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
