[PATCH 01/17] powerpc/ftrace: Fix dropping weak symbols with older toolchains

[Christophe Leroy]

Le 19/06/2023 à 11:47, Naveen N Rao a écrit :
> The minimum level of gcc supported for building the kernel is v5.1.
> v5.x releases of gcc emitted a three instruction sequence for
> -mprofile-kernel:
> 	mflr	r0
> 	std	r0, 16(r1)
> 	bl	_mcount
> 
> It is only with the v6.x releases that gcc started emitting the two
> instruction sequence for -mprofile-kernel, omitting the second store
> instruction.
> 
> With the older three instruction sequence, the actual ftrace location
> can be the 5th instruction into a function. Update the allowed offset
> for ftrace location from 12 to 16 to accommodate the same.
> 
> Cc: stable at vger.kernel.org
> Fixes: 7af82ff90a2b06 ("powerpc/ftrace: Ignore weak functions")
> Signed-off-by: Naveen N Rao <naveen at kernel.org>

Reviewed-by: Christophe Leroy <christophe.leroy at csgroup.eu>

> ---
>   arch/powerpc/include/asm/ftrace.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
> index 91c049d51d0e10..2edc6269b1a357 100644
> --- a/arch/powerpc/include/asm/ftrace.h
> +++ b/arch/powerpc/include/asm/ftrace.h
> @@ -12,7 +12,7 @@
>   
>   /* Ignore unused weak functions which will have larger offsets */
>   #ifdef CONFIG_MPROFILE_KERNEL
> -#define FTRACE_MCOUNT_MAX_OFFSET	12
> +#define FTRACE_MCOUNT_MAX_OFFSET	16
>   #elif defined(CONFIG_PPC32)
>   #define FTRACE_MCOUNT_MAX_OFFSET	8
>   #endif