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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"
"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"
"debug/elf"
"debug/macho"
"encoding/base64"
"encoding/binary"
"fmt"
"internal/buildcfg"
"io"
"io/ioutil"
"log"
"os"
"os/exec"
"path/filepath"
"runtime"
"strings"
"sync"
)
// 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
}
// 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)
}
// mkArchVecSym 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
Androiddynld string
Linuxdynld string
Freebsddynld string
Netbsddynld string
Openbsddynld string
Dragonflydynld string
Solarisdynld string
// 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 Elfreloc1,
// 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)
Elfreloc1 func(*Link, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int, int64) bool
ElfrelocSize uint32 // size of an ELF relocation record, must match Elfreloc1.
Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
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)
}
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
Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
)
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)
}
}
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 {
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)
}
elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
ctxt.loader = loader.NewLoader(flags, elfsetstring1, &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 := ctxt.loader.UndefinedRelocTargets(1)
if len(undefs) > 0 {
any = true
}
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)
}
}
}
// We've loaded all the code now.
ctxt.Loaded = true
importcycles()
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 := ctxt.loader.UndefinedRelocTargets(1)
if len(undefs) > 0 {
any = true
}
}
// 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)
}
}
// 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 {
if !strings.HasPrefix(name, "type.") {
return name
}
if strings.HasPrefix(name, "type.runtime.") {
return name
}
if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
return name
}
hash := notsha256.Sum256([]byte(name))
prefix := "type."
if name[5] == '.' {
prefix = "type.."
}
return prefix + base64.StdEncoding.EncodeToString(hash[:6])
}
/*
* look for the next file in an archive.
* adapted from libmach.
*/
func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
if off&1 != 0 {
off++
}
bp.MustSeek(off, 0)
var buf [SAR_HDR]byte
if n, err := io.ReadFull(bp, buf[:]); err != nil {
if n == 0 && err != io.EOF {
return -1
}
return 0
}
a.name = artrim(buf[0:16])
a.date = artrim(buf[16:28])
a.uid = artrim(buf[28:34])
a.gid = artrim(buf[34:40])
a.mode = artrim(buf[40:48])
a.size = artrim(buf[48:58])
a.fmag = artrim(buf[58:60])
arsize := atolwhex(a.size)
if arsize&1 != 0 {
arsize++
}
return arsize + SAR_HDR
}
func loadobjfile(ctxt *Link, lib *sym.Library) {
pkg := objabi.PathToPrefix(lib.Pkg)
if ctxt.Debugvlog > 1 {
ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
}
f, err := bio.Open(lib.File)
if err != nil {
Exitf("cannot open file %s: %v", lib.File, err)
}
defer f.Close()
defer func() {
if pkg == "main" && !lib.Main {
Exitf("%s: not package main", lib.File)
}
}()
for i := 0; i < len(ARMAG); i++ {
if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
continue
}
/* load it as a regular file */
l := f.MustSeek(0, 2)
f.MustSeek(0, 0)
ldobj(ctxt, f, lib, l, lib.File, lib.File)
return
}
/*
* load all the object files from the archive now.
* this gives us sequential file access and keeps us
* from needing to come back later to pick up more
* objects. it breaks the usual C archive model, but
* this is Go, not C. the common case in Go is that
* we need to load all the objects, and then we throw away
* the individual symbols that are unused.
*
* loading every object will also make it possible to
* load foreign objects not referenced by __.PKGDEF.
*/
var arhdr ArHdr
off := f.Offset()
for {
l := nextar(f, off, &arhdr)
if l == 0 {
break
}
if l < 0 {
Exitf("%s: malformed archive", lib.File)
}
off += l
// __.PKGDEF isn't a real Go object file, and it's
// absent in -linkobj builds anyway. Skipping it
// ensures consistency between -linkobj and normal
// build modes.
if arhdr.name == pkgdef {
continue
}
if arhdr.name == "dynimportfail" {
dynimportfail = append(dynimportfail, lib.Pkg)
}
if arhdr.name == "preferlinkext" {
// Ignore this directive if -linkmode has been
// set explicitly.
if ctxt.LinkMode == LinkAuto {
preferlinkext = append(preferlinkext, lib.Pkg)
}
}
// Skip other special (non-object-file) sections that
// build tools may have added. Such sections must have
// short names so that the suffix is not truncated.
if len(arhdr.name) < 16 {
if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
continue
}
}
pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
l = atolwhex(arhdr.size)
ldobj(ctxt, f, lib, l, pname, lib.File)
}
}
type Hostobj struct {
ld func(*Link, *bio.Reader, string, int64, string)
pkg string
pn string
file string
off int64
length int64
}
var hostobj []Hostobj
// These packages can use internal linking mode.
