Re: Q: put_user_try & co (Was: [PATCH 1/5] Split wait_noreap_copyout())

[Andreas Schwab]

Oleg Nesterov <oleg@xxxxxxxxxx> writes:

> Pseudo-code:
>
> 	#define put_user_try				\
> 		do {					\
> 			__label__  __efault_label;	\
>
>
> 	#define put_user_catch(err)			\
> 			err = 0;			\
> 			if (0) {			\
> 			__efault_label:			\
> 				err = -EFAULT;		\
> 			}				\
> 		while (0)
> 		
>
> 	#define __put_user_asm_ex(...)				\
> 		asm volatile(					\
> 			"1:	mov ..."			\
> 			_ASM_EXTABLE(1b, &__efault_label)	\
> 		     	: : ...)

The address of local labels can only be used in connection with computed
gotos, otherwise you get unspecified results.

Andreas.

-- 
Andreas Schwab, schwab@xxxxxxxxxxxxxx
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