Fāng-ruì Sòng <mask...@google.com> writes: > On Thu, Mar 10, 2022 at 11:48 AM Nick Desaulniers > <ndesaulni...@google.com> wrote: >> >> On Tue, Mar 8, 2022 at 9:53 PM Fangrui Song <mask...@google.com> wrote: >> > >> > DT_RELACOUNT is an ELF dynamic tag inherited from SunOS indicating the >> > number of R_*_RELATIVE relocations. It is optional but {ld.lld,ld.lld} >> > -z combreloc always creates it (if non-zero) to slightly speed up glibc >> > ld.so relocation resolving by avoiding R_*R_PPC64_RELATIVE type >> > comparison. The tag is otherwise nearly unused in the wild and I'd >> > recommend that software avoids using it. >> > >> > lld>=14.0.0 (since commit da0e5b885b25cf4ded0fa89b965dc6979ac02ca9) >> > underestimates DT_RELACOUNT for ppc64 when position-independent long >> > branch thunks are used. Correcting it needs non-trivial arch-specific >> > complexity which I'd prefer to avoid. Since our code always compares the >> > relocation type with R_PPC64_RELATIVE, replacing every occurrence of >> > DT_RELACOUNT with DT_RELASZ/sizeof(Elf64_Rela)=DT_RELASZ/24 is a correct >> > alternative. >> >> checking that sizeof(Elf64_Rela) == 24, yep: https://godbolt.org/z/bb4aKbo5T >> >> > >> > DT_RELASZ is in practice bounded by an uint32_t. Dividing x by 24 can be >> > implemented as (uint32_t)(x*0xaaaaaaab) >> 4. >> >> Yep: https://godbolt.org/z/x9445ePPv >> >> > >> > Link: https://github.com/ClangBuiltLinux/linux/issues/1581 >> > Reported-by: Nathan Chancellor <nat...@kernel.org> >> > Signed-off-by: Fangrui Song <mask...@google.com> >> > --- >> > arch/powerpc/boot/crt0.S | 28 +++++++++++++++++----------- >> > arch/powerpc/kernel/reloc_64.S | 15 +++++++++------ >> > 2 files changed, 26 insertions(+), 17 deletions(-) ...
> I rebased the patch on > git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > master and got a conflict. > Seems that > https://lore.kernel.org/linuxppc-dev/20220309061822.168173-1-...@ozlabs.ru/T/#u > ("[PATCH kernel v4] powerpc/64: Add UADDR64 relocation support") fixed > the issue. > It just doesn't change arch/powerpc/boot/crt0.S Yeah sorry, I applied Alexey's v4 just before I saw your patch arrive on the list. If one of you can rework this so it applies on top that would be great :) cheers