cmd/internal/ld: put read-only relocated data into .data.rel.ro when making a shared object
Currently Go produces shared libraries that cannot be shared between processes
because they have relocations against the text segment (not text section). This
fixes this by moving some data to sections with magic names recognized by the
static linker.
The change in genasmsym to add STYPELINK to the switch should fix things on
darwin/arm64.
Fixes #10914
Updates #9210
Change-Id: Iab4a6678dd04cec6114e683caac5cf31b1063309
Reviewed-on: https://go-review.googlesource.com/14306
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/misc/cgo/testcshared/test.bash b/misc/cgo/testcshared/test.bash
index 57221bc..1b7fec1 100755
--- a/misc/cgo/testcshared/test.bash
+++ b/misc/cgo/testcshared/test.bash
@@ -81,6 +81,13 @@
GOPATH=$(pwd) go build -buildmode=c-shared $suffix -o libgo.$libext src/libgo/libgo.go
binpush libgo.$libext
+if [ "$goos" == "linux" ]; then
+ if readelf -d libgo.$libext | grep TEXTREL >/dev/null; then
+ echo "libgo.$libext has TEXTREL set"
+ exit 1
+ fi
+fi
+
# test0: exported symbols in shared lib are accessible.
# TODO(iant): using _shared here shouldn't really be necessary.
$(go env CC) $(go env GOGCCFLAGS) -I ${installdir} -o testp main0.c libgo.$libext
diff --git a/misc/cgo/testshared/shared_test.go b/misc/cgo/testshared/shared_test.go
index 2e12364..7f677d6 100644
--- a/misc/cgo/testshared/shared_test.go
+++ b/misc/cgo/testshared/shared_test.go
@@ -163,6 +163,45 @@
}
}
+func hasDynTag(f *elf.File, tag elf.DynTag) bool {
+ ds := f.SectionByType(elf.SHT_DYNAMIC)
+ if ds == nil {
+ return false
+ }
+ d, err := ds.Data()
+ if err != nil {
+ return false
+ }
+ for len(d) > 0 {
+ var t elf.DynTag
+ switch f.Class {
+ case elf.ELFCLASS32:
+ t = elf.DynTag(f.ByteOrder.Uint32(d[0:4]))
+ d = d[8:]
+ case elf.ELFCLASS64:
+ t = elf.DynTag(f.ByteOrder.Uint64(d[0:8]))
+ d = d[16:]
+ }
+ if t == tag {
+ return true
+ }
+ }
+ return false
+}
+
+// The shared library does not have relocations against the text segment.
+func TestNoTextrel(t *testing.T) {
+ sopath := filepath.Join(gorootInstallDir, soname)
+ f, err := elf.Open(sopath)
+ if err != nil {
+ t.Fatal("elf.Open failed: ", err)
+ }
+ defer f.Close()
+ if hasDynTag(f, elf.DT_TEXTREL) {
+ t.Errorf("%s has DT_TEXTREL set", soname)
+ }
+}
+
// The install command should have created a "shlibname" file for the
// listed packages (and runtime/cgo) indicating the name of the shared
// library containing it.
