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@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
>
> 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@xxxxxxxxxx>
>
> to the resulting patch if you would like.
I'll go add that now, thanks for catching this!
greg k-h
