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authorPaul Mackerras <paulus@ozlabs.org>2016-11-03 06:10:55 +0100
committerMichael Ellerman <mpe@ellerman.id.au>2017-01-25 03:34:18 +0100
commitb492f7e4e07a28e706db26cf4943bb0911435426 (patch)
tree2e5ce673c7553a9faccc17100785235cc8df9d0d /arch/powerpc/include/asm/checksum.h
parentpowerpc/powernv: Report size of OPAL memcons log (diff)
downloadlinux-b492f7e4e07a28e706db26cf4943bb0911435426.tar.xz
linux-b492f7e4e07a28e706db26cf4943bb0911435426.zip
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>
Diffstat (limited to 'arch/powerpc/include/asm/checksum.h')
-rw-r--r--arch/powerpc/include/asm/checksum.h17
1 files changed, 12 insertions, 5 deletions
diff --git a/arch/powerpc/include/asm/checksum.h b/arch/powerpc/include/asm/checksum.h
index 1e8fceb308a5..5b1a6e39afa7 100644
--- a/arch/powerpc/include/asm/checksum.h
+++ b/arch/powerpc/include/asm/checksum.h
@@ -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;