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SubjectRe: [PATCH 4/8] s390/entry: workaround llvm's IAS limitations
Hi Heiko,

On Wed, May 11, 2022 at 02:05:28PM +0200, Heiko Carstens wrote:
> llvm's integrated assembler cannot handle immediate values which are
> calculated with two local labels:
>
> <instantiation>:3:13: error: invalid operand for instruction
> clgfi %r14,.Lsie_done - .Lsie_gmap
>
> Workaround this by adding clang specific code which reads the specific
> value from memory. Since this code is within the hot paths of the kernel
> and adds an additional memory reference, keep the original code, and add
> ifdef'ed code.
>
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> ---
> arch/s390/kernel/entry.S | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
> index e1664b45090f..ff7a75078e93 100644
> --- a/arch/s390/kernel/entry.S
> +++ b/arch/s390/kernel/entry.S
> @@ -171,8 +171,19 @@ _LPP_OFFSET = __LC_LPP
> .macro OUTSIDE reg,start,end,outside_label
> larl %r14,\start
> slgrk %r14,\reg,%r14
> +#ifdef CONFIG_CC_IS_CLANG

I intend to put this series through my build and boot test matrix later
today but one fly by comment in the meantime. Should this be
CONFIG_AS_IS_LLVM if this is an integrated assembler limitation, rather
than a clang one?

> + clgfrl %r14,.Lrange_size\@
> +#else
> clgfi %r14,\end - \start
> +#endif
> jhe \outside_label
> +#ifdef CONFIG_CC_IS_CLANG
> + .section .rodata, "a"
> + .align 4
> +.Lrange_size\@:
> + .long \end - \start
> + .previous
> +#endif
> .endm
>
> .macro SIEEXIT
> --
> 2.32.0
>
>

Cheers,
Nathan

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