// Others trigger external mode.
var internalpkg = []string{
"crypto/internal/boring",
"crypto/internal/boring/syso",
"crypto/x509",
"net",
"os/user",
"runtime/cgo",
"runtime/race",
"runtime/msan",
"runtime/asan",
}
func ldhostobj(ld func(*Link, *bio.Reader, string, int64, string), headType objabi.HeadType, f *bio.Reader, pkg string, length int64, pn string, file string) *Hostobj {
isinternal := false
for _, intpkg := range internalpkg {
if pkg == intpkg {
isinternal = true
break
}
}
// DragonFly declares errno with __thread, which results in a symbol
// type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
// currently know how to handle TLS relocations, hence we have to
// force external linking for any libraries that link in code that
// uses errno. This can be removed if the Go linker ever supports
// these relocation types.
if headType == objabi.Hdragonfly {
if pkg == "net" || pkg == "os/user" {
isinternal = false
}
}
if !isinternal {
externalobj = true
}
hostobj = append(hostobj, Hostobj{})
h := &hostobj[len(hostobj)-1]
h.ld = ld
h.pkg = pkg
h.pn = pn
h.file = file
h.off = f.Offset()
h.length = length
return h
}
func hostobjs(ctxt *Link) {
if ctxt.LinkMode != LinkInternal {
return
}
var h *Hostobj
for i := 0; i < len(hostobj); i++ {
h = &hostobj[i]
f, err := bio.Open(h.file)
if err != nil {
Exitf("cannot reopen %s: %v", h.pn, err)
}
f.MustSeek(h.off, 0)
if h.ld == nil {
Errorf(nil, "%s: unrecognized object file format", h.pn)
continue
}
h.ld(ctxt, f, h.pkg, h.length, h.pn)
f.Close()
}
}
func hostlinksetup(ctxt *Link) {
if ctxt.LinkMode != LinkExternal {
return
}
// For external link, record that we need to tell the external linker -s,
// and turn off -s internally: the external linker needs the symbol
// information for its final link.
debug_s = *FlagS
*FlagS = false
// create temporary directory and arrange cleanup
if *flagTmpdir == "" {
dir, err := ioutil.TempDir("", "go-link-")
if err != nil {
log.Fatal(err)
}
*flagTmpdir = dir
ownTmpDir = true
AtExit(func() {
os.RemoveAll(*flagTmpdir)
})
}
// change our output to temporary object file
if err := ctxt.Out.Close(); err != nil {
Exitf("error closing output file")
}
mayberemoveoutfile()
p := filepath.Join(*flagTmpdir, "go.o")
if err := ctxt.Out.Open(p); err != nil {
Exitf("cannot create %s: %v", p, err)
}
}
// hostobjCopy creates a copy of the object files in hostobj in a
// temporary directory.
func hostobjCopy() (paths []string) {
var wg sync.WaitGroup
sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
for i, h := range hostobj {
h := h
dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
paths = append(paths, dst)
wg.Add(1)
go func() {
sema <- struct{}{}
defer func() {
<-sema
wg.Done()
}()
f, err := os.Open(h.file)
if err != nil {
Exitf("cannot reopen %s: %v", h.pn, err)
}
defer f.Close()
if _, err := f.Seek(h.off, 0); err != nil {
Exitf("cannot seek %s: %v", h.pn, err)
}
w, err := os.Create(dst)
if err != nil {
Exitf("cannot create %s: %v", dst, err)
}
if _, err := io.CopyN(w, f, h.length); err != nil {
Exitf("cannot write %s: %v", dst, err)
}
if err := w.Close(); err != nil {
Exitf("cannot close %s: %v", dst, err)
}
}()
}
wg.Wait()
return paths
}
// writeGDBLinkerScript creates gcc linker script file in temp
// directory. writeGDBLinkerScript returns created file path.
// The script is used to work around gcc bug
// (see https://golang.org/issue/20183 for details).
func writeGDBLinkerScript() string {
name := "fix_debug_gdb_scripts.ld"
path := filepath.Join(*flagTmpdir, name)
src := `SECTIONS
{
.debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
{
*(.debug_gdb_scripts)
}
}
INSERT AFTER .debug_types;
`
err := ioutil.WriteFile(path, []byte(src), 0666)
if err != nil {
Errorf(nil, "WriteFile %s failed: %v", name, err)
}
return path
}
// archive builds a .a archive from the hostobj object files.
func (ctxt *Link) archive() {
if ctxt.BuildMode != BuildModeCArchive {
return
}
exitIfErrors()
if *flagExtar == "" {
*flagExtar = "ar"
}
mayberemoveoutfile()
// Force the buffer to flush here so that external
// tools will see a complete file.
if err := ctxt.Out.Close(); err != nil {
Exitf("error closing %v", *flagOutfile)
}
argv := []string{*flagExtar, "-q", "-c", "-s"}
if ctxt.HeadType == objabi.Haix {
argv = append(argv, "-X64")
}
argv = append(argv, *flagOutfile)
argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
argv = append(argv, hostobjCopy()...)
if ctxt.Debugvlog != 0 {
ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
}
// If supported, use syscall.Exec() to invoke the archive command,
// which should be the final remaining step needed for the link.
// This will reduce peak RSS for the link (and speed up linking of
// large applications), since when the archive command runs we
// won't be holding onto all of the linker's live memory.
if syscallExecSupported && !ownTmpDir {
runAtExitFuncs()
ctxt.execArchive(argv)
panic("should not get here")
}
// Otherwise invoke 'ar' in the usual way (fork + exec).
if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
Exitf("running %s failed: %v\n%s", argv[0], err, out)
}
}
func (ctxt *Link) hostlink() {
if ctxt.LinkMode != LinkExternal || nerrors > 0 {
return
}
if ctxt.BuildMode == BuildModeCArchive {
return
}
var argv []string
argv = append(argv, ctxt.extld()...)
argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
if *FlagS || debug_s {
if ctxt.HeadType == objabi.Hdarwin {
// Recent versions of macOS print
// ld: warning: option -s is obsolete and being ignored
// so do not pass any arguments.
} else {
argv = append(argv, "-s")
}
}
// On darwin, whether to combine DWARF into executable.
