cmd/link: set correct alignment of ELF note section

Otherwise the default computation in symalign kicked in, setting the
alignment to be too high. This didn't matter with GNU ld, which put
each loadable note into a separate PT_NOTE segment, but it did matter
with gold which accumulated them all into a single PT_NOTE segment,
respecting the requested alignment. In the single PT_NOTE segment
generated by gold, the incorrect section alignment made the notes
unreadable.

Fixes #21564

Change-Id: I15eb408bb04a2566c9fdfb6828e14188d9ef2280
Reviewed-on: https://go-review.googlesource.com/58290
Reviewed-by: Russ Cox <rsc@golang.org>

diff --git a/src/cmd/go/note_test.go b/src/cmd/go/note_test.go
index 289af9908a486b48f0181cdea183c73a00c22627..1bbbd0d8a06e4c9468044c59d149f9e173ef45fb 100644 (file)
--- a/src/cmd/go/note_test.go
+++ b/src/cmd/go/note_test.go
@@ -62,4 +62,23 @@ func testNoteReading(t *testing.T) {
        if id != buildID {
                t.Fatalf("buildID in hello binary = %q, want %q (linkmode=external)", id, buildID)
        }
+
+       switch runtime.GOOS {
+       case "dragonfly", "freebsd", "linux", "netbsd", "openbsd":
+               // Test while forcing use of the gold linker, since in the past
+               // we've had trouble reading the notes generated by gold.
+               err := tg.doRun([]string{"build", "-ldflags", "-buildid=" + buildID + " -linkmode=external -extldflags=-fuse-ld=gold", "-o", tg.path("hello.exe"), tg.path("hello.go")})
+               if err != nil && (tg.grepCountBoth("invalid linker") > 0 || tg.grepCountBoth("gold") > 0) {
+                       // It's not an error if gold isn't there.
+                       t.Log("skipping gold test")
+                       break
+               }
+               id, err = buildid.ReadBuildIDFromBinary(tg.path("hello.exe"))
+               if err != nil {
+                       t.Fatalf("reading build ID from hello binary (linkmode=external -extldflags=-fuse-ld=gold): %v", err)
+               }
+               if id != buildID {
+                       t.Fatalf("buildID in hello binary = %q, want %q (linkmode=external -extldflags=-fuse-ld=gold)", id, buildID)
+               }
+       }
 }

diff --git a/src/cmd/link/internal/ld/elf.go b/src/cmd/link/internal/ld/elf.go
index 2c3f99b7568f1898f569b47f38e92a559fad19b7..d6b3cb0927ee6047b5c75d51ed160c248e1a0efa 100644 (file)
--- a/src/cmd/link/internal/ld/elf.go
+++ b/src/cmd/link/internal/ld/elf.go
@@ -1874,6 +1874,7 @@ func addgonote(ctxt *Link, sectionName string, tag uint32, desc []byte) {
                s.P = append(s.P, 0)
        }
        s.Size = int64(len(s.P))
+       s.Align = 4
 }
 
 func (ctxt *Link) doelf() {