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lib.go
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lib.go
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// Inferno utils/8l/asm.c
// https://bitbucket.org/inferno-os/inferno-os/src/master/utils/8l/asm.c
//
// Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
// Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
// Portions Copyright © 1997-1999 Vita Nuova Limited
// Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
// Portions Copyright © 2004,2006 Bruce Ellis
// Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
// Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
// Portions Copyright © 2009 The Go Authors. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package ld
import (
"bytes"
"debug/elf"
"debug/macho"
"encoding/base64"
"encoding/binary"
"fmt"
"internal/buildcfg"
"io"
"log"
"os"
"os/exec"
"path/filepath"
"runtime"
"strings"
"sync"
"cmd/internal/bio"
"cmd/internal/goobj"
"cmd/internal/notsha256"
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/loadelf"
"cmd/link/internal/loader"
"cmd/link/internal/loadmacho"
"cmd/link/internal/loadpe"
"cmd/link/internal/loadxcoff"
"cmd/link/internal/sym"
)
// Data layout and relocation.
// Derived from Inferno utils/6l/l.h
// https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/l.h
//
// Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
// Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
// Portions Copyright © 1997-1999 Vita Nuova Limited
// Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
// Portions Copyright © 2004,2006 Bruce Ellis
// Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
// Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
// Portions Copyright © 2009 The Go Authors. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
// ArchSyms holds a number of architecture specific symbols used during
// relocation. Rather than allowing them universal access to all symbols,
// we keep a subset for relocation application.
type ArchSyms struct {
Rel loader.Sym
Rela loader.Sym
RelPLT loader.Sym
RelaPLT loader.Sym
LinkEditGOT loader.Sym
LinkEditPLT loader.Sym
TOC loader.Sym
DotTOC []loader.Sym // for each version
GOT loader.Sym
PLT loader.Sym
GOTPLT loader.Sym
Tlsg loader.Sym
Tlsoffset int
Dynamic loader.Sym
DynSym loader.Sym
DynStr loader.Sym
unreachableMethod loader.Sym
// Symbol containing a list of all the inittasks that need
// to be run at startup.
mainInittasks loader.Sym
}
// mkArchSym is a helper for setArchSyms, to set up a special symbol.
func (ctxt *Link) mkArchSym(name string, ver int, ls *loader.Sym) {
*ls = ctxt.loader.LookupOrCreateSym(name, ver)
ctxt.loader.SetAttrReachable(*ls, true)
}
// mkArchSymVec is similar to setArchSyms, but operates on elements within
// a slice, where each element corresponds to some symbol version.
func (ctxt *Link) mkArchSymVec(name string, ver int, ls []loader.Sym) {
ls[ver] = ctxt.loader.LookupOrCreateSym(name, ver)
ctxt.loader.SetAttrReachable(ls[ver], true)
}
// setArchSyms sets up the ArchSyms structure, and must be called before
// relocations are applied.
func (ctxt *Link) setArchSyms() {
ctxt.mkArchSym(".got", 0, &ctxt.GOT)
ctxt.mkArchSym(".plt", 0, &ctxt.PLT)
ctxt.mkArchSym(".got.plt", 0, &ctxt.GOTPLT)
ctxt.mkArchSym(".dynamic", 0, &ctxt.Dynamic)
ctxt.mkArchSym(".dynsym", 0, &ctxt.DynSym)
ctxt.mkArchSym(".dynstr", 0, &ctxt.DynStr)
ctxt.mkArchSym("runtime.unreachableMethod", abiInternalVer, &ctxt.unreachableMethod)
if ctxt.IsPPC64() {
ctxt.mkArchSym("TOC", 0, &ctxt.TOC)
ctxt.DotTOC = make([]loader.Sym, ctxt.MaxVersion()+1)
for i := 0; i <= ctxt.MaxVersion(); i++ {
if i >= sym.SymVerABICount && i < sym.SymVerStatic { // these versions are not used currently
continue
}
ctxt.mkArchSymVec(".TOC.", i, ctxt.DotTOC)
}
}
if ctxt.IsElf() {
ctxt.mkArchSym(".rel", 0, &ctxt.Rel)
ctxt.mkArchSym(".rela", 0, &ctxt.Rela)
ctxt.mkArchSym(".rel.plt", 0, &ctxt.RelPLT)
ctxt.mkArchSym(".rela.plt", 0, &ctxt.RelaPLT)
}
if ctxt.IsDarwin() {
ctxt.mkArchSym(".linkedit.got", 0, &ctxt.LinkEditGOT)
ctxt.mkArchSym(".linkedit.plt", 0, &ctxt.LinkEditPLT)
}
}
type Arch struct {
Funcalign int
Maxalign int
Minalign int
Dwarfregsp int
Dwarfreglr int
// Threshold of total text size, used for trampoline insertion. If the total
// text size is smaller than TrampLimit, we won't need to insert trampolines.
