Re: [PATCH 1/3] x86/uaccess: Add stack frame output operand in get_user inline asm

[Josh Poimboeuf <jpoimboe@redhat.com>]

On Thu, Sep 17, 2015 at 05:14:35PM -0500, Chris J Arges wrote:
> Numerous 'call without frame pointer save/setup' warnings are introduced by
> stacktool because of functions using the get_user macro. Bad stack traces could
> occur due to lack of or misplacement of stack frame setup code.
> 
> This patch forces a stack frame to be created before the inline asm code if
> CONFIG_FRAME_POINTER is enabled by listing the stack pointer as an output
> operand for the get_user inline assembly statement.
> 
> Signed-off-by: Chris J Arges <chris.j.arges@canonical.com>

Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>

> ---
>  arch/x86/include/asm/uaccess.h | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> index a8df874..55b8db5 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -176,10 +176,11 @@ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
>  ({									\
>  	int __ret_gu;							\
>  	register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);		\
> +	register void *__sp asm(_ASM_SP);				\
>  	__chk_user_ptr(ptr);						\
>  	might_fault();							\
> -	asm volatile("call __get_user_%P3"				\
> -		     : "=a" (__ret_gu), "=r" (__val_gu)			\
> +	asm volatile("call __get_user_%P4"				\
> +		     : "=a" (__ret_gu), "=r" (__val_gu), "+r" (__sp)	\
>  		     : "0" (ptr), "i" (sizeof(*(ptr))));		\
>  	(x) = (__force __typeof__(*(ptr))) __val_gu;			\
>  	__ret_gu;							\
> -- 
> 1.9.1
>