// Only macOS supports unmapped segments such as our __DWARF segment.
combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
switch ctxt.HeadType {
case objabi.Hdarwin:
if combineDwarf {
// Leave room for DWARF combining.
// -headerpad is incompatible with -fembed-bitcode.
argv = append(argv, "-Wl,-headerpad,1144")
}
if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
// -flat_namespace is deprecated on iOS.
// It is useful for supporting plugins. We don't support plugins on iOS.
// -flat_namespace may cause the dynamic linker to hang at forkExec when
// resolving a lazy binding. See issue 38824.
// Force eager resolution to work around.
argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
}
if !combineDwarf {
argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
}
case objabi.Hopenbsd:
argv = append(argv, "-Wl,-nopie")
argv = append(argv, "-pthread")
case objabi.Hwindows:
if windowsgui {
argv = append(argv, "-mwindows")
} else {
argv = append(argv, "-mconsole")
}
// Mark as having awareness of terminal services, to avoid
// ancient compatibility hacks.
argv = append(argv, "-Wl,--tsaware")
// Enable DEP
argv = append(argv, "-Wl,--nxcompat")
argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
case objabi.Haix:
argv = append(argv, "-pthread")
// prevent ld to reorder .text functions to keep the same
// first/last functions for moduledata.
argv = append(argv, "-Wl,-bnoobjreorder")
// mcmodel=large is needed for every gcc generated files, but
// ld still need -bbigtoc in order to allow larger TOC.
argv = append(argv, "-mcmodel=large")
argv = append(argv, "-Wl,-bbigtoc")
}
// Enable/disable ASLR on Windows.
addASLRargs := func(argv []string, val bool) []string {
// Old/ancient versions of GCC support "--dynamicbase" and
// "--high-entropy-va" but don't enable it by default. In
// addition, they don't accept "--disable-dynamicbase" or
// "--no-dynamicbase", so the only way to disable ASLR is to
// not pass any flags at all.
//
// More modern versions of GCC (and also clang) enable ASLR
// by default. With these compilers, however you can turn it
// off if you want using "--disable-dynamicbase" or
// "--no-dynamicbase".
//
// The strategy below is to try using "--disable-dynamicbase";
// if this succeeds, then assume we're working with more
// modern compilers and act accordingly. If it fails, assume
// an ancient compiler with ancient defaults.
var dbopt string
var heopt string
dbon := "--dynamicbase"
heon := "--high-entropy-va"
dboff := "--disable-dynamicbase"
heoff := "--disable-high-entropy-va"
if val {
dbopt = dbon
heopt = heon
} else {
// Test to see whether "--disable-dynamicbase" works.
newer := linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,"+dboff)
if newer {
// Newer compiler, which supports both on/off options.
dbopt = dboff
heopt = heoff
} else {
// older toolchain: we have to say nothing in order to
// get a no-ASLR binary.
dbopt = ""
heopt = ""
}
}
if dbopt != "" {
argv = append(argv, "-Wl,"+dbopt)
}
// enable high-entropy ASLR on 64-bit.
if ctxt.Arch.PtrSize >= 8 && heopt != "" {
argv = append(argv, "-Wl,"+heopt)
}
return argv
}
switch ctxt.BuildMode {
case BuildModeExe:
if ctxt.HeadType == objabi.Hdarwin {
if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
argv = append(argv, "-Wl,-no_pie")
}
}
if *flagRace && ctxt.HeadType == objabi.Hwindows {
// Current windows/amd64 race detector tsan support
// library can't handle PIE mode (see #53539 for more details).
// For now, explicitly disable PIE (since some compilers
// default to it) if -race is in effect.
argv = addASLRargs(argv, false)
}
case BuildModePIE:
switch ctxt.HeadType {
case objabi.Hdarwin, objabi.Haix:
case objabi.Hwindows:
if *flagAslr && *flagRace {
// Current windows/amd64 race detector tsan support
// library can't handle PIE mode (see #53539 for more details).
// Disable alsr if -race in effect.
*flagAslr = false
}
argv = addASLRargs(argv, *flagAslr)
default:
// ELF.
if ctxt.UseRelro() {
argv = append(argv, "-Wl,-z,relro")
}
argv = append(argv, "-pie")
}
case BuildModeCShared:
if ctxt.HeadType == objabi.Hdarwin {
argv = append(argv, "-dynamiclib")
} else {
if ctxt.UseRelro() {
argv = append(argv, "-Wl,-z,relro")
}
argv = append(argv, "-shared")
if ctxt.HeadType == objabi.Hwindows {
argv = addASLRargs(argv, *flagAslr)
} else {
// Pass -z nodelete to mark the shared library as
// non-closeable: a dlclose will do nothing.
argv = append(argv, "-Wl,-z,nodelete")
// Only pass Bsymbolic on non-Windows.
argv = append(argv, "-Wl,-Bsymbolic")
}
}
case BuildModeShared:
if ctxt.UseRelro() {
argv = append(argv, "-Wl,-z,relro")
}
argv = append(argv, "-shared")
case BuildModePlugin:
if ctxt.HeadType == objabi.Hdarwin {
argv = append(argv, "-dynamiclib")
} else {
if ctxt.UseRelro() {
argv = append(argv, "-Wl,-z,relro")
}
argv = append(argv, "-shared")
}
}
var altLinker string
if ctxt.IsELF && ctxt.DynlinkingGo() {
// We force all symbol resolution to be done at program startup
// because lazy PLT resolution can use large amounts of stack at
// times we cannot allow it to do so.
argv = append(argv, "-Wl,-z,now")
// Do not let the host linker generate COPY relocations. These
// can move symbols out of sections that rely on stable offsets
// from the beginning of the section (like sym.STYPE).
argv = append(argv, "-Wl,-z,nocopyreloc")
if buildcfg.GOOS == "android" {
// Use lld to avoid errors from default linker (issue #38838)
altLinker = "lld"
}
if ctxt.Arch.InFamily(sys.ARM, sys.ARM64) && buildcfg.GOOS == "linux" {
// On ARM, the GNU linker will generate COPY relocations
// even with -znocopyreloc set.
