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Re: [PATCH -v5] MIPS: tracing: Optimize the implementation

To: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: [PATCH -v5] MIPS: tracing: Optimize the implementation
From: Wu Zhangjin <wuzhangjin@gmail.com>
Date: Mon, 19 Apr 2010 17:36:08 +0800
Cc: linux-mips@linux-mips.org, Steven Rostedt <rostedt@goodmis.org>
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In-reply-to: <1271537514-19584-1-git-send-email-wuzhangjin@gmail.com>
Organization: DSLab, Lanzhou University, China
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1271537514-19584-1-git-send-email-wuzhangjin@gmail.com>
Reply-to: wuzhangjin@gmail.com
Sender: linux-mips-bounce@linux-mips.org
On Sun, 2010-04-18 at 04:51 +0800, Wu Zhangjin wrote:
[...]
> diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
[...]
>  
> @@ -45,8 +46,6 @@
>       PTR_L   a5, PT_R9(sp)
>       PTR_L   a6, PT_R10(sp)
>       PTR_L   a7, PT_R11(sp)
> -#endif
> -#ifdef CONFIG_64BIT
>       PTR_ADDIU       sp, PT_SIZE
>  #else
>       PTR_ADDIU       sp, (PT_SIZE + 8)
> @@ -71,7 +70,7 @@ _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) */
>  #endif
>  
>       move    a0, ra          /* arg1: next ip, selfaddr */
> @@ -137,25 +136,22 @@ 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   a0, PT_R12(sp)  /* arg1: the location of the return address */
>  #endif
> -#else
> +#else /* ! CONFIG_DYNAMIC_FTRACE */
>       MCOUNT_SAVE_REGS
>       move    a1, ra          /* arg2: next ip, selfaddr */
>  #endif
>  
>  #ifdef KBUILD_MCOUNT_RA_ADDRESS
> -     bnez    t0, 1f          /* non-leaf func: t0 saved the location of the 
> return address */
> +     bnez    a0, 1f          /* non-leaf func: get the location of the 
> return address from saved $12 */
>        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 */
> -#else
> -     PTR_LA  a0, PT_R1(sp)   /* arg1: &AT -> a0 */
>  #endif
> -     jal     prepare_ftrace_return

The above change has broken the static function graph tracer with
-mmcount-ra-address for it did not consider the argument 1 for static
function graph tracer, a new revision of this patch will be sent out as
"MIPS: tracing: adds misc cleanups and fixups".

Regards,
        Wu Zhangjin


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