Carsten Langgaard wrote:
>
> 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.
Been here, done that. In fact, I posted the following patch few days ago
to the list:
less_than_4units:
/*
* rem = len % NBYTES
*/
beq rem, len, copy_bytes
nop
1:
EXC( LOAD t0, 0(src), l_exc)
ADD src, src, NBYTES
SUB len, len, NBYTES
-EXC( STORE t0, 0(dst), s_exc)
+EXC( STORE t0, 0(dst), s_exc_p1u)
bne rem, len, 1b
ADD dst, dst, NBYTES
This patch also solves the problem for mips in 2.4/2.5 kernel. My
question was about the patch for mips64 and mips in 2.2 kernel.
Shall memcpy.S from 2.4/2.5 be backported to 2.2 and mips64?
Regards,
Gleb.
