Re: [PATCH,TRIVIAL] Fix csum_ipv6_magic asm memory clobber

Re: [PATCH,TRIVIAL] Fix csum_ipv6_magic asm memory clobber

[Andrew Morton]

On Thu, 1 Oct 2009 01:01:38 +0200
Samuel Thibault <samuel.thibault@ens-lyon.org> wrote:

> Actually it hit Hurd's pfinetv4 when we tried to compile it with
> gcc-4.3 (bogus checksums).

That's important information!  I updated the changelog and added the
Cc:stable, thanks.


Full patch for netdev benefit:


From: Samuel Thibault <samuel.thibault@ens-lyon.org>

Just like ip_fast_csum, the assembly snippet in csum_ipv6_magic needs a
memory clobber, as it is only passed the address of the buffer, not a
memory reference to the buffer itself.

This caused failures in Hurd's pfinetv4 when we tried to compile it with
gcc-4.3 (bogus checksums).

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86/include/asm/checksum_32.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff -puN arch/x86/include/asm/checksum_32.h~x86-fix-csum_ipv6_magic-asm-memory-clobber arch/x86/include/asm/checksum_32.h
--- a/arch/x86/include/asm/checksum_32.h~x86-fix-csum_ipv6_magic-asm-memory-clobber
+++ a/arch/x86/include/asm/checksum_32.h
@@ -161,7 +161,8 @@ static inline __sum16 csum_ipv6_magic(co
 	    "adcl $0, %0	;\n"
 	    : "=&r" (sum)
 	    : "r" (saddr), "r" (daddr),
-	      "r" (htonl(len)), "r" (htonl(proto)), "0" (sum));
+	      "r" (htonl(len)), "r" (htonl(proto)), "0" (sum)
+	    : "memory");
 
 	return csum_fold(sum);
 }
_

Re: [PATCH,TRIVIAL] Fix csum_ipv6_magic asm memory clobber

[David Miller]

From: Andrew Morton <akpm@linux-foundation.org>
Date: Wed, 30 Sep 2009 16:19:39 -0700

> From: Samuel Thibault <samuel.thibault@ens-lyon.org>
> 
> Just like ip_fast_csum, the assembly snippet in csum_ipv6_magic needs a
> memory clobber, as it is only passed the address of the buffer, not a
> memory reference to the buffer itself.
> 
> This caused failures in Hurd's pfinetv4 when we tried to compile it with
> gcc-4.3 (bogus checksums).
> 
> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

I'm happy to see this go in via the x86 tree, and thus:

Acked-by: David S. Miller <davem@davemloft.net>

Re: [PATCH,TRIVIAL] Fix csum_ipv6_magic asm memory clobber

[H. Peter Anvin]

On 09/30/2009 04:22 PM, David Miller wrote:
> From: Andrew Morton <akpm@linux-foundation.org>
> Date: Wed, 30 Sep 2009 16:19:39 -0700
> 
>> From: Samuel Thibault <samuel.thibault@ens-lyon.org>
>>
>> Just like ip_fast_csum, the assembly snippet in csum_ipv6_magic needs a
>> memory clobber, as it is only passed the address of the buffer, not a
>> memory reference to the buffer itself.
>>
>> This caused failures in Hurd's pfinetv4 when we tried to compile it with
>> gcc-4.3 (bogus checksums).
>>
>> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
>> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> 
> I'm happy to see this go in via the x86 tree, and thus:
> 
> Acked-by: David S. Miller <davem@davemloft.net>

I'll put it in x86/urgent tonight or early tomorrow morning (just about
to leave for the airport.)

	-hpa