// https://sourceware.org/bugzilla/show_bug.cgi?id=19962
//
// On ARM64, the GNU linker will fail instead of
// generating COPY relocations.
//
// In both cases, switch to gold.
altLinker = "gold"
// If gold is not installed, gcc will silently switch
// back to ld.bfd. So we parse the version information
// and provide a useful error if gold is missing.
name, args := flagExtld[0], flagExtld[1:]
args = append(args, "-fuse-ld=gold", "-Wl,--version")
cmd := exec.Command(name, args...)
if out, err := cmd.CombinedOutput(); err == nil {
if !bytes.Contains(out, []byte("GNU gold")) {
log.Fatalf("ARM external linker must be gold (issue #15696), but is not: %s", out)
}
}
}
}
if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
// Switch to ld.bfd on freebsd/arm64.
altLinker = "bfd"
// Provide a useful error if ld.bfd is missing.
name, args := flagExtld[0], flagExtld[1:]
args = append(args, "-fuse-ld=bfd", "-Wl,--version")
cmd := exec.Command(name, args...)
if out, err := cmd.CombinedOutput(); err == nil {
if !bytes.Contains(out, []byte("GNU ld")) {
log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
}
}
}
if altLinker != "" {
argv = append(argv, "-fuse-ld="+altLinker)
}
if ctxt.IsELF && len(buildinfo) > 0 {
argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
}
// On Windows, given -o foo, GCC will append ".exe" to produce
// "foo.exe". We have decided that we want to honor the -o
// option. To make this work, we append a '.' so that GCC
// will decide that the file already has an extension. We
// only want to do this when producing a Windows output file
// on a Windows host.
outopt := *flagOutfile
if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
outopt += "."
}
argv = append(argv, "-o")
argv = append(argv, outopt)
if rpath.val != "" {
argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
}
if *flagInterpreter != "" {
// Many linkers support both -I and the --dynamic-linker flags
// to set the ELF interpreter, but lld only supports
// --dynamic-linker so prefer that (ld on very old Solaris only
// supports -I but that seems less important).
argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
}
// Force global symbols to be exported for dlopen, etc.
if ctxt.IsELF {
argv = append(argv, "-rdynamic")
}
if ctxt.HeadType == objabi.Haix {
fileName := xcoffCreateExportFile(ctxt)
argv = append(argv, "-Wl,-bE:"+fileName)
}
const unusedArguments = "-Qunused-arguments"
if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
argv = append(argv, unusedArguments)
}
const compressDWARF = "-Wl,--compress-debug-sections=zlib"
if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
argv = append(argv, compressDWARF)
}
argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
argv = append(argv, hostobjCopy()...)
if ctxt.HeadType == objabi.Haix {
// We want to have C files after Go files to remove
// trampolines csects made by ld.
argv = append(argv, "-nostartfiles")
argv = append(argv, "/lib/crt0_64.o")
extld := ctxt.extld()
name, args := extld[0], extld[1:]
// Get starting files.
getPathFile := func(file string) string {
args := append(args, "-maix64", "--print-file-name="+file)
out, err := exec.Command(name, args...).CombinedOutput()
if err != nil {
log.Fatalf("running %s failed: %v\n%s", extld, err, out)
}
return strings.Trim(string(out), "\n")
}
// Since GCC version 11, the 64-bit version of GCC starting files
// are now suffixed by "_64". Even under "-maix64" multilib directory
// "crtcxa.o" is 32-bit.
crtcxa := getPathFile("crtcxa_64.o")
if !filepath.IsAbs(crtcxa) {
crtcxa = getPathFile("crtcxa.o")
}
crtdbase := getPathFile("crtdbase_64.o")
if !filepath.IsAbs(crtdbase) {
crtdbase = getPathFile("crtdbase.o")
}
argv = append(argv, crtcxa)
argv = append(argv, crtdbase)
}
if ctxt.linkShared {
seenDirs := make(map[string]bool)
seenLibs := make(map[string]bool)
addshlib := func(path string) {
dir, base := filepath.Split(path)
if !seenDirs[dir] {
argv = append(argv, "-L"+dir)
if !rpath.set {
argv = append(argv, "-Wl,-rpath="+dir)
}
seenDirs[dir] = true
}
base = strings.TrimSuffix(base, ".so")
base = strings.TrimPrefix(base, "lib")
if !seenLibs[base] {
argv = append(argv, "-l"+base)
seenLibs[base] = true
}
}
for _, shlib := range ctxt.Shlibs {
addshlib(shlib.Path)
for _, dep := range shlib.Deps {
if dep == "" {
continue
}
libpath := findshlib(ctxt, dep)
if libpath != "" {
addshlib(libpath)
}
}
}
}
// clang, unlike GCC, passes -rdynamic to the linker
// even when linking with -static, causing a linker
// error when using GNU ld. So take out -rdynamic if
// we added it. We do it in this order, rather than
// only adding -rdynamic later, so that -extldflags
// can override -rdynamic without using -static.
