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SubjectRe: [RFC][PATCH] ia64: fix csum_ipv6_magic()
On Tue, Sep 01, 2009 at 04:20:34PM -0700, Luck, Tony wrote:
> >--- a/arch/ia64/lib/ip_fast_csum.S
> >+++ b/arch/ia64/lib/ip_fast_csum.S
> >@@ -96,20 +96,22 @@ END(ip_fast_csum)
> > GLOBAL_ENTRY(csum_ipv6_magic)
> > ld4 r20=[in0],4
> > ld4 r21=[in1],4
> >- dep r15=in3,in2,32,16
> >+ zxt4 in3=in3
>
> I think this zxt4 instruction have a typo. You really want to zap the
> high part on "in2" here (the "len") parameter. "in3" contains the "proto"
> argument, which is only 16-bits. But any garbage in the high part on in3
> will be dropped by the "dep" instruction later which only pulls out the low
> 16 bits from it.
>
> So I think you meant to type:
>
> zxt4 in2=in2
>
> Does this make sense?

Yes, exactly, you are right. Thanks for spotting it. The fixed patch
follows:


[IA64] fix csum_ipv6_magic()

The 32-bit parameters (len and csum) of csum_ipv6_magic() are passed in 64-bit
registers in3 and in4. The high order 32 bits of the registers were never
cleared, and garbage was sometimes calculated into the checksum.

Fix this by clearing the high order 32 bits of the registers.

Signed-off-by: Jiri Bohac <jbohac@suse.cz>

diff --git a/arch/ia64/lib/ip_fast_csum.S b/arch/ia64/lib/ip_fast_csum.S
index 1f86aeb..9a8d23f 100644
--- a/arch/ia64/lib/ip_fast_csum.S
+++ b/arch/ia64/lib/ip_fast_csum.S
@@ -96,20 +96,22 @@ END(ip_fast_csum)
GLOBAL_ENTRY(csum_ipv6_magic)
ld4 r20=[in0],4
ld4 r21=[in1],4
- dep r15=in3,in2,32,16
+ zxt4 in2=in2
;;
ld4 r22=[in0],4
ld4 r23=[in1],4
- mux1 r15=r15,@rev
+ dep r15=in3,in2,32,16
;;
ld4 r24=[in0],4
ld4 r25=[in1],4
- shr.u r15=r15,16
+ mux1 r15=r15,@rev
add r16=r20,r21
add r17=r22,r23
+ zxt4 in4=in4
;;
ld4 r26=[in0],4
ld4 r27=[in1],4
+ shr.u r15=r15,16
add r18=r24,r25
add r8=r16,r17
;;

--
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, SUSE CZ



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