri++ {
   207  		r := relocs.At(ri)
   208  		off := r.Off()
   209  		siz := int32(r.Siz())
   210  		rs := r.Sym()
   211  		rt := r.Type()
   212  		weak := r.Weak()
   213  		if off < 0 || off+siz > int32(len(P)) {
   214  			rname := ""
   215  			if rs != 0 {
   216  				rname = ldr.SymName(rs)
   217  			}
   218  			st.err.Errorf(s, "invalid relocation %s: %d+%d not in [%d,%d)", rname, off, siz, 0, len(P))
   219  			continue
   220  		}
   221  		if siz == 0 { // informational relocation - no work to do
   222  			continue
   223  		}
   224  
   225  		var rst sym.SymKind
   226  		if rs != 0 {
   227  			rst = ldr.SymType(rs)
   228  		}
   229  
   230  		if rs != 0 && (rst == sym.Sxxx || rst == sym.SXREF) {
   231  			// When putting the runtime but not main into a shared library
   232  			// these symbols are undefined and that's OK.
   233  			if target.IsShared() || target.IsPlugin() {
   234  				if ldr.SymName(rs) == "main.main" || (!target.IsPlugin() && ldr.SymName(rs) == "main..inittask") {
   235  					sb := ldr.MakeSymbolUpdater(rs)
   236  					sb.SetType(sym.SDYNIMPORT)
   237  				} else if strings.HasPrefix(ldr.SymName(rs), "go:info.") {
   238  					// Skip go.info symbols. They are only needed to communicate
   239  					// DWARF info between the compiler and linker.
   240  					continue
   241  				}
   242  			} else if target.IsPPC64() && ldr.SymName(rs) == ".TOC." {
   243  				// TOC symbol doesn't have a type but we do assign a value
   244  				// (see the address pass) and we can resolve it.
   245  				// TODO: give it a type.
   246  			} else {
   247  				st.err.errorUnresolved(ldr, s, rs)
   248  				continue
   249  			}
   250  		}
   251  
   252  		if rt >= objabi.ElfRelocOffset {
   253  			continue
   254  		}
   255  
   256  		// We need to be able to reference dynimport symbols when linking against
   257  		// shared libraries, and AIX, Darwin, OpenBSD and Solaris always need it.
   258  		if !target.IsAIX() && !target.IsDarwin() && !target.IsSolaris() && !target.IsOpenbsd() && rs != 0 && rst == sym.SDYNIMPORT && !target.IsDynlinkingGo() && !ldr.AttrSubSymbol(rs) {
   259  			if !(target.IsPPC64() && target.IsExternal() && ldr.SymName(rs) == ".TOC.") {
   260  				st.err.Errorf(s, "unhandled relocation for %s (type %d (%s) rtype %d (%s))", ldr.SymName(rs), rst, rst, rt, sym.RelocName(target.Arch, rt))
   261  			}
   262  		}
   263  		if rs != 0 && rst != sym.STLSBSS && !weak && rt != objabi.R_METHODOFF && !ldr.AttrReachable(rs) {
   264  			st.err.Errorf(s, "unreachable sym in relocation: %s", ldr.SymName(rs))
   265  		}
   266  
   267  		var rv sym.RelocVariant
   268  		if target.IsPPC64() || target.IsS390X() {
   269  			rv = ldr.RelocVariant(s, ri)
   270  		}
   271  
   272  		// TODO(mundaym): remove this special case - see issue 14218.
   273  		if target.IsS390X() {
   274  			switch rt {
   275  			case objabi.R_PCRELDBL:
   276  				rt = objabi.R_PCREL
   277  				rv = sym.RV_390_DBL
   278  			case objabi.R_CALL:
   279  				rv = sym.RV_390_DBL
   280  			}
   281  		}
   282  
   283  		var o int64
   284  		switch rt {
   285  		default:
   286  			switch siz {
   287  			default:
   288  				st.err.Errorf(s, "bad reloc size %#x for %s", uint32(siz), ldr.SymName(rs))
   289  			case 1:
   290  				o = int64(P[off])
   291  			case 2:
   292  				o = int64(target.Arch.ByteOrder.Uint16(P[off:]))
   293  			case 4:
   294  				o = int64(target.Arch.ByteOrder.Uint32(P[off:]))
   295  			case 8:
   296  				o = int64(target.Arch.ByteOrder.Uint64(P[off:]))
   297  			}
   298  			out, n, ok := thearch.Archreloc(target, ldr, syms, r, s, o)
   299  			if target.IsExternal() {
   300  				nExtReloc += n
   301  			}
   302  			if ok {
   303  				o = out
   304  			} else {
   305  				st.err.Errorf(s, "unknown reloc to %v: %d (%s)", ldr.SymName(rs), rt, sym.RelocName(target.Arch, rt))
   306  			}
   307  		case objabi.R_TLS_LE:
   308  			if target.IsExternal() && target.IsElf() {
   309  				nExtReloc++
   310  				o = 0
   311  				if !target.IsAMD64() {
   312  					o = r.Add()
   313  				}
   314  				break
   315  			}
   316  
   317  			if target.IsElf() && target.IsARM() {
   318  				// On ELF ARM, the thread pointer is 8 bytes before
   319  				// the start of the thread-local data block, so add 8
   320  				// to the actual TLS offset (r->sym->value).
   321  				// This 8 seems to be a fundamental constant of
   322  				// ELF on ARM (or maybe Glibc on ARM); it is not
   323  				// related to the fact that our own TLS storage happens
   324  				// to take up 8 bytes.
   325  				o = 8 + ldr.SymValue(rs)
   326  			} else if target.IsElf() || target.IsPlan9() || target.IsDarwin() {
   327  				o = int64(syms.Tlsoffset) + r.Add()
   328  			} else if target.IsWindows() {
   329  				o = r.Add()
   330  			} else {
   331  				log.Fatalf("unexpected R_TLS_LE relocation for %v", target.HeadType)
   332  			}
   333  		case objabi.R_TLS_IE:
   334  			if target.IsExternal() && target.IsElf() {
   335  				nExtReloc++
   336  				o = 0
   337  				if !target.IsAMD64() {
   338  					o = r.Add()
   339  				}
   340  				if target.Is386() {
   341  					nExtReloc++ // need two ELF relocations on 386, see ../x86/asm.go:elfreloc1
   342  				}
   343  				break
   344  			}
   345  			if target.IsPIE() && target.IsElf() {
   346  				// We are linking the final executable, so we
   347  				// can optimize any TLS IE relocation to LE.
   348  				if thearch.TLSIEtoLE == nil {
   349  					log.Fatalf("internal linking of TLS IE not supported on %v", target.Arch.Family)
   350  				}
   351  				thearch.TLSIEtoLE(P, int(off), int(siz))
   352  				o = int64(syms.Tlsoffset)
   353  			} else {
   354  				log.Fatalf("cannot handle R_TLS_IE (sym %s) when linking internally", ldr.SymName(s))
   355  			}
   356  		case objabi.R_ADDR, objabi.R_PEIMAGEOFF:
   357  			if weak && !ldr.AttrReachable(rs) {
   358  				// Redirect it to runtime.unreachableMethod, which will throw if called.
   359  				rs = syms.unreachableMethod
   360  			}
   361  			if target.IsExternal() {
   362  				nExtReloc++
   363  
   364  				// set up addend for eventual relocation via outer symbol.
   365  				rs := rs
   366  				rs, off := FoldSubSymbolOffset(ldr, rs)
   367  				xadd := r.Add() + off
   368  				rst := ldr.SymType(rs)
   369  				if rst != sym.SHOSTOBJ && rst != sym.SDYNIMPORT && rst != sym.SUNDEFEXT && ldr.SymSect(rs) == nil {
   370  					st.err.Errorf(s, "missing section for relocation target %s", ldr.SymName(rs))
   371  				}
   372  
   373  				o = xadd
   374  				if target.IsElf() {
   375  					if target.IsAMD64() {
   376  						o = 0
   377  					}
   378  				} else if target.IsDarwin() {
   379  					if ldr.SymType(s).IsDWARF() {
   380  						// We generally use symbol-targeted relocations.
   381  						// DWARF tools seem to only handle section-targeted relocations,
   382  						// so generate section-targeted relocations in DWARF sections.
   383  						// See also machoreloc1.
   384  						o += ldr.SymValue(rs)
   385  					}
   386  				} else if target.IsWindows() {
   387  					// nothing to do
   388  				} else if target.IsAIX() {
   389  					o = ldr.SymValue(rs) + xadd
   390  				} else {
   391  					st.err.Errorf(s, "unhandled pcrel relocation to %s on %v", ldr.SymName(rs), target.HeadType)
   392  				}
   393  
   394  				break
   395  			}
   396  
   397  			// On AIX, a second relocation must be done by the loader,
   398  			// as section addresses can change once loaded.
   399  			// The "default" symbol address is still needed by the loader so
   400  			// the current relocation can't be skipped.
   401  			if target.IsAIX() && rst != sym.SDYNIMPORT {
   402  				// It's not possible to make a loader relocation in a
   403  				// symbol which is not inside .data section.
   404  				// FIXME: It should be forbidden to have R_ADDR from a
   405  				// symbol which isn't in .data. However, as .text has the
   406  				// same address once loaded, this is possible.
   407  				if ldr.SymSect(s).Seg == &Segdata {
   408  					Xcoffadddynrel(target, ldr, syms, s, r, ri)
   409  				}
   410  			}
   411  
   412  			o = ldr.SymValue(rs) + r.Add()
   413  			if rt == objabi.R_PEIMAGEOFF {
   414  				// The R_PEIMAGEOFF offset is a RVA, so subtract
   415  				// the base address for the executable.
   416  				o -= PEBASE
   417  			}
   418  
   419  			// On amd64, 4-byte offsets will be sign-extended, so it is impossible to
   420  			// access more than 2GB of static data; fail at link time is better than
   421  			// fail at runtime. See https://golang.org/issue/7980.
   422  			// Instead of special casing only amd64, we treat this as an error on all
   423  			// 64-bit architectures so as to be future-proof.
   424  			if int32(o) < 0 && target.Arch.PtrSize > 4 && siz == 4 {
   425  				st.err.Errorf(s, "non-pc-relative relocation address for %s is too big: %#x (%#x + %#x)", ldr.SymName(rs), uint64(o), ldr.SymValue(rs), r.Add())
   426  				errorexit()
   427  			}
   428  		case objabi.R_DWARFSECREF:
   429  			if ldr.SymSect(rs) == nil {
   430  				st.err.Errorf(s, "missing DWARF section for relocation target %s", ldr.SymName(rs))
   431  			}
   432  
   433  			if target.IsExternal() {
   434  				// On most platforms, the external linker needs to adjust DWARF references
   435  				// as it combines DWARF sections. However, on Darwin, dsymutil does the
   436  				// DWARF linking, and it understands how to follow section offsets.
   437  				// Leaving in the relocation records confuses it (see
   438  				// https://golang.org/issue/22068) so drop them for Darwin.
   439  				if !target.IsDarwin() {
   440  					nExtReloc++
   441  				}
   442  
   443  				xadd := r.Add() + ldr.SymValue(rs) - int64(ldr.SymSect(rs).Vaddr)
   444  
   445  				o = xadd
   446  				if target.IsElf() && target.IsAMD64() {
   447  					o = 0
   448  				}
   449  				break
   450  			}
   451  			o = ldr.SymValue(rs) + r.Add() - int64(ldr.SymSect(rs).Vaddr)
   452  		case objabi.R_METHODOFF:
   453  			if !ldr.AttrReachable(rs) {
   454  				// Set it to a sentinel value. The runtime knows this is not pointing to
   455  				// anything valid.
   456  				o = -1
   457  				break
   458  			}
   459  			fallthrough
   460  		case objabi.R_ADDROFF:
   461  			if weak && !ldr.AttrReachable(rs) {
   462  				continue
   463  			}
   464  			sect := ldr.SymSect(rs)
   465  			if sect == nil {
   466  				if rst == sym.SDYNIMPORT {
   467  					st.err.Errorf(s, "cannot target DYNIMPORT sym in section-relative reloc: %s", ldr.SymName(rs))
   468  				} else if rst == sym.SUNDEFEXT {
   469  					st.err.Errorf(s, "undefined symbol in relocation: %s", ldr.SymName(rs))
   470  				} else {
   471  					st.err.Errorf(s, "missing section for relocation target %s", ldr.SymName(rs))
   472  				}
   473  				continue
   474  			}
   475  
   476  			// The method offset tables using this relocation expect the offset to be relative
   477  			// to the start of the first text section, even if there are multiple.
   478  			if sect.Name == ".text" {
   479  				o = ldr.SymValue(rs) - int64(Segtext.Sections[0].Vaddr) + r.Add()
   480  			} else {
   481  				o = ldr.SymValue(rs) - int64(ldr.SymSect(rs).Vaddr) + r.Add()
   482  			}
   483  
   484  		case objabi.R_ADDRCUOFF:
   485  			// debug_range and debug_loc elements use this relocation type to get an
   486  			// offset from the start of the compile unit.
   487  			o = ldr.SymValue(rs) + r.Add() - ldr.SymValue(loader.Sym(ldr.SymUnit(rs).Textp[0]))
   488  
   489  		// r.Sym() can be 0 when CALL $(constant) is transformed from absolute PC to relative PC call.
   490  		case objabi.R_GOTPCREL:
   491  			if target.IsDynlinkingGo() && target.IsDarwin() && rs != 0 {
   492  				nExtReloc++
   493  				o = r.Add()
   494  				break
   495  			}
   496  			if target.Is386() && target.IsExternal() && target.IsELF {
   497  				nExtReloc++ // need two ELF relocations on 386, see ../x86/asm.go:elfreloc1
   498  			}
   499  			fallthrough
   500  		case objabi.R_CALL, objabi.R_PCREL:
   501  			if target.IsExternal() && rs != 0 && rst == sym.SUNDEFEXT {
   502  				// pass through to the external linker.
   503  				nExtReloc++
   504  				o = 0
   505  				break
   506  			}
   507  			if target.IsExternal() && rs != 0 && (ldr.SymSect(rs) != ldr.SymSect(s) || rt == objabi.R_GOTPCREL) {
   508  				nExtReloc++
   509  
   510  				// set up addend for eventual relocation via outer symbol.
   511  				rs := rs
   512  				rs, off := FoldSubSymbolOffset(ldr, rs)
   513  				xadd := r.Add() + off - int64(siz) // relative to address after the relocated chunk
   514  				rst := ldr.SymType(rs)
   515  				if rst != sym.SHOSTOBJ && rst != sym.SDYNIMPORT && ldr.SymSect(rs) == nil {
   516  					st.err.Errorf(s, "missing section for relocation target %s", ldr.SymName(rs))
   517  				}
   518  
   519  				o = xadd
   520  				if target.IsElf() {
   521  					if target.IsAMD64() {
   522  						o = 0
   523  					}
   524  				} else if target.IsDarwin() {
   525  					if rt == objabi.R_CALL {
   526  						if target.IsExternal() && rst == sym.SDYNIMPORT {
   527  							if target.IsAMD64() {
   528  								// AMD64 dynamic relocations are relative to the end of the relocation.
   529  								o += int64(siz)
   530  							}
   531  						} else {
   532  							if rst != sym.SHOSTOBJ {
   533  								o += int64(uint64(ldr.SymValue(rs)) - ldr.SymSect(rs).Vaddr)
   534  							}
   535  							o -= int64(off) // relative to section offset, not symbol
   536  						}
   537  					} else {
   538  						o += int64(siz)
   539  					}
   540  				} else if target.IsWindows() && target.IsAMD64() { // only amd64 needs PCREL
   541  					// PE/COFF's PC32 relocation uses the address after the relocated
   542  					// bytes as the base. Compensate by skewing the addend.
   543  					o += int64(siz)
   544  				} else {
   545  					st.err.Errorf(s, "unhandled pcrel relocation to %s on %v", ldr.SymName(rs), target.HeadType)
   546  				}
   547  
   548  				break
   549  			}
   550  
   551  			o = 0
   552  			if rs != 0 {
   553  				o = ldr.SymValue(rs)
   554  			}
   555  
   556  			o += r.Add() - (ldr.SymValue(s) + int64(off) + int64(siz))
   557  		case objabi.R_SIZE:
   558  			o = ldr.SymSize(rs) + r.Add()
   559  
   560  		case objabi.R_XCOFFREF:
   561  			if !target.IsAIX() {
   562  				st.err.Errorf(s, "find XCOFF R_REF on non-XCOFF files")
   563  			}
   564  			if !target.IsExternal() {
   565  				st.err.Errorf(s, "find XCOFF R_REF with internal linking")
   566  			}
   567  			nExtReloc++
   568  			continue
   569  
   570  		case objabi.R_DWARFFILEREF:
   571  			// We don't renumber files in dwarf.go:writelines anymore.
