plist.go

Documentation: cmd/internal/obj

     1  // Copyright 2013 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package obj
     6  
     7  import (
     8  	"cmd/internal/objabi"
     9  	"cmd/internal/src"
    10  	"fmt"
    11  	"internal/abi"
    12  	"strings"
    13  )
    14  
    15  type Plist struct {
    16  	Firstpc *Prog
    17  	Curfn   Func
    18  }
    19  
    20  // ProgAlloc is a function that allocates Progs.
    21  // It is used to provide access to cached/bulk-allocated Progs to the assemblers.
    22  type ProgAlloc func() *Prog
    23  
    24  func Flushplist(ctxt *Link, plist *Plist, newprog ProgAlloc) {
    25  	if ctxt.Pkgpath == "" {
    26  		panic("Flushplist called without Pkgpath")
    27  	}
    28  
    29  	// Build list of symbols, and assign instructions to lists.
    30  	var curtext *LSym
    31  	var etext *Prog
    32  	var text []*LSym
    33  
    34  	var plink *Prog
    35  	for p := plist.Firstpc; p != nil; p = plink {
    36  		if ctxt.Debugasm > 0 && ctxt.Debugvlog {
    37  			fmt.Printf("obj: %v\n", p)
    38  		}
    39  		plink = p.Link
    40  		p.Link = nil
    41  
    42  		switch p.As {
    43  		case AEND:
    44  			continue
    45  
    46  		case ATEXT:
    47  			s := p.From.Sym
    48  			if s == nil {
    49  				// func _() { }
    50  				curtext = nil
    51  				continue
    52  			}
    53  			text = append(text, s)
    54  			etext = p
    55  			curtext = s
    56  			continue
    57  
    58  		case AFUNCDATA:
    59  			// Rewrite reference to go_args_stackmap(SB) to the Go-provided declaration information.
    60  			if curtext == nil { // func _() {}
    61  				continue
    62  			}
    63  			switch p.To.Sym.Name {
    64  			case "go_args_stackmap":
    65  				if p.From.Type != TYPE_CONST || p.From.Offset != abi.FUNCDATA_ArgsPointerMaps {
    66  					ctxt.Diag("%s: FUNCDATA use of go_args_stackmap(SB) without FUNCDATA_ArgsPointerMaps", p.Pos)
    67  				}
    68  				p.To.Sym = ctxt.LookupDerived(curtext, curtext.Name+".args_stackmap")
    69  			case "no_pointers_stackmap":
    70  				if p.From.Type != TYPE_CONST || p.From.Offset != abi.FUNCDATA_LocalsPointerMaps {
    71  					ctxt.Diag("%s: FUNCDATA use of no_pointers_stackmap(SB) without FUNCDATA_LocalsPointerMaps", p.Pos)
    72  				}
    73  				// funcdata for functions with no local variables in frame.
    74  				// Define two zero-length bitmaps, because the same index is used
    75  				// for the local variables as for the argument frame, and assembly
    76  				// frames have two argument bitmaps, one without results and one with results.
    77  				// Write []uint32{2, 0}.
    78  				b := make([]byte, 8)
    79  				ctxt.Arch.ByteOrder.PutUint32(b, 2)
    80  				s := ctxt.GCLocalsSym(b)
    81  				if !s.OnList() {
    82  					ctxt.Globl(s, int64(len(s.P)), int(RODATA|DUPOK))
    83  				}
    84  				p.To.Sym = s
    85  			}
    86  
    87  		}
    88  
    89  		if curtext == nil {
    90  			etext = nil
    91  			continue
    92  		}
    93  		etext.Link = p
    94  		etext = p
    95  	}
    96  
    97  	if newprog == nil {
    98  		newprog = ctxt.NewProg
    99  	}
   100  
   101  	// Add reference to Go arguments for assembly functions without them.
   102  	if ctxt.IsAsm {
   103  		pkgPrefix := objabi.PathToPrefix(ctxt.Pkgpath) + "."
   104  		for _, s := range text {
   105  			if !strings.HasPrefix(s.Name, pkgPrefix) {
   106  				continue
   107  			}
   108  			// The current args_stackmap generation in the compiler assumes
   109  			// that the function in question is ABI0, so avoid introducing
   110  			// an args_stackmap reference if the func is not ABI0 (better to
   111  			// have no stackmap than an incorrect/lying stackmap).
   112  			if s.ABI() != ABI0 {
   113  				continue
   114  			}
   115  			// runtime.addmoduledata is a host ABI function, so it doesn't
   116  			// need FUNCDATA anyway. Moreover, cmd/link has special logic
   117  			// for linking it in eccentric build modes, which breaks if it
   118  			// has FUNCDATA references (e.g., cmd/cgo/internal/testplugin).
