This is a note to let you know that I've just added the patch titled
kbuild: Fix changing ELF file type for output of gen_btf for big endian
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kbuild-fix-changing-elf-file-type-for-output-of-gen_btf-for-big-endian.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e3a9ee963ad8ba677ca925149812c5932b49af69 Mon Sep 17 00:00:00 2001
From: Nathan Chancellor <nathan@xxxxxxxxxx>
Date: Mon, 12 Feb 2024 19:05:10 -0700
Subject: kbuild: Fix changing ELF file type for output of gen_btf for big endian
From: Nathan Chancellor <nathan@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Fixes: 90ceddcb4950 ("bpf: Support llvm-objcopy for vmlinux BTF")
Link: https://github.com/llvm/llvm-project/pull/75643
Suggested-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Reviewed-by: Fangrui Song <maskray@xxxxxxxxxx>
Reviewed-by: Nicolas Schier <nicolas@xxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: Justin Stitt <justinstitt@xxxxxxxxxx>
Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
scripts/link-vmlinux.sh | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -135,8 +135,13 @@ 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
+ et_rel='\0\1'
+ else
+ et_rel='\1\0'
+ fi
+ printf "${et_rel}" | dd of=${2} conv=notrunc bs=1 seek=16 status=none
}
# Create ${2} .S file with all symbols from the ${1} object file
Patches currently in stable-queue which might be from nathan@xxxxxxxxxx are
queue-6.6/modpost-add-.ltext-and-.ltext.-to-text_sections.patch
queue-6.6/um-fix-adding-no-pie-for-clang.patch
queue-6.6/kbuild-fix-changing-elf-file-type-for-output-of-gen_btf-for-big-endian.patch
