On Mon, Sep 16, 2024 at 5:05 AM Michael Ellerman <m...@ellerman.id.au> wrote:
>
> The 'ld' and 'std' instructions require a 4-byte aligned displacement
> because they are DS-form instructions. But the "m" asm constraint
> doesn't enforce that.
>
> That can lead to build errors if the compiler chooses a non-aligned
> displacement, as seen with GCC 14:
>
> /tmp/ccuSzwiR.s: Assembler messages:
> /tmp/ccuSzwiR.s:2579: Error: operand out of domain (39 is not a multiple of
> 4)
> make[5]: *** [scripts/Makefile.build:229: net/core/page_pool.o] Error 1
>
> Dumping the generated assembler shows:
>
> ld 8,39(8) # MEM[(const struct atomic64_t *)_29].counter, t
>
> Use the YZ constraints to tell the compiler either to generate a DS-form
> displacement, or use an X-form instruction, either of which prevents the
> build error.
>
> See commit 2d43cc701b96 ("powerpc/uaccess: Fix build errors seen with
> GCC 13/14") for more details on the constraint letters.
>
> Fixes: 9f0cbea0d8cc ("[POWERPC] Implement atomic{, 64}_{read, write}()
> without volatile")
> Cc: sta...@vger.kernel.org # v2.6.24+
> Reported-by: Stephen Rothwell <s...@canb.auug.org.au>
> Closes: https://lore.kernel.org/all/20240913125302.0a06b...@canb.auug.org.au
> Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
I'm not familiar enough with the code around the changes, but I have
been able to confirm cherry-picking this resolves the build issue I'm
seeing on net-next, so, FWIW,
Tested-by: Mina Almasry <almasrym...@google.com>
--
Thanks,
Mina
