Re: [PATCH] s390/boot: Workaround current 'llvm-objdump -t -j ...' behavior

[Heiko Carstens <hca@linux.ibm.com>]

Hi Nathan,

On Tue, Feb 20, 2024 at 01:44:48PM -0700, Nathan Chancellor wrote:
> When building with OBJDUMP=llvm-objdump, there are a series of warnings
> from the section comparisons that arch/s390/boot/Makefile performs
> between vmlinux and arch/s390/boot/vmlinux:
...
> It may be possible to change llvm-objdump's behavior to match GNU
> objdump's behavior but the difficulty of that task has not yet been
> explored. The combination of '$(OBJDUMP) -t -j' is not common in the
> kernel tree on a whole, so workaround this tool difference by grepping
> for the sections in the full symbol table output in a similar manner to
> the sed invocation. This results in no visible change for GNU objdump
> users while fixing the warnings for OBJDUMP=llvm-objdump, further
> enabling use of LLVM=1 for ARCH=s390 with versions of LLVM that have
> support for s390 in ld.lld and llvm-objcopy.
> 
> Reported-by: Heiko Carstens <hca@linux.ibm.com>
> Closes: https://lore.kernel.org/20240219113248.16287-C-hca@linux.ibm.com/
> Link: https://github.com/ClangBuiltLinux/linux/issues/859
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
> s390 llvm-objcopy support may be backported to LLVM 18.1.0 in time for
> the final release.
> 
> https://github.com/llvm/llvm-project/pull/82324
> 
> s390 ld.lld has already made it into release/18.x:
> 
> https://github.com/llvm/llvm-project/commit/0a44c3792a6ff799df5f100670d7e19d1bc49f03
> 
> If the objcopy change makes 18.1.0 final, features + this change should
> build cleanly with LLVM 18.1.0+ using LLVM=1 :)
> ---
>  arch/s390/boot/Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

This seems to work like expected (also verified with a couple of scenarios
where things are supposed to break).

So compiling the kernel with LLVM=1 finally works on s390!

Patch applied - Thanks a lot!