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lib/checksum.c: fix endianess bug

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The new generic checksum code has a small dependency on endianess and
worked only on big-endian systems. I could not find a nice efficient
way to express this, so I added an #ifdef. Using
'result += le16_to_cpu(*buff);' would have worked as well, but
would be slightly less efficient on big-endian systems and IMHO
would not be clearer.

Also fix a bug that prevents this from working on 64-bit machines.
If you have a 64-bit CPU and want to use the generic checksum
code, you should probably do some more optimizations anyway, but
at least the code should not break.

Reported-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
This commit is contained in:
Arnd Bergmann 2009-06-19 10:41:19 +02:00
parent fcec9bf124
commit 32a9ff9cc5
1 changed files with 9 additions and 1 deletions
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10
lib/checksum.c
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@ -55,7 +55,11 @@ static unsigned int do_csum(const unsigned char *buff, int len)
goto out;
odd = 1 & (unsigned long) buff;
if (odd) {
#ifdef __LITTLE_ENDIAN
result = *buff;
#else
result += (*buff << 8);
#endif
len--;
buff++;
}
@ -71,7 +75,7 @@ static unsigned int do_csum(const unsigned char *buff, int len)
if (count) {
unsigned long carry = 0;
do {
unsigned long w = *(unsigned long *) buff;
unsigned long w = *(unsigned int *) buff;
count--;
buff += 4;
result += carry;
@ -87,7 +91,11 @@ static unsigned int do_csum(const unsigned char *buff, int len)
}
}
if (len & 1)
#ifdef __LITTLE_ENDIAN
result += *buff;
#else
result += (*buff << 8);
#endif
result = from32to16(result);
if (odd)
result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);