* Andy Lutomirski <[email protected]> wrote:
> On Mon, Feb 13, 2017 at 2:13 AM, Dmitry Safonov <[email protected]>
> wrote:
> > Kernel erases R8..R11 registers prior returning to userspace
> > from int80: https://lkml.org/lkml/2009/10/1/164
> >
> > GCC can reuse this registers and doesn't expect them to change
> > during syscall invocation. I met this kind of bug in CRIU once
> > gcc 6.1 and clang stored local variables in those registers
> > and the kernel zerofied them during syscall:
> > https://github.com/xemul/criu/commit/990d33f1a1cdd17bca6c2eb059ab3be2564f7fa2
> >
> > By that reason I suggest to add those registers to clobbers
> > in selftests. Also, as notted by Andy - removed unneeded clobber
> > for flags in int 0x80 inline asm.
>
> Acked-by: Andy Lutomirski <[email protected]>
>
> Although these days we could preserve these regs in the kernel at the cost of
> (I
> think) 4 bytes of text and zero runtime overhead.
I think we should try that...
Thanks,
Ingo