// It is pretty close to the offset range of a direct CALL machine instruction.
// We leave some room for extra stuff like PLT stubs.
TrampLimit uint64
// Empty spaces between codeblocks will be padded with this value.
// For example an architecture might want to pad with a trap instruction to
// catch wayward programs. Architectures that do not define a padding value
// are padded with zeros.
CodePad []byte
// Plan 9 variables.
Plan9Magic uint32
Plan9_64Bit bool
Adddynrel func(*Target, *loader.Loader, *ArchSyms, loader.Sym, loader.Reloc, int) bool
Archinit func(*Link)
// Archreloc is an arch-specific hook that assists in relocation processing
// (invoked by 'relocsym'); it handles target-specific relocation tasks.
// Here "rel" is the current relocation being examined, "sym" is the symbol
// containing the chunk of data to which the relocation applies, and "off"
// is the contents of the to-be-relocated data item (from sym.P). Return
// value is the appropriately relocated value (to be written back to the
// same spot in sym.P), number of external _host_ relocations needed (i.e.
// ELF/Mach-O/etc. relocations, not Go relocations, this must match ELF.Reloc1,
// etc.), and a boolean indicating success/failure (a failing value indicates
// a fatal error).
Archreloc func(*Target, *loader.Loader, *ArchSyms, loader.Reloc, loader.Sym,
int64) (relocatedOffset int64, nExtReloc int, ok bool)
// Archrelocvariant is a second arch-specific hook used for
// relocation processing; it handles relocations where r.Type is
// insufficient to describe the relocation (r.Variant !=
// sym.RV_NONE). Here "rel" is the relocation being applied, "sym"
// is the symbol containing the chunk of data to which the
// relocation applies, and "off" is the contents of the
// to-be-relocated data item (from sym.P). Return is an updated
// offset value.
Archrelocvariant func(target *Target, ldr *loader.Loader, rel loader.Reloc,
rv sym.RelocVariant, sym loader.Sym, offset int64, data []byte) (relocatedOffset int64)
// Generate a trampoline for a call from s to rs if necessary. ri is
// index of the relocation.
Trampoline func(ctxt *Link, ldr *loader.Loader, ri int, rs, s loader.Sym)
// Assembling the binary breaks into two phases, writing the code/data/
// dwarf information (which is rather generic), and some more architecture
// specific work like setting up the elf headers/dynamic relocations, etc.
// The phases are called "Asmb" and "Asmb2". Asmb2 needs to be defined for
// every architecture, but only if architecture has an Asmb function will
// it be used for assembly. Otherwise a generic assembly Asmb function is
// used.
Asmb func(*Link, *loader.Loader)
Asmb2 func(*Link, *loader.Loader)
// Extreloc is an arch-specific hook that converts a Go relocation to an
// external relocation. Return the external relocation and whether it is
// needed.
Extreloc func(*Target, *loader.Loader, loader.Reloc, loader.Sym) (loader.ExtReloc, bool)
Gentext func(*Link, *loader.Loader) // Generate text before addressing has been performed.
Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
// Generate additional symbols for the native symbol table just prior to
// code generation.
GenSymsLate func(*Link, *loader.Loader)
// TLSIEtoLE converts a TLS Initial Executable relocation to
// a TLS Local Executable relocation.
//
// This is possible when a TLS IE relocation refers to a local
// symbol in an executable, which is typical when internally
// linking PIE binaries.
TLSIEtoLE func(P []byte, off, size int)
// optional override for assignAddress
AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
// ELF specific information.