// Similarly for -Wl,--dynamic-linker.
checkStatic := func(arg string) {
if ctxt.IsELF && arg == "-static" {
for i := range argv {
if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
argv[i] = "-static"
}
}
}
}
for _, p := range ldflag {
argv = append(argv, p)
checkStatic(p)
}
// When building a program with the default -buildmode=exe the
// gc compiler generates code requires DT_TEXTREL in a
// position independent executable (PIE). On systems where the
// toolchain creates PIEs by default, and where DT_TEXTREL
// does not work, the resulting programs will not run. See
// issue #17847. To avoid this problem pass -no-pie to the
// toolchain if it is supported.
if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
// GCC uses -no-pie, clang uses -nopie.
for _, nopie := range []string{"-no-pie", "-nopie"} {
if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
argv = append(argv, nopie)
break
}
}
}
for _, p := range flagExtldflags {
argv = append(argv, p)
checkStatic(p)
}
if ctxt.HeadType == objabi.Hwindows {
// Determine which linker we're using. Add in the extldflags in
// case used has specified "-fuse-ld=...".
extld := ctxt.extld()
name, args := extld[0], extld[1:]
args = append(args, flagExtldflags...)
args = append(args, "-Wl,--version")
cmd := exec.Command(name, args...)
usingLLD := false
if out, err := cmd.CombinedOutput(); err == nil {
if bytes.Contains(out, []byte("LLD ")) {
usingLLD = true
}
}
// use gcc linker script to work around gcc bug
// (see https://golang.org/issue/20183 for details).
if !usingLLD {
p := writeGDBLinkerScript()
argv = append(argv, "-Wl,-T,"+p)
}
if *flagRace {
if p := ctxt.findLibPath("libsynchronization.a"); p != "libsynchronization.a" {
argv = append(argv, "-lsynchronization")
}
}
// libmingw32 and libmingwex have some inter-dependencies,
// so must use linker groups.
argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
argv = append(argv, peimporteddlls()...)
}
if ctxt.Debugvlog != 0 {
ctxt.Logf("host link:")
for _, v := range argv {
ctxt.Logf(" %q", v)
}
ctxt.Logf("\n")
}
out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
if err != nil {
Exitf("running %s failed: %v\n%s", argv[0], err, out)
}
// Filter out useless linker warnings caused by bugs outside Go.
// See also cmd/go/internal/work/exec.go's gccld method.
var save [][]byte
var skipLines int
for _, line := range bytes.SplitAfter(out, []byte("\n")) {
// golang.org/issue/26073 - Apple Xcode bug
if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
continue
}
if skipLines > 0 {
skipLines--
continue
}
// Remove TOC overflow warning on AIX.
if bytes.Contains(line, []byte("ld: 0711-783")) {
skipLines = 2
continue
}
save = append(save, line)
}
out = bytes.Join(save, nil)
if len(out) > 0 {
// always print external output even if the command is successful, so that we don't
// swallow linker warnings (see https://golang.org/issue/17935).
if ctxt.IsDarwin() && ctxt.IsAMD64() {
const noPieWarning = "ld: warning: -no_pie is deprecated when targeting new OS versions\n"
if i := bytes.Index(out, []byte(noPieWarning)); i >= 0 {
// swallow -no_pie deprecation warning, issue 54482
out = append(out[:i], out[i+len(noPieWarning):]...)
}
}
ctxt.Logf("%s", out)
}
if combineDwarf {
// Find "dsymutils" and "strip" tools using CC --print-prog-name.
var cc []string
cc = append(cc, ctxt.extld()...)
cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
cc = append(cc, "--print-prog-name", "dsymutil")
out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
if err != nil {
Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
}
dsymutilCmd := strings.TrimSuffix(string(out), "\n")
cc[len(cc)-1] = "strip"
out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
if err != nil {
Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
}
stripCmd := strings.TrimSuffix(string(out), "\n")
dsym := filepath.Join(*flagTmpdir, "go.dwarf")
if out, err := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
}
// Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
// They contain temporary file paths and make the build not reproducible.
if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
}
// Skip combining if `dsymutil` didn't generate a file. See #11994.
if _, err := os.Stat(dsym); os.IsNotExist(err) {
return
}
// For os.Rename to work reliably, must be in same directory as outfile.
combinedOutput := *flagOutfile + "~"
exef, err := os.Open(*flagOutfile)
if err != nil {
Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
}
defer exef.Close()
exem, err := macho.NewFile(exef)
if err != nil {
Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
}
if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
}
os.Remove(*flagOutfile)
if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
Exitf("%s: %v", os.Args[0], err)
}
}
if ctxt.NeedCodeSign() {
err := machoCodeSign(ctxt, *flagOutfile)
if err != nil {
Exitf("%s: code signing failed: %v", os.Args[0], err)
}
}
}
var createTrivialCOnce sync.Once
func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
createTrivialCOnce.Do(func() {
src := filepath.Join(*flagTmpdir, "trivial.c")
if err := ioutil.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
Errorf(nil, "WriteFile trivial.c failed: %v", err)
}
})
flagsWithNextArgSkip := []string{
"-F",
"-l",
"-L",
"-framework",
"-Wl,-framework",
"-Wl,-rpath",
"-Wl,-undefined",
}
flagsWithNextArgKeep := []string{
"-arch",
"-isysroot",
"--sysroot",
"-target",
}
prefixesToKeep := []string{
"-f",
"-m",
"-p",
"-Wl,",
"-arch",
"-isysroot",
"--sysroot",
"-target",
}
flags := hostlinkArchArgs(arch)
keep := false
skip := false
for _, f := range append(flagExtldflags, ldflag...) {
if keep {
flags = append(flags, f)
keep = false
} else if skip {
skip = false
} else if f == "" || f[0] != '-' {
} else if contains(flagsWithNextArgSkip, f) {
skip = true
} else if contains(flagsWithNextArgKeep, f) {
flags = append(flags, f)
keep = true
} else {
for _, p := range prefixesToKeep {
if strings.HasPrefix(f, p) {
flags = append(flags, f)
break
}
}
}
}
if altLinker != "" {
flags = append(flags, "-fuse-ld="+altLinker)
}
flags = append(flags, flag, "trivial.c")
cmd := exec.Command(linker, flags...)
