[TCWG CI] Regression caused by binutils: aarch64: Disallow copy relocations on protected data
ci_notify@linaro.org
ci_notify@linaro.org
Fri Jun 24 10:42:11 GMT 2022
[TCWG CI] Regression caused by binutils: aarch64: Disallow copy relocations on protected data:
commit 90b7a5df152a64d2bea20beb438e8b81049a5c30
Author: Fangrui Song <i@maskray.me>
aarch64: Disallow copy relocations on protected data
Results regressed to
# reset_artifacts:
-10
# true:
0
# build_abe binutils:
1
# First few build errors in logs:
# 00:04:27 make[3]: [Makefile:1786: aarch64-unknown-linux-gnu/bits/largefile-config.h] Error 1 (ignored)
# 00:04:27 make[3]: [Makefile:1787: aarch64-unknown-linux-gnu/bits/largefile-config.h] Error 1 (ignored)
# 00:09:43 collect2: error: ld returned 1 exit status
# 00:09:43 make[3]: *** [Makefile:3023: build/genenums] Error 1
# 00:09:44 collect2: error: ld returned 1 exit status
# 00:09:44 make[3]: *** [Makefile:3023: build/genmddeps] Error 1
# 00:09:50 make[2]: *** [Makefile:5005: all-stage2-gcc] Error 2
# 00:09:50 make[1]: *** [Makefile:25739: stage2-bubble] Error 2
# 00:09:50 make: *** [Makefile:1072: all] Error 2
from
# reset_artifacts:
-10
# true:
0
# build_abe binutils:
1
# build_abe bootstrap_lto:
2
THIS IS THE END OF INTERESTING STUFF. BELOW ARE LINKS TO BUILDS, REPRODUCTION INSTRUCTIONS, AND THE RAW COMMIT.
This commit has regressed these CI configurations:
- tcwg_gcc_bootstrap/master-aarch64-bootstrap_lto
First_bad build: https://ci.linaro.org/job/tcwg_gcc_bootstrap-bisect-master-aarch64-bootstrap_lto/7/artifact/artifacts/build-90b7a5df152a64d2bea20beb438e8b81049a5c30/
Last_good build: https://ci.linaro.org/job/tcwg_gcc_bootstrap-bisect-master-aarch64-bootstrap_lto/7/artifact/artifacts/build-f18acc9c4e5d18f4783f3a7d59e3ec95d7af0199/
Baseline build: https://ci.linaro.org/job/tcwg_gcc_bootstrap-bisect-master-aarch64-bootstrap_lto/7/artifact/artifacts/build-baseline/
Even more details: https://ci.linaro.org/job/tcwg_gcc_bootstrap-bisect-master-aarch64-bootstrap_lto/7/artifact/artifacts/
Reproduce builds:
<cut>
mkdir investigate-binutils-90b7a5df152a64d2bea20beb438e8b81049a5c30
cd investigate-binutils-90b7a5df152a64d2bea20beb438e8b81049a5c30
# Fetch scripts
git clone https://git.linaro.org/toolchain/jenkins-scripts
# Fetch manifests and test.sh script
mkdir -p artifacts/manifests
curl -o artifacts/manifests/build-baseline.sh https://ci.linaro.org/job/tcwg_gcc_bootstrap-bisect-master-aarch64-bootstrap_lto/7/artifact/artifacts/manifests/build-baseline.sh --fail
curl -o artifacts/manifests/build-parameters.sh https://ci.linaro.org/job/tcwg_gcc_bootstrap-bisect-master-aarch64-bootstrap_lto/7/artifact/artifacts/manifests/build-parameters.sh --fail
curl -o artifacts/test.sh https://ci.linaro.org/job/tcwg_gcc_bootstrap-bisect-master-aarch64-bootstrap_lto/7/artifact/artifacts/test.sh --fail
chmod +x artifacts/test.sh
# Reproduce the baseline build (build all pre-requisites)
./jenkins-scripts/tcwg_gnu-build.sh @@ artifacts/manifests/build-baseline.sh
# Save baseline build state (which is then restored in artifacts/test.sh)
mkdir -p ./bisect
rsync -a --del --delete-excluded --exclude /bisect/ --exclude /artifacts/ --exclude /binutils/ ./ ./bisect/baseline/
cd binutils
# Reproduce first_bad build
git checkout --detach 90b7a5df152a64d2bea20beb438e8b81049a5c30
../artifacts/test.sh
# Reproduce last_good build
git checkout --detach f18acc9c4e5d18f4783f3a7d59e3ec95d7af0199
../artifacts/test.sh
cd ..
</cut>
Full commit (up to 1000 lines):
<cut>
commit 90b7a5df152a64d2bea20beb438e8b81049a5c30
Author: Fangrui Song <i@maskray.me>
Date: Wed Jun 22 10:55:12 2022 -0700
aarch64: Disallow copy relocations on protected data
If an executable has copy relocations for extern protected data, that
can only work if the shared object containing the definition is built
with assumptions (a) the compiler emits GOT-generating relocations (b)
the linker produces R_*_GLOB_DAT instead of R_*_RELATIVE. Otherwise the
shared object uses its own definition directly and the executable
accesses a stale copy. Note: the GOT relocations defeat the purpose of
protected visibility as an optimization, and it turns out this never
worked perfectly.
glibc 2.36 will warn on copy relocations on protected data. Let's
produce a warning at link time, matching ld.lld which has been used on
many aarch64 OSes.