ELF ELFArch
}
var (
thearch Arch
lcSize int32
rpath Rpath
spSize int32
symSize int32
)
const (
MINFUNC = 16 // minimum size for a function
)
// Symbol version of ABIInternal symbols. It is sym.SymVerABIInternal if ABI wrappers
// are used, 0 otherwise.
var abiInternalVer = sym.SymVerABIInternal
// DynlinkingGo reports whether we are producing Go code that can live
// in separate shared libraries linked together at runtime.
func (ctxt *Link) DynlinkingGo() bool {
if !ctxt.Loaded {
panic("DynlinkingGo called before all symbols loaded")
}
return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins
}
// CanUsePlugins reports whether a plugins can be used
func (ctxt *Link) CanUsePlugins() bool {
if !ctxt.Loaded {
panic("CanUsePlugins called before all symbols loaded")
}
return ctxt.canUsePlugins
}
// NeedCodeSign reports whether we need to code-sign the output binary.
func (ctxt *Link) NeedCodeSign() bool {
return ctxt.IsDarwin() && ctxt.IsARM64()
}
var (
dynlib []string
ldflag []string
havedynamic int
Funcalign int
iscgo bool
elfglobalsymndx int
interpreter string
debug_s bool // backup old value of debug['s']
HEADR int32
nerrors int
liveness int64 // size of liveness data (funcdata), printed if -v
// See -strictdups command line flag.
checkStrictDups int // 0=off 1=warning 2=error
strictDupMsgCount int
)
var (
Segtext sym.Segment
Segrodata sym.Segment
Segrelrodata sym.Segment
Segdata sym.Segment
Segdwarf sym.Segment
Segpdata sym.Segment // windows-only
Segxdata sym.Segment // windows-only
Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf, &Segpdata, &Segxdata}
)
const pkgdef = "__.PKGDEF"
var (
// externalobj is set to true if we see an object compiled by
// the host compiler that is not from a package that is known
// to support internal linking mode.
externalobj = false
// dynimportfail is a list of packages for which generating
// the dynimport file, _cgo_import.go, failed. If there are
// any of these objects, we must link externally. Issue 52863.
dynimportfail []string
// preferlinkext is a list of packages for which the Go command
// noticed use of peculiar C flags. If we see any of these,
// default to linking externally unless overridden by the
// user. See issues #58619, #58620, and #58848.
preferlinkext []string
// unknownObjFormat is set to true if we see an object whose
// format we don't recognize.
unknownObjFormat = false
theline string
)
func Lflag(ctxt *Link, arg string) {
ctxt.Libdir = append(ctxt.Libdir, arg)
}
/*
* Unix doesn't like it when we write to a running (or, sometimes,
* recently run) binary, so remove the output file before writing it.
* On Windows 7, remove() can force a subsequent create() to fail.
* S_ISREG() does not exist on Plan 9.
*/
func mayberemoveoutfile() {
if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
return
}
os.Remove(*flagOutfile)
}
func libinit(ctxt *Link) {
Funcalign = thearch.Funcalign
// add goroot to the end of the libdir list.
suffix := ""
suffixsep := ""
if *flagInstallSuffix != "" {
suffixsep = "_"
suffix = *flagInstallSuffix
} else if *flagRace {
suffixsep = "_"
suffix = "race"
} else if *flagMsan {
suffixsep = "_"
suffix = "msan"
} else if *flagAsan {
suffixsep = "_"
suffix = "asan"
}
if buildcfg.GOROOT != "" {
Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
}
mayberemoveoutfile()
if err := ctxt.Out.Open(*flagOutfile); err != nil {
Exitf("cannot create %s: %v", *flagOutfile, err)
}
if *flagEntrySymbol == "" {
switch ctxt.BuildMode {
case BuildModeCShared, BuildModeCArchive:
*flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
case BuildModeExe, BuildModePIE:
*flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
case BuildModeShared, BuildModePlugin:
// No *flagEntrySymbol for -buildmode=shared and plugin
default:
Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
}
}
}
func exitIfErrors() {
if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
mayberemoveoutfile()
Exit(2)
}
}
func errorexit() {
exitIfErrors()
Exit(0)
}
func loadinternal(ctxt *Link, name string) *sym.Library {
zerofp := goobj.FingerprintType{}
if ctxt.linkShared && ctxt.PackageShlib != nil {
if shlib := ctxt.PackageShlib[name]; shlib != "" {
return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
}
}
if ctxt.PackageFile != nil {
if pname := ctxt.PackageFile[name]; pname != "" {
return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
}
ctxt.Logf("loadinternal: cannot find %s\n", name)
return nil
}
for _, libdir := range ctxt.Libdir {
if ctxt.linkShared {
shlibname := filepath.Join(libdir, name+".shlibname")
if ctxt.Debugvlog != 0 {
ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
}
if _, err := os.Stat(shlibname); err == nil {
return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
}
}
pname := filepath.Join(libdir, name+".a")
if ctxt.Debugvlog != 0 {
ctxt.Logf("searching for %s.a in %s\n", name, pname)
}
if _, err := os.Stat(pname); err == nil {
return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
}
}
if name == "runtime" {
Exitf("error: unable to find runtime.a")
}
ctxt.Logf("warning: unable to find %s.a\n", name)
return nil
}
// extld returns the current external linker.
