On Wed, Feb 21, 2024 at 09:54:24AM -0700, Nathan Chancellor wrote:
Hi Greg,
On Wed, Feb 21, 2024 at 02:07:11PM +0100, Greg Kroah-Hartman wrote:
5.15-stable review patch. If anyone has any objections, please let me know.
From: Nathan Chancellor nathan@kernel.org
commit e3a9ee963ad8ba677ca925149812c5932b49af69 upstream.
Commit 90ceddcb4950 ("bpf: Support llvm-objcopy for vmlinux BTF") changed the ELF type of .btf.vmlinux.bin.o to ET_REL via dd, which works fine for little endian platforms:
00000000 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 |.ELF............| -00000010 03 00 b7 00 01 00 00 00 00 00 00 80 00 80 ff ff |................| +00000010 01 00 b7 00 01 00 00 00 00 00 00 80 00 80 ff ff |................|
However, for big endian platforms, it changes the wrong byte, resulting in an invalid ELF file type, which ld.lld rejects:
00000000 7f 45 4c 46 02 02 01 00 00 00 00 00 00 00 00 00 |.ELF............| -00000010 00 03 00 16 00 00 00 01 00 00 00 00 00 10 00 00 |................| +00000010 01 03 00 16 00 00 00 01 00 00 00 00 00 10 00 00 |................|
Type: <unknown>: 103
ld.lld: error: .btf.vmlinux.bin.o: unknown file type
Fix this by updating the entire 16-bit e_type field rather than just a single byte, so that everything works correctly for all platforms and linkers.
00000000 7f 45 4c 46 02 02 01 00 00 00 00 00 00 00 00 00 |.ELF............| -00000010 00 03 00 16 00 00 00 01 00 00 00 00 00 10 00 00 |................| +00000010 00 01 00 16 00 00 00 01 00 00 00 00 00 10 00 00 |................|
Type: REL (Relocatable file)
While in the area, update the comment to mention that binutils 2.35+ matches LLD's behavior of rejecting an ET_EXEC input, which occurred after the comment was added.
Cc: stable@vger.kernel.org Fixes: 90ceddcb4950 ("bpf: Support llvm-objcopy for vmlinux BTF") Link: https://github.com/llvm/llvm-project/pull/75643 Suggested-by: Masahiro Yamada masahiroy@kernel.org Signed-off-by: Nathan Chancellor nathan@kernel.org Reviewed-by: Fangrui Song maskray@google.com Reviewed-by: Nicolas Schier nicolas@fjasle.eu Reviewed-by: Kees Cook keescook@chromium.org Reviewed-by: Justin Stitt justinstitt@google.com Signed-off-by: Masahiro Yamada masahiroy@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
scripts/link-vmlinux.sh | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -236,8 +236,13 @@ gen_btf() ${OBJCOPY} --only-section=.BTF --set-section-flags .BTF=alloc,readonly \ --strip-all ${1} ${2} 2>/dev/null # Change e_type to ET_REL so that it can be used to link final vmlinux.
- # Unlike GNU ld, lld does not allow an ET_EXEC input.
- printf '\1' | dd of=${2} conv=notrunc bs=1 seek=16 status=none
- # GNU ld 2.35+ and lld do not allow an ET_EXEC input.
- if is_enabled CONFIG_CPU_BIG_ENDIAN; then
You may have missed my mail on the email saying this had been applied (I didn't cc a lore list so no link):
Ick, I did get it but it got lost in the shuffle, my fault.
I do not think this backport is correct for trees that do not have commit 7d153696e5db ("kbuild: do not include include/config/auto.conf from shell scripts"), even if it applies cleanly, as is_enabled() is not available.
I think this diff should be squashed in to the patch for 5.15 and earlier, you can add
[nathan: Fix silent conflict due to lack of 7d153696e5db in older trees] Signed-off-by: Nathan Chancellor nathan@kernel.org
to the resulting patch if you would like.
I'll go add that now, thanks for catching this!
greg k-h