   572  			continue
   573  
   574  		case objabi.R_CONST:
   575  			o = r.Add()
   576  
   577  		case objabi.R_GOTOFF:
   578  			o = ldr.SymValue(rs) + r.Add() - ldr.SymValue(syms.GOT)
   579  		}
   580  
   581  		if target.IsPPC64() || target.IsS390X() {
   582  			if rv != sym.RV_NONE {
   583  				o = thearch.Archrelocvariant(target, ldr, r, rv, s, o, P)
   584  			}
   585  		}
   586  
   587  		switch siz {
   588  		default:
   589  			st.err.Errorf(s, "bad reloc size %#x for %s", uint32(siz), ldr.SymName(rs))
   590  		case 1:
   591  			P[off] = byte(int8(o))
   592  		case 2:
   593  			if (rt == objabi.R_PCREL || rt == objabi.R_CALL) && o != int64(int16(o)) {
   594  				st.err.Errorf(s, "pc-relative relocation address for %s is too big: %#x", ldr.SymName(rs), o)
   595  			} else if o != int64(int16(o)) && o != int64(uint16(o)) {
   596  				st.err.Errorf(s, "non-pc-relative relocation address for %s is too big: %#x", ldr.SymName(rs), uint64(o))
   597  			}
   598  			target.Arch.ByteOrder.PutUint16(P[off:], uint16(o))
   599  		case 4:
   600  			if (rt == objabi.R_PCREL || rt == objabi.R_CALL) && o != int64(int32(o)) {
   601  				st.err.Errorf(s, "pc-relative relocation address for %s is too big: %#x", ldr.SymName(rs), o)
   602  			} else if o != int64(int32(o)) && o != int64(uint32(o)) {
   603  				st.err.Errorf(s, "non-pc-relative relocation address for %s is too big: %#x", ldr.SymName(rs), uint64(o))
   604  			}
   605  			target.Arch.ByteOrder.PutUint32(P[off:], uint32(o))
   606  		case 8:
   607  			target.Arch.ByteOrder.PutUint64(P[off:], uint64(o))
   608  		}
   609  	}
   610  	if target.IsExternal() {
   611  		// We'll stream out the external relocations in asmb2 (e.g. elfrelocsect)
   612  		// and we only need the count here.
   613  		atomic.AddUint32(&ldr.SymSect(s).Relcount, uint32(nExtReloc))
   614  	}
   615  }
   616  
   617  // Convert a Go relocation to an external relocation.
   618  func extreloc(ctxt *Link, ldr *loader.Loader, s loader.Sym, r loader.Reloc) (loader.ExtReloc, bool) {
   619  	var rr loader.ExtReloc
   620  	target := &ctxt.Target
   621  	siz := int32(r.Siz())
   622  	if siz == 0 { // informational relocation - no work to do
   623  		return rr, false
   624  	}
   625  
   626  	rt := r.Type()
   627  	if rt >= objabi.ElfRelocOffset {
   628  		return rr, false
   629  	}
   630  	rr.Type = rt
   631  	rr.Size = uint8(siz)
   632  
   633  	// TODO(mundaym): remove this special case - see issue 14218.
   634  	if target.IsS390X() {
   635  		switch rt {
   636  		case objabi.R_PCRELDBL:
   637  			rt = objabi.R_PCREL
   638  		}
   639  	}
   640  
   641  	switch rt {
   642  	default:
   643  		return thearch.Extreloc(target, ldr, r, s)
   644  
   645  	case objabi.R_TLS_LE, objabi.R_TLS_IE:
   646  		if target.IsElf() {
   647  			rs := r.Sym()
   648  			rr.Xsym = rs
   649  			if rr.Xsym == 0 {
   650  				rr.Xsym = ctxt.Tlsg
   651  			}
   652  			rr.Xadd = r.Add()
   653  			break
   654  		}
   655  		return rr, false
   656  
   657  	case objabi.R_ADDR, objabi.R_PEIMAGEOFF:
   658  		// set up addend for eventual relocation via outer symbol.
   659  		rs := r.Sym()
   660  		if r.Weak() && !ldr.AttrReachable(rs) {
   661  			rs = ctxt.ArchSyms.unreachableMethod
   662  		}
   663  		rs, off := FoldSubSymbolOffset(ldr, rs)
   664  		rr.Xadd = r.Add() + off
   665  		rr.Xsym = rs
   666  
   667  	case objabi.R_DWARFSECREF:
   668  		// On most platforms, the external linker needs to adjust DWARF references
   669  		// as it combines DWARF sections. However, on Darwin, dsymutil does the
   670  		// DWARF linking, and it understands how to follow section offsets.
   671  		// Leaving in the relocation records confuses it (see
   672  		// https://golang.org/issue/22068) so drop them for Darwin.
   673  		if target.IsDarwin() {
   674  			return rr, false
   675  		}
   676  		rs := r.Sym()
   677  		rr.Xsym = loader.Sym(ldr.SymSect(rs).Sym)
   678  		rr.Xadd = r.Add() + ldr.SymValue(rs) - int64(ldr.SymSect(rs).Vaddr)
   679  
   680  	// r.Sym() can be 0 when CALL $(constant) is transformed from absolute PC to relative PC call.
   681  	case objabi.R_GOTPCREL, objabi.R_CALL, objabi.R_PCREL:
   682  		rs := r.Sym()
   683  		if rt == objabi.R_GOTPCREL && target.IsDynlinkingGo() && target.IsDarwin() && rs != 0 {
   684  			rr.Xadd = r.Add()
   685  			rr.Xadd -= int64(siz) // relative to address after the relocated chunk
   686  			rr.Xsym = rs
   687  			break
   688  		}
   689  		if rs != 0 && ldr.SymType(rs) == sym.SUNDEFEXT {
   690  			// pass through to the external linker.
   691  			rr.Xadd = 0
   692  			if target.IsElf() {
   693  				rr.Xadd -= int64(siz)
   694  			}
   695  			rr.Xsym = rs
   696  			break
   697  		}
   698  		if rs != 0 && (ldr.SymSect(rs) != ldr.SymSect(s) || rt == objabi.R_GOTPCREL) {
   699  			// set up addend for eventual relocation via outer symbol.
   700  			rs := rs
   701  			rs, off := FoldSubSymbolOffset(ldr, rs)
   702  			rr.Xadd = r.Add() + off
   703  			rr.Xadd -= int64(siz) // relative to address after the relocated chunk
   704  			rr.Xsym = rs
   705  			break
   706  		}
   707  		return rr, false
   708  
   709  	case objabi.R_XCOFFREF:
   710  		return ExtrelocSimple(ldr, r), true
   711  
   712  	// These reloc types don't need external relocations.
   713  	case objabi.R_ADDROFF, objabi.R_METHODOFF, objabi.R_ADDRCUOFF,
   714  		objabi.R_SIZE, objabi.R_CONST, objabi.R_GOTOFF:
   715  		return rr, false
   716  	}
   717  	return rr, true
   718  }
   719  
   720  // ExtrelocSimple creates a simple external relocation from r, with the same
   721  // symbol and addend.
   722  func ExtrelocSimple(ldr *loader.Loader, r loader.Reloc) loader.ExtReloc {
   723  	var rr loader.ExtReloc
   724  	rs := r.Sym()
   725  	rr.Xsym = rs
   726  	rr.Xadd = r.Add()
   727  	rr.Type = r.Type()
   728  	rr.Size = r.Siz()
   729  	return rr
   730  }
   731  
   732  // ExtrelocViaOuterSym creates an external relocation from r targeting the
   733  // outer symbol and folding the subsymbol's offset into the addend.
   734  func ExtrelocViaOuterSym(ldr *loader.Loader, r loader.Reloc, s loader.Sym) loader.ExtReloc {
   735  	// set up addend for eventual relocation via outer symbol.
   736  	var rr loader.ExtReloc
   737  	rs := r.Sym()
   738  	rs, off := FoldSubSymbolOffset(ldr, rs)
   739  	rr.Xadd = r.Add() + off
   740  	rst := ldr.SymType(rs)
   741  	if rst != sym.SHOSTOBJ && rst != sym.SDYNIMPORT && rst != sym.SUNDEFEXT && ldr.SymSect(rs) == nil {
   742  		ldr.Errorf(s, "missing section for %s", ldr.SymName(rs))
   743  	}
   744  	rr.Xsym = rs
   745  	rr.Type = r.Type()
   746  	rr.Size = r.Siz()
   747  	return rr
   748  }
   749  
   750  // relocSymState hold state information needed when making a series of
   751  // successive calls to relocsym(). The items here are invariant
   752  // (meaning that they are set up once initially and then don't change
   753  // during the execution of relocsym), with the exception of a slice
   754  // used to facilitate batch allocation of external relocations. Calls
   755  // to relocsym happen in parallel; the assumption is that each
   756  // parallel thread will have its own state object.
   757  type relocSymState struct {
   758  	target *Target
   759  	ldr    *loader.Loader
   760  	err    *ErrorReporter
   761  	syms   *ArchSyms
   762  }
   763  
   764  // makeRelocSymState creates a relocSymState container object to
   765  // pass to relocsym(). If relocsym() calls happen in parallel,
   766  // each parallel thread should have its own state object.
   767  func (ctxt *Link) makeRelocSymState() *relocSymState {
   768  	return &relocSymState{
   769  		target: &ctxt.Target,
   770  		ldr:    ctxt.loader,
   771  		err:    &ctxt.ErrorReporter,
   772  		syms:   &ctxt.ArchSyms,
   773  	}
   774  }
   775  
   776  // windynrelocsym examines a text symbol 's' and looks for relocations
   777  // from it that correspond to references to symbols defined in DLLs,
   778  // then fixes up those relocations as needed. A reference to a symbol
   779  // XYZ from some DLL will fall into one of two categories: an indirect
   780  // ref via "__imp_XYZ", or a direct ref to "XYZ". Here's an example of
   781  // an indirect ref (this is an excerpt from objdump -ldr):
   782  //
   783  //	     1c1: 48 89 c6                     	movq	%rax, %rsi
   784  //	     1c4: ff 15 00 00 00 00            	callq	*(%rip)
   785  //			00000000000001c6:  IMAGE_REL_AMD64_REL32	__imp__errno
   786  //
   787  // In the assembly above, the code loads up the value of __imp_errno
   788  // and then does an indirect call to that value.
   789  //
   790  // Here is what a direct reference might look like:
   791  //
   792  //	     137: e9 20 06 00 00               	jmp	0x75c <pow+0x75c>
   793  //	     13c: e8 00 00 00 00               	callq	0x141 <pow+0x141>
   794  //			000000000000013d:  IMAGE_REL_AMD64_REL32	_errno
   795  //
   796  // The assembly below dispenses with the import symbol and just makes
   797  // a direct call to _errno.
   798  //
   799  // The code below handles indirect refs by redirecting the target of
   800  // the relocation from "__imp_XYZ" to "XYZ" (since the latter symbol
   801  // is what the Windows loader is expected to resolve). For direct refs
   802  // the call is redirected to a stub, where the stub first loads the
   803  // symbol and then direct an indirect call to that value.
   804  //
   805  // Note that for a given symbol (as above) it is perfectly legal to
   806  // have both direct and indirect references.
   807  func windynrelocsym(ctxt *Link, rel *loader.SymbolBuilder, s loader.Sym) error {
   808  	var su *loader.SymbolBuilder
   809  	relocs := ctxt.loader.Relocs(s)
   810  	for ri := 0; ri < relocs.Count(); ri++ {
   811  		r := relocs.At(ri)
   812  		if r.IsMarker() {
   813  			continue // skip marker relocations
   814  		}
   815  		targ := r.Sym()
   816  		if targ == 0 {
   817  			continue
   818  		}
   819  		if !ctxt.loader.AttrReachable(targ) {
   820  			if r.Weak() {
   821  				continue
   822  			}
   823  			return fmt.Errorf("dynamic relocation to unreachable symbol %s",
   824  				ctxt.loader.SymName(targ))
   825  		}
   826  		tgot := ctxt.loader.SymGot(targ)
   827  		if tgot == loadpe.RedirectToDynImportGotToken {
   828  
   829  			// Consistency check: name should be __imp_X
   830  			sname := ctxt.loader.SymName(targ)
   831  			if !strings.HasPrefix(sname, "__imp_") {
   832  				return fmt.Errorf("internal error in windynrelocsym: redirect GOT token applied to non-import symbol %s", sname)
   833  			}
   834  
   835  			// Locate underlying symbol (which originally had type
   836  			// SDYNIMPORT but has since been retyped to SWINDOWS).
   837  			ds, err := loadpe.LookupBaseFromImport(targ, ctxt.loader, ctxt.Arch)
   838  			if err != nil {
   839  				return err
   840  			}
   841  			dstyp := ctxt.loader.SymType(ds)
   842  			if dstyp != sym.SWINDOWS {
   843  				return fmt.Errorf("internal error in windynrelocsym: underlying sym for %q has wrong type %s", sname, dstyp.String())
   844  			}
   845  
   846  			// Redirect relocation to the dynimport.
   847  			r.SetSym(ds)
   848  			continue
   849  		}
   850  
   851  		tplt := ctxt.loader.SymPlt(targ)
   852  		if tplt == loadpe.CreateImportStubPltToken {
   853  
   854  			// Consistency check: don't want to see both PLT and GOT tokens.
   855  			if tgot != -1 {
   856  				return fmt.Errorf("internal error in windynrelocsym: invalid GOT setting %d for reloc to %s", tgot, ctxt.loader.SymName(targ))
   857  			}
   858  
   859  			// make dynimport JMP table for PE object files.
   860  			tplt := int32(rel.Size())
   861  			ctxt.loader.SetPlt(targ, tplt)
   862  
   863  			if su == nil {
   864  				su = ctxt.loader.MakeSymbolUpdater(s)
   865  			}
   866  			r.SetSym(rel.Sym())
   867  			r.SetAdd(int64(tplt))
   868  
   869  			// jmp *addr
   870  			switch ctxt.Arch.Family {
   871  			default:
   872  				return fmt.Errorf("internal error in windynrelocsym: unsupported arch %v", ctxt.Arch.Family)
   873  			case sys.I386:
   874  				rel.AddUint8(0xff)
   875  				rel.AddUint8(0x25)
   876  				rel.AddAddrPlus(ctxt.Arch, targ, 0)
   877  				rel.AddUint8(0x90)
   878  				rel.AddUint8(0x90)
   879  			case sys.AMD64:
   880  				rel.AddUint8(0xff)
   881  				rel.AddUint8(0x24)
   882  				rel.AddUint8(0x25)
   883  				rel.AddAddrPlus4(ctxt.Arch, targ, 0)
   884  				rel.AddUint8(0x90)
   885  			}
   886  		} else if tplt >= 0 {
   887  			if su == nil {
   888  				su = ctxt.loader.MakeSymbolUpdater(s)
   889  			}
   890  			r.SetSym(rel.Sym())
   891  			r.SetAdd(int64(tplt))
   892  		}
   893  	}
   894  	return nil
   895  }
   896  
   897  // windynrelocsyms generates jump table to C library functions that will be
   898  // added later. windynrelocsyms writes the table into .rel symbol.
   899  func (ctxt *Link) windynrelocsyms() {
   900  	if !(ctxt.IsWindows() && iscgo && ctxt.IsInternal()) {
   901  		return
   902  	}
   903  
   904  	rel := ctxt.loader.CreateSymForUpdate(".rel", 0)
   905  	rel.SetType(sym.STEXT)
   906  
   907  	for _, s := range ctxt.Textp {
   908  		if err := windynrelocsym(ctxt, rel, s); err != nil {
   909  			ctxt.Errorf(s, "%v", err)
   910  		}
   911  	}
   912  
   913  	ctxt.Textp = append(ctxt.Textp, rel.Sym())
   914  }
   915  
   916  func dynrelocsym(ctxt *Link, s loader.Sym) {
   917  	target := &ctxt.Target
   918  	ldr := ctxt.loader
   919  	syms := &ctxt.ArchSyms
   920  	relocs := ldr.Relocs(s)
   921  	for ri := 0; ri < relocs.Count(); ri++ {
   922  		r := relocs.At(ri)
   923  		if r.IsMarker() {
   924  			continue // skip marker relocations
   925  		}
   926  		rSym := r.Sym()
   927  		if r.Weak() && !ldr.AttrReachable(rSym) {
   928  			continue
   929  		}
   930  		if ctxt.BuildMode == BuildModePIE && ctxt.LinkMode == LinkInternal {
   931  			// It's expected that some relocations will be done
   932  			// later by relocsym (R_TLS_LE, R_ADDROFF), so
   933  			// don't worry if Adddynrel returns false.
   934  			thearch.Adddynrel(target, ldr, syms, s, r, ri)
   935  			continue
   936  		}
   937  
   938  		if rSym != 0 && ldr.SymType(rSym) == sym.SDYNIMPORT || r.Type() >= objabi.ElfRelocOffset {
   939  			if rSym != 0 && !ldr.AttrReachable(rSym) {
   940  				ctxt.Errorf(s, "dynamic relocation to unreachable symbol %s", ldr.SymName(rSym))
   941  			}
   942  			if !thearch.Adddynrel(target, ldr, syms, s, r, ri) {
   943  				ctxt.Errorf(s, "unsupported dynamic relocation for symbol %s (type=%d (%s) stype=%d (%s))", ldr.SymName(rSym), r.Type(), sym.RelocName(ctxt.Arch, r.Type()), ldr.SymType(rSym), ldr.SymType(rSym))
   944  			}
   945  		}
   946  	}
   947  }
   948  
   949  func (state *dodataState) dynreloc(ctxt *Link) {
   950  	if ctxt.HeadType == objabi.Hwindows {
   951  		return
   952  	}
   953  	// -d suppresses dynamic loader format, so we may as well not
   954  	// compute these sections or mark their symbols as reachable.
   955  	if *FlagD {
   956  		return
   957  	}
   958  
   959  	for _, s := range ctxt.Textp {
   960  		dynrelocsym(ctxt, s)
   961  	}
   962  	for _, syms := range state.data {
   963  		for _, s := range syms {
   964  			dynrelocsym(ctxt, s)
   965  		}
   966  	}
   967  	if ctxt.IsELF {
   968  		elfdynhash(ctxt)
   969  	}
   970  }
   971  
   972  func CodeblkPad(ctxt *Link, out *OutBuf, addr int64, size int64, pad []byte) {
   973  	writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, ctxt.Textp, addr, size, pad)
   974  }
   975  
   976  const blockSize = 1 << 20 // 1MB chunks written at a time.
