linux-kernel - Re: [PATCH] x86_32: Fix module version table mismatch.

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Date:	Tue, 23 Apr 2013 17:14:01 +0300
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:	arjan@...radead.org, hpa@...or.com, james.hogan@...tec.com,
	Rusty Russell <rusty@...tcorp.com.au>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86_32: Fix module version table mismatch.

On Tue, Apr 23, 2013 at 3:40 PM, Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
> Commit a4b6a77b "module: fix symbol versioning with symbol prefixes" broke
> loading of net/ipv6/ipv6.ko

I would rephrase this to "any module uses memcmp, e.g. ipv6"
Otherwise: Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
...and
Tested-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> built with CONFIG_MODVERSIONS=y for x86_32.
>
>   # modprobe ipv6
>   FATAL: Error inserting ipv6 (/lib/modules/3.9.0-rc8-next-20130422/kernel/net/ipv6/ipv6.ko): Invalid argument
>   # dmesg
>   ipv6: no symbol version for memcmp
>   ipv6: Unknown symbol memcmp (err -22)
>
> The reason for breakage is that check_version() in kernel/module.c tries to
> find symname == "memcmp" but versions[i].name == "__builtin_memcmp".
>
> The reason for versions[i].name == "__builtin_memcmp" is that
> memcmp() for x86_32 is defined as
>
>   #define memcmp __builtin_memcmp
>
> in arch/x86/include/asm/string_32.h while memcmp() for x86_64 is defined as
>
>   int memcmp(const void *cs, const void *ct, size_t count);
>
> in arch/x86/include/asm/string_64.h.
>
> Since __builtin_memcmp is a gcc's built-in function which might emit a call to
> memcmp, __builtin_memcmp should not be used for versions[i].name field.
>
> In order to make sure that versions[i].name == "memcmp", make the definition of
> memcmp() for x86_32 identical with that of x86_64.
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Cc: James Hogan <james.hogan@...tec.com>
> Cc: Rusty Russell <rusty@...tcorp.com.au>
> ---
>  arch/x86/include/asm/string_32.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
> index 3d3e835..bb85b4e 100644
> --- a/arch/x86/include/asm/string_32.h
> +++ b/arch/x86/include/asm/string_32.h
> @@ -199,7 +199,7 @@ static inline void *__memcpy3d(void *to, const void *from, size_t len)
>  #define __HAVE_ARCH_MEMMOVE
>  void *memmove(void *dest, const void *src, size_t n);
>
> -#define memcmp __builtin_memcmp
> +int memcmp(const void *cs, const void *ct, size_t count);
>
>  #define __HAVE_ARCH_MEMCHR
>  extern void *memchr(const void *cs, int c, size_t count);
> --
> 1.7.1



--
With Best Regards,
Andy Shevchenko
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