[1/2] powerpc/64: Fix checksum folding in csum_tcpudp_nofold and ip_fast_csum_nofold

Michael Ellerman patch-notifications at ellerman.id.au
Fri Jan 27 11:40:32 AEDT 2017

On Thu, 2016-11-03 at 05:10:55 UTC, Paul Mackerras wrote:
> 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 at ozlabs.org>

Applied to powerpc next, thanks.



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