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powerpc/32: Fix csum_partial_copy_generic()

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Commit 7aef413656 ("powerpc32: rewrite csum_partial_copy_generic()
based on copy_tofrom_user()") introduced a bug when destination
address is odd and initial csum is not null

In that (rare) case the initial csum value has to be rotated one byte
as well as the resulting value is

This patch also fixes related comments

Fixes: 7aef413656 ("powerpc32: rewrite csum_partial_copy_generic() based on copy_tofrom_user()")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Christophe Leroy 2016-08-02 10:07:05 +02:00 committed by Michael Ellerman
parent c6d2ee09c2
commit 1bc8b816cb
1 changed files with 4 additions and 3 deletions
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7
arch/powerpc/lib/checksum_32.S
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@ -127,8 +127,9 @@ _GLOBAL(csum_partial_copy_generic)
stw r7,12(r1)
stw r8,8(r1)
andi. r0,r4,1 /* is destination address even ? */
cmplwi cr7,r0,0
rlwinm r0,r4,3,0x8
rlwnm r6,r6,r0,0,31 /* odd destination address: rotate one byte */
cmplwi cr7,r0,0 /* is destination address even ? */
addic r12,r6,0
addi r6,r4,-4
neg r0,r4
@ -237,7 +238,7 @@ _GLOBAL(csum_partial_copy_generic)
66: addze r3,r12
addi r1,r1,16
beqlr+ cr7
rlwinm r3,r3,8,0,31 /* swap bytes for odd destination */
rlwinm r3,r3,8,0,31 /* odd destination address: rotate one byte */
blr
/* read fault */