[PATCH] arm: fix returning wrong CALLER_ADDRx

[Dave Martin]

On Fri, Jan 11, 2013 at 04:18:10PM +0900, Keun-O Park wrote:
> From: sahara <keun-o.park at windriver.com>
> 
> This makes return_address return correct value for ftrace feature.
> unwind_frame does not update frame->lr but frame->pc for backtrace.
> And, the initialization for data.addr was missing so that wrong value
> returned when unwind_frame failed.
> 
> Signed-off-by: sahara <keun-o.park at windriver.com>

Reviewed-by: Dave Martin <dave.martin at linaro.org>

This is the same as a patch I previously posted:
http://lists.infradead.org/pipermail/linux-arm-kernel/2012-November/129381.html

...except for the initialisation of data.addr to NULL, which is needed
in order to prevent a garbage pointer being returned in the case where
the unwinder fails to unwind a frame before the required level
is reached.

Cheers
---Dave

> ---
>  arch/arm/kernel/return_address.c |    5 +++--
>  1 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/kernel/return_address.c b/arch/arm/kernel/return_address.c
> index 8085417..fafedd8 100644
> --- a/arch/arm/kernel/return_address.c
> +++ b/arch/arm/kernel/return_address.c
> @@ -26,7 +26,7 @@ static int save_return_addr(struct stackframe *frame, void *d)
>  	struct return_address_data *data = d;
>  
>  	if (!data->level) {
> -		data->addr = (void *)frame->lr;
> +		data->addr = (void *)frame->pc;
>  
>  		return 1;
>  	} else {
> @@ -41,7 +41,8 @@ void *return_address(unsigned int level)
>  	struct stackframe frame;
>  	register unsigned long current_sp asm ("sp");
>  
> -	data.level = level + 1;
> +	data.level = level + 2;
> +	data.addr = NULL;
>  
>  	frame.fp = (unsigned long)__builtin_frame_address(0);
>  	frame.sp = current_sp;
> -- 
> 1.7.1
> 
> 
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