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powerpc/64: Fix checksum folding in csum_tcpudp_nofold and ip_fast_csum_nofold 

These functions compute an IP checksum by computing a 64-bit sum and
folding it to 32 bits (the "nofold" in their names refers to folding
down to 16 bits).  However, doing (u32) (s + (s >> 32)) is not
sufficient to fold a 64-bit sum to 32 bits correctly.  The addition
can produce a carry out from bit 31, which needs to be added in to
the sum to produce the correct result.

To fix this, we copy the from64to32() function from lib/checksum.c
and use that.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Paul Mackerras 2016-11-03 16:10:55 +11:00 committed by Michael Ellerman
parent 14a41d6b75
commit b492f7e4e0
1 changed files with 12 additions and 5 deletions
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17
arch/powerpc/include/asm/checksum.h
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@ -53,17 +53,25 @@ static inline __sum16 csum_fold(__wsum sum)
return (__force __sum16)(~((__force u32)sum + tmp) >> 16);
}
static inline u32 from64to32(u64 x)
{
/* add up 32-bit and 32-bit for 32+c bit */
x = (x & 0xffffffff) + (x >> 32);
/* add up carry.. */
x = (x & 0xffffffff) + (x >> 32);
return (u32)x;
}
static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, __u32 len,
__u8 proto, __wsum sum)
{
#ifdef __powerpc64__
unsigned long s = (__force u32)sum;
u64 s = (__force u32)sum;
s += (__force u32)saddr;
s += (__force u32)daddr;
s += proto + len;
s += (s >> 32);
return (__force __wsum) s;
return (__force __wsum) from64to32(s);
#else
__asm__("\n\
addc %0,%0,%1 \n\
@ -123,8 +131,7 @@ static inline __wsum ip_fast_csum_nofold(const void *iph, unsigned int ihl)
for (i = 0; i < ihl - 1; i++, ptr++)
s += *ptr;
s += (s >> 32);
return (__force __wsum)s;
return (__force __wsum)from64to32(s);
#else
__wsum sum, tmp;