Re: [PATCH] ARM: add get_user() support for 8 byte types

On Mon, Nov 12, 2012 at 06:31:50PM -0600, Rob Clark wrote:

right, that is what I was worried about.. but what about something along the lines of:

case 8: {						\
	if (sizeof(x) < 8)				\
		__get_user_x(__r2, __p, __e, __l, 4);	\
	else						\
		__get_user_x(__r2, __p, __e, __l, 8);	\
	break;						\
}							\

maybe we need a special variant of __get_user_8() instead to get the right 32bits on big vs little endian systems, but I think something roughly along these lines could work.

The problem with that is... big endian systems - where the 32-bit word we want is the second one, so you can't just reduce that down to a 32-bit access like that. You also need to add an offset to the pointer in the BE case (which can be done.)

I'd suggest calling the 4-byte version in there __get_user_xb() and doing the 4-byte offset for BE inside that (or aliasing it to __get_user_x for LE systems).