   977  
   978  // writeBlocks writes a specified chunk of symbols to the output buffer. It
   979  // breaks the write up into ≥blockSize chunks to write them out, and schedules
   980  // as many goroutines as necessary to accomplish this task. This call then
   981  // blocks, waiting on the writes to complete. Note that we use the sem parameter
   982  // to limit the number of concurrent writes taking place.
   983  func writeBlocks(ctxt *Link, out *OutBuf, sem chan int, ldr *loader.Loader, syms []loader.Sym, addr, size int64, pad []byte) {
   984  	for i, s := range syms {
   985  		if ldr.SymValue(s) >= addr && !ldr.AttrSubSymbol(s) {
   986  			syms = syms[i:]
   987  			break
   988  		}
   989  	}
   990  
   991  	var wg sync.WaitGroup
   992  	max, lastAddr, written := int64(blockSize), addr+size, int64(0)
   993  	for addr < lastAddr {
   994  		// Find the last symbol we'd write.
   995  		idx := -1
   996  		for i, s := range syms {
   997  			if ldr.AttrSubSymbol(s) {
   998  				continue
   999  			}
  1000  
  1001  			// If the next symbol's size would put us out of bounds on the total length,
  1002  			// stop looking.
  1003  			end := ldr.SymValue(s) + ldr.SymSize(s)
  1004  			if end > lastAddr {
  1005  				break
  1006  			}
  1007  
  1008  			// We're gonna write this symbol.
  1009  			idx = i
  1010  
  1011  			// If we cross over the max size, we've got enough symbols.
  1012  			if end > addr+max {
  1013  				break
  1014  			}
  1015  		}
  1016  
  1017  		// If we didn't find any symbols to write, we're done here.
  1018  		if idx < 0 {
  1019  			break
  1020  		}
  1021  
  1022  		// Compute the length to write, including padding.
  1023  		// We need to write to the end address (lastAddr), or the next symbol's
  1024  		// start address, whichever comes first. If there is no more symbols,
  1025  		// just write to lastAddr. This ensures we don't leave holes between the
  1026  		// blocks or at the end.
  1027  		length := int64(0)
  1028  		if idx+1 < len(syms) {
  1029  			// Find the next top-level symbol.
  1030  			// Skip over sub symbols so we won't split a container symbol
  1031  			// into two blocks.
  1032  			next := syms[idx+1]
  1033  			for ldr.AttrSubSymbol(next) {
  1034  				idx++
  1035  				next = syms[idx+1]
  1036  			}
  1037  			length = ldr.SymValue(next) - addr
  1038  		}
  1039  		if length == 0 || length > lastAddr-addr {
  1040  			length = lastAddr - addr
  1041  		}
  1042  
  1043  		// Start the block output operator.
  1044  		if o, err := out.View(uint64(out.Offset() + written)); err == nil {
  1045  			sem <- 1
  1046  			wg.Add(1)
  1047  			go func(o *OutBuf, ldr *loader.Loader, syms []loader.Sym, addr, size int64, pad []byte) {
  1048  				writeBlock(ctxt, o, ldr, syms, addr, size, pad)
  1049  				wg.Done()
  1050  				<-sem
  1051  			}(o, ldr, syms, addr, length, pad)
  1052  		} else { // output not mmaped, don't parallelize.
  1053  			writeBlock(ctxt, out, ldr, syms, addr, length, pad)
  1054  		}
  1055  
  1056  		// Prepare for the next loop.
  1057  		if idx != -1 {
  1058  			syms = syms[idx+1:]
  1059  		}
  1060  		written += length
  1061  		addr += length
  1062  	}
  1063  	wg.Wait()
  1064  }
  1065  
  1066  func writeBlock(ctxt *Link, out *OutBuf, ldr *loader.Loader, syms []loader.Sym, addr, size int64, pad []byte) {
  1067  
  1068  	st := ctxt.makeRelocSymState()
  1069  
  1070  	// This doesn't distinguish the memory size from the file
  1071  	// size, and it lays out the file based on Symbol.Value, which
  1072  	// is the virtual address. DWARF compression changes file sizes,
  1073  	// so dwarfcompress will fix this up later if necessary.
  1074  	eaddr := addr + size
  1075  	for _, s := range syms {
  1076  		if ldr.AttrSubSymbol(s) {
  1077  			continue
  1078  		}
  1079  		val := ldr.SymValue(s)
  1080  		if val >= eaddr {
  1081  			break
  1082  		}
  1083  		if val < addr {
  1084  			ldr.Errorf(s, "phase error: addr=%#x but val=%#x sym=%s type=%v sect=%v sect.addr=%#x", addr, val, ldr.SymName(s), ldr.SymType(s), ldr.SymSect(s).Name, ldr.SymSect(s).Vaddr)
  1085  			errorexit()
  1086  		}
  1087  		if addr < val {
  1088  			out.WriteStringPad("", int(val-addr), pad)
  1089  			addr = val
  1090  		}
  1091  		P := out.WriteSym(ldr, s)
  1092  		st.relocsym(s, P)
  1093  		if ldr.IsGeneratedSym(s) {
  1094  			f := ctxt.generatorSyms[s]
  1095  			f(ctxt, s)
  1096  		}
  1097  		addr += int64(len(P))
  1098  		siz := ldr.SymSize(s)
  1099  		if addr < val+siz {
  1100  			out.WriteStringPad("", int(val+siz-addr), pad)
  1101  			addr = val + siz
  1102  		}
  1103  		if addr != val+siz {
  1104  			ldr.Errorf(s, "phase error: addr=%#x value+size=%#x", addr, val+siz)
  1105  			errorexit()
  1106  		}
  1107  		if val+siz >= eaddr {
  1108  			break
  1109  		}
  1110  	}
  1111  
  1112  	if addr < eaddr {
  1113  		out.WriteStringPad("", int(eaddr-addr), pad)
  1114  	}
  1115  }
  1116  
  1117  type writeFn func(*Link, *OutBuf, int64, int64)
  1118  
  1119  // writeParallel handles scheduling parallel execution of data write functions.
  1120  func writeParallel(wg *sync.WaitGroup, fn writeFn, ctxt *Link, seek, vaddr, length uint64) {
  1121  	if out, err := ctxt.Out.View(seek); err != nil {
  1122  		ctxt.Out.SeekSet(int64(seek))
  1123  		fn(ctxt, ctxt.Out, int64(vaddr), int64(length))
  1124  	} else {
  1125  		wg.Add(1)
  1126  		go func() {
  1127  			defer wg.Done()
  1128  			fn(ctxt, out, int64(vaddr), int64(length))
  1129  		}()
  1130  	}
  1131  }
  1132  
  1133  func datblk(ctxt *Link, out *OutBuf, addr, size int64) {
  1134  	writeDatblkToOutBuf(ctxt, out, addr, size)
  1135  }
  1136  
  1137  // Used only on Wasm for now.
  1138  func DatblkBytes(ctxt *Link, addr int64, size int64) []byte {
  1139  	buf := make([]byte, size)
  1140  	out := &OutBuf{heap: buf}
  1141  	writeDatblkToOutBuf(ctxt, out, addr, size)
  1142  	return buf
  1143  }
  1144  
  1145  func writeDatblkToOutBuf(ctxt *Link, out *OutBuf, addr int64, size int64) {
  1146  	writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, ctxt.datap, addr, size, zeros[:])
  1147  }
  1148  
  1149  func dwarfblk(ctxt *Link, out *OutBuf, addr int64, size int64) {
  1150  	// Concatenate the section symbol lists into a single list to pass
  1151  	// to writeBlocks.
  1152  	//
  1153  	// NB: ideally we would do a separate writeBlocks call for each
  1154  	// section, but this would run the risk of undoing any file offset
  1155  	// adjustments made during layout.
  1156  	n := 0
  1157  	for i := range dwarfp {
  1158  		n += len(dwarfp[i].syms)
  1159  	}
  1160  	syms := make([]loader.Sym, 0, n)
  1161  	for i := range dwarfp {
  1162  		syms = append(syms, dwarfp[i].syms...)
  1163  	}
  1164  	writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, syms, addr, size, zeros[:])
  1165  }
  1166  
  1167  func pdatablk(ctxt *Link, out *OutBuf, addr int64, size int64) {
  1168  	writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, sehp.pdata, addr, size, zeros[:])
  1169  }
  1170  
  1171  func xdatablk(ctxt *Link, out *OutBuf, addr int64, size int64) {
  1172  	writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, sehp.xdata, addr, size, zeros[:])
  1173  }
  1174  
  1175  var covCounterDataStartOff, covCounterDataLen uint64
  1176  
  1177  var zeros [512]byte
  1178  
  1179  var (
  1180  	strdata  = make(map[string]string)
  1181  	strnames []string
  1182  )
  1183  
  1184  func addstrdata1(ctxt *Link, arg string) {
  1185  	eq := strings.Index(arg, "=")
  1186  	dot := strings.LastIndex(arg[:eq+1], ".")
  1187  	if eq < 0 || dot < 0 {
  1188  		Exitf("-X flag requires argument of the form importpath.name=value")
  1189  	}
  1190  	pkg := arg[:dot]
  1191  	if ctxt.BuildMode == BuildModePlugin && pkg == "main" {
  1192  		pkg = *flagPluginPath
  1193  	}
  1194  	pkg = objabi.PathToPrefix(pkg)
  1195  	name := pkg + arg[dot:eq]
  1196  	value := arg[eq+1:]
  1197  	if _, ok := strdata[name]; !ok {
  1198  		strnames = append(strnames, name)
  1199  	}
  1200  	strdata[name] = value
  1201  }
  1202  
  1203  // addstrdata sets the initial value of the string variable name to value.
  1204  func addstrdata(arch *sys.Arch, l *loader.Loader, name, value string) {
  1205  	s := l.Lookup(name, 0)
  1206  	if s == 0 {
  1207  		return
  1208  	}
  1209  	if goType := l.SymGoType(s); goType == 0 {
  1210  		return
  1211  	} else if typeName := l.SymName(goType); typeName != "type:string" {
  1212  		Errorf(nil, "%s: cannot set with -X: not a var of type string (%s)", name, typeName)
  1213  		return
  1214  	}
  1215  	if !l.AttrReachable(s) {
  1216  		return // don't bother setting unreachable variable
  1217  	}
  1218  	bld := l.MakeSymbolUpdater(s)
  1219  	if bld.Type() == sym.SBSS {
  1220  		bld.SetType(sym.SDATA)
  1221  	}
  1222  
  1223  	p := fmt.Sprintf("%s.str", name)
  1224  	sbld := l.CreateSymForUpdate(p, 0)
  1225  	sbld.Addstring(value)
  1226  	sbld.SetType(sym.SRODATA)
  1227  
  1228  	// Don't reset the variable's size. String variable usually has size of
  1229  	// 2*PtrSize, but in ASAN build it can be larger due to red zone.
  1230  	// (See issue 56175.)
  1231  	bld.SetData(make([]byte, arch.PtrSize*2))
  1232  	bld.SetReadOnly(false)
  1233  	bld.ResetRelocs()
  1234  	bld.SetAddrPlus(arch, 0, sbld.Sym(), 0)
  1235  	bld.SetUint(arch, int64(arch.PtrSize), uint64(len(value)))
  1236  }
  1237  
  1238  func (ctxt *Link) dostrdata() {
  1239  	for _, name := range strnames {
  1240  		addstrdata(ctxt.Arch, ctxt.loader, name, strdata[name])
  1241  	}
  1242  }
  1243  
  1244  // addgostring adds str, as a Go string value, to s. symname is the name of the
  1245  // symbol used to define the string data and must be unique per linked object.
  1246  func addgostring(ctxt *Link, ldr *loader.Loader, s *loader.SymbolBuilder, symname, str string) {
  1247  	sdata := ldr.CreateSymForUpdate(symname, 0)
  1248  	if sdata.Type() != sym.Sxxx {
  1249  		ctxt.Errorf(s.Sym(), "duplicate symname in addgostring: %s", symname)
  1250  	}
  1251  	sdata.SetLocal(true)
  1252  	sdata.SetType(sym.SRODATA)
  1253  	sdata.SetSize(int64(len(str)))
  1254  	sdata.SetData([]byte(str))
  1255  	s.AddAddr(ctxt.Arch, sdata.Sym())
  1256  	s.AddUint(ctxt.Arch, uint64(len(str)))
  1257  }
  1258  
  1259  func addinitarrdata(ctxt *Link, ldr *loader.Loader, s loader.Sym) {
  1260  	p := ldr.SymName(s) + ".ptr"
  1261  	sp := ldr.CreateSymForUpdate(p, 0)
  1262  	sp.SetType(sym.SINITARR)
  1263  	sp.SetSize(0)
  1264  	sp.SetDuplicateOK(true)
  1265  	sp.AddAddr(ctxt.Arch, s)
  1266  }
  1267  
  1268  // symalign returns the required alignment for the given symbol s.
  1269  func symalign(ldr *loader.Loader, s loader.Sym) int32 {
  1270  	min := int32(thearch.Minalign)
  1271  	align := ldr.SymAlign(s)
  1272  	if align >= min {
  1273  		return align
  1274  	} else if align != 0 {
  1275  		return min
  1276  	}
  1277  	align = int32(thearch.Maxalign)
  1278  	ssz := ldr.SymSize(s)
  1279  	for int64(align) > ssz && align > min {
  1280  		align >>= 1
  1281  	}
  1282  	ldr.SetSymAlign(s, align)
  1283  	return align
  1284  }
  1285  
  1286  func aligndatsize(state *dodataState, datsize int64, s loader.Sym) int64 {
  1287  	return Rnd(datsize, int64(symalign(state.ctxt.loader, s)))
  1288  }
  1289  
  1290  const debugGCProg = false
  1291  
  1292  type GCProg struct {
  1293  	ctxt *Link
  1294  	sym  *loader.SymbolBuilder
  1295  	w    gcprog.Writer
  1296  }
  1297  
  1298  func (p *GCProg) Init(ctxt *Link, name string) {
  1299  	p.ctxt = ctxt
  1300  	p.sym = ctxt.loader.CreateSymForUpdate(name, 0)
  1301  	p.w.Init(p.writeByte())
  1302  	if debugGCProg {
  1303  		fmt.Fprintf(os.Stderr, "ld: start GCProg %s\n", name)
  1304  		p.w.Debug(os.Stderr)
  1305  	}
  1306  }
  1307  
  1308  func (p *GCProg) writeByte() func(x byte) {
  1309  	return func(x byte) {
  1310  		p.sym.AddUint8(x)
  1311  	}
  1312  }
  1313  
  1314  func (p *GCProg) End(size int64) {
  1315  	p.w.ZeroUntil(size / int64(p.ctxt.Arch.PtrSize))
  1316  	p.w.End()
  1317  	if debugGCProg {
  1318  		fmt.Fprintf(os.Stderr, "ld: end GCProg\n")
  1319  	}
  1320  }
  1321  
  1322  func (p *GCProg) AddSym(s loader.Sym) {
  1323  	ldr := p.ctxt.loader
  1324  	typ := ldr.SymGoType(s)
  1325  
  1326  	// Things without pointers should be in sym.SNOPTRDATA or sym.SNOPTRBSS;
  1327  	// everything we see should have pointers and should therefore have a type.
  1328  	if typ == 0 {
  1329  		switch ldr.SymName(s) {
  1330  		case "runtime.data", "runtime.edata", "runtime.bss", "runtime.ebss":
  1331  			// Ignore special symbols that are sometimes laid out
  1332  			// as real symbols. See comment about dyld on darwin in
  1333  			// the address function.
  1334  			return
  1335  		}
  1336  		p.ctxt.Errorf(p.sym.Sym(), "missing Go type information for global symbol %s: size %d", ldr.SymName(s), ldr.SymSize(s))
  1337  		return
  1338  	}
  1339  
  1340  	ptrsize := int64(p.ctxt.Arch.PtrSize)
  1341  	typData := ldr.Data(typ)
  1342  	nptr := decodetypePtrdata(p.ctxt.Arch, typData) / ptrsize
  1343  
  1344  	if debugGCProg {
  1345  		fmt.Fprintf(os.Stderr, "gcprog sym: %s at %d (ptr=%d+%d)\n", ldr.SymName(s), ldr.SymValue(s), ldr.SymValue(s)/ptrsize, nptr)
  1346  	}
  1347  
  1348  	sval := ldr.SymValue(s)
  1349  	if !decodetypeUsegcprog(p.ctxt.Arch, typData) {
  1350  		// Copy pointers from mask into program.
  1351  		mask := decodetypeGcmask(p.ctxt, typ)
  1352  		for i := int64(0); i < nptr; i++ {
  1353  			if (mask[i/8]>>uint(i%8))&1 != 0 {
  1354  				p.w.Ptr(sval/ptrsize + i)
  1355  			}
  1356  		}
  1357  		return
  1358  	}
  1359  
  1360  	// Copy program.
  1361  	prog := decodetypeGcprog(p.ctxt, typ)
  1362  	p.w.ZeroUntil(sval / ptrsize)
  1363  	p.w.Append(prog[4:], nptr)
  1364  }
  1365  
  1366  // cutoff is the maximum data section size permitted by the linker
  1367  // (see issue #9862).
