On Mon, Feb 13, 2017 at 2:18 PM, <h...@zytor.com> wrote: > 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.
Sure, but we should still apply Dmitry's patches first.