cmd.Dir = *flagTmpdir
cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
out, err := cmd.CombinedOutput()
// GCC says "unrecognized command line option ‘-no-pie’"
// clang says "unknown argument: '-no-pie'"
return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
}
// hostlinkArchArgs returns arguments to pass to the external linker
// based on the architecture.
func hostlinkArchArgs(arch *sys.Arch) []string {
switch arch.Family {
case sys.I386:
return []string{"-m32"}
case sys.AMD64:
if buildcfg.GOOS == "darwin" {
return []string{"-arch", "x86_64", "-m64"}
}
return []string{"-m64"}
case sys.S390X:
return []string{"-m64"}
case sys.ARM:
return []string{"-marm"}
case sys.ARM64:
if buildcfg.GOOS == "darwin" {
return []string{"-arch", "arm64"}
}
case sys.Loong64:
return []string{"-mabi=lp64d"}
case sys.MIPS64:
return []string{"-mabi=64"}
case sys.MIPS:
return []string{"-mabi=32"}
case sys.PPC64:
if buildcfg.GOOS == "aix" {
return []string{"-maix64"}
} else {
return []string{"-m64"}
}
}
return nil
}
var wantHdr = objabi.HeaderString()
// ldobj loads an input object. If it is a host object (an object
// compiled by a non-Go compiler) it returns the Hostobj pointer. If
// it is a Go object, it returns nil.
func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
pkg := objabi.PathToPrefix(lib.Pkg)
eof := f.Offset() + length
start := f.Offset()
c1 := bgetc(f)
c2 := bgetc(f)
c3 := bgetc(f)
c4 := bgetc(f)
f.MustSeek(start, 0)
unit := &sym.CompilationUnit{Lib: lib}
lib.Units = append(lib.Units, unit)
magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
if magic == 0x7f454c46 { // \x7F E L F
ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
if err != nil {
Errorf(nil, "%v", err)
return
}
ehdr.Flags = flags
ctxt.Textp = append(ctxt.Textp, textp...)
}
return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
}
if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
if err != nil {
Errorf(nil, "%v", err)
return
}
ctxt.Textp = append(ctxt.Textp, textp...)
}
return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
}
switch c1<<8 | c2 {
case 0x4c01, // 386
0x6486, // amd64
0xc401, // arm
0x64aa: // arm64
ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
if err != nil {
Errorf(nil, "%v", err)
return
}
if len(rsrc) != 0 {
setpersrc(ctxt, rsrc)
}
ctxt.Textp = append(ctxt.Textp, textp...)
}
return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
}
if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
if err != nil {
Errorf(nil, "%v", err)
return
}
ctxt.Textp = append(ctxt.Textp, textp...)
}
return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
}
if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
// An unrecognized object is just passed to the external linker.
// If we try to read symbols from this object, we will
// report an error at that time.
unknownObjFormat = true
return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
}
/* check the header */
line, err := f.ReadString('\n')
if err != nil {
Errorf(nil, "truncated object file: %s: %v", pn, err)
return nil
}
if !strings.HasPrefix(line, "go object ") {
if strings.HasSuffix(pn, ".go") {
Exitf("%s: uncompiled .go source file", pn)
return nil
}
if line == ctxt.Arch.Name {
// old header format: just $GOOS
Errorf(nil, "%s: stale object file", pn)
return nil
}
Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
return nil
}
// First, check that the basic GOOS, GOARCH, and Version match.
if line != wantHdr {
Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
}
// Skip over exports and other info -- ends with \n!\n.
//
// Note: It's possible for "\n!\n" to appear within the binary
// package export data format. To avoid truncating the package
// definition prematurely (issue 21703), we keep track of
// how many "$$" delimiters we've seen.
import0 := f.Offset()
c1 = '\n' // the last line ended in \n
c2 = bgetc(f)
c3 = bgetc(f)
markers := 0
for {
if c1 == '\n' {
if markers%2 == 0 && c2 == '!' && c3 == '\n' {
break
}
if c2 == '$' && c3 == '$' {
markers++
}
}
c1 = c2
c2 = c3
c3 = bgetc(f)
if c3 == -1 {
Errorf(nil, "truncated object file: %s", pn)
return nil
}
}
import1 := f.Offset()
f.MustSeek(import0, 0)
ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
f.MustSeek(import1, 0)
fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
// Check fingerprint, to ensure the importing and imported packages
// have consistent view of symbol indices.
// Normally the go command should ensure this. But in case something
// goes wrong, it could lead to obscure bugs like run-time crash.
