Re: [RFC] de-asmify the x86-64 system call slowpath

[Linus Torvalds]

On Sun, Jan 26, 2014 at 4:22 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> Umm...  Can't uprobe_notify_resume() modify regs as well?

Probably.

.. and on the other hand, we should actually be able to use 'sysret'
for signal handling on x86-64, because while sysret destroys %rcx and
doesn't allow for returning to odd modes, for calling a signal handler
I don't think we really care..

> While we
> are at it, when we start using the same thing on 32bit kernels, we'll
> need to watch out for execve() - the reason why start_thread() sets
> TIF_NOTIFY_RESUME is to force us away from sysexit path.  IIRC, vm86
> is another thing to watch out for (same reasons).

Yes, the 32-bit code I didn't want to touch, partly because I no
longer have a test-case. And it does end up having some more
interesting cases.

                 Linus
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