linux-kernel - Re: [PATCH v2] powerpc/uaccess: Implement unsafe_put

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Date:   Wed, 15 Apr 2020 17:37:47 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, npiggin@...il.com,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2] powerpc/uaccess: Implement unsafe_put_user() using 'asm goto'

Hi!

On Wed, Apr 15, 2020 at 09:25:59AM +0000, Christophe Leroy wrote:
> +#define __put_user_goto(x, ptr, label) \
> +	__put_user_nocheck_goto((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), label)

This line gets too long, can you break it up somehow?

> +#define __put_user_asm_goto(x, addr, label, op)			\
> +	asm volatile goto(					\
> +		"1:	" op "%U1%X1 %0,%1	# put_user\n"	\
> +		EX_TABLE(1b, %l2)				\
> +		:						\
> +		: "r" (x), "m" (*addr)				\
> +		:						\
> +		: label)

Same "%Un" problem as in the other patch.  You could use "m<>" here,
but maybe just dropping "%Un" is better.

> +#ifdef __powerpc64__
> +#define __put_user_asm2_goto(x, ptr, label)			\
> +	__put_user_asm_goto(x, ptr, label, "std")
> +#else /* __powerpc64__ */
> +#define __put_user_asm2_goto(x, addr, label)			\
> +	asm volatile goto(					\
> +		"1:	stw%U1%X1 %0, %1\n"			\
> +		"2:	stw%U1%X1 %L0, %L1\n"			\
> +		EX_TABLE(1b, %l2)				\
> +		EX_TABLE(2b, %l2)				\
> +		:						\
> +		: "r" (x), "m" (*addr)				\
> +		:						\
> +		: label)
> +#endif /* __powerpc64__ */

Here, you should drop it for sure.

Rest looks fine.

Reviewed-by: Segher Boessenkool <segher@...nel.crashing.org>


Segher