// Check it here to be sure.
if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
lib.Fingerprint = fingerprint
}
checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
}
addImports(ctxt, lib, pn)
return nil
}
// symbolsAreUnresolved scans through the loader's list of unresolved
// symbols and checks to see whether any of them match the names of the
// symbols in 'want'. Return value is a list of bools, with list[K] set
// to true if there is an unresolved reference to the symbol in want[K].
func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
returnAllUndefs := -1
undefs := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
seen := make(map[loader.Sym]struct{})
rval := make([]bool, len(want))
wantm := make(map[string]int)
for k, w := range want {
wantm[w] = k
}
count := 0
for _, s := range undefs {
if _, ok := seen[s]; ok {
continue
}
seen[s] = struct{}{}
if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
rval[k] = true
count++
if count == len(want) {
return rval
}
}
}
return rval
}
// hostObject reads a single host object file (compare to "hostArchive").
// This is used as part of internal linking when we need to pull in
// files such as "crt?.o".
func hostObject(ctxt *Link, objname string, path string) {
if ctxt.Debugvlog > 1 {
ctxt.Logf("hostObject(%s)\n", path)
}
objlib := sym.Library{
Pkg: objname,
}
f, err := bio.Open(path)
if err != nil {
Exitf("cannot open host object %q file %s: %v", objname, path, err)
}
defer f.Close()
h := ldobj(ctxt, f, &objlib, 0, path, path)
if h.ld == nil {
Exitf("unrecognized object file format in %s", path)
}
f.MustSeek(h.off, 0)
h.ld(ctxt, f, h.pkg, h.length, h.pn)
}
func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
if libfp != srcfp {
Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
}
}
func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
data := make([]byte, sym.Size)
sect := f.Sections[sym.Section]
if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
Errorf(nil, "reading %s from non-data section", sym.Name)
}
n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
if uint64(n) != sym.Size {
Errorf(nil, "reading contents of %s: %v", sym.Name, err)
}
return data
}
func readwithpad(r io.Reader, sz int32) ([]byte, error) {
data := make([]byte, Rnd(int64(sz), 4))
_, err := io.ReadFull(r, data)
if err != nil {
return nil, err
}
data = data[:sz]
return data, nil
}
func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
for _, sect := range f.Sections {
if sect.Type != elf.SHT_NOTE {
continue
}
r := sect.Open()
for {
var namesize, descsize, noteType int32
err := binary.Read(r, f.ByteOrder, &namesize)
if err != nil {
if err == io.EOF {
break
}
return nil, fmt.Errorf("read namesize failed: %v", err)
}
err = binary.Read(r, f.ByteOrder, &descsize)
if err != nil {
return nil, fmt.Errorf("read descsize failed: %v", err)
}
err = binary.Read(r, f.ByteOrder, ¬eType)
if err != nil {
return nil, fmt.Errorf("read type failed: %v", err)
}
noteName, err := readwithpad(r, namesize)
if err != nil {
return nil, fmt.Errorf("read name failed: %v", err)
}
desc, err := readwithpad(r, descsize)
if err != nil {
return nil, fmt.Errorf("read desc failed: %v", err)
}
if string(name) == string(noteName) && typ == noteType {
return desc, nil
}
}
}
return nil, nil
}
func findshlib(ctxt *Link, shlib string) string {
if filepath.IsAbs(shlib) {
return shlib
}
for _, libdir := range ctxt.Libdir {
libpath := filepath.Join(libdir, shlib)
if _, err := os.Stat(libpath); err == nil {
return libpath
}
}
Errorf(nil, "cannot find shared library: %s", shlib)
return ""
}
func ldshlibsyms(ctxt *Link, shlib string) {
var libpath string
if filepath.IsAbs(shlib) {
libpath = shlib
shlib = filepath.Base(shlib)
} else {
libpath = findshlib(ctxt, shlib)
if libpath == "" {
return
}
}
for _, processedlib := range ctxt.Shlibs {
if processedlib.Path == libpath {
return
}
}
if ctxt.Debugvlog > 1 {
ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
}
f, err := elf.Open(libpath)
if err != nil {
Errorf(nil, "cannot open shared library: %s", libpath)
return
}
// Keep the file open as decodetypeGcprog needs to read from it.
// TODO: fix. Maybe mmap the file.
//defer f.Close()
hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
if err != nil {
Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
return
}
depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
if err != nil {
Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
return
}
var deps []string
for _, dep := range strings.Split(string(depsbytes), "\n") {
if dep == "" {
continue
}
if !filepath.IsAbs(dep) {
// If the dep can be interpreted as a path relative to the shlib
// in which it was found, do that. Otherwise, we will leave it
// to be resolved by libdir lookup.
abs := filepath.Join(filepath.Dir(libpath), dep)
if _, err := os.Stat(abs); err == nil {
dep = abs
}
}
deps = append(deps, dep)
}
syms, err := f.DynamicSymbols()
if err != nil {
Errorf(nil, "cannot read symbols from shared library: %s", libpath)
return
}
for _, elfsym := range syms {
if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
continue
}
// Symbols whose names start with "type." are compiler
// generated, so make functions with that prefix internal.
ver := 0
symname := elfsym.Name // (unmangled) symbol name
if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type.") {
ver = abiInternalVer
} else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
// Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
if strings.HasSuffix(elfsym.Name, ".abiinternal") {
ver = sym.SymVerABIInternal
symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
} else if strings.HasSuffix(elfsym.Name, ".abi0") {
ver = 0
symname = strings.TrimSuffix(elfsym.Name, ".abi0")
}
}
l := ctxt.loader
s := l.LookupOrCreateSym(symname, ver)
// Because loadlib above loads all .a files before loading
// any shared libraries, any non-dynimport symbols we find
// that duplicate symbols already loaded should be ignored
// (the symbols from the .a files "win").