func (ctxt *Link) extld() []string {
if len(flagExtld) == 0 {
// Return the default external linker for the platform.
// This only matters when link tool is called directly without explicit -extld,
// go tool already passes the correct linker in other cases.
switch buildcfg.GOOS {
case "darwin", "freebsd", "openbsd":
flagExtld = []string{"clang"}
default:
flagExtld = []string{"gcc"}
}
}
return flagExtld
}
// findLibPathCmd uses cmd command to find gcc library libname.
// It returns library full path if found, or "none" if not found.
func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
extld := ctxt.extld()
name, args := extld[0], extld[1:]
args = append(args, hostlinkArchArgs(ctxt.Arch)...)
args = append(args, cmd)
if ctxt.Debugvlog != 0 {
ctxt.Logf("%s %v\n", extld, args)
}
out, err := exec.Command(name, args...).Output()
if err != nil {
if ctxt.Debugvlog != 0 {
ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
}
return "none"
}
return strings.TrimSpace(string(out))
}
// findLibPath searches for library libname.
// It returns library full path if found, or "none" if not found.
func (ctxt *Link) findLibPath(libname string) string {
return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
}
func (ctxt *Link) loadlib() {
var flags uint32
switch *FlagStrictDups {
case 0:
// nothing to do
case 1, 2:
flags |= loader.FlagStrictDups
default:
log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
}
ctxt.loader = loader.NewLoader(flags, &ctxt.ErrorReporter.ErrorReporter)
ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
return ctxt.loader.SymName(s)
}
// ctxt.Library grows during the loop, so not a range loop.
i := 0
for ; i < len(ctxt.Library); i++ {
lib := ctxt.Library[i]
if lib.Shlib == "" {
if ctxt.Debugvlog > 1 {
ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
}
loadobjfile(ctxt, lib)
}
}
// load internal packages, if not already
if *flagRace {
loadinternal(ctxt, "runtime/race")
}
if *flagMsan {
loadinternal(ctxt, "runtime/msan")
}
if *flagAsan {
loadinternal(ctxt, "runtime/asan")
}
loadinternal(ctxt, "runtime")
for ; i < len(ctxt.Library); i++ {
lib := ctxt.Library[i]
if lib.Shlib == "" {
loadobjfile(ctxt, lib)
}
}
// At this point, the Go objects are "preloaded". Not all the symbols are
// added to the symbol table (only defined package symbols are). Looking
// up symbol by name may not get expected result.
iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
// Plugins a require cgo support to function. Similarly, plugins may require additional
// internal linker support on some platforms which may not be implemented.
ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
// We now have enough information to determine the link mode.
determineLinkMode(ctxt)
if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
// This indicates a user requested -linkmode=external.
