linux-kernel - [PATCH 05/11] x86/entry: Move cld to the start of idtentry

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Message-Id: <20211208110833.65366-6-jiangshanlai@gmail.com>
Date:   Wed,  8 Dec 2021 19:08:27 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, xen-devel@...ts.xenproject.org,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH 05/11] x86/entry: Move cld to the start of idtentry

From: Lai Jiangshan <laijs@...ux.alibaba.com>

Make it next to CLAC

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
---
 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 72ceb4b70822..ee1d4adcdab0 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -356,6 +356,7 @@ SYM_CODE_END(ret_from_fork)
 SYM_CODE_START(\asmsym)
 	UNWIND_HINT_IRET_REGS offset=\has_error_code*8
 	ASM_CLAC
+	cld
 
 	.if \has_error_code == 0
 		pushq	$-1			/* ORIG_RAX: no syscall to restart */
@@ -423,6 +424,7 @@ SYM_CODE_END(\asmsym)
 SYM_CODE_START(\asmsym)
 	UNWIND_HINT_IRET_REGS
 	ASM_CLAC
+	cld
 
 	pushq	$-1			/* ORIG_RAX: no syscall to restart */
 
@@ -478,6 +480,7 @@ SYM_CODE_END(\asmsym)
 SYM_CODE_START(\asmsym)
 	UNWIND_HINT_IRET_REGS
 	ASM_CLAC
+	cld
 
 	/*
 	 * If the entry is from userspace, switch stacks and treat it as
@@ -539,6 +542,7 @@ SYM_CODE_END(\asmsym)
 SYM_CODE_START(\asmsym)
 	UNWIND_HINT_IRET_REGS offset=8
 	ASM_CLAC
+	cld
 
 	/* paranoid_entry returns GS information for paranoid_exit in EBX. */
 	call	paranoid_entry
@@ -853,7 +857,6 @@ 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
 
@@ -971,7 +974,6 @@ SYM_CODE_END(paranoid_exit)
  */
 SYM_CODE_START_LOCAL(error_entry)
 	UNWIND_HINT_FUNC
-	cld
 	testb	$3, CS+8(%rsp)
 	jz	.Lerror_kernelspace
 
@@ -1104,6 +1106,7 @@ SYM_CODE_START(asm_exc_nmi)
 	 */
 
 	ASM_CLAC
+	cld
 
 	/* Use %rdx as our temp variable throughout */
 	pushq	%rdx
@@ -1123,7 +1126,6 @@ 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