diff --git a/src/cmd/link/internal/ld/elf.go b/src/cmd/link/internal/ld/elf.go
index be9e22946a38684287b7e839e59c53b391dc1735..79fa0f4bbdeb4945fb764b9a01f9ea4d8d9e1c8e 100644
--- a/src/cmd/link/internal/ld/elf.go
+++ b/src/cmd/link/internal/ld/elf.go
@@ -805,13 +805,19 @@ func elfwritefreebsdsig(out *OutBuf) int {
return int(sh.Size)
}
-func addbuildinfo(val string) {
+func addbuildinfo(ctxt *Link) {
+ val := *flagHostBuildid
if val == "gobuildid" {
buildID := *flagBuildid
if buildID == "" {
Exitf("-B gobuildid requires a Go build ID supplied via -buildid")
}
+ if ctxt.IsDarwin() {
+ buildinfo = uuidFromGoBuildId(buildID)
+ return
+ }
+
hashedBuildID := notsha256.Sum256([]byte(buildID))
buildinfo = hashedBuildID[:20]
@@ -821,11 +827,13 @@ func addbuildinfo(val string) {
if !strings.HasPrefix(val, "0x") {
Exitf("-B argument must start with 0x: %s", val)
}
-
ov := val
val = val[2:]
- const maxLen = 32
+ maxLen := 32
+ if ctxt.IsDarwin() {
+ maxLen = 16
+ }
if hex.DecodedLen(len(val)) > maxLen {
Exitf("-B option too long (max %d digits): %s", maxLen, ov)
}
diff --git a/src/cmd/link/internal/ld/macho.go b/src/cmd/link/internal/ld/macho.go
index a36043c777a2c320aa6873cc78917775bc1a6945..9f64f26592c15d381f0565cc77756996f3404946 100644
--- a/src/cmd/link/internal/ld/macho.go
+++ b/src/cmd/link/internal/ld/macho.go
@@ -296,6 +296,8 @@ func getMachoHdr() *MachoHdr {
return &machohdr
}
+// Create a new Mach-O load command. ndata is the number of 32-bit words for
+// the data (not including the load command header).
func newMachoLoad(arch *sys.Arch, type_ uint32, ndata uint32) *MachoLoad {
if arch.PtrSize == 8 && (ndata&1 != 0) {
ndata++
@@ -850,6 +852,20 @@ func asmbMacho(ctxt *Link) {
}
}
+ if ctxt.IsInternal() && len(buildinfo) > 0 {
+ ml := newMachoLoad(ctxt.Arch, LC_UUID, 4)
+ // Mach-O UUID is 16 bytes
+ if len(buildinfo) < 16 {
+ buildinfo = append(buildinfo, make([]byte, 16)...)
+ }
+ // By default, buildinfo is already in UUIDv3 format
+ // (see uuidFromGoBuildId).
+ ml.data[0] = ctxt.Arch.ByteOrder.Uint32(buildinfo)
+ ml.data[1] = ctxt.Arch.ByteOrder.Uint32(buildinfo[4:])
+ ml.data[2] = ctxt.Arch.ByteOrder.Uint32(buildinfo[8:])
+ ml.data[3] = ctxt.Arch.ByteOrder.Uint32(buildinfo[12:])
+ }
+
if ctxt.IsInternal() && ctxt.NeedCodeSign() {
ml := newMachoLoad(ctxt.Arch, LC_CODE_SIGNATURE, 2)
ml.data[0] = uint32(codesigOff)
diff --git a/src/cmd/link/internal/ld/macho_update_uuid.go b/src/cmd/link/internal/ld/macho_update_uuid.go
new file mode 100644
index 0000000000000000000000000000000000000000..14c03064be115883eac174217404b3669749d7b3
--- /dev/null
+++ b/src/cmd/link/internal/ld/macho_update_uuid.go
@@ -0,0 +1,47 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ld
+
+// This file provides helper functions for updating/rewriting the UUID
+// load command within a Go go binary generated on Darwin using
+// external linking. Why is it necessary to update the UUID load
+// command? See issue #64947 for more detail, but the short answer is
+// that newer versions of the Macos toolchain (the newer linker in
+// particular) appear to compute the UUID based not just on the
+// content of the object files being linked but also on things like
+// the timestamps/paths of the objects; this makes it
+// difficult/impossible to support reproducible builds. Since we try
+// hard to maintain build reproducibility for Go, the APIs here
+// compute a new UUID (based on the Go build ID) and write it to the
+// final executable generated by the external linker.
+
+import (
+ "cmd/internal/notsha256"
+)
+
+// uuidFromGoBuildId hashes the Go build ID and returns a slice of 16
+// bytes suitable for use as the payload in a Macho LC_UUID load
+// command.
