cmd/internal/ld: store the libraries a shared library was linked against in a note
The motivation for this is the innocuous looking test case that is added. This
creates a stack exe -> libdep2.so -> libdep.so -> libruntime.so. The problem
comes from the fact that a function from libdep.so gets inlined all the way
into exe. This (unsurprisingly) means that the object file for exe references
symbols from libdep.so, which means that -ldep needs to be passed when linking
exe and it isn't. The fix is simply to pass it -- there is no harm in passing
it when it's not needed.
The thing is, it's not clear at all in the current code to see how the linker
can know that libdep2 is linked against libdep. It could look through the
DT_NEEDED entries in libdep2 and try to guess which are Go libraries, but it
feels better to be explicit. So this adds another SHT_NOTE section that lists
the shared libraries a shared library was linked against, and makes sure the
complete set of depended upon shared libraries is passed to the external
linker.
Change-Id: I79aa6f98b4db4721d657a7eb7b7f062269bf49e2
Reviewed-on: https://go-review.googlesource.com/10376
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/cmd/link/internal/ld/elf.go b/src/cmd/link/internal/ld/elf.go
index 83f10d3..68d21f4 100644
--- a/src/cmd/link/internal/ld/elf.go
+++ b/src/cmd/link/internal/ld/elf.go
@@ -9,7 +9,9 @@
"crypto/sha1"
"encoding/binary"
"fmt"
+ "path/filepath"
"sort"
+ "strings"
)
/*
@@ -1205,6 +1207,7 @@
const (
ELF_NOTE_GOPKGLIST_TAG = 1
ELF_NOTE_GOABIHASH_TAG = 2
+ ELF_NOTE_GODEPS_TAG = 3
)
var ELF_NOTE_GO_NAME = []byte("GO\x00\x00")
@@ -1697,6 +1700,7 @@
if Buildmode == BuildmodeShared {
Addstring(shstrtab, ".note.go.abihash")
Addstring(shstrtab, ".note.go.pkg-list")
+ Addstring(shstrtab, ".note.go.deps")
}
}
@@ -1904,6 +1908,11 @@
}
addgonote(".note.go.abihash", ELF_NOTE_GOABIHASH_TAG, h.Sum([]byte{}))
addgonote(".note.go.pkg-list", ELF_NOTE_GOPKGLIST_TAG, []byte(pkglistfornote))
+ var deplist []string
+ for _, shlib := range Ctxt.Shlibs {
+ deplist = append(deplist, filepath.Base(shlib.Path))
+ }
+ addgonote(".note.go.deps", ELF_NOTE_GODEPS_TAG, []byte(strings.Join(deplist, "\n")))
}
}
@@ -1976,6 +1985,8 @@
sh = elfshname(".note.go.abihash")
sh.type_ = SHT_NOTE
sh.flags = SHF_ALLOC
+ sh = elfshname(".note.go.deps")
+ sh.type_ = SHT_NOTE
}
goto elfobj
}
diff --git a/src/cmd/link/internal/ld/go.go b/src/cmd/link/internal/ld/go.go
index 875b8d2..80a6c6e 100644
--- a/src/cmd/link/internal/ld/go.go
+++ b/src/cmd/link/internal/ld/go.go
@@ -653,15 +653,14 @@
}
if Buildmode == BuildmodeShared {
- // Mark all symbols as reachable when building a
- // shared library.
+ // Mark all symbols defined in this library as reachable when
+ // building a shared library.
