Re: [PATCH v2 0/5] loongarch: add relaxation support

[Xiaotian Wu]

在 2023-06-12星期一的 06:35 +0800，Xi Ruoyao via Grub-devel写道：
> On Wed, 2023-06-07 at 15:34 +0800, Xiaotian Wu wrote:
> > Because the binutils of the loongarch architecture adds relaxation
> > support [1], the next version of binutils will not be able to build
> > grub.
> > 
> > So we added the R_LARCH_B16, R_LARCH_B21 and R_LARCH_RELAX
> > relocations
> > to enhance grub compatibility.
> 
> Wouldn't it be easier to just pass -mno-relax to the toolchain when
> we
> build GRUB?  I don't think it makes too much sense to perform
> relaxation
> on a boot loader.  The boot loader is generally the coldest code
> paths
> in a system, so relaxing it won't give any real benefit (well, if you
> reboot a system 100 times you may finally save one second), but
> increases the maintenance burden.
> 

Yes, it's easy to pass -mno-relax, but binutils-2.40 doesn't support
this option.

> Consider a new relaxation pattern is added after we release GRUB
> 2.12. 
> Then if we simply pass -mno-relax, GRUB 2.12 will continue to work. 
> But
> if we try to "support" relaxation this way, every distro will have to
> patch GRUB 2.12 when the toolchain is updated.
> 

GRUB 2.12 has not been released yet. If this patch can be merged before
the release of grub 2.12, every distribution does not need to be
patched. Moreover, both binutils-2.40 and future binutils 2.41+ will be
able to compile normally.

> > [1]:
> > https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=56576f4a722b7398d35802ecf7d4185c27d6d69b
> > 
> > v1->v2:
> > - split patch
> > - drop cast code
> > 
> > Xiaotian Wu (5):
> >   Use the correct format specifier for formatted output
> >   loongarch: Optimize code using pc variable
> >   loongarch: Rename function names
> >   loongarch: Add ELF relocation types documentation and comments
> >   loongarch: Add relaxation support
> > 
> >  grub-core/kern/arm64/dl_helper.c       |  4 +-
> >  grub-core/kern/loongarch64/dl.c        | 21 +++++++-
> >  grub-core/kern/loongarch64/dl_helper.c | 72
> > ++++++++++++++++++++++++-
> > -
> >  include/grub/elf.h                     |  3 ++
> >  include/grub/loongarch64/reloc.h       |  6 ++-
> >  util/grub-mkimagexx.c                  | 28 ++++++++--
> >  util/grub-module-verifier.c            |  3 ++
> >  7 files changed, 124 insertions(+), 13 deletions(-)
> > 
> 

-- 
Best Regards
Xiaotian Wu