Re: [PATCH 2/9] tracing: MIPS: mcount.S: Fixup of the 32bit support with gcc 4.5

[David Daney <david.s.daney@gmail.com>]

On 05/12/2010 06:23 AM, Wu Zhangjin wrote:
> From: Wu Zhangjin<wuzhangjin@gmail.com>
>
> As the doc[1] of gcc-4.5 shows, the -mmcount-ra-address uses register
> $12 to transfer the stack offset of the return address to the _mcount
> function. in 64bit kernel, $12 is t0, but in 32bit kernel, it is t4, so,
> we need to use $12 instead of t0 here to cover the 64bit and 32bit
> support.
>
> [1] Gcc doc: MIPS Options
> http://gcc.gnu.org/onlinedocs/gcc/MIPS-Options.html
>
> Signed-off-by: Wu Zhangjin<wuzhangjin@gmail.com>

Would it be better to do?:

#define MCOUNT_RA_ADDRESS_REG $12

s/t0/MCOUNT_RA_ADDRESS_REG/g

David Daney

> ---
>   arch/mips/kernel/mcount.S |   10 +++++-----
>   1 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
> index e256bf9..92d1540 100644
> --- a/arch/mips/kernel/mcount.S
> +++ b/arch/mips/kernel/mcount.S
> @@ -69,7 +69,7 @@ _mcount:
>
>   	MCOUNT_SAVE_REGS
>   #ifdef KBUILD_MCOUNT_RA_ADDRESS
> -	PTR_S	t0, PT_R12(sp)	/* t0 saved the location of the return address(at) by -mmcount-ra-address */
> +	PTR_S	$12, PT_R12(sp)	/* $12 saved the location of the return address(at) by -mmcount-ra-address */
>   #endif
>
>   	move	a0, ra		/* arg1: next ip, selfaddr */
> @@ -135,7 +135,7 @@ NESTED(ftrace_graph_caller, PT_SIZE, ra)
>   #ifdef CONFIG_DYNAMIC_FTRACE
>   	PTR_L	a1, PT_R31(sp)	/* load the original ra from the stack */
>   #ifdef KBUILD_MCOUNT_RA_ADDRESS
> -	PTR_L	t0, PT_R12(sp)	/* load the original t0 from the stack */
> +	PTR_L	$12, PT_R12(sp)	/* load the original $12 from the stack */
>   #endif
>   #else
>   	MCOUNT_SAVE_REGS
> @@ -143,10 +143,10 @@ NESTED(ftrace_graph_caller, PT_SIZE, ra)
>   #endif
>
>   #ifdef KBUILD_MCOUNT_RA_ADDRESS
> -	bnez	t0, 1f		/* non-leaf func: t0 saved the location of the return address */
> +	bnez	$12, 1f		/* non-leaf func: $12 saved the location of the return address */
>   	 nop
> -	PTR_LA	t0, PT_R1(sp)	/* leaf func: get the location of at(old ra) from our own stack */
> -1:	move	a0, t0		/* arg1: the location of the return address */
> +	PTR_LA	$12, PT_R1(sp)	/* leaf func: get the location of at(old ra) from our own stack */
> +1:	move	a0, $12		/* arg1: the location of the return address */
>   #else
>   	PTR_LA	a0, PT_R1(sp)	/* arg1:&AT ->  a0 */
>   #endif