On Tue, Feb 24, 2015 at 4:00 PM, Denys Vlasenko <dvlas...@redhat.com> wrote: > Avoid redundant load of %r11 (it is already loaded a few instructions before). > Do not needlessly increment %rsp - we are going to return to userspace > via SYSRET, this insn doesn't use stack for return. > > 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/include/asm/calling.h | 3 +++ > arch/x86/kernel/entry_64.S | 5 ++--- > 2 files changed, 5 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/include/asm/calling.h b/arch/x86/include/asm/calling.h > index 3374235..f1a962f 100644 > --- a/arch/x86/include/asm/calling.h > +++ b/arch/x86/include/asm/calling.h > @@ -176,6 +176,9 @@ For 32-bit we have the following conventions - kernel is > built with > .macro RESTORE_C_REGS_EXCEPT_RCX > RESTORE_C_REGS_HELPER 1,0,1,1,1 > .endm > + .macro RESTORE_C_REGS_EXCEPT_R11 > + RESTORE_C_REGS_HELPER 1,1,0,1,1 > + .endm > .macro RESTORE_RSI_RDI > RESTORE_C_REGS_HELPER 0,0,0,0,0 > .endm > diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S > index 4b3f3c1..e5e0a55 100644 > --- a/arch/x86/kernel/entry_64.S > +++ b/arch/x86/kernel/entry_64.S > @@ -756,9 +756,8 @@ retint_swapgs: /* return to user-space */ > */ > irq_return_via_sysret: > CFI_REMEMBER_STATE > - RESTORE_C_REGS > - REMOVE_PT_GPREGS_FROM_STACK 8 > - movq (RSP-RIP)(%rsp),%rsp > + RESTORE_C_REGS_EXCEPT_R11 > + movq RSP(%rsp),%rsp
I think this needs a comment. --Andy > USERGS_SYSRET64 > CFI_RESTORE_STATE > > -- > 1.8.1.4 > -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
