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Makefile: use -z pack-relative-relocs

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Commit 27f2a4db76e8 ("Makefile: fix GDB warning with CONFIG_RELR")
added --use-android-relr-tags to fix a GDB warning

BFD: /android0/linux-next/vmlinux: unknown type [0x13] section `.relr.dyn'

The GDB warning has been fixed in version 11.2.

The DT_ANDROID_RELR tag was deprecated since DT_RELR was standardized.
Thus, --use-android-relr-tags should be removed. While making the
change, try -z pack-relative-relocs, which is supported since LLD 15.
Keep supporting --pack-dyn-relocs=relr as well for older LLD versions.
There is no indication of obsolescence for --pack-dyn-relocs=relr.

As of today, GNU ld supports the latter option for x86 and powerpc64
ports and has no intention to support --pack-dyn-relocs=relr. In the
absence of the glibc symbol version GLIBC_ABI_DT_RELR,
--pack-dyn-relocs=relr and -z pack-relative-relocs are identical in
ld.lld.

GNU ld and newer versions of LLD report warnings (instead of errors) for
unknown -z options. Only errors lead to non-zero exit codes. Therefore,
we should test --pack-dyn-relocs=relr before testing
-z pack-relative-relocs.

Link: https://github.com/ClangBuiltLinux/linux/issues/1057
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=a619b58721f0a03fd91c27670d3e4c2fb0d88f1e
Signed-off-by: Fangrui Song <maskray@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Fangrui Song 2023-04-11 20:09:44 +00:00 committed by Masahiro Yamada
parent ddc72c9659
commit ccb2d173b9
2 changed files with 8 additions and 3 deletions
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3
Makefile
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@ -1113,7 +1113,8 @@ LDFLAGS_vmlinux += -X
endif
ifeq ($(CONFIG_RELR),y)
LDFLAGS_vmlinux += --pack-dyn-relocs=relr --use-android-relr-tags
# ld.lld before 15 did not support -z pack-relative-relocs.
LDFLAGS_vmlinux += $(call ld-option,--pack-dyn-relocs=relr,-z pack-relative-relocs)
endif
# We never want expected sections to be placed heuristically by the

8
scripts/tools-support-relr.sh
View File

@ -7,8 +7,12 @@ trap "rm -f $tmp_file.o $tmp_file $tmp_file.bin" EXIT
cat << "END" | $CC -c -x c - -o $tmp_file.o >/dev/null 2>&1
void *p = &p;
END
$LD $tmp_file.o -shared -Bsymbolic --pack-dyn-relocs=relr \
--use-android-relr-tags -o $tmp_file
# ld.lld before 15 did not support -z pack-relative-relocs.
if ! $LD $tmp_file.o -shared -Bsymbolic --pack-dyn-relocs=relr -o $tmp_file 2>/dev/null; then
$LD $tmp_file.o -shared -Bsymbolic -z pack-relative-relocs -o $tmp_file 2>&1 |
grep -q pack-relative-relocs && exit 1
fi
# Despite printing an error message, GNU nm still exits with exit code 0 if it
# sees a relr section. So we need to check that nothing is printed to stderr.