  1368  const cutoff = 2e9 // 2 GB (or so; looks better in errors than 2^31)
  1369  
  1370  // check accumulated size of data sections
  1371  func (state *dodataState) checkdatsize(symn sym.SymKind) {
  1372  	if state.datsize > cutoff {
  1373  		Errorf(nil, "too much data, last section %v (%d, over %v bytes)", symn, state.datsize, cutoff)
  1374  	}
  1375  }
  1376  
  1377  func checkSectSize(sect *sym.Section) {
  1378  	// TODO: consider using 4 GB size limit for DWARF sections, and
  1379  	// make sure we generate unsigned offset in relocations and check
  1380  	// for overflow.
  1381  	if sect.Length > cutoff {
  1382  		Errorf(nil, "too much data in section %s (%d, over %v bytes)", sect.Name, sect.Length, cutoff)
  1383  	}
  1384  }
  1385  
  1386  // fixZeroSizedSymbols gives a few special symbols with zero size some space.
  1387  func fixZeroSizedSymbols(ctxt *Link) {
  1388  	// The values in moduledata are filled out by relocations
  1389  	// pointing to the addresses of these special symbols.
  1390  	// Typically these symbols have no size and are not laid
  1391  	// out with their matching section.
  1392  	//
  1393  	// However on darwin, dyld will find the special symbol
  1394  	// in the first loaded module, even though it is local.
  1395  	//
  1396  	// (An hypothesis, formed without looking in the dyld sources:
  1397  	// these special symbols have no size, so their address
  1398  	// matches a real symbol. The dynamic linker assumes we
  1399  	// want the normal symbol with the same address and finds
  1400  	// it in the other module.)
  1401  	//
  1402  	// To work around this we lay out the symbls whose
  1403  	// addresses are vital for multi-module programs to work
  1404  	// as normal symbols, and give them a little size.
  1405  	//
  1406  	// On AIX, as all DATA sections are merged together, ld might not put
  1407  	// these symbols at the beginning of their respective section if there
  1408  	// aren't real symbols, their alignment might not match the
  1409  	// first symbol alignment. Therefore, there are explicitly put at the
  1410  	// beginning of their section with the same alignment.
  1411  	if !(ctxt.DynlinkingGo() && ctxt.HeadType == objabi.Hdarwin) && !(ctxt.HeadType == objabi.Haix && ctxt.LinkMode == LinkExternal) {
  1412  		return
  1413  	}
  1414  
  1415  	ldr := ctxt.loader
  1416  	bss := ldr.CreateSymForUpdate("runtime.bss", 0)
  1417  	bss.SetSize(8)
  1418  	ldr.SetAttrSpecial(bss.Sym(), false)
  1419  
  1420  	ebss := ldr.CreateSymForUpdate("runtime.ebss", 0)
  1421  	ldr.SetAttrSpecial(ebss.Sym(), false)
  1422  
  1423  	data := ldr.CreateSymForUpdate("runtime.data", 0)
  1424  	data.SetSize(8)
  1425  	ldr.SetAttrSpecial(data.Sym(), false)
  1426  
  1427  	edata := ldr.CreateSymForUpdate("runtime.edata", 0)
  1428  	ldr.SetAttrSpecial(edata.Sym(), false)
  1429  
  1430  	if ctxt.HeadType == objabi.Haix {
  1431  		// XCOFFTOC symbols are part of .data section.
  1432  		edata.SetType(sym.SXCOFFTOC)
  1433  	}
  1434  
  1435  	noptrbss := ldr.CreateSymForUpdate("runtime.noptrbss", 0)
  1436  	noptrbss.SetSize(8)
  1437  	ldr.SetAttrSpecial(noptrbss.Sym(), false)
  1438  
  1439  	enoptrbss := ldr.CreateSymForUpdate("runtime.enoptrbss", 0)
  1440  	ldr.SetAttrSpecial(enoptrbss.Sym(), false)
  1441  
  1442  	noptrdata := ldr.CreateSymForUpdate("runtime.noptrdata", 0)
  1443  	noptrdata.SetSize(8)
  1444  	ldr.SetAttrSpecial(noptrdata.Sym(), false)
  1445  
  1446  	enoptrdata := ldr.CreateSymForUpdate("runtime.enoptrdata", 0)
  1447  	ldr.SetAttrSpecial(enoptrdata.Sym(), false)
  1448  
  1449  	types := ldr.CreateSymForUpdate("runtime.types", 0)
  1450  	types.SetType(sym.STYPE)
  1451  	types.SetSize(8)
  1452  	ldr.SetAttrSpecial(types.Sym(), false)
  1453  
  1454  	etypes := ldr.CreateSymForUpdate("runtime.etypes", 0)
  1455  	etypes.SetType(sym.SFUNCTAB)
  1456  	ldr.SetAttrSpecial(etypes.Sym(), false)
  1457  
  1458  	if ctxt.HeadType == objabi.Haix {
  1459  		rodata := ldr.CreateSymForUpdate("runtime.rodata", 0)
  1460  		rodata.SetType(sym.SSTRING)
  1461  		rodata.SetSize(8)
  1462  		ldr.SetAttrSpecial(rodata.Sym(), false)
  1463  
  1464  		erodata := ldr.CreateSymForUpdate("runtime.erodata", 0)
  1465  		ldr.SetAttrSpecial(erodata.Sym(), false)
  1466  	}
  1467  }
  1468  
  1469  // makeRelroForSharedLib creates a section of readonly data if necessary.
  1470  func (state *dodataState) makeRelroForSharedLib(target *Link) {
  1471  	if !target.UseRelro() {
  1472  		return
  1473  	}
  1474  
  1475  	// "read only" data with relocations needs to go in its own section
  1476  	// when building a shared library. We do this by boosting objects of
  1477  	// type SXXX with relocations to type SXXXRELRO.
  1478  	ldr := target.loader
  1479  	for _, symnro := range sym.ReadOnly {
  1480  		symnrelro := sym.RelROMap[symnro]
  1481  
  1482  		ro := []loader.Sym{}
  1483  		relro := state.data[symnrelro]
  1484  
  1485  		for _, s := range state.data[symnro] {
  1486  			relocs := ldr.Relocs(s)
  1487  			isRelro := relocs.Count() > 0
  1488  			switch state.symType(s) {
  1489  			case sym.STYPE, sym.STYPERELRO, sym.SGOFUNCRELRO:
  1490  				// Symbols are not sorted yet, so it is possible
  1491  				// that an Outer symbol has been changed to a
  1492  				// relro Type before it reaches here.
  1493  				isRelro = true
  1494  			case sym.SFUNCTAB:
  1495  				if ldr.SymName(s) == "runtime.etypes" {
  1496  					// runtime.etypes must be at the end of
  1497  					// the relro data.
  1498  					isRelro = true
  1499  				}
  1500  			case sym.SGOFUNC:
  1501  				// The only SGOFUNC symbols that contain relocations are .stkobj,
  1502  				// and their relocations are of type objabi.R_ADDROFF,
  1503  				// which always get resolved during linking.
  1504  				isRelro = false
  1505  			}
  1506  			if isRelro {
  1507  				state.setSymType(s, symnrelro)
  1508  				if outer := ldr.OuterSym(s); outer != 0 {
  1509  					state.setSymType(outer, symnrelro)
  1510  				}
  1511  				relro = append(relro, s)
  1512  			} else {
  1513  				ro = append(ro, s)
  1514  			}
  1515  		}
  1516  
  1517  		// Check that we haven't made two symbols with the same .Outer into
  1518  		// different types (because references two symbols with non-nil Outer
  1519  		// become references to the outer symbol + offset it's vital that the
  1520  		// symbol and the outer end up in the same section).
  1521  		for _, s := range relro {
  1522  			if outer := ldr.OuterSym(s); outer != 0 {
  1523  				st := state.symType(s)
  1524  				ost := state.symType(outer)
  1525  				if st != ost {
  1526  					state.ctxt.Errorf(s, "inconsistent types for symbol and its Outer %s (%v != %v)",
  1527  						ldr.SymName(outer), st, ost)
  1528  				}
  1529  			}
  1530  		}
  1531  
  1532  		state.data[symnro] = ro
  1533  		state.data[symnrelro] = relro
  1534  	}
  1535  }
  1536  
  1537  // dodataState holds bits of state information needed by dodata() and the
  1538  // various helpers it calls. The lifetime of these items should not extend
  1539  // past the end of dodata().
  1540  type dodataState struct {
  1541  	// Link context
  1542  	ctxt *Link
  1543  	// Data symbols bucketed by type.
  1544  	data [sym.SXREF][]loader.Sym
  1545  	// Max alignment for each flavor of data symbol.
  1546  	dataMaxAlign [sym.SXREF]int32
  1547  	// Overridden sym type
  1548  	symGroupType []sym.SymKind
  1549  	// Current data size so far.
  1550  	datsize int64
  1551  }
  1552  
  1553  // A note on symType/setSymType below:
  1554  //
  1555  // In the legacy linker, the types of symbols (notably data symbols) are
  1556  // changed during the symtab() phase so as to insure that similar symbols
  1557  // are bucketed together, then their types are changed back again during
  1558  // dodata. Symbol to section assignment also plays tricks along these lines
  1559  // in the case where a relro segment is needed.
  1560  //
  1561  // The value returned from setType() below reflects the effects of
  1562  // any overrides made by symtab and/or dodata.
  1563  
  1564  // symType returns the (possibly overridden) type of 's'.
  1565  func (state *dodataState) symType(s loader.Sym) sym.SymKind {
  1566  	if int(s) < len(state.symGroupType) {
  1567  		if override := state.symGroupType[s]; override != 0 {
  1568  			return override
  1569  		}
  1570  	}
  1571  	return state.ctxt.loader.SymType(s)
  1572  }
  1573  
  1574  // setSymType sets a new override type for 's'.
  1575  func (state *dodataState) setSymType(s loader.Sym, kind sym.SymKind) {
  1576  	if s == 0 {
  1577  		panic("bad")
  1578  	}
  1579  	if int(s) < len(state.symGroupType) {
  1580  		state.symGroupType[s] = kind
  1581  	} else {
  1582  		su := state.ctxt.loader.MakeSymbolUpdater(s)
  1583  		su.SetType(kind)
  1584  	}
  1585  }
  1586  
  1587  func (ctxt *Link) dodata(symGroupType []sym.SymKind) {
  1588  
  1589  	// Give zeros sized symbols space if necessary.
  1590  	fixZeroSizedSymbols(ctxt)
  1591  
  1592  	// Collect data symbols by type into data.
  1593  	state := dodataState{ctxt: ctxt, symGroupType: symGroupType}
  1594  	ldr := ctxt.loader
  1595  	for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
  1596  		if !ldr.AttrReachable(s) || ldr.AttrSpecial(s) || ldr.AttrSubSymbol(s) ||
  1597  			!ldr.TopLevelSym(s) {
  1598  			continue
  1599  		}
  1600  
  1601  		st := state.symType(s)
  1602  
  1603  		if st <= sym.STEXT || st >= sym.SXREF {
  1604  			continue
  1605  		}
  1606  		state.data[st] = append(state.data[st], s)
  1607  
  1608  		// Similarly with checking the onlist attr.
  1609  		if ldr.AttrOnList(s) {
  1610  			log.Fatalf("symbol %s listed multiple times", ldr.SymName(s))
  1611  		}
  1612  		ldr.SetAttrOnList(s, true)
  1613  	}
  1614  
  1615  	// Now that we have the data symbols, but before we start
  1616  	// to assign addresses, record all the necessary
  1617  	// dynamic relocations. These will grow the relocation
  1618  	// symbol, which is itself data.
  1619  	//
  1620  	// On darwin, we need the symbol table numbers for dynreloc.
  1621  	if ctxt.HeadType == objabi.Hdarwin {
  1622  		machosymorder(ctxt)
  1623  	}
  1624  	state.dynreloc(ctxt)
  1625  
  1626  	// Move any RO data with relocations to a separate section.
  1627  	state.makeRelroForSharedLib(ctxt)
  1628  
  1629  	// Set alignment for the symbol with the largest known index,
  1630  	// so as to trigger allocation of the loader's internal
  1631  	// alignment array. This will avoid data races in the parallel
  1632  	// section below.
  1633  	lastSym := loader.Sym(ldr.NSym() - 1)
  1634  	ldr.SetSymAlign(lastSym, ldr.SymAlign(lastSym))
  1635  
  1636  	// Sort symbols.
  1637  	var wg sync.WaitGroup
  1638  	for symn := range state.data {
  1639  		symn := sym.SymKind(symn)
  1640  		wg.Add(1)
  1641  		go func() {
  1642  			state.data[symn], state.dataMaxAlign[symn] = state.dodataSect(ctxt, symn, state.data[symn])
  1643  			wg.Done()
  1644  		}()
  1645  	}
  1646  	wg.Wait()
  1647  
  1648  	if ctxt.IsELF {
  1649  		// Make .rela and .rela.plt contiguous, the ELF ABI requires this
  1650  		// and Solaris actually cares.
  1651  		syms := state.data[sym.SELFROSECT]
  1652  		reli, plti := -1, -1
  1653  		for i, s := range syms {
  1654  			switch ldr.SymName(s) {
  1655  			case ".rel.plt", ".rela.plt":
  1656  				plti = i
  1657  			case ".rel", ".rela":
  1658  				reli = i
  1659  			}
  1660  		}
  1661  		if reli >= 0 && plti >= 0 && plti != reli+1 {
  1662  			var first, second int
  1663  			if plti > reli {
  1664  				first, second = reli, plti
  1665  			} else {
  1666  				first, second = plti, reli
  1667  			}
  1668  			rel, plt := syms[reli], syms[plti]
  1669  			copy(syms[first+2:], syms[first+1:second])
  1670  			syms[first+0] = rel
  1671  			syms[first+1] = plt
  1672  
  1673  			// Make sure alignment doesn't introduce a gap.
  1674  			// Setting the alignment explicitly prevents
  1675  			// symalign from basing it on the size and
  1676  			// getting it wrong.
  1677  			ldr.SetSymAlign(rel, int32(ctxt.Arch.RegSize))
  1678  			ldr.SetSymAlign(plt, int32(ctxt.Arch.RegSize))
  1679  		}
  1680  		state.data[sym.SELFROSECT] = syms
  1681  	}
  1682  
  1683  	if ctxt.HeadType == objabi.Haix && ctxt.LinkMode == LinkExternal {
  1684  		// These symbols must have the same alignment as their section.
  1685  		// Otherwise, ld might change the layout of Go sections.
  1686  		ldr.SetSymAlign(ldr.Lookup("runtime.data", 0), state.dataMaxAlign[sym.SDATA])
  1687  		ldr.SetSymAlign(ldr.Lookup("runtime.bss", 0), state.dataMaxAlign[sym.SBSS])
  1688  	}
  1689  
  1690  	// Create *sym.Section objects and assign symbols to sections for
  1691  	// data/rodata (and related) symbols.
  1692  	state.allocateDataSections(ctxt)
  1693  
  1694  	state.allocateSEHSections(ctxt)
  1695  
  1696  	// Create *sym.Section objects and assign symbols to sections for
  1697  	// DWARF symbols.
  1698  	state.allocateDwarfSections(ctxt)
  1699  
  1700  	/* number the sections */
  1701  	n := int16(1)
  1702  
  1703  	for _, sect := range Segtext.Sections {
  1704  		sect.Extnum = n
  1705  		n++
  1706  	}
  1707  	for _, sect := range Segrodata.Sections {
  1708  		sect.Extnum = n
  1709  		n++
  1710  	}
  1711  	for _, sect := range Segrelrodata.Sections {
  1712  		sect.Extnum = n
  1713  		n++
  1714  	}
  1715  	for _, sect := range Segdata.Sections {
  1716  		sect.Extnum = n
  1717  		n++
  1718  	}
  1719  	for _, sect := range Segdwarf.Sections {
  1720  		sect.Extnum = n
  1721  		n++
  1722  	}
  1723  	for _, sect := range Segpdata.Sections {
  1724  		sect.Extnum = n
  1725  		n++
  1726  	}
  1727  	for _, sect := range Segxdata.Sections {
  1728  		sect.Extnum = n
  1729  		n++
  1730  	}
  1731  }
  1732  
  1733  // allocateDataSectionForSym creates a new sym.Section into which a
  1734  // single symbol will be placed. Here "seg" is the segment into which
  1735  // the section will go, "s" is the symbol to be placed into the new
  1736  // section, and "rwx" contains permissions for the section.
  1737  func (state *dodataState) allocateDataSectionForSym(seg *sym.Segment, s loader.Sym, rwx int) *sym.Section {
  1738  	ldr := state.ctxt.loader
  1739  	sname := ldr.SymName(s)
  1740  	if strings.HasPrefix(sname, "go:") {
  1741  		sname = ".go." + sname[len("go:"):]
  1742  	}
  1743  	sect := addsection(ldr, state.ctxt.Arch, seg, sname, rwx)
  1744  	sect.Align = symalign(ldr, s)
  1745  	state.datsize = Rnd(state.datsize, int64(sect.Align))
  1746  	sect.Vaddr = uint64(state.datsize)
  1747  	return sect
  1748  }
  1749  
  1750  // allocateNamedDataSection creates a new sym.Section for a category
  1751  // of data symbols. Here "seg" is the segment into which the section
  1752  // will go, "sName" is the name to give to the section, "types" is a
  1753  // range of symbol types to be put into the section, and "rwx"
  1754  // contains permissions for the section.
