I have started to look a little bit at the LTP tests.
And one of the testcases that fails (actually it doesn't fail as it
supposed to do) is the syscall getsockopt.
I think the failure is due to the copy_to_user(0, from, 4) call returns
0, which I wouldn't expect when the destination pointer is NULL.

I think the problem is in the __copy_user function in
arch/mips/lib/memcpy.
It tries to handle the exception, which we get because the destination
pointer is NULL, by returning the number of uncopied bytes in $a2 to the
caller.
But in this case the length is only 4 bytes, and the copying is done by
a single 'sw'. The problem is the length ($a2) is decreased by 4 before
the 'sw' is executed.
The 'sw' fails and __copy_user terminates, but returns with $a2 = 0
(instead 4).

I thing the following patch will solve the problem.

/Carsten



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