linux-kernel - Re: [v2, 06/21] powerpc: Avoid comparison of unsigned long >= 0 in __access

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Date:   Wed, 14 Mar 2018 20:28:27 +1100 (AEDT)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Mathieu Malaterre <malat@...ian.org>
Cc:     Mathieu Malaterre <malat@...ian.org>, linux-kernel@...r.kernel.org,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [v2, 06/21] powerpc: Avoid comparison of unsigned long >= 0 in __access_ok

On Fri, 2018-03-02 at 19:50:51 UTC, Mathieu Malaterre wrote:
> Rewrite function-like macro into regular static inline function to avoid a
> warning during macro expansion.
> Fix warning (treated as error in W=1):
> 
>   CC      arch/powerpc/kernel/signal_32.o
> In file included from ./include/linux/uaccess.h:14:0,
>                  from ./include/asm-generic/termios-base.h:8,
>                  from ./arch/powerpc/include/asm/termios.h:20,
>                  from ./include/uapi/linux/termios.h:6,
>                  from ./include/linux/tty.h:7,
>                  from arch/powerpc/kernel/signal_32.c:36:
> ./include/asm-generic/termios-base.h: In function ‘user_termio_to_kernel_termios’:
> ./arch/powerpc/include/asm/uaccess.h:52:35: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits]
>    (((size) == 0) || (((size) - 1) <= ((segment).seg - (addr)))))
>                                    ^
> ./arch/powerpc/include/asm/uaccess.h:58:3: note: in expansion of macro ‘__access_ok’
>    __access_ok((__force unsigned long)(addr), (size), get_fs()))
>    ^~~~~~~~~~~
> ./arch/powerpc/include/asm/uaccess.h:262:6: note: in expansion of macro ‘access_ok’
>   if (access_ok(VERIFY_READ, __gu_addr, (size)))   \
>       ^~~~~~~~~
> ./arch/powerpc/include/asm/uaccess.h:80:2: note: in expansion of macro ‘__get_user_check’
>   __get_user_check((x), (ptr), sizeof(*(ptr)))
>   ^~~~~~~~~~~~~~~~
> ./include/asm-generic/termios-base.h:36:6: note: in expansion of macro ‘get_user’
>   if (get_user(termios->c_line, &termio->c_line) < 0)
>       ^~~~~~~~
> [...]
> cc1: all warnings being treated as errors
> 
> Suggested-by: Segher Boessenkool <segher@...nel.crashing.org>
> Signed-off-by: Mathieu Malaterre <malat@...ian.org>
> Reviewed-by: Christophe Leroy <christophe.leroy@....fr>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/ef85dffd4251ff6c23056651f6f83b

cheers