  1755  func (state *dodataState) allocateNamedDataSection(seg *sym.Segment, sName string, types []sym.SymKind, rwx int) *sym.Section {
  1756  	sect := addsection(state.ctxt.loader, state.ctxt.Arch, seg, sName, rwx)
  1757  	if len(types) == 0 {
  1758  		sect.Align = 1
  1759  	} else if len(types) == 1 {
  1760  		sect.Align = state.dataMaxAlign[types[0]]
  1761  	} else {
  1762  		for _, symn := range types {
  1763  			align := state.dataMaxAlign[symn]
  1764  			if sect.Align < align {
  1765  				sect.Align = align
  1766  			}
  1767  		}
  1768  	}
  1769  	state.datsize = Rnd(state.datsize, int64(sect.Align))
  1770  	sect.Vaddr = uint64(state.datsize)
  1771  	return sect
  1772  }
  1773  
  1774  // assignDsymsToSection assigns a collection of data symbols to a
  1775  // newly created section. "sect" is the section into which to place
  1776  // the symbols, "syms" holds the list of symbols to assign,
  1777  // "forceType" (if non-zero) contains a new sym type to apply to each
  1778  // sym during the assignment, and "aligner" is a hook to call to
  1779  // handle alignment during the assignment process.
  1780  func (state *dodataState) assignDsymsToSection(sect *sym.Section, syms []loader.Sym, forceType sym.SymKind, aligner func(state *dodataState, datsize int64, s loader.Sym) int64) {
  1781  	ldr := state.ctxt.loader
  1782  	for _, s := range syms {
  1783  		state.datsize = aligner(state, state.datsize, s)
  1784  		ldr.SetSymSect(s, sect)
  1785  		if forceType != sym.Sxxx {
  1786  			state.setSymType(s, forceType)
  1787  		}
  1788  		ldr.SetSymValue(s, int64(uint64(state.datsize)-sect.Vaddr))
  1789  		state.datsize += ldr.SymSize(s)
  1790  	}
  1791  	sect.Length = uint64(state.datsize) - sect.Vaddr
  1792  }
  1793  
  1794  func (state *dodataState) assignToSection(sect *sym.Section, symn sym.SymKind, forceType sym.SymKind) {
  1795  	state.assignDsymsToSection(sect, state.data[symn], forceType, aligndatsize)
  1796  	state.checkdatsize(symn)
  1797  }
  1798  
  1799  // allocateSingleSymSections walks through the bucketed data symbols
  1800  // with type 'symn', creates a new section for each sym, and assigns
  1801  // the sym to a newly created section. Section name is set from the
  1802  // symbol name. "Seg" is the segment into which to place the new
  1803  // section, "forceType" is the new sym.SymKind to assign to the symbol
  1804  // within the section, and "rwx" holds section permissions.
  1805  func (state *dodataState) allocateSingleSymSections(seg *sym.Segment, symn sym.SymKind, forceType sym.SymKind, rwx int) {
  1806  	ldr := state.ctxt.loader
  1807  	for _, s := range state.data[symn] {
  1808  		sect := state.allocateDataSectionForSym(seg, s, rwx)
  1809  		ldr.SetSymSect(s, sect)
  1810  		state.setSymType(s, forceType)
  1811  		ldr.SetSymValue(s, int64(uint64(state.datsize)-sect.Vaddr))
  1812  		state.datsize += ldr.SymSize(s)
  1813  		sect.Length = uint64(state.datsize) - sect.Vaddr
  1814  	}
  1815  	state.checkdatsize(symn)
  1816  }
  1817  
  1818  // allocateNamedSectionAndAssignSyms creates a new section with the
  1819  // specified name, then walks through the bucketed data symbols with
  1820  // type 'symn' and assigns each of them to this new section. "Seg" is
  1821  // the segment into which to place the new section, "secName" is the
  1822  // name to give to the new section, "forceType" (if non-zero) contains
  1823  // a new sym type to apply to each sym during the assignment, and
  1824  // "rwx" holds section permissions.
  1825  func (state *dodataState) allocateNamedSectionAndAssignSyms(seg *sym.Segment, secName string, symn sym.SymKind, forceType sym.SymKind, rwx int) *sym.Section {
  1826  
  1827  	sect := state.allocateNamedDataSection(seg, secName, []sym.SymKind{symn}, rwx)
  1828  	state.assignDsymsToSection(sect, state.data[symn], forceType, aligndatsize)
  1829  	return sect
  1830  }
  1831  
  1832  // allocateDataSections allocates sym.Section objects for data/rodata
  1833  // (and related) symbols, and then assigns symbols to those sections.
  1834  func (state *dodataState) allocateDataSections(ctxt *Link) {
  1835  	// Allocate sections.
  1836  	// Data is processed before segtext, because we need
  1837  	// to see all symbols in the .data and .bss sections in order
  1838  	// to generate garbage collection information.
  1839  
  1840  	// Writable data sections that do not need any specialized handling.
  1841  	writable := []sym.SymKind{
  1842  		sym.SBUILDINFO,
  1843  		sym.SELFSECT,
  1844  		sym.SMACHO,
  1845  		sym.SMACHOGOT,
  1846  		sym.SWINDOWS,
  1847  	}
  1848  	for _, symn := range writable {
  1849  		state.allocateSingleSymSections(&Segdata, symn, sym.SDATA, 06)
  1850  	}
  1851  	ldr := ctxt.loader
  1852  
  1853  	// writable .got (note that for PIE binaries .got goes in relro)
  1854  	if len(state.data[sym.SELFGOT]) > 0 {
  1855  		state.allocateNamedSectionAndAssignSyms(&Segdata, ".got", sym.SELFGOT, sym.SDATA, 06)
  1856  	}
  1857  
  1858  	/* pointer-free data */
  1859  	sect := state.allocateNamedSectionAndAssignSyms(&Segdata, ".noptrdata", sym.SNOPTRDATA, sym.SDATA, 06)
  1860  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.noptrdata", 0), sect)
  1861  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.enoptrdata", 0), sect)
  1862  
  1863  	hasinitarr := ctxt.linkShared
  1864  
  1865  	/* shared library initializer */
  1866  	switch ctxt.BuildMode {
  1867  	case BuildModeCArchive, BuildModeCShared, BuildModeShared, BuildModePlugin:
  1868  		hasinitarr = true
  1869  	}
  1870  
  1871  	if ctxt.HeadType == objabi.Haix {
  1872  		if len(state.data[sym.SINITARR]) > 0 {
  1873  			Errorf(nil, "XCOFF format doesn't allow .init_array section")
  1874  		}
  1875  	}
  1876  
  1877  	if hasinitarr && len(state.data[sym.SINITARR]) > 0 {
  1878  		state.allocateNamedSectionAndAssignSyms(&Segdata, ".init_array", sym.SINITARR, sym.Sxxx, 06)
  1879  	}
  1880  
  1881  	/* data */
  1882  	sect = state.allocateNamedSectionAndAssignSyms(&Segdata, ".data", sym.SDATA, sym.SDATA, 06)
  1883  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.data", 0), sect)
  1884  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.edata", 0), sect)
  1885  	dataGcEnd := state.datsize - int64(sect.Vaddr)
  1886  
  1887  	// On AIX, TOC entries must be the last of .data
  1888  	// These aren't part of gc as they won't change during the runtime.
  1889  	state.assignToSection(sect, sym.SXCOFFTOC, sym.SDATA)
  1890  	state.checkdatsize(sym.SDATA)
  1891  	sect.Length = uint64(state.datsize) - sect.Vaddr
  1892  
  1893  	/* bss */
  1894  	sect = state.allocateNamedSectionAndAssignSyms(&Segdata, ".bss", sym.SBSS, sym.Sxxx, 06)
  1895  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.bss", 0), sect)
  1896  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.ebss", 0), sect)
  1897  	bssGcEnd := state.datsize - int64(sect.Vaddr)
  1898  
  1899  	// Emit gcdata for bss symbols now that symbol values have been assigned.
  1900  	gcsToEmit := []struct {
  1901  		symName string
  1902  		symKind sym.SymKind
  1903  		gcEnd   int64
  1904  	}{
  1905  		{"runtime.gcdata", sym.SDATA, dataGcEnd},
  1906  		{"runtime.gcbss", sym.SBSS, bssGcEnd},
  1907  	}
  1908  	for _, g := range gcsToEmit {
  1909  		var gc GCProg
  1910  		gc.Init(ctxt, g.symName)
  1911  		for _, s := range state.data[g.symKind] {
  1912  			gc.AddSym(s)
  1913  		}
  1914  		gc.End(g.gcEnd)
  1915  	}
  1916  
  1917  	/* pointer-free bss */
  1918  	sect = state.allocateNamedSectionAndAssignSyms(&Segdata, ".noptrbss", sym.SNOPTRBSS, sym.Sxxx, 06)
  1919  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.noptrbss", 0), sect)
  1920  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.enoptrbss", 0), sect)
  1921  
  1922  	// Code coverage counters are assigned to the .noptrbss section.
  1923  	// We assign them in a separate pass so that they stay aggregated
  1924  	// together in a single blob (coverage runtime depends on this).
  1925  	covCounterDataStartOff = sect.Length
  1926  	state.assignToSection(sect, sym.SCOVERAGE_COUNTER, sym.SNOPTRBSS)
  1927  	covCounterDataLen = sect.Length - covCounterDataStartOff
  1928  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.covctrs", 0), sect)
  1929  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.ecovctrs", 0), sect)
  1930  
  1931  	// Coverage instrumentation counters for libfuzzer.
  1932  	if len(state.data[sym.SLIBFUZZER_8BIT_COUNTER]) > 0 {
  1933  		sect := state.allocateNamedSectionAndAssignSyms(&Segdata, ".go.fuzzcntrs", sym.SLIBFUZZER_8BIT_COUNTER, sym.Sxxx, 06)
  1934  		ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.__start___sancov_cntrs", 0), sect)
  1935  		ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.__stop___sancov_cntrs", 0), sect)
  1936  		ldr.SetSymSect(ldr.LookupOrCreateSym("internal/fuzz._counters", 0), sect)
  1937  		ldr.SetSymSect(ldr.LookupOrCreateSym("internal/fuzz._ecounters", 0), sect)
  1938  	}
  1939  
  1940  	// Assign runtime.end to the last section of data segment.
  1941  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.end", 0), Segdata.Sections[len(Segdata.Sections)-1])
  1942  
  1943  	if len(state.data[sym.STLSBSS]) > 0 {
  1944  		var sect *sym.Section
  1945  		// FIXME: not clear why it is sometimes necessary to suppress .tbss section creation.
  1946  		if (ctxt.IsELF || ctxt.HeadType == objabi.Haix) && (ctxt.LinkMode == LinkExternal || !*FlagD) {
  1947  			sect = addsection(ldr, ctxt.Arch, &Segdata, ".tbss", 06)
  1948  			sect.Align = int32(ctxt.Arch.PtrSize)
  1949  			// FIXME: why does this need to be set to zero?
  1950  			sect.Vaddr = 0
  1951  		}
  1952  		state.datsize = 0
  1953  
  1954  		for _, s := range state.data[sym.STLSBSS] {
  1955  			state.datsize = aligndatsize(state, state.datsize, s)
  1956  			if sect != nil {
  1957  				ldr.SetSymSect(s, sect)
  1958  			}
  1959  			ldr.SetSymValue(s, state.datsize)
  1960  			state.datsize += ldr.SymSize(s)
  1961  		}
  1962  		state.checkdatsize(sym.STLSBSS)
  1963  
  1964  		if sect != nil {
  1965  			sect.Length = uint64(state.datsize)
  1966  		}
  1967  	}
  1968  
  1969  	/*
  1970  	 * We finished data, begin read-only data.
  1971  	 * Not all systems support a separate read-only non-executable data section.
  1972  	 * ELF and Windows PE systems do.
  1973  	 * OS X and Plan 9 do not.
  1974  	 * And if we're using external linking mode, the point is moot,
  1975  	 * since it's not our decision; that code expects the sections in
  1976  	 * segtext.
  1977  	 */
  1978  	var segro *sym.Segment
  1979  	if ctxt.IsELF && ctxt.LinkMode == LinkInternal {
  1980  		segro = &Segrodata
  1981  	} else if ctxt.HeadType == objabi.Hwindows {
  1982  		segro = &Segrodata
  1983  	} else {
  1984  		segro = &Segtext
  1985  	}
  1986  
  1987  	state.datsize = 0
  1988  
  1989  	/* read-only executable ELF, Mach-O sections */
  1990  	if len(state.data[sym.STEXT]) != 0 {
  1991  		culprit := ldr.SymName(state.data[sym.STEXT][0])
  1992  		Errorf(nil, "dodata found an sym.STEXT symbol: %s", culprit)
  1993  	}
  1994  	state.allocateSingleSymSections(&Segtext, sym.SELFRXSECT, sym.SRODATA, 05)
  1995  	state.allocateSingleSymSections(&Segtext, sym.SMACHOPLT, sym.SRODATA, 05)
  1996  
  1997  	/* read-only data */
  1998  	sect = state.allocateNamedDataSection(segro, ".rodata", sym.ReadOnly, 04)
  1999  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.rodata", 0), sect)
  2000  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.erodata", 0), sect)
  2001  	if !ctxt.UseRelro() {
  2002  		ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.types", 0), sect)
  2003  		ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.etypes", 0), sect)
  2004  	}
  2005  	for _, symn := range sym.ReadOnly {
  2006  		symnStartValue := state.datsize
  2007  		if len(state.data[symn]) != 0 {
  2008  			symnStartValue = aligndatsize(state, symnStartValue, state.data[symn][0])
  2009  		}
  2010  		state.assignToSection(sect, symn, sym.SRODATA)
  2011  		setCarrierSize(symn, state.datsize-symnStartValue)
  2012  		if ctxt.HeadType == objabi.Haix {
  2013  			// Read-only symbols might be wrapped inside their outer
  2014  			// symbol.
  2015  			// XCOFF symbol table needs to know the size of
  2016  			// these outer symbols.
  2017  			xcoffUpdateOuterSize(ctxt, state.datsize-symnStartValue, symn)
  2018  		}
  2019  	}
  2020  
  2021  	/* read-only ELF, Mach-O sections */
  2022  	state.allocateSingleSymSections(segro, sym.SELFROSECT, sym.SRODATA, 04)
  2023  
  2024  	// There is some data that are conceptually read-only but are written to by
  2025  	// relocations. On GNU systems, we can arrange for the dynamic linker to
  2026  	// mprotect sections after relocations are applied by giving them write
  2027  	// permissions in the object file and calling them ".data.rel.ro.FOO". We
  2028  	// divide the .rodata section between actual .rodata and .data.rel.ro.rodata,
  2029  	// but for the other sections that this applies to, we just write a read-only
  2030  	// .FOO section or a read-write .data.rel.ro.FOO section depending on the
  2031  	// situation.
  2032  	// TODO(mwhudson): It would make sense to do this more widely, but it makes
  2033  	// the system linker segfault on darwin.
  2034  	const relroPerm = 06
  2035  	const fallbackPerm = 04
  2036  	relroSecPerm := fallbackPerm
  2037  	genrelrosecname := func(suffix string) string {
  2038  		if suffix == "" {
  2039  			return ".rodata"
  2040  		}
  2041  		return suffix
  2042  	}
  2043  	seg := segro
  2044  
  2045  	if ctxt.UseRelro() {
  2046  		segrelro := &Segrelrodata
  2047  		if ctxt.LinkMode == LinkExternal && !ctxt.IsAIX() && !ctxt.IsDarwin() {
  2048  			// Using a separate segment with an external
  2049  			// linker results in some programs moving
  2050  			// their data sections unexpectedly, which
  2051  			// corrupts the moduledata. So we use the
  2052  			// rodata segment and let the external linker
  2053  			// sort out a rel.ro segment.
  2054  			segrelro = segro
  2055  		} else {
  2056  			// Reset datsize for new segment.
  2057  			state.datsize = 0
  2058  		}
  2059  
  2060  		if !ctxt.IsDarwin() { // We don't need the special names on darwin.
  2061  			genrelrosecname = func(suffix string) string {
  2062  				return ".data.rel.ro" + suffix
  2063  			}
  2064  		}
  2065  
  2066  		relroReadOnly := []sym.SymKind{}
  2067  		for _, symnro := range sym.ReadOnly {
  2068  			symn := sym.RelROMap[symnro]
  2069  			relroReadOnly = append(relroReadOnly, symn)
  2070  		}
  2071  		seg = segrelro
  2072  		relroSecPerm = relroPerm
  2073  
  2074  		/* data only written by relocations */
  2075  		sect = state.allocateNamedDataSection(segrelro, genrelrosecname(""), relroReadOnly, relroSecPerm)
  2076  
  2077  		ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.types", 0), sect)
  2078  		ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.etypes", 0), sect)
  2079  
  2080  		for i, symnro := range sym.ReadOnly {
  2081  			if i == 0 && symnro == sym.STYPE && ctxt.HeadType != objabi.Haix {
  2082  				// Skip forward so that no type
  2083  				// reference uses a zero offset.
  2084  				// This is unlikely but possible in small
  2085  				// programs with no other read-only data.
  2086  				state.datsize++
  2087  			}
  2088  
  2089  			symn := sym.RelROMap[symnro]
  2090  			symnStartValue := state.datsize
  2091  			if len(state.data[symn]) != 0 {
  2092  				symnStartValue = aligndatsize(state, symnStartValue, state.data[symn][0])
  2093  			}
  2094  
  2095  			for _, s := range state.data[symn] {
  2096  				outer := ldr.OuterSym(s)
  2097  				if s != 0 && ldr.SymSect(outer) != nil && ldr.SymSect(outer) != sect {
  2098  					ctxt.Errorf(s, "s.Outer (%s) in different section from s, %s != %s", ldr.SymName(outer), ldr.SymSect(outer).Name, sect.Name)
  2099  				}
  2100  			}
  2101  			state.assignToSection(sect, symn, sym.SRODATA)
  2102  			setCarrierSize(symn, state.datsize-symnStartValue)
  2103  			if ctxt.HeadType == objabi.Haix {
  2104  				// Read-only symbols might be wrapped inside their outer
  2105  				// symbol.
