cmd/link: merge note sections into one segment

The ld from binutils merges note sections into one PT_NOTE
segment.
We should do that for consistency with binutils.

Change-Id: I45703525c720972d49c36c4f10ac47d1628b5698
Reviewed-on: https://go-review.googlesource.com/c/go/+/265957
Trust: Meng Zhuo <mzh@golangcn.org>
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
Run-TryBot: Meng Zhuo <mzh@golangcn.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

diff --git a/src/cmd/link/elf_test.go b/src/cmd/link/elf_test.go
index 012c0b51696f8ddfcaae71d48ae8ba5ae315215e..760d9ea60d92d53555a271800350dcc3988ab1a0 100644 (file)
--- a/src/cmd/link/elf_test.go
+++ b/src/cmd/link/elf_test.go
@@ -201,6 +201,61 @@ func TestMinusRSymsWithSameName(t *testing.T) {
        }
 }
 
+func TestMergeNoteSections(t *testing.T) {
+       testenv.MustHaveGoBuild(t)
+       expected := 1
+
+       switch runtime.GOOS {
+       case "linux", "freebsd", "dragonfly":
+       case "openbsd", "netbsd":
+               // These OSes require independent segment
+               expected = 2
+       default:
+               t.Skip("We should only test on elf output.")
+       }
+       t.Parallel()
+
+       goFile := filepath.Join(t.TempDir(), "notes.go")
+       if err := ioutil.WriteFile(goFile, []byte(goSource), 0444); err != nil {
+               t.Fatal(err)
+       }
+       outFile := filepath.Join(t.TempDir(), "notes.exe")
+       goTool := testenv.GoToolPath(t)
+       // sha1sum of "gopher"
+       id := "0xf4e8cd51ce8bae2996dc3b74639cdeaa1f7fee5f"
+       cmd := exec.Command(goTool, "build", "-o", outFile, "-ldflags",
+               "-B "+id, goFile)
+       cmd.Dir = t.TempDir()
+       if out, err := cmd.CombinedOutput(); err != nil {
+               t.Logf("%s", out)
+               t.Fatal(err)
+       }
+
+       ef, err := elf.Open(outFile)
+       if err != nil {
+               t.Fatalf("open elf file failed:%v", err)
+       }
+       defer ef.Close()
+       sec := ef.Section(".note.gnu.build-id")
+       if sec == nil {
+               t.Fatalf("can't find gnu build id")
+       }
+
+       sec = ef.Section(".note.go.buildid")
+       if sec == nil {
+               t.Fatalf("can't find go build id")
+       }
+       cnt := 0
+       for _, ph := range ef.Progs {
+               if ph.Type == elf.PT_NOTE {
+                       cnt += 1
+               }
+       }
+       if cnt != expected {
+               t.Fatalf("want %d PT_NOTE segment, got %d", expected, cnt)
+       }
+}
+
 const pieSourceTemplate = `
 package main
 

diff --git a/src/cmd/link/internal/ld/elf.go b/src/cmd/link/internal/ld/elf.go
index fb75c761a14cbc68dee095ba51d34c776821357c..4a143dfcaa10acfdd2088baf6e26a25368864982 100644 (file)
--- a/src/cmd/link/internal/ld/elf.go
+++ b/src/cmd/link/internal/ld/elf.go
@@ -1682,13 +1682,18 @@ func asmbElf(ctxt *Link) {
 
        var pph *ElfPhdr
        var pnote *ElfPhdr
+       getpnote := func() *ElfPhdr {
+               if pnote == nil {
+                       pnote = newElfPhdr()
+                       pnote.Type = elf.PT_NOTE
+                       pnote.Flags = elf.PF_R
+               }
+               return pnote
+       }
        if *flagRace && ctxt.IsNetbsd() {
                sh := elfshname(".note.netbsd.pax")
                resoff -= int64(elfnetbsdpax(sh, uint64(startva), uint64(resoff)))
-               pnote = newElfPhdr()
-               pnote.Type = elf.PT_NOTE
-               pnote.Flags = elf.PF_R
-               phsh(pnote, sh)
+               phsh(getpnote(), sh)
        }
        if ctxt.LinkMode == LinkExternal {
                /* skip program headers */
@@ -1787,7 +1792,6 @@ func asmbElf(ctxt *Link) {
                phsh(ph, sh)
        }
 
-       pnote = nil
        if ctxt.HeadType == objabi.Hnetbsd || ctxt.HeadType == objabi.Hopenbsd {
                var sh *ElfShdr
                switch ctxt.HeadType {
@@ -1799,34 +1803,23 @@ func asmbElf(ctxt *Link) {
                        sh = elfshname(".note.openbsd.ident")
                        resoff -= int64(elfopenbsdsig(sh, uint64(startva), uint64(resoff)))
                }
-
-               pnote = newElfPhdr()
-               pnote.Type = elf.PT_NOTE
-               pnote.Flags = elf.PF_R
-               phsh(pnote, sh)
+               // netbsd and openbsd require ident in an independent segment.
+               pnotei := newElfPhdr()
+               pnotei.Type = elf.PT_NOTE
+               pnotei.Flags = elf.PF_R
+               phsh(pnotei, sh)
        }
 
        if len(buildinfo) > 0 {
                sh := elfshname(".note.gnu.build-id")
                resoff -= int64(elfbuildinfo(sh, uint64(startva), uint64(resoff)))
-
-               if pnote == nil {
-                       pnote = newElfPhdr()
-                       pnote.Type = elf.PT_NOTE
-                       pnote.Flags = elf.PF_R
-               }
-
-               phsh(pnote, sh)
+               phsh(getpnote(), sh)
        }
 
        if *flagBuildid != "" {
                sh := elfshname(".note.go.buildid")
                resoff -= int64(elfgobuildid(sh, uint64(startva), uint64(resoff)))
-
-               pnote := newElfPhdr()
-               pnote.Type = elf.PT_NOTE
-               pnote.Flags = elf.PF_R
-               phsh(pnote, sh)
+               phsh(getpnote(), sh)
        }
 
        // Additions to the reserved area must be above this line.