// The startup code uses an import of runtime/cgo to decide
// whether to initialize the TLS. So give it one. This could
// be handled differently but it's an unusual case.
if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
Exitf("cannot implicitly include runtime/cgo in a shared library")
}
for ; i < len(ctxt.Library); i++ {
lib := ctxt.Library[i]
if lib.Shlib == "" {
loadobjfile(ctxt, lib)
}
}
}
}
// Add non-package symbols and references of externally defined symbols.
ctxt.loader.LoadSyms(ctxt.Arch)
// Load symbols from shared libraries, after all Go object symbols are loaded.
for _, lib := range ctxt.Library {
if lib.Shlib != "" {
if ctxt.Debugvlog > 1 {
ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
}
ldshlibsyms(ctxt, lib.Shlib)
}
}
// Process cgo directives (has to be done before host object loading).
ctxt.loadcgodirectives()
// Conditionally load host objects, or setup for external linking.
hostobjs(ctxt)
hostlinksetup(ctxt)
if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
// If we have any undefined symbols in external
// objects, try to read them from the libgcc file.
any := false
undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
if len(undefs) > 0 {
any = true
if ctxt.Debugvlog > 1 {
ctxt.Logf("loadlib: first unresolved is %s [%d] from %s [%d]\n",
ctxt.loader.SymName(undefs[0]), undefs[0],
ctxt.loader.SymName(froms[0]), froms[0])
}
}
if any {
if *flagLibGCC == "" {
*flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
}
if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
// On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
// In this case we fail to load libgcc.a and can encounter link
// errors - see if we can find libcompiler_rt.a instead.
*flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
}
if ctxt.HeadType == objabi.Hwindows {
loadWindowsHostArchives(ctxt)
}
if *flagLibGCC != "none" {
hostArchive(ctxt, *flagLibGCC)
}
// For glibc systems, the linker setup used by GCC
// looks like
//
// GROUP ( /lib/x86_64-linux-gnu/libc.so.6
// /usr/lib/x86_64-linux-gnu/libc_nonshared.a
// AS_NEEDED ( /lib64/ld-linux-x86-64.so.2 ) )
//
// where libc_nonshared.a contains a small set of
// symbols including "__stack_chk_fail_local" and a
// few others. Thus if we are doing internal linking
// and "__stack_chk_fail_local" is unresolved (most
// likely due to the use of -fstack-protector), try
// loading libc_nonshared.a to resolve it.
//
// On Alpine Linux (musl-based), the library providing
// this symbol is called libssp_nonshared.a.
isunresolved := symbolsAreUnresolved(ctxt, []string{"__stack_chk_fail_local"})
if isunresolved[0] {
if p := ctxt.findLibPath("libc_nonshared.a"); p != "none" {
hostArchive(ctxt, p)
}
if p := ctxt.findLibPath("libssp_nonshared.a"); p != "none" {
hostArchive(ctxt, p)
}
}
}
}
// We've loaded all the code now.
ctxt.Loaded = true
strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
}
// loadWindowsHostArchives loads in host archives and objects when
// doing internal linking on windows. Older toolchains seem to require
// just a single pass through the various archives, but some modern
// toolchains when linking a C program with mingw pass library paths
// multiple times to the linker, e.g. "... -lmingwex -lmingw32 ...
// -lmingwex -lmingw32 ...". To accommodate this behavior, we make two
// passes over the host archives below.
func loadWindowsHostArchives(ctxt *Link) {
any := true
for i := 0; any && i < 2; i++ {
// Link crt2.o (if present) to resolve "atexit" when
// using LLVM-based compilers.
isunresolved := symbolsAreUnresolved(ctxt, []string{"atexit"})
if isunresolved[0] {
if p := ctxt.findLibPath("crt2.o"); p != "none" {
hostObject(ctxt, "crt2", p)
}
}
if *flagRace {
if p := ctxt.findLibPath("libsynchronization.a"); p != "none" {
hostArchive(ctxt, p)
}
}
if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
hostArchive(ctxt, p)
}
if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
hostArchive(ctxt, p)
}
// Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
// (see https://golang.org/issue/23649 for details).
if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
hostArchive(ctxt, p)
}
any = false
undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
if len(undefs) > 0 {
any = true
if ctxt.Debugvlog > 1 {
ctxt.Logf("loadWindowsHostArchives: remaining unresolved is %s [%d] from %s [%d]\n",
ctxt.loader.SymName(undefs[0]), undefs[0],
ctxt.loader.SymName(froms[0]), froms[0])
}
}
}
// If needed, create the __CTOR_LIST__ and __DTOR_LIST__
// symbols (referenced by some of the mingw support library
// routines). Creation of these symbols is normally done by the
// linker if not already present.