  2106  				// XCOFF symbol table needs to know the size of
  2107  				// these outer symbols.
  2108  				xcoffUpdateOuterSize(ctxt, state.datsize-symnStartValue, symn)
  2109  			}
  2110  		}
  2111  		sect.Length = uint64(state.datsize) - sect.Vaddr
  2112  
  2113  		state.allocateSingleSymSections(segrelro, sym.SELFRELROSECT, sym.SRODATA, relroSecPerm)
  2114  	}
  2115  
  2116  	/* typelink */
  2117  	sect = state.allocateNamedDataSection(seg, genrelrosecname(".typelink"), []sym.SymKind{sym.STYPELINK}, relroSecPerm)
  2118  
  2119  	typelink := ldr.CreateSymForUpdate("runtime.typelink", 0)
  2120  	ldr.SetSymSect(typelink.Sym(), sect)
  2121  	typelink.SetType(sym.SRODATA)
  2122  	state.datsize += typelink.Size()
  2123  	state.checkdatsize(sym.STYPELINK)
  2124  	sect.Length = uint64(state.datsize) - sect.Vaddr
  2125  
  2126  	/* itablink */
  2127  	sect = state.allocateNamedDataSection(seg, genrelrosecname(".itablink"), []sym.SymKind{sym.SITABLINK}, relroSecPerm)
  2128  
  2129  	itablink := ldr.CreateSymForUpdate("runtime.itablink", 0)
  2130  	ldr.SetSymSect(itablink.Sym(), sect)
  2131  	itablink.SetType(sym.SRODATA)
  2132  	state.datsize += itablink.Size()
  2133  	state.checkdatsize(sym.SITABLINK)
  2134  	sect.Length = uint64(state.datsize) - sect.Vaddr
  2135  
  2136  	/* gosymtab */
  2137  	sect = state.allocateNamedSectionAndAssignSyms(seg, genrelrosecname(".gosymtab"), sym.SSYMTAB, sym.SRODATA, relroSecPerm)
  2138  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.symtab", 0), sect)
  2139  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.esymtab", 0), sect)
  2140  
  2141  	/* gopclntab */
  2142  	sect = state.allocateNamedSectionAndAssignSyms(seg, genrelrosecname(".gopclntab"), sym.SPCLNTAB, sym.SRODATA, relroSecPerm)
  2143  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pclntab", 0), sect)
  2144  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pcheader", 0), sect)
  2145  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.funcnametab", 0), sect)
  2146  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.cutab", 0), sect)
  2147  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.filetab", 0), sect)
  2148  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pctab", 0), sect)
  2149  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.functab", 0), sect)
  2150  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.epclntab", 0), sect)
  2151  	setCarrierSize(sym.SPCLNTAB, int64(sect.Length))
  2152  	if ctxt.HeadType == objabi.Haix {
  2153  		xcoffUpdateOuterSize(ctxt, int64(sect.Length), sym.SPCLNTAB)
  2154  	}
  2155  
  2156  	// 6g uses 4-byte relocation offsets, so the entire segment must fit in 32 bits.
  2157  	if state.datsize != int64(uint32(state.datsize)) {
  2158  		Errorf(nil, "read-only data segment too large: %d", state.datsize)
  2159  	}
  2160  
  2161  	siz := 0
  2162  	for symn := sym.SELFRXSECT; symn < sym.SXREF; symn++ {
  2163  		siz += len(state.data[symn])
  2164  	}
  2165  	ctxt.datap = make([]loader.Sym, 0, siz)
  2166  	for symn := sym.SELFRXSECT; symn < sym.SXREF; symn++ {
  2167  		ctxt.datap = append(ctxt.datap, state.data[symn]...)
  2168  	}
  2169  }
  2170  
  2171  // allocateDwarfSections allocates sym.Section objects for DWARF
  2172  // symbols, and assigns symbols to sections.
  2173  func (state *dodataState) allocateDwarfSections(ctxt *Link) {
  2174  
  2175  	alignOne := func(state *dodataState, datsize int64, s loader.Sym) int64 { return datsize }
  2176  
  2177  	ldr := ctxt.loader
  2178  	for i := 0; i < len(dwarfp); i++ {
  2179  		// First the section symbol.
  2180  		s := dwarfp[i].secSym()
  2181  		sect := state.allocateNamedDataSection(&Segdwarf, ldr.SymName(s), []sym.SymKind{}, 04)
  2182  		ldr.SetSymSect(s, sect)
  2183  		sect.Sym = sym.LoaderSym(s)
  2184  		curType := ldr.SymType(s)
  2185  		state.setSymType(s, sym.SRODATA)
  2186  		ldr.SetSymValue(s, int64(uint64(state.datsize)-sect.Vaddr))
  2187  		state.datsize += ldr.SymSize(s)
  2188  
  2189  		// Then any sub-symbols for the section symbol.
  2190  		subSyms := dwarfp[i].subSyms()
  2191  		state.assignDsymsToSection(sect, subSyms, sym.SRODATA, alignOne)
  2192  
  2193  		for j := 0; j < len(subSyms); j++ {
  2194  			s := subSyms[j]
  2195  			if ctxt.HeadType == objabi.Haix && curType == sym.SDWARFLOC {
  2196  				// Update the size of .debug_loc for this symbol's
  2197  				// package.
  2198  				addDwsectCUSize(".debug_loc", ldr.SymPkg(s), uint64(ldr.SymSize(s)))
  2199  			}
  2200  		}
  2201  		sect.Length = uint64(state.datsize) - sect.Vaddr
  2202  		checkSectSize(sect)
  2203  	}
  2204  }
  2205  
  2206  // allocateSEHSections allocate a sym.Section object for SEH
  2207  // symbols, and assigns symbols to sections.
  2208  func (state *dodataState) allocateSEHSections(ctxt *Link) {
  2209  	if len(sehp.pdata) > 0 {
  2210  		sect := state.allocateNamedDataSection(&Segpdata, ".pdata", []sym.SymKind{}, 04)
  2211  		state.assignDsymsToSection(sect, sehp.pdata, sym.SRODATA, aligndatsize)
  2212  		state.checkdatsize(sym.SSEHSECT)
  2213  	}
  2214  	if len(sehp.xdata) > 0 {
  2215  		sect := state.allocateNamedDataSection(&Segxdata, ".xdata", []sym.SymKind{}, 04)
  2216  		state.assignDsymsToSection(sect, sehp.xdata, sym.SRODATA, aligndatsize)
  2217  		state.checkdatsize(sym.SSEHSECT)
  2218  	}
  2219  }
  2220  
  2221  type symNameSize struct {
  2222  	name string
  2223  	sz   int64
  2224  	val  int64
  2225  	sym  loader.Sym
  2226  }
  2227  
  2228  func (state *dodataState) dodataSect(ctxt *Link, symn sym.SymKind, syms []loader.Sym) (result []loader.Sym, maxAlign int32) {
  2229  	var head, tail, zerobase loader.Sym
  2230  	ldr := ctxt.loader
  2231  	sl := make([]symNameSize, len(syms))
  2232  
  2233  	// For ppc64, we want to interleave the .got and .toc sections
  2234  	// from input files. Both are type sym.SELFGOT, so in that case
  2235  	// we skip size comparison and do the name comparison instead
  2236  	// (conveniently, .got sorts before .toc).
  2237  	checkSize := symn != sym.SELFGOT
  2238  
  2239  	for k, s := range syms {
  2240  		ss := ldr.SymSize(s)
  2241  		sl[k] = symNameSize{sz: ss, sym: s}
  2242  		if !checkSize {
  2243  			sl[k].name = ldr.SymName(s)
  2244  		}
  2245  		ds := int64(len(ldr.Data(s)))
  2246  		switch {
  2247  		case ss < ds:
  2248  			ctxt.Errorf(s, "initialize bounds (%d < %d)", ss, ds)
  2249  		case ss < 0:
  2250  			ctxt.Errorf(s, "negative size (%d bytes)", ss)
  2251  		case ss > cutoff:
  2252  			ctxt.Errorf(s, "symbol too large (%d bytes)", ss)
  2253  		}
  2254  
  2255  		// If the usually-special section-marker symbols are being laid
  2256  		// out as regular symbols, put them either at the beginning or
  2257  		// end of their section.
  2258  		if (ctxt.DynlinkingGo() && ctxt.HeadType == objabi.Hdarwin) || (ctxt.HeadType == objabi.Haix && ctxt.LinkMode == LinkExternal) {
  2259  			switch ldr.SymName(s) {
  2260  			case "runtime.text", "runtime.bss", "runtime.data", "runtime.types", "runtime.rodata",
  2261  				"runtime.noptrdata", "runtime.noptrbss":
  2262  				head = s
  2263  				continue
  2264  			case "runtime.etext", "runtime.ebss", "runtime.edata", "runtime.etypes", "runtime.erodata",
  2265  				"runtime.enoptrdata", "runtime.enoptrbss":
  2266  				tail = s
  2267  				continue
  2268  			}
  2269  		}
  2270  	}
  2271  	zerobase = ldr.Lookup("runtime.zerobase", 0)
  2272  
  2273  	// Perform the sort.
  2274  	if symn != sym.SPCLNTAB {
  2275  		sort.Slice(sl, func(i, j int) bool {
  2276  			si, sj := sl[i].sym, sl[j].sym
  2277  			isz, jsz := sl[i].sz, sl[j].sz
  2278  			switch {
  2279  			case si == head, sj == tail:
  2280  				return true
  2281  			case sj == head, si == tail:
  2282  				return false
  2283  			// put zerobase right after all the zero-sized symbols,
  2284  			// so zero-sized symbols have the same address as zerobase.
  2285  			case si == zerobase:
  2286  				return jsz != 0 // zerobase < nonzero-sized
  2287  			case sj == zerobase:
  2288  				return isz == 0 // 0-sized < zerobase
  2289  			}
  2290  			if checkSize {
  2291  				if isz != jsz {
  2292  					return isz < jsz
  2293  				}
  2294  			} else {
  2295  				iname := sl[i].name
  2296  				jname := sl[j].name
  2297  				if iname != jname {
  2298  					return iname < jname
  2299  				}
  2300  			}
  2301  			return si < sj
  2302  		})
  2303  	} else {
  2304  		// PCLNTAB was built internally, and already has the proper order.
  2305  	}
  2306  
  2307  	// Set alignment, construct result
  2308  	syms = syms[:0]
  2309  	for k := range sl {
  2310  		s := sl[k].sym
  2311  		if s != head && s != tail {
  2312  			align := symalign(ldr, s)
  2313  			if maxAlign < align {
  2314  				maxAlign = align
  2315  			}
  2316  		}
  2317  		syms = append(syms, s)
  2318  	}
  2319  
  2320  	return syms, maxAlign
  2321  }
  2322  
  2323  // Add buildid to beginning of text segment, on non-ELF systems.
  2324  // Non-ELF binary formats are not always flexible enough to
  2325  // give us a place to put the Go build ID. On those systems, we put it
  2326  // at the very beginning of the text segment.
  2327  // This “header” is read by cmd/go.
  2328  func (ctxt *Link) textbuildid() {
  2329  	if ctxt.IsELF || *flagBuildid == "" {
  2330  		return
  2331  	}
  2332  
  2333  	ldr := ctxt.loader
  2334  	s := ldr.CreateSymForUpdate("go:buildid", 0)
  2335  	// The \xff is invalid UTF-8, meant to make it less likely
  2336  	// to find one of these accidentally.
  2337  	data := "\xff Go build ID: " + strconv.Quote(*flagBuildid) + "\n \xff"
  2338  	s.SetType(sym.STEXT)
  2339  	s.SetData([]byte(data))
  2340  	s.SetSize(int64(len(data)))
  2341  
  2342  	ctxt.Textp = append(ctxt.Textp, 0)
  2343  	copy(ctxt.Textp[1:], ctxt.Textp)
  2344  	ctxt.Textp[0] = s.Sym()
  2345  }
  2346  
  2347  func (ctxt *Link) buildinfo() {
  2348  	// Write the buildinfo symbol, which go version looks for.
  2349  	// The code reading this data is in package debug/buildinfo.
  2350  	ldr := ctxt.loader
  2351  	s := ldr.CreateSymForUpdate("go:buildinfo", 0)
  2352  	s.SetType(sym.SBUILDINFO)
  2353  	s.SetAlign(16)
  2354  	// The \xff is invalid UTF-8, meant to make it less likely
  2355  	// to find one of these accidentally.
  2356  	const prefix = "\xff Go buildinf:" // 14 bytes, plus 2 data bytes filled in below
  2357  	data := make([]byte, 32)
  2358  	copy(data, prefix)
  2359  	data[len(prefix)] = byte(ctxt.Arch.PtrSize)
  2360  	data[len(prefix)+1] = 0
  2361  	if ctxt.Arch.ByteOrder == binary.BigEndian {
  2362  		data[len(prefix)+1] = 1
  2363  	}
  2364  	data[len(prefix)+1] |= 2 // signals new pointer-free format
  2365  	data = appendString(data, strdata["runtime.buildVersion"])
  2366  	data = appendString(data, strdata["runtime.modinfo"])
  2367  	// MacOS linker gets very upset if the size os not a multiple of alignment.
  2368  	for len(data)%16 != 0 {
  2369  		data = append(data, 0)
  2370  	}
  2371  	s.SetData(data)
  2372  	s.SetSize(int64(len(data)))
  2373  
  2374  	// Add reference to go:buildinfo from the rodata section,
  2375  	// so that external linking with -Wl,--gc-sections does not
  2376  	// delete the build info.
  2377  	sr := ldr.CreateSymForUpdate("go:buildinfo.ref", 0)
  2378  	sr.SetType(sym.SRODATA)
  2379  	sr.SetAlign(int32(ctxt.Arch.PtrSize))
  2380  	sr.AddAddr(ctxt.Arch, s.Sym())
  2381  }
  2382  
  2383  // appendString appends s to data, prefixed by its varint-encoded length.
  2384  func appendString(data []byte, s string) []byte {
  2385  	var v [binary.MaxVarintLen64]byte
  2386  	n := binary.PutUvarint(v[:], uint64(len(s)))
  2387  	data = append(data, v[:n]...)
  2388  	data = append(data, s...)
  2389  	return data
  2390  }
  2391  
  2392  // assign addresses to text
  2393  func (ctxt *Link) textaddress() {
  2394  	addsection(ctxt.loader, ctxt.Arch, &Segtext, ".text", 05)
  2395  
  2396  	// Assign PCs in text segment.
  2397  	// Could parallelize, by assigning to text
  2398  	// and then letting threads copy down, but probably not worth it.
  2399  	sect := Segtext.Sections[0]
  2400  
  2401  	sect.Align = int32(Funcalign)
  2402  
  2403  	ldr := ctxt.loader
  2404  
  2405  	if *flagRandLayout != 0 {
  2406  		r := rand.New(rand.NewSource(*flagRandLayout))
  2407  		textp := ctxt.Textp
  2408  		i := 0
  2409  		// don't move the buildid symbol
  2410  		if len(textp) > 0 && ldr.SymName(textp[0]) == "go:buildid" {
  2411  			i++
  2412  		}
  2413  		// Skip over C symbols, as functions in a (C object) section must stay together.
  2414  		// TODO: maybe we can move a section as a whole.
  2415  		// Note: we load C symbols before Go symbols, so we can scan from the start.
  2416  		for i < len(textp) && (ldr.SubSym(textp[i]) != 0 || ldr.AttrSubSymbol(textp[i])) {
  2417  			i++
  2418  		}
  2419  		textp = textp[i:]
  2420  		r.Shuffle(len(textp), func(i, j int) {
  2421  			textp[i], textp[j] = textp[j], textp[i]
  2422  		})
  2423  	}
  2424  
  2425  	text := ctxt.xdefine("runtime.text", sym.STEXT, 0)
  2426  	etext := ctxt.xdefine("runtime.etext", sym.STEXT, 0)
  2427  	ldr.SetSymSect(text, sect)
  2428  	if ctxt.IsAIX() && ctxt.IsExternal() {
  2429  		// Setting runtime.text has a real symbol prevents ld to
  2430  		// change its base address resulting in wrong offsets for
  2431  		// reflect methods.
  2432  		u := ldr.MakeSymbolUpdater(text)
  2433  		u.SetAlign(sect.Align)
  2434  		u.SetSize(8)
  2435  	}
  2436  
  2437  	if (ctxt.DynlinkingGo() && ctxt.IsDarwin()) || (ctxt.IsAIX() && ctxt.IsExternal()) {
  2438  		ldr.SetSymSect(etext, sect)
  2439  		ctxt.Textp = append(ctxt.Textp, etext, 0)
  2440  		copy(ctxt.Textp[1:], ctxt.Textp)
  2441  		ctxt.Textp[0] = text
  2442  	}
  2443  
  2444  	start := uint64(Rnd(*FlagTextAddr, int64(Funcalign)))
  2445  	va := start
  2446  	n := 1
  2447  	sect.Vaddr = va
  2448  
  2449  	limit := thearch.TrampLimit
  2450  	if limit == 0 {
  2451  		limit = 1 << 63 // unlimited
  2452  	}
  2453  	if *FlagDebugTextSize != 0 {
  2454  		limit = uint64(*FlagDebugTextSize)
  2455  	}
  2456  	if *FlagDebugTramp > 1 {
  2457  		limit = 1 // debug mode, force generating trampolines for everything
  2458  	}
  2459  
  2460  	if ctxt.IsAIX() && ctxt.IsExternal() {
  2461  		// On AIX, normally we won't generate direct calls to external symbols,
  2462  		// except in one test, cmd/go/testdata/script/link_syso_issue33139.txt.