   119  			//
   120  			// TODO(cherryyz): Fix cmd/link's handling of plugins (see
   121  			// discussion on CL 523355).
   122  			if s.Name == "runtime.addmoduledata" {
   123  				continue
   124  			}
   125  			foundArgMap, foundArgInfo := false, false
   126  			for p := s.Func().Text; p != nil; p = p.Link {
   127  				if p.As == AFUNCDATA && p.From.Type == TYPE_CONST {
   128  					if p.From.Offset == abi.FUNCDATA_ArgsPointerMaps {
   129  						foundArgMap = true
   130  					}
   131  					if p.From.Offset == abi.FUNCDATA_ArgInfo {
   132  						foundArgInfo = true
   133  					}
   134  					if foundArgMap && foundArgInfo {
   135  						break
   136  					}
   137  				}
   138  			}
   139  			if !foundArgMap {
   140  				p := Appendp(s.Func().Text, newprog)
   141  				p.As = AFUNCDATA
   142  				p.From.Type = TYPE_CONST
   143  				p.From.Offset = abi.FUNCDATA_ArgsPointerMaps
   144  				p.To.Type = TYPE_MEM
   145  				p.To.Name = NAME_EXTERN
   146  				p.To.Sym = ctxt.LookupDerived(s, s.Name+".args_stackmap")
   147  			}
   148  			if !foundArgInfo {
   149  				p := Appendp(s.Func().Text, newprog)
   150  				p.As = AFUNCDATA
   151  				p.From.Type = TYPE_CONST
   152  				p.From.Offset = abi.FUNCDATA_ArgInfo
   153  				p.To.Type = TYPE_MEM
   154  				p.To.Name = NAME_EXTERN
   155  				p.To.Sym = ctxt.LookupDerived(s, fmt.Sprintf("%s.arginfo%d", s.Name, s.ABI()))
   156  			}
   157  		}
   158  	}
   159  
   160  	// Turn functions into machine code images.
   161  	for _, s := range text {
   162  		mkfwd(s)
   163  		if ctxt.Arch.ErrorCheck != nil {
   164  			ctxt.Arch.ErrorCheck(ctxt, s)
   165  		}
   166  		linkpatch(ctxt, s, newprog)
   167  		ctxt.Arch.Preprocess(ctxt, s, newprog)
   168  		ctxt.Arch.Assemble(ctxt, s, newprog)
   169  		if ctxt.Errors > 0 {
   170  			continue
   171  		}
   172  		linkpcln(ctxt, s)
   173  		ctxt.populateDWARF(plist.Curfn, s)
   174  		if ctxt.Headtype == objabi.Hwindows && ctxt.Arch.SEH != nil {
   175  			s.Func().sehUnwindInfoSym = ctxt.Arch.SEH(ctxt, s)
   176  		}
   177  	}
   178  }
   179  
   180  func (ctxt *Link) InitTextSym(s *LSym, flag int, start src.XPos) {
   181  	if s == nil {
   182  		// func _() { }
   183  		return
   184  	}
   185  	if s.Func() != nil {
   186  		ctxt.Diag("%s: symbol %s redeclared\n\t%s: other declaration of symbol %s", ctxt.PosTable.Pos(start), s.Name, ctxt.PosTable.Pos(s.Func().Text.Pos), s.Name)
   187  		return
   188  	}
   189  	s.NewFuncInfo()
   190  	if s.OnList() {
   191  		ctxt.Diag("%s: symbol %s redeclared", ctxt.PosTable.Pos(start), s.Name)
   192  		return
   193  	}
   194  	if strings.HasPrefix(s.Name, `"".`) {
   195  		ctxt.Diag("%s: unqualified symbol name: %s", ctxt.PosTable.Pos(start), s.Name)
   196  	}
   197  
   198  	// startLine should be the same line number that would be displayed via
   199  	// pcln, etc for the declaration (i.e., relative line number, as
   200  	// adjusted by //line).