+func uuidFromGoBuildId(buildID string) []byte {
+ if buildID == "" {
+ return make([]byte, 16)
+ }
+ hashedBuildID := notsha256.Sum256([]byte(buildID))
+ rv := hashedBuildID[:16]
+
+ // RFC 4122 conformance (see RFC 4122 Sections 4.2.2, 4.1.3). We
+ // want the "version" of this UUID to appear as 'hashed' as opposed
+ // to random or time-based. This is something of a fiction since
+ // we're not actually hashing using MD5 or SHA1, but it seems better
+ // to use this UUID flavor than any of the others. This is similar
+ // to how other linkers handle this (for example this code in lld:
+ // https://github.com/llvm/llvm-project/blob/2a3a79ce4c2149d7787d56f9841b66cacc9061d0/lld/MachO/Writer.cpp#L524).
+ rv[6] &= 0x0f
+ rv[6] |= 0x30
+ rv[8] &= 0x3f
+ rv[8] |= 0xc0
+
+ return rv
+}
diff --git a/src/cmd/link/internal/ld/main.go b/src/cmd/link/internal/ld/main.go
index feb4ba5c1725f1654a188642791230a4fce700fe..c04608ebd113daaa82fe95f854762ea691d8777a 100644
--- a/src/cmd/link/internal/ld/main.go
+++ b/src/cmd/link/internal/ld/main.go
@@ -93,6 +93,7 @@ var (
flagN = flag.Bool("n", false, "no-op (deprecated)")
FlagS = flag.Bool("s", false, "disable symbol table")
flag8 bool // use 64-bit addresses in symbol table
+ flagHostBuildid = flag.String("B", "", "set ELF NT_GNU_BUILD_ID `note` or Mach-O UUID; use \"gobuildid\" to generate it from the Go build ID")
flagInterpreter = flag.String("I", "", "use `linker` as ELF dynamic linker")
FlagDebugTramp = flag.Int("debugtramp", 0, "debug trampolines")
FlagDebugTextSize = flag.Int("debugtextsize", 0, "debug text section max size")
@@ -190,7 +191,6 @@ func Main(arch *sys.Arch, theArch Arch) {
flag.Var(&ctxt.LinkMode, "linkmode", "set link `mode`")
flag.Var(&ctxt.BuildMode, "buildmode", "set build `mode`")
flag.BoolVar(&ctxt.compressDWARF, "compressdwarf", true, "compress DWARF if possible")
- objabi.Flagfn1("B", "add an ELF NT_GNU_BUILD_ID `note` when using ELF; use \"gobuildid\" to generate it from the Go build ID", addbuildinfo)
objabi.Flagfn1("L", "add specified `directory` to library path", func(a string) { Lflag(ctxt, a) })
objabi.AddVersionFlag() // -V
objabi.Flagfn1("X", "add string value `definition` of the form importpath.name=value", func(s string) { addstrdata1(ctxt, s) })
@@ -287,6 +287,10 @@ func Main(arch *sys.Arch, theArch Arch) {
*flagBuildid = "go-openbsd"
}
+ if *flagHostBuildid != "" {
+ addbuildinfo(ctxt)
+ }
+
// enable benchmarking
var bench *benchmark.Metrics
if len(*benchmarkFlag) != 0 {
diff --git a/test/fixedbugs/issue14636.go b/test/fixedbugs/issue14636.go
index c8e751fb613c2e8120201dc3bd2c7bdd67b24e66..a866c9a9e30e8e7465d50905baf93cb683813d03 100644
--- a/test/fixedbugs/issue14636.go
+++ b/test/fixedbugs/issue14636.go
@@ -12,22 +12,29 @@ import (
"bytes"
"log"
"os/exec"
+ "runtime"
"strings"
)
func main() {
- checkLinkOutput("", "-B argument must start with 0x")
+ // The cannot open file error indicates that the parsing of -B flag
+ // succeeded and it failed at a later step.
checkLinkOutput("0", "-B argument must start with 0x")
- checkLinkOutput("0x", "usage")
+ checkLinkOutput("0x", "cannot open file nonexistent.o")
checkLinkOutput("0x0", "-B argument must have even number of digits")
- checkLinkOutput("0x00", "usage")
+ checkLinkOutput("0x00", "cannot open file nonexistent.o")
checkLinkOutput("0xYZ", "-B argument contains invalid hex digit")
- checkLinkOutput("0x"+strings.Repeat("00", 32), "usage")
- checkLinkOutput("0x"+strings.Repeat("00", 33), "-B option too long (max 32 digits)")
+
+ maxLen := 32
+ if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
+ maxLen = 16
+ }
+ checkLinkOutput("0x"+strings.Repeat("00", maxLen), "cannot open file nonexistent.o")
+ checkLinkOutput("0x"+strings.Repeat("00", maxLen+1), "-B option too long")
}
func checkLinkOutput(buildid string, message string) {
- cmd := exec.Command("go", "tool", "link", "-B", buildid)
+ cmd := exec.Command("go", "tool", "link", "-B", buildid, "nonexistent.o")
out, err := cmd.CombinedOutput()
if err == nil {
log.Fatalf("expected cmd/link to fail")
@@ -39,6 +46,6 @@ func checkLinkOutput(buildid string, message string) {
}
if !strings.Contains(firstLine, message) {
- log.Fatalf("cmd/link output did not include expected message %q: %s", message, firstLine)
+ log.Fatalf("%s: cmd/link output did not include expected message %q: %s", buildid, message, firstLine)
}
}