diff --git a/src/cmd/link/internal/ld/elf_test.go b/src/cmd/link/internal/ld/elf_test.go index 37f0e77336..776fc1b4f9 100644 --- a/src/cmd/link/internal/ld/elf_test.go +++ b/src/cmd/link/internal/ld/elf_test.go @@ -14,6 +14,7 @@ import ( "os/exec" "path/filepath" "runtime" + "strings" "testing" ) @@ -123,7 +124,7 @@ func TestNoDuplicateNeededEntries(t *testing.T) { var count int for _, lib := range libs { - if lib == "libc.so" { + if lib == "libc.so" || strings.HasPrefix(lib, "libc.so.") { count++ } } diff --git a/src/cmd/link/internal/ld/go.go b/src/cmd/link/internal/ld/go.go index a6cd4c0541..fbc7a78d0e 100644 --- a/src/cmd/link/internal/ld/go.go +++ b/src/cmd/link/internal/ld/go.go @@ -18,6 +18,8 @@ import ( "fmt" "io" "os" + "sort" + "strconv" "strings" ) @@ -289,6 +291,62 @@ func setCgoAttr(ctxt *Link, lookup func(string, int) loader.Sym, file string, pk return } +// openbsdTrimLibVersion indicates whether a shared library is +// versioned and if it is, returns the unversioned name. The +// OpenBSD library naming scheme is lib.so.. +func openbsdTrimLibVersion(lib string) (string, bool) { + parts := strings.Split(lib, ".") + if len(parts) != 4 { + return "", false + } + if parts[1] != "so" { + return "", false + } + if _, err := strconv.Atoi(parts[2]); err != nil { + return "", false + } + if _, err := strconv.Atoi(parts[3]); err != nil { + return "", false + } + return fmt.Sprintf("%s.%s", parts[0], parts[1]), true +} + +// dedupLibrariesOpenBSD dedups a list of shared libraries, treating versioned +// and unversioned libraries as equivalents. Versioned libraries are preferred +// and retained over unversioned libraries. This avoids the situation where +// the use of cgo results in a DT_NEEDED for a versioned library (for example, +// libc.so.96.1), while a dynamic import specifies an unversioned library (for +// example, libc.so) - this would otherwise result in two DT_NEEDED entries +// for the same library, resulting in a failure when ld.so attempts to load +// the Go binary. +func dedupLibrariesOpenBSD(ctxt *Link, libs []string) []string { + libraries := make(map[string]string) + for _, lib := range libs { + if name, ok := openbsdTrimLibVersion(lib); ok { + // Record unversioned name as seen. + seenlib[name] = true + libraries[name] = lib + } else if _, ok := libraries[lib]; !ok { + libraries[lib] = lib + } + } + + libs = nil + for _, lib := range libraries { + libs = append(libs, lib) + } + sort.Strings(libs) + + return libs +} + +func dedupLibraries(ctxt *Link, libs []string) []string { + if ctxt.Target.IsOpenbsd() { + return dedupLibrariesOpenBSD(ctxt, libs) + } + return libs +} + var seenlib = make(map[string]bool) func adddynlib(ctxt *Link, lib string) { @@ -385,7 +443,7 @@ func (ctxt *Link) addexport() { for _, exp := range ctxt.dynexp { Adddynsym(ctxt.loader, &ctxt.Target, &ctxt.ArchSyms, exp) } - for _, lib := range dynlib { + for _, lib := range dedupLibraries(ctxt, dynlib) { adddynlib(ctxt, lib) } } diff --git a/src/cmd/link/internal/ld/go_test.go b/src/cmd/link/internal/ld/go_test.go new file mode 100644 index 0000000000..0197196023 --- /dev/null +++ b/src/cmd/link/internal/ld/go_test.go @@ -0,0 +1,121 @@ +// 