Tkhai Kirill wrote:
When we are in the label cc_dword_align, registers %o0 and %o1 have the same last 2 bits,
but it's not guaranteed one of they is zero. So we can get unaligned memory access
in label ccte. Example of parameters which lead to this:
%o0=0x7ff183e9, %o1=0x8e709e7d, %g1=3
I just wanted to add that I also got unaligned accesses in the checksum
calculation on the SPARC32/LEON. Bad alignment is bad for performance of
course, in my case the MNA-trap handler was erroneous storing
incorrectly and that was the reason for me to notice it. I did not look
at the reason for the unaligned access in the first place though.
Daniel
commit 2492218c63dca0fb4f041bdc366d243ae3426b40
Author: Daniel Hellstrom <daniel@xxxxxxxxxxx>
Date: Tue Feb 1 12:39:59 2011 -0800
sparc32: unaligned memory access (MNA) trap handler bug
Since commit f0e98c387e61de00646be31fab4c2fa0224e1efb ("[SPARC]: Fix
link errors with gcc-4.3") the MNA trap handler does not emulate
stores to unaligned addresses correctly. MNA operation from both
kernel and user space are affected.
A typical effect of this bug is nr_frags in skbs are overwritten
during buffer copying/checksum-calculation, or maximally 6 bytes
of data in the network buffer will be overwitten with garbage.
Signed-off-by: Daniel Hellstrom <daniel@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
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