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
USERGS_SYSRET64
CFI_RESTORE_STATE
--
1.8.1.4
--
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