[go] cmd/link: don't update offset of existing ELF section name
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Ian Lance Taylor (Gerrit)
Dec 2, 2025, 8:03:35 PM (8 hours ago) Dec 2
to goph...@pubsubhelper.golang.org, Ian Lance Taylor, golang-co...@googlegroups.com
Ian Lance Taylor has uploaded the change for review![]( "Open in Gerrit")
Commit message
cmd/link: don't update offset of existing ELF section name
Fixes #76656
Change-Id: If2e823ba1577700af00f5883e4ea5c139e4749c1
Change diff
diff --git a/src/cmd/link/elf_test.go b/src/cmd/link/elf_test.go
index f11cc4b..adf255a 100644
--- a/src/cmd/link/elf_test.go
+++ b/src/cmd/link/elf_test.go
@@ -11,6 +11,7 @@
"cmd/internal/hash"
"cmd/link/internal/ld"
"debug/elf"
+ "encoding/binary"
"fmt"
"internal/platform"
"internal/testenv"
@@ -22,6 +23,7 @@
"sync"
"testing"
"text/template"
+ "unsafe"
)
func getCCAndCCFLAGS(t *testing.T, env []string) (string, []string) {
@@ -677,12 +679,23 @@
}
func TestELFHeadersSorted(t *testing.T) {
+ for _, buildmode := range []string{"exe", "pie"} {
+ t.Run(buildmode, func(t *testing.T) {
+ testELFHeadersSorted(t, buildmode)
+ })
+ }
+}
+
+func testELFHeadersSorted(t *testing.T, buildmode string) {
testenv.MustHaveGoBuild(t)
// We can only test this for internal linking mode.
// For external linking the external linker will
// decide how to sort the sections.
testenv.MustInternalLink(t, testenv.NoSpecialBuildTypes)
+ if buildmode == "pie" {
+ testenv.MustInternalLinkPIE(t)
+ }
t.Parallel()
@@ -693,12 +706,71 @@
}
exe := filepath.Join(tmpdir, "x.exe")
- cmd := goCmd(t, "build", "-ldflags=-linkmode=internal", "-o", exe, src)
+ cmd := goCmd(t, "build", "-buildmode="+buildmode, "-ldflags=-linkmode=internal", "-o", exe, src)
if out, err := cmd.CombinedOutput(); err != nil {
t.Fatalf("build failed: %v, output:\n%s", err, out)
}
- ef, err := elf.Open(exe)
+ // Check that the first section header is all zeroes.
+ f, err := os.Open(exe)
+ if err != nil {
+ t.Fatal(err)
+ }
+ defer f.Close()
+
+ var ident [elf.EI_NIDENT]byte
+ if _, err := f.Read(ident[:]); err != nil {
+ t.Fatal(err)
+ }
+
+ var bo binary.ByteOrder
+ switch elf.Data(ident[elf.EI_DATA]) {
+ case elf.ELFDATA2LSB:
+ bo = binary.LittleEndian
+ case elf.ELFDATA2MSB:
+ bo = binary.BigEndian
+ default:
+ t.Fatalf("unrecognized data encoding %d", ident[elf.EI_DATA])
+ }
+
+ var shoff int64
+ var shsize int
+ switch elf.Class(ident[elf.EI_CLASS]) {
+ case elf.ELFCLASS32:
+ var hdr elf.Header32
+ data := make([]byte, unsafe.Sizeof(hdr))
+ if _, err := f.ReadAt(data, 0); err != nil {
+ t.Fatal(err)
+ }
+ shoff = int64(bo.Uint32(data[unsafe.Offsetof(hdr.Shoff):]))
+ shsize = int(unsafe.Sizeof(elf.Section32{}))
+
+ case elf.ELFCLASS64:
+ var hdr elf.Header64
+ data := make([]byte, unsafe.Sizeof(hdr))
+ if _, err := f.ReadAt(data, 0); err != nil {
+ t.Fatal(err)
+ }
+ shoff = int64(bo.Uint64(data[unsafe.Offsetof(hdr.Shoff):]))
+ shsize = int(unsafe.Sizeof(elf.Section64{}))
+
+ default:
+ t.Fatalf("unrecognized class %d", ident[elf.EI_CLASS])
+ }
+
+ if shoff > 0 {
+ data := make([]byte, shsize)
+ if _, err := f.ReadAt(data, shoff); err != nil {
+ t.Fatal(err)
+ }
+ for i, c := range data {
+ if c != 0 {
+ t.Errorf("section header 0 byte %d is %d, should be zero", i, c)
+ }
+ }
+ }
+
+ ef, err := elf.NewFile(f)
if err != nil {
t.Fatal(err)
}
diff --git a/src/cmd/link/internal/ld/elf.go b/src/cmd/link/internal/ld/elf.go
index c948022..12218fe 100644
--- a/src/cmd/link/internal/ld/elf.go
+++ b/src/cmd/link/internal/ld/elf.go
@@ -434,7 +434,9 @@
// are likely to be the only match.
for _, sh := range shdr {
if suffix, ok := strings.CutPrefix(sh.nameString, elfRelType); ok {
- m[suffix] = off + uint32(len(elfRelType))
+ if _, found := m[suffix]; !found {
+ m[suffix] = off + uint32(len(elfRelType))
+ }
writeString(sh.nameString)
}
}
Change information
Files:
- M src/cmd/link/elf_test.go
- M src/cmd/link/internal/ld/elf.go
Change size: M
Delta: 2 files changed, 77 insertions(+), 3 deletions(-)
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Keith Randall (Gerrit)
Dec 2, 2025, 8:16:38 PM (7 hours ago) Dec 2
to Ian Lance Taylor, goph...@pubsubhelper.golang.org, Keith Randall, Cherry Mui, Russ Cox, Than McIntosh, Gopher Robot, Go LUCI, golang-co...@googlegroups.com
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Keith Randall voted Code-Review+2![]( "Open in Gerrit")
| Code-Review | +2 |
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Keith Randall (Gerrit)
Dec 2, 2025, 8:16:56 PM (7 hours ago) Dec 2
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Michael Stapelberg (Gerrit)
3:21 AM (24 minutes ago) 3:21 AM
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Gopher Robot (Gerrit)
3:22 AM (22 minutes ago) 3:22 AM
to Ian Lance Taylor, goph...@pubsubhelper.golang.org, golang-...@googlegroups.com, Michael Stapelberg, Go LUCI, Keith Randall, Keith Randall, Cherry Mui, Russ Cox, Than McIntosh, golang-co...@googlegroups.com
Gopher Robot submitted the change![]( "Open in Gerrit")
Change information
Commit message:
cmd/link: don't update offset of existing ELF section name
Fixes #76656
Change-Id: If2e823ba1577700af00f5883e4ea5c139e4749c1
Reviewed-on: https://go-review.googlesource.com/c/go/+/726100
Reviewed-by: Keith Randall <k...@golang.org>
Reviewed-by: Keith Randall <k...@google.com>
Reviewed-by: Michael Stapelberg <stape...@google.com>
Auto-Submit: Ian Lance Taylor <ia...@golang.org>
LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>
Files:
- M src/cmd/link/elf_test.go
- M src/cmd/link/internal/ld/elf.go
Change size: M
Delta: 2 files changed, 77 insertions(+), 3 deletions(-)
Branch: refs/heads/master
Submit Requirements:
Code-Review: +1 by Keith Randall, +2 by Michael Stapelberg, +2 by Keith Randall
TryBots-Pass: LUCI-TryBot-Result+1 by Go LUCI
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