for s := Ctxt.Allsym; s != nil; s = s.Allsym {
- if s.Type != 0 {
+ if s.Type != 0 && s.Type != obj.SDYNIMPORT {
mark(s)
}
}
- mark(Linkrlookup(Ctxt, "main.main", 0))
- mark(Linkrlookup(Ctxt, "main.init", 0))
+ markflood()
} else {
mark(Linklookup(Ctxt, INITENTRY, 0))
if Linkshared && Buildmode == BuildmodeExe {
diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index 26d7229..8caac0f 100644
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -983,15 +983,35 @@
argv = append(argv, fmt.Sprintf("%s/go.o", tmpdir))
if Linkshared {
- for _, shlib := range Ctxt.Shlibs {
- dir, base := filepath.Split(shlib.Path)
- argv = append(argv, "-L"+dir)
- if !rpath.set {
- argv = append(argv, "-Wl,-rpath="+dir)
+ seenDirs := make(map[string]bool)
+ seenLibs := make(map[string]bool)
+ addshlib := func(path string) {
+ dir, base := filepath.Split(path)
+ if !seenDirs[dir] {
+ argv = append(argv, "-L"+dir)
+ if !rpath.set {
+ argv = append(argv, "-Wl,-rpath="+dir)
+ }
+ seenDirs[dir] = true
}
base = strings.TrimSuffix(base, ".so")
base = strings.TrimPrefix(base, "lib")
- argv = append(argv, "-l"+base)
+ if !seenLibs[base] {
+ argv = append(argv, "-l"+base)
+ seenLibs[base] = true
+ }
+ }
+ for _, shlib := range Ctxt.Shlibs {
+ addshlib(shlib.Path)
+ for _, dep := range shlib.Deps {
+ if dep == "" {
+ continue
+ }
+ libpath := findshlib(dep)
+ if libpath != "" {
+ addshlib(libpath)
+ }
+ }
}
}
@@ -1214,18 +1234,20 @@
return nil, nil
}
-func ldshlibsyms(shlib string) {
- found := false
- libpath := ""
+func findshlib(shlib string) string {
for _, libdir := range Ctxt.Libdir {
- libpath = filepath.Join(libdir, shlib)
+ libpath := filepath.Join(libdir, shlib)
if _, err := os.Stat(libpath); err == nil {
- found = true
- break
+ return libpath
}
}
- if !found {
- Diag("cannot find shared library: %s", shlib)
+ Diag("cannot find shared library: %s", shlib)
+ return ""
+}
+
+func ldshlibsyms(shlib string) {
+ libpath := findshlib(shlib)
+ if libpath == "" {
return
}
for _, processedlib := range Ctxt.Shlibs {
@@ -1251,6 +1273,13 @@
return
}
+ depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
+ if err != nil {
+ Diag("cannot read dep list from shared library %s: %v", libpath, err)
+ return
+ }
+ deps := strings.Split(string(depsbytes), "\n")
+
syms, err := f.Symbols()
if err != nil {
Diag("cannot read symbols from shared library: %s", libpath)
@@ -1272,12 +1301,6 @@
if elf.ST_TYPE(s.Info) == elf.STT_NOTYPE || elf.ST_TYPE(s.Info) == elf.STT_SECTION {
continue
}
- if s.Section == elf.SHN_UNDEF {
- continue
- }
- if strings.HasPrefix(s.Name, "_") {
- continue
- }
if strings.HasPrefix(s.Name, "runtime.gcbits.") {
gcmasks[s.Value] = readelfsymboldata(f, &s)
}
@@ -1285,7 +1308,7 @@
continue
}
lsym := Linklookup(Ctxt, s.Name, 0)
- if lsym.Type != 0 && lsym.Dupok == 0 {
+ if lsym.Type != 0 && lsym.Type != obj.SDYNIMPORT && lsym.Dupok == 0 {
Diag(
"Found duplicate symbol %s reading from %s, first found in %s",
s.Name, shlib, lsym.File)
@@ -1342,7 +1365,7 @@
Ctxt.Etextp = last
}
- Ctxt.Shlibs = append(Ctxt.Shlibs, Shlib{Path: libpath, Hash: hash})
+ Ctxt.Shlibs = append(Ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps})
}
func mywhatsys() {
diff --git a/src/cmd/link/internal/ld/link.go b/src/cmd/link/internal/ld/link.go
index 4b034a4..a288148 100644
--- a/src/cmd/link/internal/ld/link.go
+++ b/src/cmd/link/internal/ld/link.go
@@ -117,6 +117,7 @@
type Shlib struct {
Path string
Hash []byte
+ Deps []string
}
type Link struct {
