[PATCH V4 4/7] x86/entry: Move cld to the start of idtentry

From: Lai Jiangshan
Date: Fri Mar 18 2022 - 10:30:12 EST


From: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>

Make it next to CLAC

Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
---
arch/x86/entry/entry_64.S | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 666109d56f6b..8121b9f3fceb 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -360,6 +360,7 @@ SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS offset=\has_error_code*8
ENDBR
ASM_CLAC
+ cld

.if \has_error_code == 0
pushq $-1 /* ORIG_RAX: no syscall to restart */
@@ -428,6 +429,7 @@ SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS
ENDBR
ASM_CLAC
+ cld

pushq $-1 /* ORIG_RAX: no syscall to restart */

@@ -484,6 +486,7 @@ SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS
ENDBR
ASM_CLAC
+ cld

/*
* If the entry is from userspace, switch stacks and treat it as
@@ -546,6 +549,7 @@ SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS offset=8
ENDBR
ASM_CLAC
+ cld

/* paranoid_entry returns GS information for paranoid_exit in EBX. */
call paranoid_entry
@@ -871,7 +875,6 @@ SYM_CODE_END(xen_failsafe_callback)
*/
SYM_CODE_START_LOCAL(paranoid_entry)
UNWIND_HINT_FUNC
- cld
PUSH_AND_CLEAR_REGS save_ret=1
ENCODE_FRAME_POINTER 8

@@ -989,7 +992,6 @@ SYM_CODE_END(paranoid_exit)
*/
SYM_CODE_START_LOCAL(error_entry)
UNWIND_HINT_FUNC
- cld
testb $3, CS+8(%rsp)
jz .Lerror_kernelspace

@@ -1123,6 +1125,7 @@ SYM_CODE_START(asm_exc_nmi)
*/

ASM_CLAC
+ cld

/* Use %rdx as our temp variable throughout */
pushq %rdx
@@ -1142,7 +1145,6 @@ SYM_CODE_START(asm_exc_nmi)
*/

swapgs
- cld
FENCE_SWAPGS_USER_ENTRY
SWITCH_TO_KERNEL_CR3 scratch_reg=%rdx
movq %rsp, %rdx
--
2.19.1.6.gb485710b