want := []string{"__CTOR_LIST__", "__DTOR_LIST__"}
isunresolved := symbolsAreUnresolved(ctxt, want)
for k, w := range want {
if isunresolved[k] {
sb := ctxt.loader.CreateSymForUpdate(w, 0)
sb.SetType(sym.SDATA)
sb.AddUint64(ctxt.Arch, 0)
sb.SetReachable(true)
ctxt.loader.SetAttrSpecial(sb.Sym(), true)
}
}
// Fix up references to DLL import symbols now that we're done
// pulling in new objects.
if err := loadpe.PostProcessImports(); err != nil {
Errorf(nil, "%v", err)
}
// TODO: maybe do something similar to peimporteddlls to collect
// all lib names and try link them all to final exe just like
// libmingwex.a and libmingw32.a:
/*
for:
#cgo windows LDFLAGS: -lmsvcrt -lm
import:
libmsvcrt.a libm.a
*/
}
// loadcgodirectives reads the previously discovered cgo directives, creating
// symbols in preparation for host object loading or use later in the link.
func (ctxt *Link) loadcgodirectives() {
l := ctxt.loader
hostObjSyms := make(map[loader.Sym]struct{})
for _, d := range ctxt.cgodata {
setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
}
ctxt.cgodata = nil
if ctxt.LinkMode == LinkInternal {
// Drop all the cgo_import_static declarations.
// Turns out we won't be needing them.
for symIdx := range hostObjSyms {
if l.SymType(symIdx) == sym.SHOSTOBJ {
// If a symbol was marked both
// cgo_import_static and cgo_import_dynamic,
// then we want to make it cgo_import_dynamic
// now.
su := l.MakeSymbolUpdater(symIdx)
if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
su.SetType(sym.SDYNIMPORT)
} else {
su.SetType(0)
}
}
}
}
}
// Set up flags and special symbols depending on the platform build mode.
// This version works with loader.Loader.
func (ctxt *Link) linksetup() {
switch ctxt.BuildMode {
case BuildModeCShared, BuildModePlugin:
symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
sb := ctxt.loader.MakeSymbolUpdater(symIdx)
sb.SetType(sym.SNOPTRDATA)
sb.AddUint8(1)
case BuildModeCArchive:
symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
sb := ctxt.loader.MakeSymbolUpdater(symIdx)
sb.SetType(sym.SNOPTRDATA)
sb.AddUint8(1)
}
// Recalculate pe parameters now that we have ctxt.LinkMode set.
if ctxt.HeadType == objabi.Hwindows {
Peinit(ctxt)
}
if ctxt.LinkMode == LinkExternal {
// When external linking, we are creating an object file. The
// absolute address is irrelevant.
*FlagTextAddr = 0
}
// If there are no dynamic libraries needed, gcc disables dynamic linking.
// Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
// assumes that a dynamic binary always refers to at least one dynamic library.
// Rather than be a source of test cases for glibc, disable dynamic linking
// the same way that gcc would.
//
// Exception: on OS X, programs such as Shark only work with dynamic
// binaries, so leave it enabled on OS X (Mach-O) binaries.
// Also leave it enabled on Solaris which doesn't support
// statically linked binaries.
if ctxt.BuildMode == BuildModeExe {
if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
*FlagD = true
}
}
if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
sb := ctxt.loader.MakeSymbolUpdater(toc)
sb.SetType(sym.SDYNIMPORT)
}
// The Android Q linker started to complain about underalignment of the our TLS
// section. We don't actually use the section on android, so don't
// generate it.
if buildcfg.GOOS != "android" {
tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
sb := ctxt.loader.MakeSymbolUpdater(tlsg)
// runtime.tlsg is used for external linking on platforms that do not define
// a variable to hold g in assembly (currently only intel).
if sb.Type() == 0 {
sb.SetType(sym.STLSBSS)
sb.SetSize(int64(ctxt.Arch.PtrSize))
} else if sb.Type() != sym.SDYNIMPORT {
Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
}
ctxt.loader.SetAttrReachable(tlsg, true)
ctxt.Tlsg = tlsg
}
var moduledata loader.Sym
var mdsb *loader.SymbolBuilder
if ctxt.BuildMode == BuildModePlugin {
moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
ctxt.loader.SetAttrLocal(moduledata, true)
} else {
moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
}
if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
// If the module (toolchain-speak for "executable or shared
// library") we are linking contains the runtime package, it
// will define the runtime.firstmoduledata symbol and we
// truncate it back to 0 bytes so we can define its entire
// contents in symtab.go:symtab().