if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
continue
}
su := l.MakeSymbolUpdater(s)
su.SetType(sym.SDYNIMPORT)
l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
su.SetSize(int64(elfsym.Size))
if elfsym.Section != elf.SHN_UNDEF {
// Set .File for the library that actually defines the symbol.
l.SetSymPkg(s, libpath)
// The decodetype_* functions in decodetype.go need access to
// the type data.
sname := l.SymName(s)
if strings.HasPrefix(sname, "type.") && !strings.HasPrefix(sname, "type..") {
su.SetData(readelfsymboldata(ctxt, f, &elfsym))
}
}
if symname != elfsym.Name {
l.SetSymExtname(s, elfsym.Name)
}
}
ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
}
func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
sect := ldr.NewSection()
sect.Rwx = uint8(rwx)
sect.Name = name
sect.Seg = seg
sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
seg.Sections = append(seg.Sections, sect)
return sect
}
func usage() {
fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
objabi.Flagprint(os.Stderr)
Exit(2)
}
type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
const (
// see also https://9p.io/magic/man2html/1/nm
TextSym SymbolType = 'T'
DataSym SymbolType = 'D'
BSSSym SymbolType = 'B'
UndefinedSym SymbolType = 'U'
TLSSym SymbolType = 't'
FrameSym SymbolType = 'm'
ParamSym SymbolType = 'p'
AutoSym SymbolType = 'a'
// Deleted auto (not a real sym, just placeholder for type)
DeletedAutoSym = 'x'
)
// defineInternal defines a symbol used internally by the go runtime.
func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
s := ctxt.loader.CreateSymForUpdate(p, 0)
s.SetType(t)
s.SetSpecial(true)
s.SetLocal(true)
return s.Sym()
}
func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
s := ctxt.defineInternal(p, t)
ctxt.loader.SetSymValue(s, v)
return s
}
func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
if uint64(addr) >= Segdata.Vaddr {
return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
}
if uint64(addr) >= Segtext.Vaddr {
return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
}
ldr.Errorf(s, "invalid datoff %#x", addr)
return 0
}
func Entryvalue(ctxt *Link) int64 {
a := *flagEntrySymbol
if a[0] >= '0' && a[0] <= '9' {
return atolwhex(a)
}
ldr := ctxt.loader
s := ldr.Lookup(a, 0)
st := ldr.SymType(s)
if st == 0 {
return *FlagTextAddr
}
if !ctxt.IsAIX() && st != sym.STEXT {
ldr.Errorf(s, "entry not text")
}
return ldr.SymValue(s)
}
func (ctxt *Link) callgraph() {
if !*FlagC {
return
}
ldr := ctxt.loader
for _, s := range ctxt.Textp {
relocs := ldr.Relocs(s)
for i := 0; i < relocs.Count(); i++ {
r := relocs.At(i)
rs := r.Sym()
if rs == 0 {
continue
}
if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
}
}
}
}
func Rnd(v int64, r int64) int64 {
if r <= 0 {
return v
}
v += r - 1
c := v % r
if c < 0 {
c += r
}
v -= c
return v
}
func bgetc(r *bio.Reader) int {
c, err := r.ReadByte()
if err != nil {
if err != io.EOF {
log.Fatalf("reading input: %v", err)
}
return -1
}
return int(c)
}
type markKind uint8 // for postorder traversal
const (
_ markKind = iota
visiting
visited
)
func postorder(libs []*sym.Library) []*sym.Library {
order := make([]*sym.Library, 0, len(libs)) // hold the result
mark := make(map[*sym.Library]markKind, len(libs))
for _, lib := range libs {
dfs(lib, mark, &order)
}
return order
}
func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
if mark[lib] == visited {
return
}
if mark[lib] == visiting {
panic("found import cycle while visiting " + lib.Pkg)
}
mark[lib] = visiting
for _, i := range lib.Imports {
dfs(i, mark, order)
}
mark[lib] = visited
*order = append(*order, lib)
}
func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
// If putelfsym created a local version of this symbol, use that in all
// relocations.
les := ctxt.loader.SymLocalElfSym(s)
if les != 0 {
return les
} else {
return ctxt.loader.SymElfSym(s)
}
}
func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
if ldr.SymGot(s) >= 0 {
return
}
Adddynsym(ldr, target, syms, s)
got := ldr.MakeSymbolUpdater(syms.GOT)
ldr.SetGot(s, int32(got.Size()))
got.AddUint(target.Arch, 0)
if target.IsElf() {
if target.Arch.PtrSize == 8 {
rela := ldr.MakeSymbolUpdater(syms.Rela)
rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
rela.AddUint64(target.Arch, 0)
} else {
rel := ldr.MakeSymbolUpdater(syms.Rel)
rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
}
} else if target.IsDarwin() {
leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
if target.IsPIE() && target.IsInternal() {
// Mach-O relocations are a royal pain to lay out.
// They use a compact stateful bytecode representation.
// Here we record what are needed and encode them later.
MachoAddBind(int64(ldr.SymGot(s)), s)
}
} else {
ldr.Errorf(s, "addgotsym: unsupported binary format")
}
}
Zerion Mini Shell 1.0