Note: x86 requires GNU_PROPERTY_NO_COPY_ON_PROTECTED to have the error.
This is to largely due to GCC 5's "x86-64: Optimize access to globals in
PIE with copy reloc" which started to use direct access relocations for
external data symbols in -fpie mode.
GCC's aarch64 port does not have the change. Nowadays with most builds
switching to -fpie/-fpic, aarch64 mostly doesn't need to worry about
copy relocations. So for aarch64 we simply don't check
GNU_PROPERTY_NO_COPY_ON_PROTECTED.
---
bfd/elfnn-aarch64.c | 28 +++++++++++++++++++++++++-
ld/testsuite/ld-aarch64/aarch64-elf.exp | 9 +++++++++
ld/testsuite/ld-aarch64/copy-reloc-protected.d | 2 ++
ld/testsuite/ld-aarch64/protected.s | 8 ++++++++
4 files changed, 46 insertions(+), 1 deletion(-)
diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index ca24a6b5678..81311fc5a32 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -2579,6 +2579,9 @@ struct elf_aarch64_link_hash_entry
this symbol. */
unsigned int got_type;
+ /* TRUE if symbol is defined as a protected symbol. */
+ unsigned int def_protected : 1;
+
/* A pointer to the most recently used stub hash entry against this
symbol. */
struct elf_aarch64_stub_hash_entry *stub_cache;
@@ -2855,9 +2858,16 @@ elfNN_aarch64_copy_indirect_symbol (struct bfd_link_info *info,
static void
elfNN_aarch64_merge_symbol_attribute (struct elf_link_hash_entry *h,
unsigned int st_other,
- bool definition ATTRIBUTE_UNUSED,
+ bool definition,
bool dynamic ATTRIBUTE_UNUSED)
{
+ if (definition)
+ {
+ struct elf_aarch64_link_hash_entry *eh
+ = (struct elf_aarch64_link_hash_entry *)h;
+ eh->def_protected = ELF_ST_VISIBILITY (st_other) == STV_PROTECTED;
+ }
+
unsigned int isym_sto = st_other & ~ELF_ST_VISIBILITY (-1);
unsigned int h_sto = h->other & ~ELF_ST_VISIBILITY (-1);
@@ -8701,6 +8711,22 @@ elfNN_aarch64_allocate_dynrelocs (struct elf_link_hash_entry *h, void *inf)
if (h->dyn_relocs == NULL)
return true;
+ for (p = h->dyn_relocs; p != NULL; p = p->next)
+ if (eh->def_protected)
+ {
+ /* Disallow copy relocations against protected symbol. */
+ asection *s = p->sec->output_section;
+ if (s != NULL && (s->flags & SEC_READONLY) != 0)
+ {
+ info->callbacks->einfo
+ /* xgettext:c-format */
+ (_ ("%F%P: %pB: copy relocation against non-copyable "
+ "protected symbol `%s'\n"),
+ p->sec->owner, h->root.root.string);
+ return false;
+ }
+ }
+
/* In the shared -Bsymbolic case, discard space allocated for
dynamic pc-relative relocs against symbols which turn out to be
defined in regular objects. For the normal shared case, discard
diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp
index 64476f111e0..31162277bd9 100644
--- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
+++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
@@ -407,6 +407,8 @@ set aarch64elflinktests {
{copy-reloc-exe-2.s} {{objdump -R copy-reloc-2.d}} "copy-reloc-2"}
{"ld-aarch64/exe with copy relocation elimination" "-e0 tmpdir/copy-reloc-so.so" "" ""
{copy-reloc-exe-eliminate.s} {{objdump -R copy-reloc-eliminate.d}} "copy-reloc-elimination"}
+ {"Build .so with protected data" "-shared" "" "" {protected.s}
+ {} "protected.so"}
{"ld-aarch64/so with global func" "-shared" "" "" {func-in-so.s}
{} "func-in-so.so"}
{"ld-aarch64/func sym hash opt for exe"
@@ -416,8 +418,15 @@ set aarch64elflinktests {
{} "libbti-plt-so.so"}
}
+set aarch64elfcclinktests [list \
+ [list "copy relocation on protected data" \
+ "-no-pie tmpdir/copy-reloc-exe.o tmpdir/protected.so" "" \
+ {} {{error_output copy-reloc-protected.d}} "copy-reloc-protected"]
+]
+
if [check_shared_lib_support] {
run_ld_link_tests $aarch64elflinktests
+ run_cc_link_tests $aarch64elfcclinktests
}
run_dump_test "bti-plt-3"
diff --git a/ld/testsuite/ld-aarch64/copy-reloc-protected.d b/ld/testsuite/ld-aarch64/copy-reloc-protected.d
new file mode 100644
index 00000000000..99a356a3df6
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/copy-reloc-protected.d
@@ -0,0 +1,2 @@
+.*: tmpdir/copy-reloc-exe.o: copy relocation against non-copyable protected symbol `global_a'
+#...
diff --git a/ld/testsuite/ld-aarch64/protected.s b/ld/testsuite/ld-aarch64/protected.s
new file mode 100644
index 00000000000..eb3fb402dc4
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/protected.s
@@ -0,0 +1,8 @@
+.global global_a
+.protected global_a
+.type global_a, %object
+.size global_a, 4
+
+.data
+global_a:
+.word 0xcafedead
</cut>
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