On February 13, 2017 11:06:04 AM PST, Andy Lutomirski <l...@amacapital.net> wrote: >On Mon, Feb 13, 2017 at 2:13 AM, Dmitry Safonov ><dsafo...@virtuozzo.com> 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 <l...@kernel.org> > >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. > >--Andy
If we can do so that cheaply I think we should. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
