cmd/link: avoid duplicate DT_NEEDED entries

When adding a new library entry, ensure we record it as seen to avoid
adding duplicates of it.

Fixes #39256

Change-Id: Id309adf80c533d78fd485517c18bc9ab5f1d29fb
Reviewed-on: https://go-review.googlesource.com/c/go/+/235257
Run-TryBot: Joel Sing <joel@sing.id.au>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

diff --git a/src/cmd/link/internal/ld/elf.go b/src/cmd/link/internal/ld/elf.go
index 957f5081f67a615a113d51b2bd82a0988a03b4d8..2862f65f9f3a906aff01ab7ca830d3a367e405fc 100644 (file)
--- a/src/cmd/link/internal/ld/elf.go
+++ b/src/cmd/link/internal/ld/elf.go
@@ -2378,6 +2378,7 @@ func elfadddynsym(ldr *loader.Loader, target *Target, syms *ArchSyms, s loader.S
                if target.Arch.Family == sys.AMD64 && !cgoeDynamic && dil != "" && !seenlib[dil] {
                        du := ldr.MakeSymbolUpdater(syms.Dynamic)
                        Elfwritedynent(target.Arch, du, DT_NEEDED, uint64(dstru.Addstring(dil)))
+                       seenlib[dil] = true
                }
        } else {
 

diff --git a/src/cmd/link/internal/ld/elf_test.go b/src/cmd/link/internal/ld/elf_test.go
index 8e86beb1ec79dc7694abec5a831f298348b72369..37f0e77336b2f5047b1bd9ca2c9277055a0e828f 100644 (file)
--- a/src/cmd/link/internal/ld/elf_test.go
+++ b/src/cmd/link/internal/ld/elf_test.go
@@ -13,6 +13,7 @@ import (
        "os"
        "os/exec"
        "path/filepath"
+       "runtime"
        "testing"
 )
 
@@ -77,3 +78,57 @@ func main() {
                t.Fatalf("Unexpected sh info, want greater than 0, got: %d", section.Info)
        }
 }
+
+func TestNoDuplicateNeededEntries(t *testing.T) {
+       testenv.MustHaveGoBuild(t)
+       testenv.MustHaveCGO(t)
+
+       // run this test on just a small set of platforms (no need to test it
+       // across the board given the nature of the test).
+       pair := runtime.GOOS + "-" + runtime.GOARCH
+       switch pair {
+       case "linux-amd64", "freebsd-amd64", "openbsd-amd64":
+       default:
+               t.Skip("no need for test on " + pair)
+       }
+
+       t.Parallel()
+
+       dir, err := ioutil.TempDir("", "no-dup-needed")
+       if err != nil {
+               t.Fatalf("Failed to create temp dir: %v", err)
+       }
+       defer os.RemoveAll(dir)
+
+       wd, err := os.Getwd()
+       if err != nil {
+               t.Fatalf("Failed to get working directory: %v", err)
+       }
+
+       path := filepath.Join(dir, "x")
+       argv := []string{"build", "-o", path, filepath.Join(wd, "testdata", "issue39256")}
+       out, err := exec.Command(testenv.GoToolPath(t), argv...).CombinedOutput()
+       if err != nil {
+               t.Fatalf("Build failure: %s\n%s\n", err, string(out))
+       }
+
+       f, err := elf.Open(path)
+       if err != nil {
+               t.Fatalf("Failed to open ELF file: %v", err)
+       }
+       libs, err := f.ImportedLibraries()
+       if err != nil {
+               t.Fatalf("Failed to read imported libraries: %v", err)
+       }
+
+       var count int
+       for _, lib := range libs {
+               if lib == "libc.so" {
+                       count++
+               }
+       }
+
+       if got, want := count, 1; got != want {
+               t.Errorf("Got %d entries for `libc.so`, want %d", got, want)
+       }
+}

diff --git a/src/cmd/link/internal/ld/testdata/issue39256/x.go b/src/cmd/link/internal/ld/testdata/issue39256/x.go
new file mode 100644 (file)
index 0000000..d8562ad
--- /dev/null
+++ b/src/cmd/link/internal/ld/testdata/issue39256/x.go
@@ -0,0 +1,20 @@
+// Copyright 2020 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 main
+
+import (
+       _ "unsafe"
+)
+
+//go:cgo_import_dynamic libc_getpid getpid "libc.so"
+//go:cgo_import_dynamic libc_kill kill "libc.so"
+//go:cgo_import_dynamic libc_close close "libc.so"
+//go:cgo_import_dynamic libc_open open "libc.so"
+
+func trampoline()
+
+func main() {
+       trampoline()
+}

diff --git a/src/cmd/link/internal/ld/testdata/issue39256/x.s b/src/cmd/link/internal/ld/testdata/issue39256/x.s
new file mode 100644 (file)
index 0000000..41a54b2
--- /dev/null
+++ b/src/cmd/link/internal/ld/testdata/issue39256/x.s
@@ -0,0 +1,10 @@
+// Copyright 2020 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.
+
+TEXT ·trampoline(SB),0,$0
+       CALL    libc_getpid(SB)
+       CALL    libc_kill(SB)
+       CALL    libc_open(SB)
+       CALL    libc_close(SB)
+       RET