   201  	_, startLine := ctxt.getFileIndexAndLine(start)
   202  
   203  	s.Func().FuncID = objabi.GetFuncID(s.Name, flag&WRAPPER != 0 || flag&ABIWRAPPER != 0)
   204  	s.Func().FuncFlag = ctxt.toFuncFlag(flag)
   205  	s.Func().StartLine = startLine
   206  	s.Set(AttrOnList, true)
   207  	s.Set(AttrDuplicateOK, flag&DUPOK != 0)
   208  	s.Set(AttrNoSplit, flag&NOSPLIT != 0)
   209  	s.Set(AttrReflectMethod, flag&REFLECTMETHOD != 0)
   210  	s.Set(AttrWrapper, flag&WRAPPER != 0)
   211  	s.Set(AttrABIWrapper, flag&ABIWRAPPER != 0)
   212  	s.Set(AttrNeedCtxt, flag&NEEDCTXT != 0)
   213  	s.Set(AttrNoFrame, flag&NOFRAME != 0)
   214  	s.Set(AttrPkgInit, flag&PKGINIT != 0)
   215  	s.Type = objabi.STEXT
   216  	ctxt.Text = append(ctxt.Text, s)
   217  
   218  	// Set up DWARF entries for s
   219  	ctxt.dwarfSym(s)
   220  }
   221  
   222  func (ctxt *Link) toFuncFlag(flag int) abi.FuncFlag {
   223  	var out abi.FuncFlag
   224  	if flag&TOPFRAME != 0 {
   225  		out |= abi.FuncFlagTopFrame
   226  	}
   227  	if ctxt.IsAsm {
   228  		out |= abi.FuncFlagAsm
   229  	}
   230  	return out
   231  }
   232  
   233  func (ctxt *Link) Globl(s *LSym, size int64, flag int) {
   234  	ctxt.GloblPos(s, size, flag, src.NoXPos)
   235  }
   236  func (ctxt *Link) GloblPos(s *LSym, size int64, flag int, pos src.XPos) {
   237  	if s.OnList() {
   238  		// TODO: print where the first declaration was.
   239  		ctxt.Diag("%s: symbol %s redeclared", ctxt.PosTable.Pos(pos), s.Name)
   240  	}
   241  	s.Set(AttrOnList, true)
   242  	ctxt.Data = append(ctxt.Data, s)
   243  	s.Size = size
   244  	if s.Type == 0 {
   245  		s.Type = objabi.SBSS
   246  	}
   247  	if flag&DUPOK != 0 {
   248  		s.Set(AttrDuplicateOK, true)
   249  	}
   250  	if flag&RODATA != 0 {
   251  		s.Type = objabi.SRODATA
   252  	} else if flag&NOPTR != 0 {
   253  		if s.Type == objabi.SDATA {
   254  			s.Type = objabi.SNOPTRDATA
   255  		} else {
   256  			s.Type = objabi.SNOPTRBSS
   257  		}
   258  	} else if flag&TLSBSS != 0 {
   259  		s.Type = objabi.STLSBSS
   260  	}
   261  }
   262  
   263  // EmitEntryLiveness generates PCDATA Progs after p to switch to the
   264  // liveness map active at the entry of function s. It returns the last
   265  // Prog generated.
   266  func (ctxt *Link) EmitEntryLiveness(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
   267  	pcdata := ctxt.EmitEntryStackMap(s, p, newprog)
   268  	pcdata = ctxt.EmitEntryUnsafePoint(s, pcdata, newprog)
   269  	return pcdata
   270  }
   271  
   272  // Similar to EmitEntryLiveness, but just emit stack map.
   273  func (ctxt *Link) EmitEntryStackMap(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
   274  	pcdata := Appendp(p, newprog)
   275  	pcdata.Pos = s.Func().Text.Pos
   276  	pcdata.As = APCDATA
   277  	pcdata.From.Type = TYPE_CONST
   278  	pcdata.From.Offset = abi.PCDATA_StackMapIndex
   279  	pcdata.To.Type = TYPE_CONST
   280  	pcdata.To.Offset = -1 // pcdata starts at -1 at function entry
   281  
   282  	return pcdata
   283  }
   284  
   285  // Similar to EmitEntryLiveness, but just emit unsafe point map.
   286  func (ctxt *Link) EmitEntryUnsafePoint(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
   287  	pcdata := Appendp(p, newprog)
   288  	pcdata.Pos = s.Func().Text.Pos
   289  	pcdata.As = APCDATA
   290  	pcdata.From.Type = TYPE_CONST
   291  	pcdata.From.Offset = abi.PCDATA_UnsafePoint
   292  	pcdata.To.Type = TYPE_CONST
   293  	pcdata.To.Offset = -1
   294  
   295  	return pcdata
   296  }
   297  
   298  // StartUnsafePoint generates PCDATA Progs after p to mark the
   299  // beginning of an unsafe point. The unsafe point starts immediately
   300  // after p.
   301  // It returns the last Prog generated.
