On Fri, Mar 24, 2023 at 2:22 PM Fangrui Song <maskray@xxxxxxxxxx> wrote:
>
> 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.
>
> 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.
>
> 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@xxxxxxxxxx>
Thanks v2 looks better. IIUC, this will first try to test+use
`--pack-dyn-relocs=relr` in preference to `-z pack-relative-relocs`.
Do we want to reorder the preference, for both the test and actual
flag used?
> ---
> Makefile | 3 ++-
> scripts/tools-support-relr.sh | 8 ++++++--
> 2 files changed, 8 insertions(+), 3 deletions(-)
> ---
> Changes from v1:
> * Keep supporting --pack-dyn-relocs=relr for older ld.lld versions
>
> diff --git a/Makefile b/Makefile
> index a2c310df2145..e23a85476d5d 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -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
> diff --git a/scripts/tools-support-relr.sh b/scripts/tools-support-relr.sh
> index cb55878bd5b8..4c121946e517 100755
> --- a/scripts/tools-support-relr.sh
> +++ b/scripts/tools-support-relr.sh
> @@ -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.
> --
> 2.40.0.348.gf938b09366-goog
>
--
Thanks,
~Nick Desaulniers
