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cmd/link/internal/ld: rewrite LC_UUID for darwin external links

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When building Go binaries using external linking, rewrite the LC_UUID
Macho load command to replace the content placed there by the external
linker, so as to ensure that we get reproducible builds.

Updates #64947.

Change-Id: I263a89d1a067807404febbc801d4dade33bc3288
Reviewed-on: https://go-review.googlesource.com/c/go/+/586079
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This commit is contained in:
Than McIntosh 2024-05-20 14:52:57 +00:00
parent f9ba2cff22
commit 3bcefa5276
3 changed files with 154 additions and 19 deletions
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55
src/cmd/link/internal/ld/lib.go
View file

@ -1356,6 +1356,8 @@ INSERT AFTER .debug_types;
return path
}
type machoUpdateFunc func(ctxt *Link, exef *os.File, exem *macho.File, outexe string) error
// archive builds a .a archive from the hostobj object files.
func (ctxt *Link) archive() {
if ctxt.BuildMode != BuildModeCArchive {
@ -1969,6 +1971,30 @@ func (ctxt *Link) hostlink() {
ctxt.Logf("%s", out)
}
// Helper for updating a Macho binary in some way (shared between
// dwarf combining and UUID update).
updateMachoOutFile := func(op string, updateFunc machoUpdateFunc) {
// For os.Rename to work reliably, must be in same directory as outfile.
rewrittenOutput := *flagOutfile + "~"
exef, err := os.Open(*flagOutfile)
if err != nil {
Exitf("%s: %s failed: %v", os.Args[0], op, 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 := updateFunc(ctxt, exef, exem, rewrittenOutput); err != nil {
Exitf("%s: %s failed: %v", os.Args[0], op, err)
}
os.Remove(*flagOutfile)
if err := os.Rename(rewrittenOutput, *flagOutfile); err != nil {
Exitf("%s: %v", os.Args[0], err)
}
}
uuidUpdated := false
if combineDwarf {
// Find "dsymutils" and "strip" tools using CC --print-prog-name.
var cc []string
@ -2028,24 +2054,17 @@ func (ctxt *Link) hostlink() {
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)
}
updateMachoOutFile("combining dwarf",
func(ctxt *Link, exef *os.File, exem *macho.File, outexe string) error {
return machoCombineDwarf(ctxt, exef, exem, dsym, outexe)
})
uuidUpdated = true
}
if ctxt.IsDarwin() && !uuidUpdated && *flagBuildid != "" {
updateMachoOutFile("rewriting uuid",
func(ctxt *Link, exef *os.File, exem *macho.File, outexe string) error {
return machoRewriteUuid(ctxt, exef, exem, outexe)
})
}
if ctxt.NeedCodeSign() {
err := machoCodeSign(ctxt, *flagOutfile)