Re: [PATCH v5 02/16] powerpc: Override __ALIGN and __ALIGN_STR macros

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 28/10/2022 à 16:33, Sathvika Vasireddy a écrit :
> In a subsequent patch, we would want to annotate powerpc assembly functions
> with SYM_FUNC_START_LOCAL macro. This macro depends on __ALIGN macro.
> 
> The default expansion of __ALIGN macro is:
>          #define __ALIGN      .align 4,0x90
> 
> So, override __ALIGN and __ALIGN_STR macros to use the same alignment as
> that of the existing _GLOBAL macro. Also, do not pad with 0x90, because
> repeated 0x90s are not a nop or trap on powerpc.

By the way, do we know what the instruction 0x90909090 is on powerpc ? 
Is that something valid or not ?

> 
> Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
> Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
> ---
>   arch/powerpc/include/asm/linkage.h | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/linkage.h b/arch/powerpc/include/asm/linkage.h
> index b71b9582e754..b88d1d2cf304 100644
> --- a/arch/powerpc/include/asm/linkage.h
> +++ b/arch/powerpc/include/asm/linkage.h
> @@ -4,6 +4,9 @@
>   
>   #include <asm/types.h>
>   
> +#define __ALIGN		.align 2
> +#define __ALIGN_STR	".align 2"
> +
>   #ifdef CONFIG_PPC64_ELF_ABI_V1
>   #define cond_syscall(x) \
>   	asm ("\t.weak " #x "\n\t.set " #x ", sys_ni_syscall\n"		\