   302  func (ctxt *Link) StartUnsafePoint(p *Prog, newprog ProgAlloc) *Prog {
   303  	pcdata := Appendp(p, newprog)
   304  	pcdata.As = APCDATA
   305  	pcdata.From.Type = TYPE_CONST
   306  	pcdata.From.Offset = abi.PCDATA_UnsafePoint
   307  	pcdata.To.Type = TYPE_CONST
   308  	pcdata.To.Offset = abi.UnsafePointUnsafe
   309  
   310  	return pcdata
   311  }
   312  
   313  // EndUnsafePoint generates PCDATA Progs after p to mark the end of an
   314  // unsafe point, restoring the register map index to oldval.
   315  // The unsafe point ends right after p.
   316  // It returns the last Prog generated.
   317  func (ctxt *Link) EndUnsafePoint(p *Prog, newprog ProgAlloc, oldval int64) *Prog {
   318  	pcdata := Appendp(p, newprog)
   319  	pcdata.As = APCDATA
   320  	pcdata.From.Type = TYPE_CONST
   321  	pcdata.From.Offset = abi.PCDATA_UnsafePoint
   322  	pcdata.To.Type = TYPE_CONST
   323  	pcdata.To.Offset = oldval
   324  
   325  	return pcdata
   326  }
   327  
   328  // MarkUnsafePoints inserts PCDATAs to mark nonpreemptible and restartable
   329  // instruction sequences, based on isUnsafePoint and isRestartable predicate.
   330  // p0 is the start of the instruction stream.
   331  // isUnsafePoint(p) returns true if p is not safe for async preemption.
   332  // isRestartable(p) returns true if we can restart at the start of p (this Prog)
   333  // upon async preemption. (Currently multi-Prog restartable sequence is not
   334  // supported.)
   335  // isRestartable can be nil. In this case it is treated as always returning false.
   336  // If isUnsafePoint(p) and isRestartable(p) are both true, it is treated as
   337  // an unsafe point.
   338  func MarkUnsafePoints(ctxt *Link, p0 *Prog, newprog ProgAlloc, isUnsafePoint, isRestartable func(*Prog) bool) {
   339  	if isRestartable == nil {
   340  		// Default implementation: nothing is restartable.
   341  		isRestartable = func(*Prog) bool { return false }
   342  	}
   343  	prev := p0
   344  	prevPcdata := int64(-1) // entry PC data value
   345  	prevRestart := int64(0)
   346  	for p := prev.Link; p != nil; p, prev = p.Link, p {
   347  		if p.As == APCDATA && p.From.Offset == abi.PCDATA_UnsafePoint {
   348  			prevPcdata = p.To.Offset
   349  			continue
   350  		}
   351  		if prevPcdata == abi.UnsafePointUnsafe {
   352  			continue // already unsafe
   353  		}
   354  		if isUnsafePoint(p) {
   355  			q := ctxt.StartUnsafePoint(prev, newprog)
   356  			q.Pc = p.Pc
   357  			q.Link = p
   358  			// Advance to the end of unsafe point.
   359  			for p.Link != nil && isUnsafePoint(p.Link) {
   360  				p = p.Link
   361  			}
   362  			if p.Link == nil {
   363  				break // Reached the end, don't bother marking the end
   364  			}
   365  			p = ctxt.EndUnsafePoint(p, newprog, prevPcdata)
   366  			p.Pc = p.Link.Pc
   367  			continue
   368  		}
   369  		if isRestartable(p) {
   370  			val := int64(abi.UnsafePointRestart1)
   371  			if val == prevRestart {
   372  				val = abi.UnsafePointRestart2
   373  			}
   374  			prevRestart = val
   375  			q := Appendp(prev, newprog)
   376  			q.As = APCDATA
   377  			q.From.Type = TYPE_CONST
   378  			q.From.Offset = abi.PCDATA_UnsafePoint
   379  			q.To.Type = TYPE_CONST
   380  			q.To.Offset = val
   381  			q.Pc = p.Pc
   382  			q.Link = p
   383  
   384  			if p.Link == nil {
   385  				break // Reached the end, don't bother marking the end
   386  			}
   387  			if isRestartable(p.Link) {
   388  				// Next Prog is also restartable. No need to mark the end
   389  				// of this sequence. We'll just go ahead mark the next one.
   390  				continue
   391  			}
   392  			p = Appendp(p, newprog)
   393  			p.As = APCDATA
   394  			p.From.Type = TYPE_CONST
   395  			p.From.Offset = abi.PCDATA_UnsafePoint
   396  			p.To.Type = TYPE_CONST
   397  			p.To.Offset = prevPcdata
   398  			p.Pc = p.Link.Pc
   399  		}
   400  	}
   401  }
   402
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