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SubjectRe: [PATCH] arch: avr32: add dummy syscalls
On Sun, Feb 03, 2013 at 09:35:39PM -0800, H?vard Skinnemoen wrote:

> Right.
>
> > But yes, 32bit/32bit/64bit/32bit is another interesting case -
> > fanotify_mark is 32/32/64/32/32. From what ABI says it would seem to
> > be r12/r11/r8:r9/r10/stack, but if I understand you correctly, we'll
> > end up wanting *two* arguments on stack...
>
> Yes, I think there may be a difference between the IAR and gcc ABI
> here. But I could be wrong.

Umm... avr32_function_arg() in atmel 4.4.3 patch:
if (arg_rsize == 8)
{
/* use r11:r10 or r9:r8. */
if (!(GET_USED_INDEX (cum, 1) || GET_USED_INDEX (cum, 2)))
index = 1;
else if ((last_reg_index == 4) &&
!(GET_USED_INDEX (cum, 3) || GET_USED_INDEX (cum, 4)))
index = 3;
else
index = -1;
}
else if (arg_rsize == 4)
{ /* Use first available register */
index = 0;
while (index <= last_reg_index && GET_USED_INDEX (cum, index))
index++;
if (index > last_reg_index)
index = -1;
}

So it will use the gap in case of 32/32/64/32; the first two calls will
take index 0 and 1 (r12 and r11 resp.), the third will take 3 and 4
(r9:r8) and the fourth will take 2 (r10). Relevant part of
avr32_function_arg_advance():
/* Mark the used registers as "used". */
if (GET_REG_INDEX (cum) >= 0)
{
SET_USED_INDEX (cum, GET_REG_INDEX (cum));
if (arg_rsize == 8)
{
SET_USED_INDEX (cum, (GET_REG_INDEX (cum) + 1));
}
}
i.e. the third argument will only stomp on 3 and 4, leaving 2 unused.

And as far as I can see, their 4.3.3 patch does the same thing...


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