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 ld + +import ( + "cmd/internal/objabi" + "internal/testenv" + "io/ioutil" + "os" + "os/exec" + "path/filepath" + "reflect" + "runtime" + "testing" +) + +func TestDedupLibraries(t *testing.T) { + ctxt := &Link{} + ctxt.Target.HeadType = objabi.Hlinux + + libs := []string{"libc.so", "libc.so.6"} + + got := dedupLibraries(ctxt, libs) + if !reflect.DeepEqual(got, libs) { + t.Errorf("dedupLibraries(%v) = %v, want %v", libs, got, libs) + } +} + +func TestDedupLibrariesOpenBSD(t *testing.T) { + ctxt := &Link{} + ctxt.Target.HeadType = objabi.Hopenbsd + + tests := []struct { + libs []string + want []string + }{ + { + libs: []string{"libc.so"}, + want: []string{"libc.so"}, + }, + { + libs: []string{"libc.so", "libc.so.96.1"}, + want: []string{"libc.so.96.1"}, + }, + { + libs: []string{"libc.so.96.1", "libc.so"}, + want: []string{"libc.so.96.1"}, + }, + { + libs: []string{"libc.a", "libc.so.96.1"}, + want: []string{"libc.a", "libc.so.96.1"}, + }, + { + libs: []string{"libpthread.so", "libc.so"}, + want: []string{"libc.so", "libpthread.so"}, + }, + { + libs: []string{"libpthread.so.26.1", "libpthread.so", "libc.so.96.1", "libc.so"}, + want: []string{"libc.so.96.1", "libpthread.so.26.1"}, + }, + { + libs: []string{"libpthread.so.26.1", "libpthread.so", "libc.so.96.1", "libc.so", "libfoo.so"}, + want: []string{"libc.so.96.1", "libfoo.so", "libpthread.so.26.1"}, + }, + } + + for _, test := range tests { + t.Run("dedup", func(t *testing.T) { + got := dedupLibraries(ctxt, test.libs) + if !reflect.DeepEqual(got, test.want) { + t.Errorf("dedupLibraries(%v) = %v, want %v", test.libs, got, test.want) + } + }) + } +} + +func TestDedupLibrariesOpenBSDLink(t *testing.T) { + // The behavior we're checking for is of interest only on OpenBSD. + if runtime.GOOS != "openbsd" { + t.Skip("test only useful on openbsd") + } + + testenv.MustHaveGoBuild(t) + testenv.MustHaveCGO(t) + t.Parallel() + + dir, err := ioutil.TempDir("", "dedup-build") + if err != nil { + t.Fatal(err) + } + defer os.RemoveAll(dir) + + // cgo_import_dynamic both the unversioned libraries and pull in the + // net package to get a cgo package with a versioned library. + srcFile := filepath.Join(dir, "x.go") + src := `package main + +import ( + _ "net" +) + +//go:cgo_import_dynamic _ _ "libc.so" + +func main() {}` + if err := ioutil.WriteFile(srcFile, []byte(src), 0644); err != nil { + t.Fatal(err) + } + + exe := filepath.Join(dir, "deduped.exe") + out, err := exec.Command(testenv.GoToolPath(t), "build", "-o", exe, srcFile).CombinedOutput() + if err != nil { + t.Fatalf("build failure: %s\n%s\n", err, string(out)) + } + + // Result should be runnable. + if _, err = exec.Command(exe).CombinedOutput(); err != nil { + t.Fatal(err) + } +} diff --git a/src/cmd/link/internal/ld/testdata/issue39256/x.go b/src/cmd/link/internal/ld/testdata/issue39256/x.go index d8562ad172..97bc1cc407 100644 --- a/src/cmd/link/internal/ld/testdata/issue39256/x.go +++ b/src/cmd/link/internal/ld/testdata/issue39256/x.go @@ -13,6 +13,8 @@ import ( //go:cgo_import_dynamic libc_close close "libc.so" //go:cgo_import_dynamic libc_open open "libc.so" +//go:cgo_import_dynamic _ _ "libc.so" + func trampoline() func main() {