pkgspecial.go

Documentation: cmd/internal/objabi

     1  // Copyright 2023 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 objabi
     6  
     7  import "sync"
     8  
     9  // PkgSpecial indicates special build properties of a given runtime-related
    10  // package.
    11  type PkgSpecial struct {
    12  	// Runtime indicates that this package is "runtime" or imported by
    13  	// "runtime". This has several effects (which maybe should be split out):
    14  	//
    15  	// - Implicit allocation is disallowed.
    16  	//
    17  	// - Various runtime pragmas are enabled.
    18  	//
    19  	// - Optimizations are always enabled.
    20  	//
    21  	// - Checkptr is always disabled.
    22  	//
    23  	// This should be set for runtime and all packages it imports, and may be
    24  	// set for additional packages.
    25  	Runtime bool
    26  
    27  	// NoInstrument indicates this package should not receive sanitizer
    28  	// instrumentation. In many of these, instrumentation could cause infinite
    29  	// recursion. This is all runtime packages, plus those that support the
    30  	// sanitizers.
    31  	NoInstrument bool
    32  
    33  	// NoRaceFunc indicates functions in this package should not get
    34  	// racefuncenter/racefuncexit instrumentation Memory accesses in these
    35  	// packages are either uninteresting or will cause false positives.
    36  	NoRaceFunc bool
    37  
    38  	// AllowAsmABI indicates that assembly in this package is allowed to use ABI
    39  	// selectors in symbol names. Generally this is needed for packages that
    40  	// interact closely with the runtime package or have performance-critical
    41  	// assembly.
    42  	AllowAsmABI bool
    43  }
    44  
    45  var runtimePkgs = []string{
    46  	"runtime",
    47  
    48  	"internal/runtime/atomic",
    49  	"internal/runtime/exithook",
    50  	"runtime/internal/math",
    51  	"runtime/internal/sys",
    52  	"internal/runtime/syscall",
    53  
    54  	"internal/abi",
    55  	"internal/bytealg",
    56  	"internal/byteorder",
    57  	"internal/chacha8rand",
    58  	"internal/coverage/rtcov",
    59  	"internal/cpu",
    60  	"internal/goarch",
    61  	"internal/godebugs",
    62  	"internal/goexperiment",
    63  	"internal/goos",
    64  	"internal/profilerecord",
    65  	"internal/stringslite",
    66  }
    67  
    68  // extraNoInstrumentPkgs is the set of packages in addition to runtimePkgs that
    69  // should have NoInstrument set.
    70  var extraNoInstrumentPkgs = []string{
    71  	"runtime/race",
    72  	"runtime/msan",
    73  	"runtime/asan",
    74  	// We omit bytealg even though it's imported by runtime because it also
    75  	// backs a lot of package bytes. Currently we don't have a way to omit race
    76  	// instrumentation when used from the runtime while keeping race
    77  	// instrumentation when used from user code. Somehow this doesn't seem to
    78  	// cause problems, though we may be skating on thin ice. See #61204.
    79  	"-internal/bytealg",
    80  }
    81  
    82  var noRaceFuncPkgs = []string{"sync", "sync/atomic", "internal/runtime/atomic"}
    83  
    84  var allowAsmABIPkgs = []string{
    85  	"runtime",
    86  	"reflect",
    87  	"syscall",
    88  	"internal/bytealg",
    89  	"internal/chacha8rand",
    90  	"internal/runtime/syscall",
    91  	"runtime/internal/startlinetest",
    92  }
    93  
    94  var (
    95  	pkgSpecials     map[string]PkgSpecial
    96  	pkgSpecialsOnce sync.Once
    97  )
    98  
    99  // LookupPkgSpecial returns special build properties for the given package path.
   100  func LookupPkgSpecial(pkgPath string) PkgSpecial {
   101  	pkgSpecialsOnce.Do(func() {
   102  		// Construct pkgSpecials from various package lists. This lets us use
   103  		// more flexible logic, while keeping the final map simple, and avoids
   104  		// the init-time cost of a map.
   105  		pkgSpecials = make(map[string]PkgSpecial)
   106  		set := func(elt string, f func(*PkgSpecial)) {
   107  			s := pkgSpecials[elt]
   108  			f(&s)
   109  			pkgSpecials[elt] = s
   110  		}
   111  		for _, pkg := range runtimePkgs {
   112  			set(pkg, func(ps *PkgSpecial) { ps.Runtime = true; ps.NoInstrument = true })
   113  		}
   114  		for _, pkg := range extraNoInstrumentPkgs {
   115  			if pkg[0] == '-' {
   116  				set(pkg[1:], func(ps *PkgSpecial) { ps.NoInstrument = false })
   117  			} else {
   118  				set(pkg, func(ps *PkgSpecial) { ps.NoInstrument = true })
   119  			}
   120  		}
   121  		for _, pkg := range noRaceFuncPkgs {
   122  			set(pkg, func(ps *PkgSpecial) { ps.NoRaceFunc = true })
   123  		}
   124  		for _, pkg := range allowAsmABIPkgs {
   125  			set(pkg, func(ps *PkgSpecial) { ps.AllowAsmABI = true })
   126  		}
   127  	})
   128  	return pkgSpecials[pkgPath]
   129  }
   130
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