linux-kernel - Re: memcmp in modules

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Date:	Mon, 22 Apr 2013 23:26:05 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	andy.shevchenko@...il.com, arjan@...radead.org, hpa@...or.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: memcmp in modules

Andy Shevchenko wrote:
> What did I miss?

Well, as of linux-next-20130422, memcmp() is not correctly exported to modules.
Since linux-3.9-rc8 correctly exports memcmp(), this problem seems to be introduced
in linux-next tree. Also, this problem seems to involve CONFIG_MODVERSIONS=y.

  [root@...alhost linux-next]# modprobe ipv6
  FATAL: Error inserting ipv6 (/lib/modules/3.9.0-rc8-next-20130422/kernel/net/ipv6/ipv6.ko): Invalid argument
  [root@...alhost linux-next]# dmesg
  ipv6: no symbol version for memcmp
  ipv6: Unknown symbol memcmp (err -22)

Since arch/x86/include/asm/string_64.h uses

  int memcmp(const void *cs, const void *ct, size_t count);

while arch/x86/include/asm/string_32.h uses

  #define memcmp __builtin_memcmp

changing to what you have tried

  #define memcmp(a, b, n) __builtin_memcmp(a, b, n)

or changing to what x86_64 does

  int memcmp(const void *cs, const void *ct, size_t count);

might solve this problem. But I don't know which one is correct solution...
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