Commit-ID: d441c1f2b73ec742c2e55be804ebc6fee130c77f
Gitweb: http://git.kernel.org/tip/d441c1f2b73ec742c2e55be804ebc6fee130c77f
Author: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
AuthorDate: Thu, 26 Feb 2015 14:40:38 -0800
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 4 Mar 2015 22:50:52 +0100
x86/asm/entry/64: Simplify optimistic SYSRET
Avoid redundant load of %r11 (it is already loaded a few
instructions before).
Also simplify %rsp restoration, instead of two steps:
add $0x80, %rsp
mov 0x18(%rsp), %rsp
we can do a simplified single step to restore user-space RSP:
mov 0x98(%rsp), %rsp
and get the same result.
Signed-off-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
[ Clarified the changelog. ]
Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Will Drewry <wad@xxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1aef69b346a6db0d99cdfb0f5ba83e8c985e27d7.1424989793.git.luto@xxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/include/asm/calling.h | 3 +++
arch/x86/kernel/entry_64.S | 6 +++---
2 files changed, 6 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 858e94e..bc15278 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -757,9 +757,9 @@ 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
+ /* r11 is already restored (see code above) */
+ RESTORE_C_REGS_EXCEPT_R11
+ movq RSP(%rsp),%rsp
USERGS_SYSRET64
CFI_RESTORE_STATE
--
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