mdsb.SetSize(0)
// In addition, on ARM, the runtime depends on the linker
// recording the value of GOARM.
if ctxt.Arch.Family == sys.ARM {
goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
sb := ctxt.loader.MakeSymbolUpdater(goarm)
sb.SetType(sym.SDATA)
sb.SetSize(0)
sb.AddUint8(uint8(buildcfg.GOARM))
}
// Set runtime.disableMemoryProfiling bool if
// runtime.MemProfile is not retained in the binary after
// deadcode (and we're not dynamically linking).
memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
sb.SetType(sym.SDATA)
sb.SetSize(0)
sb.AddUint8(1) // true bool
}
} else {
// If OTOH the module does not contain the runtime package,
// create a local symbol for the moduledata.
moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
ctxt.loader.SetAttrLocal(moduledata, true)
}
// In all cases way we mark the moduledata as noptrdata to hide it from
// the GC.
mdsb.SetType(sym.SNOPTRDATA)
ctxt.loader.SetAttrReachable(moduledata, true)
ctxt.Moduledata = moduledata
if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
sb := ctxt.loader.MakeSymbolUpdater(got)
sb.SetType(sym.SDYNIMPORT)
ctxt.loader.SetAttrReachable(got, true)
}
}
// DWARF-gen and other phases require that the unit Textp slices
// be populated, so that it can walk the functions in each unit.
// Call into the loader to do this (requires that we collect the
// set of internal libraries first). NB: might be simpler if we
// moved isRuntimeDepPkg to cmd/internal and then did the test in
// loader.AssignTextSymbolOrder.
ctxt.Library = postorder(ctxt.Library)
intlibs := []bool{}
for _, lib := range ctxt.Library {
intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
}
ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
}
// mangleTypeSym shortens the names of symbols that represent Go types
// if they are visible in the symbol table.
//
// As the names of these symbols are derived from the string of
// the type, they can run to many kilobytes long. So we shorten
// them using a SHA-1 when the name appears in the final binary.
// This also removes characters that upset external linkers.
//
// These are the symbols that begin with the prefix 'type.' and
// contain run-time type information used by the runtime and reflect
// packages. All Go binaries contain these symbols, but only
// those programs loaded dynamically in multiple parts need these
// symbols to have entries in the symbol table.
func (ctxt *Link) mangleTypeSym() {
if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
return
}
ldr := ctxt.loader
for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
if !ldr.AttrReachable(s) && !ctxt.linkShared {
// If -linkshared, the GCProg generation code may need to reach
// out to the shared library for the type descriptor's data, even
// the type descriptor itself is not actually needed at run time
// (therefore not reachable). We still need to mangle its name,
// so it is consistent with the one stored in the shared library.
continue
}
name := ldr.SymName(s)
newName := typeSymbolMangle(name)
if newName != name {
ldr.SetSymExtname(s, newName)
// When linking against a shared library, the Go object file may
// have reference to the original symbol name whereas the shared
// library provides a symbol with the mangled name. We need to
// copy the payload of mangled to original.
// XXX maybe there is a better way to do this.
dup := ldr.Lookup(newName, ldr.SymVersion(s))
if dup != 0 {
st := ldr.SymType(s)
dt := ldr.SymType(dup)
if st == sym.Sxxx && dt != sym.Sxxx {
ldr.CopySym(dup, s)
}
}
}
}
}
// typeSymbolMangle mangles the given symbol name into something shorter.
//
// Keep the type:. prefix, which parts of the linker (like the
// DWARF generator) know means the symbol is not decodable.
// Leave type:runtime. symbols alone, because other parts of
// the linker manipulates them.
func typeSymbolMangle(name string) string {
isType := strings.HasPrefix(name, "type:")
if !isType && !strings.Contains(name, "@") {
// Issue 58800: instantiated symbols may include a type name, which may contain "@"
return name
}
if strings.HasPrefix(name, "type:runtime.") {
return name
}
if strings.HasPrefix(name, "go:string.") {
// String symbols will be grouped to a single go:string.* symbol.
// No need to mangle individual symbol names.
return name
}
if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529