  2463  		// That test doesn't make much sense, and I'm not sure it ever works.
  2464  		// Just generate trampoline for now (which will turn a direct call to
  2465  		// an indirect call, which at least builds).
  2466  		limit = 1
  2467  	}
  2468  
  2469  	// First pass: assign addresses assuming the program is small and will
  2470  	// not require trampoline generation.
  2471  	big := false
  2472  	for _, s := range ctxt.Textp {
  2473  		sect, n, va = assignAddress(ctxt, sect, n, s, va, false, big)
  2474  		if va-start >= limit {
  2475  			big = true
  2476  			break
  2477  		}
  2478  	}
  2479  
  2480  	// Second pass: only if it is too big, insert trampolines for too-far
  2481  	// jumps and targets with unknown addresses.
  2482  	if big {
  2483  		// reset addresses
  2484  		for _, s := range ctxt.Textp {
  2485  			if s != text {
  2486  				resetAddress(ctxt, s)
  2487  			}
  2488  		}
  2489  		va = start
  2490  
  2491  		ntramps := 0
  2492  		var curPkg string
  2493  		for i, s := range ctxt.Textp {
  2494  			// When we find the first symbol in a package, perform a
  2495  			// single iteration that assigns temporary addresses to all
  2496  			// of the text in the same package, using the maximum possible
  2497  			// number of trampolines. This allows for better decisions to
  2498  			// be made regarding reachability and the need for trampolines.
  2499  			if symPkg := ldr.SymPkg(s); symPkg != "" && curPkg != symPkg {
  2500  				curPkg = symPkg
  2501  				vaTmp := va
  2502  				for j := i; j < len(ctxt.Textp); j++ {
  2503  					curSym := ctxt.Textp[j]
  2504  					if symPkg := ldr.SymPkg(curSym); symPkg == "" || curPkg != symPkg {
  2505  						break
  2506  					}
  2507  					// We do not pass big to assignAddress here, as this
  2508  					// can result in side effects such as section splitting.
  2509  					sect, n, vaTmp = assignAddress(ctxt, sect, n, curSym, vaTmp, false, false)
  2510  					vaTmp += maxSizeTrampolines(ctxt, ldr, curSym, false)
  2511  				}
  2512  			}
  2513  
  2514  			// Reset address for current symbol.
  2515  			if s != text {
  2516  				resetAddress(ctxt, s)
  2517  			}
  2518  
  2519  			// Assign actual address for current symbol.
  2520  			sect, n, va = assignAddress(ctxt, sect, n, s, va, false, big)
  2521  
  2522  			// Resolve jumps, adding trampolines if they are needed.
  2523  			trampoline(ctxt, s)
  2524  
  2525  			// lay down trampolines after each function
  2526  			for ; ntramps < len(ctxt.tramps); ntramps++ {
  2527  				tramp := ctxt.tramps[ntramps]
  2528  				if ctxt.IsAIX() && strings.HasPrefix(ldr.SymName(tramp), "runtime.text.") {
  2529  					// Already set in assignAddress
  2530  					continue
  2531  				}
  2532  				sect, n, va = assignAddress(ctxt, sect, n, tramp, va, true, big)
  2533  			}
  2534  		}
  2535  
  2536  		// merge tramps into Textp, keeping Textp in address order
  2537  		if ntramps != 0 {
  2538  			newtextp := make([]loader.Sym, 0, len(ctxt.Textp)+ntramps)
  2539  			i := 0
  2540  			for _, s := range ctxt.Textp {
  2541  				for ; i < ntramps && ldr.SymValue(ctxt.tramps[i]) < ldr.SymValue(s); i++ {
  2542  					newtextp = append(newtextp, ctxt.tramps[i])
  2543  				}
  2544  				newtextp = append(newtextp, s)
  2545  			}
  2546  			newtextp = append(newtextp, ctxt.tramps[i:ntramps]...)
  2547  
  2548  			ctxt.Textp = newtextp
  2549  		}
  2550  	}
  2551  
  2552  	// Add MinLC size after etext, so it won't collide with the next symbol
  2553  	// (which may confuse some symbolizer).
  2554  	sect.Length = va - sect.Vaddr + uint64(ctxt.Arch.MinLC)
  2555  	ldr.SetSymSect(etext, sect)
  2556  	if ldr.SymValue(etext) == 0 {
  2557  		// Set the address of the start/end symbols, if not already
  2558  		// (i.e. not darwin+dynlink or AIX+external, see above).
  2559  		ldr.SetSymValue(etext, int64(va))
  2560  		ldr.SetSymValue(text, int64(Segtext.Sections[0].Vaddr))
  2561  	}
  2562  }
  2563  
  2564  // assigns address for a text symbol, returns (possibly new) section, its number, and the address.
  2565  func assignAddress(ctxt *Link, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp, big bool) (*sym.Section, int, uint64) {
  2566  	ldr := ctxt.loader
  2567  	if thearch.AssignAddress != nil {
  2568  		return thearch.AssignAddress(ldr, sect, n, s, va, isTramp)
  2569  	}
  2570  
  2571  	ldr.SetSymSect(s, sect)
  2572  	if ldr.AttrSubSymbol(s) {
  2573  		return sect, n, va
  2574  	}
  2575  
  2576  	align := ldr.SymAlign(s)
  2577  	if align == 0 {
  2578  		align = int32(Funcalign)
  2579  	}
  2580  	va = uint64(Rnd(int64(va), int64(align)))
  2581  	if sect.Align < align {
  2582  		sect.Align = align
  2583  	}
  2584  
  2585  	funcsize := uint64(abi.MINFUNC) // spacing required for findfunctab
  2586  	if ldr.SymSize(s) > abi.MINFUNC {
  2587  		funcsize = uint64(ldr.SymSize(s))
  2588  	}
  2589  
  2590  	// If we need to split text sections, and this function doesn't fit in the current
  2591  	// section, then create a new one.
  2592  	//
  2593  	// Only break at outermost syms.
  2594  	if big && splitTextSections(ctxt) && ldr.OuterSym(s) == 0 {
  2595  		// For debugging purposes, allow text size limit to be cranked down,
  2596  		// so as to stress test the code that handles multiple text sections.
  2597  		var textSizelimit uint64 = thearch.TrampLimit
  2598  		if *FlagDebugTextSize != 0 {
  2599  			textSizelimit = uint64(*FlagDebugTextSize)
  2600  		}
  2601  
  2602  		// Sanity check: make sure the limit is larger than any
  2603  		// individual text symbol.
  2604  		if funcsize > textSizelimit {
  2605  			panic(fmt.Sprintf("error: text size limit %d less than text symbol %s size of %d", textSizelimit, ldr.SymName(s), funcsize))
  2606  		}
  2607  
  2608  		if va-sect.Vaddr+funcsize+maxSizeTrampolines(ctxt, ldr, s, isTramp) > textSizelimit {
  2609  			sectAlign := int32(thearch.Funcalign)
  2610  			if ctxt.IsPPC64() {
  2611  				// Align the next text section to the worst case function alignment likely
  2612  				// to be encountered when processing function symbols. The start address
  2613  				// is rounded against the final alignment of the text section later on in
  2614  				// (*Link).address. This may happen due to usage of PCALIGN directives
  2615  				// larger than Funcalign, or usage of ISA 3.1 prefixed instructions
  2616  				// (see ISA 3.1 Book I 1.9).
  2617  				const ppc64maxFuncalign = 64
  2618  				sectAlign = ppc64maxFuncalign
  2619  				va = uint64(Rnd(int64(va), ppc64maxFuncalign))
  2620  			}
  2621  
  2622  			// Set the length for the previous text section
  2623  			sect.Length = va - sect.Vaddr
  2624  
  2625  			// Create new section, set the starting Vaddr
  2626  			sect = addsection(ctxt.loader, ctxt.Arch, &Segtext, ".text", 05)
  2627  
  2628  			sect.Vaddr = va
  2629  			sect.Align = sectAlign
  2630  			ldr.SetSymSect(s, sect)
  2631  
  2632  			// Create a symbol for the start of the secondary text sections
  2633  			ntext := ldr.CreateSymForUpdate(fmt.Sprintf("runtime.text.%d", n), 0)
  2634  			ntext.SetSect(sect)
  2635  			if ctxt.IsAIX() {
  2636  				// runtime.text.X must be a real symbol on AIX.
  2637  				// Assign its address directly in order to be the
  2638  				// first symbol of this new section.
  2639  				ntext.SetType(sym.STEXT)
  2640  				ntext.SetSize(int64(abi.MINFUNC))
  2641  				ntext.SetOnList(true)
  2642  				ntext.SetAlign(sectAlign)
  2643  				ctxt.tramps = append(ctxt.tramps, ntext.Sym())
  2644  
  2645  				ntext.SetValue(int64(va))
  2646  				va += uint64(ntext.Size())
  2647  
  2648  				if align := ldr.SymAlign(s); align != 0 {
  2649  					va = uint64(Rnd(int64(va), int64(align)))
  2650  				} else {
  2651  					va = uint64(Rnd(int64(va), int64(Funcalign)))
  2652  				}
  2653  			}
  2654  			n++
  2655  		}
  2656  	}
  2657  
  2658  	ldr.SetSymValue(s, 0)
  2659  	for sub := s; sub != 0; sub = ldr.SubSym(sub) {
  2660  		ldr.SetSymValue(sub, ldr.SymValue(sub)+int64(va))
  2661  		if ctxt.Debugvlog > 2 {
  2662  			fmt.Println("assign text address:", ldr.SymName(sub), ldr.SymValue(sub))
  2663  		}
  2664  	}
  2665  
  2666  	va += funcsize
  2667  
  2668  	return sect, n, va
  2669  }
  2670  
  2671  func resetAddress(ctxt *Link, s loader.Sym) {
  2672  	ldr := ctxt.loader
  2673  	if ldr.OuterSym(s) != 0 {
  2674  		return
  2675  	}
  2676  	oldv := ldr.SymValue(s)
  2677  	for sub := s; sub != 0; sub = ldr.SubSym(sub) {
  2678  		ldr.SetSymValue(sub, ldr.SymValue(sub)-oldv)
  2679  	}
  2680  }
  2681  
  2682  // Return whether we may need to split text sections.
  2683  //
  2684  // On PPC64x, when external linking, a text section should not be
  2685  // larger than 2^25 bytes due to the size of call target offset field
  2686  // in the 'bl' instruction. Splitting into smaller text sections
  2687  // smaller than this limit allows the system linker to modify the long
  2688  // calls appropriately. The limit allows for the space needed for
  2689  // tables inserted by the linker.
  2690  //
  2691  // The same applies to Darwin/ARM64, with 2^27 byte threshold.
  2692  //
  2693  // Similarly for ARM, we split sections (at 2^25 bytes) to avoid
  2694  // inconsistencies between the Go linker's reachability calculations
  2695  // (e.g. will direct call from X to Y need a trampoline) and similar
  2696  // machinery in the external linker; see #58425 for more on the
  2697  // history here.
  2698  func splitTextSections(ctxt *Link) bool {
  2699  	return (ctxt.IsARM() || ctxt.IsPPC64() || (ctxt.IsARM64() && ctxt.IsDarwin())) && ctxt.IsExternal()
  2700  }
  2701  
  2702  // On Wasm, we reserve 4096 bytes for zero page, then 8192 bytes for wasm_exec.js
  2703  // to store command line args and environment variables.
  2704  // Data sections starts from at least address 12288.
  2705  // Keep in sync with wasm_exec.js.
  2706  const wasmMinDataAddr = 4096 + 8192
  2707  
  2708  // address assigns virtual addresses to all segments and sections and
  2709  // returns all segments in file order.
  2710  func (ctxt *Link) address() []*sym.Segment {
  2711  	var order []*sym.Segment // Layout order
  2712  
  2713  	va := uint64(*FlagTextAddr)
  2714  	order = append(order, &Segtext)
  2715  	Segtext.Rwx = 05
  2716  	Segtext.Vaddr = va
  2717  	for i, s := range Segtext.Sections {
  2718  		va = uint64(Rnd(int64(va), int64(s.Align)))
  2719  		s.Vaddr = va
  2720  		va += s.Length
  2721  
  2722  		if ctxt.IsWasm() && i == 0 && va < wasmMinDataAddr {
  2723  			va = wasmMinDataAddr
  2724  		}
  2725  	}
  2726  
  2727  	Segtext.Length = va - uint64(*FlagTextAddr)
  2728  
  2729  	if len(Segrodata.Sections) > 0 {
  2730  		// align to page boundary so as not to mix
  2731  		// rodata and executable text.
  2732  		//
  2733  		// Note: gold or GNU ld will reduce the size of the executable
  2734  		// file by arranging for the relro segment to end at a page
  2735  		// boundary, and overlap the end of the text segment with the
  2736  		// start of the relro segment in the file.  The PT_LOAD segments
  2737  		// will be such that the last page of the text segment will be
  2738  		// mapped twice, once r-x and once starting out rw- and, after
  2739  		// relocation processing, changed to r--.
  2740  		//
  2741  		// Ideally the last page of the text segment would not be
  2742  		// writable even for this short period.
  2743  		va = uint64(Rnd(int64(va), *FlagRound))
  2744  
  2745  		order = append(order, &Segrodata)
  2746  		Segrodata.Rwx = 04
  2747  		Segrodata.Vaddr = va
  2748  		for _, s := range Segrodata.Sections {
  2749  			va = uint64(Rnd(int64(va), int64(s.Align)))
  2750  			s.Vaddr = va
  2751  			va += s.Length
  2752  		}
  2753  
  2754  		Segrodata.Length = va - Segrodata.Vaddr
  2755  	}
  2756  	if len(Segrelrodata.Sections) > 0 {
  2757  		// align to page boundary so as not to mix
  2758  		// rodata, rel-ro data, and executable text.
  2759  		va = uint64(Rnd(int64(va), *FlagRound))
  2760  		if ctxt.HeadType == objabi.Haix {
  2761  			// Relro data are inside data segment on AIX.
  2762  			va += uint64(XCOFFDATABASE) - uint64(XCOFFTEXTBASE)
  2763  		}
  2764  
  2765  		order = append(order, &Segrelrodata)
  2766  		Segrelrodata.Rwx = 06
  2767  		Segrelrodata.Vaddr = va
  2768  		for _, s := range Segrelrodata.Sections {
  2769  			va = uint64(Rnd(int64(va), int64(s.Align)))
  2770  			s.Vaddr = va
  2771  			va += s.Length
  2772  		}
  2773  
  2774  		Segrelrodata.Length = va - Segrelrodata.Vaddr
  2775  	}
  2776  
  2777  	va = uint64(Rnd(int64(va), *FlagRound))
  2778  	if ctxt.HeadType == objabi.Haix && len(Segrelrodata.Sections) == 0 {
  2779  		// Data sections are moved to an unreachable segment
  2780  		// to ensure that they are position-independent.
  2781  		// Already done if relro sections exist.
  2782  		va += uint64(XCOFFDATABASE) - uint64(XCOFFTEXTBASE)
  2783  	}
  2784  	order = append(order, &Segdata)
  2785  	Segdata.Rwx = 06
  2786  	Segdata.Vaddr = va
  2787  	var data *sym.Section
  2788  	var noptr *sym.Section
  2789  	var bss *sym.Section
  2790  	var noptrbss *sym.Section
  2791  	var fuzzCounters *sym.Section
  2792  	for i, s := range Segdata.Sections {
  2793  		if (ctxt.IsELF || ctxt.HeadType == objabi.Haix) && s.Name == ".tbss" {
  2794  			continue
  2795  		}
  2796  		vlen := int64(s.Length)
  2797  		if i+1 < len(Segdata.Sections) && !((ctxt.IsELF || ctxt.HeadType == objabi.Haix) && Segdata.Sections[i+1].Name == ".tbss") {
  2798  			vlen = int64(Segdata.Sections[i+1].Vaddr - s.Vaddr)
  2799  		}
  2800  		s.Vaddr = va
  2801  		va += uint64(vlen)
  2802  		Segdata.Length = va - Segdata.Vaddr
  2803  		switch s.Name {
  2804  		case ".data":
  2805  			data = s
  2806  		case ".noptrdata":
  2807  			noptr = s
  2808  		case ".bss":
  2809  			bss = s
  2810  		case ".noptrbss":
  2811  			noptrbss = s
  2812  		case ".go.fuzzcntrs":
  2813  			fuzzCounters = s
  2814  		}
  2815  	}
  2816  
  2817  	// Assign Segdata's Filelen omitting the BSS. We do this here
  2818  	// simply because right now we know where the BSS starts.
  2819  	Segdata.Filelen = bss.Vaddr - Segdata.Vaddr
  2820  
  2821  	if len(Segpdata.Sections) > 0 {
  2822  		va = uint64(Rnd(int64(va), *FlagRound))
  2823  		order = append(order, &Segpdata)
  2824  		Segpdata.Rwx = 04
  2825  		Segpdata.Vaddr = va
  2826  		// Segpdata.Sections is intended to contain just one section.
  2827  		// Loop through the slice anyway for consistency.
