Hi Greg, On Mon, Feb 19, 2024 at 06:02:36PM +0100, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > > 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 5.15-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-5.15 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 > @@ -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 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@xxxxxxxxxx> to the resulting patch if you would like. Cheers, Nathan diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index 007bb773b222..5a5a0cfad69d 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -237,7 +237,7 @@ gen_btf() --strip-all ${1} ${2} 2>/dev/null # Change e_type to ET_REL so that it can be used to link final vmlinux. # GNU ld 2.35+ and lld do not allow an ET_EXEC input. - if is_enabled CONFIG_CPU_BIG_ENDIAN; then + if [ -n "${CONFIG_CPU_BIG_ENDIAN}" ]; then et_rel='\0\1' else et_rel='\1\0'
