Reduce the number of variables modified by the loop in do_csum() by 1,
which seems like a good idea. On Nios II (a RISC CPU with 3-operand
instruction set) it reduces the loop from 7 to 6 instructions, including
the conditional branch.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
When do_csum gets unaligned data, we really need to treat
the first byte as an even byte, not an odd byte, because
we swap the two halves later.
Found by Mike's checksum-selftest module.
Reported-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Mike Frysinger suggested that do_csum should be optional
so that an architecture can use the generic checksum code
but still provide an optimized fast-path for the most
critical function.
This can mean an implementation using inline assembly,
or in case of Alpha one using 64-bit arithmetic in C.
Cc: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
The use of 'unsigned long' variables in the 32-bit part of do_csum()
is confusing at best, and potentially broken for long input on 64-bit
machines.
This changes the code to use 'unsigned int' instead, which makes
the code behave in the same (correct) way on both 32 and 64 bit
machines.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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>
Add a generic (unoptimized) implementation of checksum.c in pure C
for use by all architectures that cannot be bother with implementing
their own version.
Based on microblaze code by Michal Simek <monstr@monstr.eu>
Cc: Michal Simek <monstr@monstr.eu>
Signed-off-by: Remis Lima Baima <remis.developer@googlemail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
