On Thu, Mar 19, 2015 at 06:17:48PM +0100, Denys Vlasenko wrote:
> FIXUP_TOP_OF_STACK is only necessary because we don't save %r11
> to pt_regs->r11 on SYSCALL64 fast path, but we want ptrace to see
> it populated.
>
> Bite the bullet, add a single additional PUSH insn, and remove
> FIXUP_TOP_OF_STACK.
>
> RESTORE_TOP_OF_STACK is already a nop. Remove it too.
>
> On SandyBridge CPU, it does not get slower:
> measured 54.22 ns per getpid syscall before and after last two changes
> on defconfig kernel.
>
> Signed-off-by: Denys Vlasenko <dvlas...@redhat.com>
> CC: Linus Torvalds <torva...@linux-foundation.org>
> CC: Steven Rostedt <rost...@goodmis.org>
> CC: Ingo Molnar <mi...@kernel.org>
> CC: Borislav Petkov <b...@alien8.de>
> CC: "H. Peter Anvin" <h...@zytor.com>
> CC: Andy Lutomirski <l...@amacapital.net>
> CC: Oleg Nesterov <o...@redhat.com>
> CC: Frederic Weisbecker <fweis...@gmail.com>
> CC: Alexei Starovoitov <a...@plumgrid.com>
> CC: Will Drewry <w...@chromium.org>
> CC: Kees Cook <keesc...@chromium.org>
> CC: x...@kernel.org
> CC: linux-kernel@vger.kernel.org
> ---
> arch/x86/kernel/entry_64.S | 35 ++---------------------------------
> 1 file changed, 2 insertions(+), 33 deletions(-)
Nice diffstat.
Acked-by: Borislav Petkov <b...@suse.de>
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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