  2828  		for _, s := range Segpdata.Sections {
  2829  			va = uint64(Rnd(int64(va), int64(s.Align)))
  2830  			s.Vaddr = va
  2831  			va += s.Length
  2832  		}
  2833  		Segpdata.Length = va - Segpdata.Vaddr
  2834  	}
  2835  
  2836  	if len(Segxdata.Sections) > 0 {
  2837  		va = uint64(Rnd(int64(va), *FlagRound))
  2838  		order = append(order, &Segxdata)
  2839  		Segxdata.Rwx = 04
  2840  		Segxdata.Vaddr = va
  2841  		// Segxdata.Sections is intended to contain just one section.
  2842  		// Loop through the slice anyway for consistency.
  2843  		for _, s := range Segxdata.Sections {
  2844  			va = uint64(Rnd(int64(va), int64(s.Align)))
  2845  			s.Vaddr = va
  2846  			va += s.Length
  2847  		}
  2848  		Segxdata.Length = va - Segxdata.Vaddr
  2849  	}
  2850  
  2851  	va = uint64(Rnd(int64(va), *FlagRound))
  2852  	order = append(order, &Segdwarf)
  2853  	Segdwarf.Rwx = 06
  2854  	Segdwarf.Vaddr = va
  2855  	for i, s := range Segdwarf.Sections {
  2856  		vlen := int64(s.Length)
  2857  		if i+1 < len(Segdwarf.Sections) {
  2858  			vlen = int64(Segdwarf.Sections[i+1].Vaddr - s.Vaddr)
  2859  		}
  2860  		s.Vaddr = va
  2861  		va += uint64(vlen)
  2862  		if ctxt.HeadType == objabi.Hwindows {
  2863  			va = uint64(Rnd(int64(va), PEFILEALIGN))
  2864  		}
  2865  		Segdwarf.Length = va - Segdwarf.Vaddr
  2866  	}
  2867  
  2868  	ldr := ctxt.loader
  2869  	var (
  2870  		rodata  = ldr.SymSect(ldr.LookupOrCreateSym("runtime.rodata", 0))
  2871  		symtab  = ldr.SymSect(ldr.LookupOrCreateSym("runtime.symtab", 0))
  2872  		pclntab = ldr.SymSect(ldr.LookupOrCreateSym("runtime.pclntab", 0))
  2873  		types   = ldr.SymSect(ldr.LookupOrCreateSym("runtime.types", 0))
  2874  	)
  2875  
  2876  	for _, s := range ctxt.datap {
  2877  		if sect := ldr.SymSect(s); sect != nil {
  2878  			ldr.AddToSymValue(s, int64(sect.Vaddr))
  2879  		}
  2880  		v := ldr.SymValue(s)
  2881  		for sub := ldr.SubSym(s); sub != 0; sub = ldr.SubSym(sub) {
  2882  			ldr.AddToSymValue(sub, v)
  2883  		}
  2884  	}
  2885  
  2886  	for _, si := range dwarfp {
  2887  		for _, s := range si.syms {
  2888  			if sect := ldr.SymSect(s); sect != nil {
  2889  				ldr.AddToSymValue(s, int64(sect.Vaddr))
  2890  			}
  2891  			sub := ldr.SubSym(s)
  2892  			if sub != 0 {
  2893  				panic(fmt.Sprintf("unexpected sub-sym for %s %s", ldr.SymName(s), ldr.SymType(s).String()))
  2894  			}
  2895  			v := ldr.SymValue(s)
  2896  			for ; sub != 0; sub = ldr.SubSym(sub) {
  2897  				ldr.AddToSymValue(s, v)
  2898  			}
  2899  		}
  2900  	}
  2901  
  2902  	for _, s := range sehp.pdata {
  2903  		if sect := ldr.SymSect(s); sect != nil {
  2904  			ldr.AddToSymValue(s, int64(sect.Vaddr))
  2905  		}
  2906  	}
  2907  	for _, s := range sehp.xdata {
  2908  		if sect := ldr.SymSect(s); sect != nil {
  2909  			ldr.AddToSymValue(s, int64(sect.Vaddr))
  2910  		}
  2911  	}
  2912  
  2913  	if ctxt.BuildMode == BuildModeShared {
  2914  		s := ldr.LookupOrCreateSym("go:link.abihashbytes", 0)
  2915  		sect := ldr.SymSect(ldr.LookupOrCreateSym(".note.go.abihash", 0))
  2916  		ldr.SetSymSect(s, sect)
  2917  		ldr.SetSymValue(s, int64(sect.Vaddr+16))
  2918  	}
  2919  
  2920  	// If there are multiple text sections, create runtime.text.n for
  2921  	// their section Vaddr, using n for index
  2922  	n := 1
  2923  	for _, sect := range Segtext.Sections[1:] {
  2924  		if sect.Name != ".text" {
  2925  			break
  2926  		}
  2927  		symname := fmt.Sprintf("runtime.text.%d", n)
  2928  		if ctxt.HeadType != objabi.Haix || ctxt.LinkMode != LinkExternal {
  2929  			// Addresses are already set on AIX with external linker
  2930  			// because these symbols are part of their sections.
  2931  			ctxt.xdefine(symname, sym.STEXT, int64(sect.Vaddr))
  2932  		}
  2933  		n++
  2934  	}
  2935  
  2936  	ctxt.xdefine("runtime.rodata", sym.SRODATA, int64(rodata.Vaddr))
  2937  	ctxt.xdefine("runtime.erodata", sym.SRODATA, int64(rodata.Vaddr+rodata.Length))
  2938  	ctxt.xdefine("runtime.types", sym.SRODATA, int64(types.Vaddr))
  2939  	ctxt.xdefine("runtime.etypes", sym.SRODATA, int64(types.Vaddr+types.Length))
  2940  
  2941  	s := ldr.Lookup("runtime.gcdata", 0)
  2942  	ldr.SetAttrLocal(s, true)
  2943  	ctxt.xdefine("runtime.egcdata", sym.SRODATA, ldr.SymAddr(s)+ldr.SymSize(s))
  2944  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.egcdata", 0), ldr.SymSect(s))
  2945  
  2946  	s = ldr.LookupOrCreateSym("runtime.gcbss", 0)
  2947  	ldr.SetAttrLocal(s, true)
  2948  	ctxt.xdefine("runtime.egcbss", sym.SRODATA, ldr.SymAddr(s)+ldr.SymSize(s))
  2949  	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.egcbss", 0), ldr.SymSect(s))
  2950  
  2951  	ctxt.xdefine("runtime.symtab", sym.SRODATA, int64(symtab.Vaddr))
  2952  	ctxt.xdefine("runtime.esymtab", sym.SRODATA, int64(symtab.Vaddr+symtab.Length))
  2953  	ctxt.xdefine("runtime.pclntab", sym.SRODATA, int64(pclntab.Vaddr))
  2954  	ctxt.defineInternal("runtime.pcheader", sym.SRODATA)
  2955  	ctxt.defineInternal("runtime.funcnametab", sym.SRODATA)
  2956  	ctxt.defineInternal("runtime.cutab", sym.SRODATA)
  2957  	ctxt.defineInternal("runtime.filetab", sym.SRODATA)
  2958  	ctxt.defineInternal("runtime.pctab", sym.SRODATA)
  2959  	ctxt.defineInternal("runtime.functab", sym.SRODATA)
  2960  	ctxt.xdefine("runtime.epclntab", sym.SRODATA, int64(pclntab.Vaddr+pclntab.Length))
  2961  	ctxt.xdefine("runtime.noptrdata", sym.SNOPTRDATA, int64(noptr.Vaddr))
  2962  	ctxt.xdefine("runtime.enoptrdata", sym.SNOPTRDATA, int64(noptr.Vaddr+noptr.Length))
  2963  	ctxt.xdefine("runtime.bss", sym.SBSS, int64(bss.Vaddr))
  2964  	ctxt.xdefine("runtime.ebss", sym.SBSS, int64(bss.Vaddr+bss.Length))
  2965  	ctxt.xdefine("runtime.data", sym.SDATA, int64(data.Vaddr))
  2966  	ctxt.xdefine("runtime.edata", sym.SDATA, int64(data.Vaddr+data.Length))
  2967  	ctxt.xdefine("runtime.noptrbss", sym.SNOPTRBSS, int64(noptrbss.Vaddr))
  2968  	ctxt.xdefine("runtime.enoptrbss", sym.SNOPTRBSS, int64(noptrbss.Vaddr+noptrbss.Length))
  2969  	ctxt.xdefine("runtime.covctrs", sym.SCOVERAGE_COUNTER, int64(noptrbss.Vaddr+covCounterDataStartOff))
  2970  	ctxt.xdefine("runtime.ecovctrs", sym.SCOVERAGE_COUNTER, int64(noptrbss.Vaddr+covCounterDataStartOff+covCounterDataLen))
  2971  	ctxt.xdefine("runtime.end", sym.SBSS, int64(Segdata.Vaddr+Segdata.Length))
  2972  
  2973  	if fuzzCounters != nil {
  2974  		ctxt.xdefine("runtime.__start___sancov_cntrs", sym.SLIBFUZZER_8BIT_COUNTER, int64(fuzzCounters.Vaddr))
  2975  		ctxt.xdefine("runtime.__stop___sancov_cntrs", sym.SLIBFUZZER_8BIT_COUNTER, int64(fuzzCounters.Vaddr+fuzzCounters.Length))
  2976  		ctxt.xdefine("internal/fuzz._counters", sym.SLIBFUZZER_8BIT_COUNTER, int64(fuzzCounters.Vaddr))
  2977  		ctxt.xdefine("internal/fuzz._ecounters", sym.SLIBFUZZER_8BIT_COUNTER, int64(fuzzCounters.Vaddr+fuzzCounters.Length))
  2978  	}
  2979  
  2980  	if ctxt.IsSolaris() {
  2981  		// On Solaris, in the runtime it sets the external names of the
  2982  		// end symbols. Unset them and define separate symbols, so we
  2983  		// keep both.
  2984  		etext := ldr.Lookup("runtime.etext", 0)
  2985  		edata := ldr.Lookup("runtime.edata", 0)
  2986  		end := ldr.Lookup("runtime.end", 0)
  2987  		ldr.SetSymExtname(etext, "runtime.etext")
  2988  		ldr.SetSymExtname(edata, "runtime.edata")
  2989  		ldr.SetSymExtname(end, "runtime.end")
  2990  		ctxt.xdefine("_etext", ldr.SymType(etext), ldr.SymValue(etext))
  2991  		ctxt.xdefine("_edata", ldr.SymType(edata), ldr.SymValue(edata))
  2992  		ctxt.xdefine("_end", ldr.SymType(end), ldr.SymValue(end))
  2993  		ldr.SetSymSect(ldr.Lookup("_etext", 0), ldr.SymSect(etext))
  2994  		ldr.SetSymSect(ldr.Lookup("_edata", 0), ldr.SymSect(edata))
  2995  		ldr.SetSymSect(ldr.Lookup("_end", 0), ldr.SymSect(end))
  2996  	}
  2997  
  2998  	if ctxt.IsPPC64() && ctxt.IsElf() {
  2999  		// Resolve .TOC. symbols for all objects. Only one TOC region is supported. If a
  3000  		// GOT section is present, compute it as suggested by the ELFv2 ABI. Otherwise,
  3001  		// choose a similar offset from the start of the data segment.
  3002  		tocAddr := int64(Segdata.Vaddr) + 0x8000
  3003  		if gotAddr := ldr.SymValue(ctxt.GOT); gotAddr != 0 {
  3004  			tocAddr = gotAddr + 0x8000
  3005  		}
  3006  		for i := range ctxt.DotTOC {
  3007  			if i >= sym.SymVerABICount && i < sym.SymVerStatic { // these versions are not used currently
  3008  				continue
  3009  			}
  3010  			if toc := ldr.Lookup(".TOC.", i); toc != 0 {
  3011  				ldr.SetSymValue(toc, tocAddr)
  3012  			}
  3013  		}
  3014  	}
  3015  
  3016  	return order
  3017  }
  3018  
  3019  // layout assigns file offsets and lengths to the segments in order.
  3020  // Returns the file size containing all the segments.
  3021  func (ctxt *Link) layout(order []*sym.Segment) uint64 {
  3022  	var prev *sym.Segment
  3023  	for _, seg := range order {
  3024  		if prev == nil {
  3025  			seg.Fileoff = uint64(HEADR)
  3026  		} else {
  3027  			switch ctxt.HeadType {
  3028  			default:
  3029  				// Assuming the previous segment was
  3030  				// aligned, the following rounding
  3031  				// should ensure that this segment's
  3032  				// VA ≡ Fileoff mod FlagRound.
  3033  				seg.Fileoff = uint64(Rnd(int64(prev.Fileoff+prev.Filelen), *FlagRound))
  3034  				if seg.Vaddr%uint64(*FlagRound) != seg.Fileoff%uint64(*FlagRound) {
  3035  					Exitf("bad segment rounding (Vaddr=%#x Fileoff=%#x FlagRound=%#x)", seg.Vaddr, seg.Fileoff, *FlagRound)
  3036  				}
  3037  			case objabi.Hwindows:
  3038  				seg.Fileoff = prev.Fileoff + uint64(Rnd(int64(prev.Filelen), PEFILEALIGN))
  3039  			case objabi.Hplan9:
  3040  				seg.Fileoff = prev.Fileoff + prev.Filelen
  3041  			}
  3042  		}
  3043  		if seg != &Segdata {
  3044  			// Link.address already set Segdata.Filelen to
  3045  			// account for BSS.
  3046  			seg.Filelen = seg.Length
  3047  		}
  3048  		prev = seg
  3049  	}
  3050  	return prev.Fileoff + prev.Filelen
  3051  }
  3052  
  3053  // add a trampoline with symbol s (to be laid down after the current function)
  3054  func (ctxt *Link) AddTramp(s *loader.SymbolBuilder) {
  3055  	s.SetType(sym.STEXT)
  3056  	s.SetReachable(true)
  3057  	s.SetOnList(true)
  3058  	ctxt.tramps = append(ctxt.tramps, s.Sym())
  3059  	if *FlagDebugTramp > 0 && ctxt.Debugvlog > 0 {
  3060  		ctxt.Logf("trampoline %s inserted\n", s.Name())
  3061  	}
  3062  }
  3063  
  3064  // compressSyms compresses syms and returns the contents of the
  3065  // compressed section. If the section would get larger, it returns nil.
  3066  func compressSyms(ctxt *Link, syms []loader.Sym) []byte {
  3067  	ldr := ctxt.loader
  3068  	var total int64
  3069  	for _, sym := range syms {
  3070  		total += ldr.SymSize(sym)
  3071  	}
  3072  
  3073  	var buf bytes.Buffer
  3074  	if ctxt.IsELF {
  3075  		switch ctxt.Arch.PtrSize {
  3076  		case 8:
  3077  			binary.Write(&buf, ctxt.Arch.ByteOrder, elf.Chdr64{
  3078  				Type:      uint32(elf.COMPRESS_ZLIB),
  3079  				Size:      uint64(total),
  3080  				Addralign: uint64(ctxt.Arch.Alignment),
  3081  			})
  3082  		case 4:
  3083  			binary.Write(&buf, ctxt.Arch.ByteOrder, elf.Chdr32{
  3084  				Type:      uint32(elf.COMPRESS_ZLIB),
  3085  				Size:      uint32(total),
  3086  				Addralign: uint32(ctxt.Arch.Alignment),
  3087  			})
  3088  		default:
  3089  			log.Fatalf("can't compress header size:%d", ctxt.Arch.PtrSize)
  3090  		}
  3091  	} else {
  3092  		buf.Write([]byte("ZLIB"))
  3093  		var sizeBytes [8]byte
  3094  		binary.BigEndian.PutUint64(sizeBytes[:], uint64(total))
  3095  		buf.Write(sizeBytes[:])
  3096  	}
  3097  
  3098  	var relocbuf []byte // temporary buffer for applying relocations
  3099  
  3100  	// Using zlib.BestSpeed achieves very nearly the same
  3101  	// compression levels of zlib.DefaultCompression, but takes
  3102  	// substantially less time. This is important because DWARF
  3103  	// compression can be a significant fraction of link time.
  3104  	z, err := zlib.NewWriterLevel(&buf, zlib.BestSpeed)
  3105  	if err != nil {
  3106  		log.Fatalf("NewWriterLevel failed: %s", err)
  3107  	}
  3108  	st := ctxt.makeRelocSymState()
  3109  	for _, s := range syms {
  3110  		// Symbol data may be read-only. Apply relocations in a
  3111  		// temporary buffer, and immediately write it out.
  3112  		P := ldr.Data(s)
  3113  		relocs := ldr.Relocs(s)
  3114  		if relocs.Count() != 0 {
  3115  			relocbuf = append(relocbuf[:0], P...)
  3116  			P = relocbuf
  3117  			st.relocsym(s, P)
  3118  		}
  3119  		if _, err := z.Write(P); err != nil {
  3120  			log.Fatalf("compression failed: %s", err)
  3121  		}
  3122  		for i := ldr.SymSize(s) - int64(len(P)); i > 0; {
  3123  			b := zeros[:]
  3124  			if i < int64(len(b)) {
  3125  				b = b[:i]
  3126  			}
  3127  			n, err := z.Write(b)
  3128  			if err != nil {
  3129  				log.Fatalf("compression failed: %s", err)
  3130  			}
  3131  			i -= int64(n)
  3132  		}
  3133  	}
  3134  	if err := z.Close(); err != nil {
  3135  		log.Fatalf("compression failed: %s", err)
  3136  	}
  3137  	if int64(buf.Len()) >= total {
  3138  		// Compression didn't save any space.
  3139  		return nil
  3140  	}
  3141  	return buf.Bytes()
  3142  }
  3143  

View as plain text