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SubjectRe: [PATCH] fix for futex_wait signal stack corruption


On Tue, 4 Dec 2007, Steven Rostedt wrote:
>
> Seems that arg3 is not used here and since the timer is 64 bits, we can
> store the bottom 32 bits in arg2 and the top in arg3 (this will work for
> both 32 and 64 bit archs).

Yes. That should work fine.

The restart logic sometimes results in odd calling conventions, and quite
frankly, we could just change how "restart_block" looks too. There is
nothing that says that it has to be

unsigned long arg0, arg1, arg2, arg3

and that particular layout was just picked on a whim. The only issue is:

- we don't want the restart block to be *too* large, since it's part of
the thread info.
- but we need to have enough room for all the system calls that want to
use the restart block, and preferably in a reasonable format.

So far, using "unsigned long" has been good enough, in that it's big
enough for a pointer and all normal arguments, but if something really
deeply wants another format or a guaranteed 64-bit word regardless of
architecture, we could make one or more of the arguments be "u64" instead.

But in this case, since there is already unused argument space, I think
that doing the "32 high bits + 32 low bits" is probably the best option.

Linus


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