linux-kernel - [PATCH 1/5] x86/entry: introduce macro idtentry_swapgs_and_switch_to_kernel

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Date:   Wed, 27 May 2020 07:31:03 +0000
From:   Lai Jiangshan <laijs@...ux.alibaba.com>
To:     linux-kernel@...r.kernel.org
Cc:     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>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH 1/5] x86/entry: introduce macro idtentry_swapgs_and_switch_to_kernel_stack

Move a portion of code to be a macro, and it will also be used in
next patch.

Just move around the code, no functionality changed.

Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
---
 arch/x86/entry/entry_64.S | 60 ++++++++++++++++++++++++++-------------
 1 file changed, 41 insertions(+), 19 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index d983a0d4bc73..5e983506f82e 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -698,28 +698,22 @@ SYM_CODE_END(\asmsym)
 #include <asm/idtentry.h>
 
 /*
- * Interrupt entry helper function.
+ * IDT entry helper macro for entering from userspace.
  *
  * Entry runs with interrupts off. Stack layout at entry:
- * +----------------------------------------------------+
- * | regs->ss						|
- * | regs->rsp						|
- * | regs->eflags					|
- * | regs->cs						|
- * | regs->ip						|
- * +----------------------------------------------------+
- * | regs->orig_ax = ~(interrupt number)		|
- * +----------------------------------------------------+
- * | return address					|
- * +----------------------------------------------------+
+ * +--------------------+
+ * | regs->ss		|
+ * | regs->rsp		|
+ * | regs->eflags	|
+ * | regs->cs		|
+ * | regs->ip		|
+ * | regs->orig_ax	|
+ * | return address	|
+ * +--------------------+
+ * The macro does swapgs and switches to current kernel stack with the
+ * same stack layout copied.
  */
-SYM_CODE_START(interrupt_entry)
-	UNWIND_HINT_IRET_REGS offset=16
-	ASM_CLAC
-	cld
-
-	testb	$3, CS-ORIG_RAX+8(%rsp)
-	jz	1f
+.macro idtentry_swapgs_and_switch_to_kernel_stack
 	SWAPGS
 	FENCE_SWAPGS_USER_ENTRY
 	/*
@@ -751,6 +745,34 @@ SYM_CODE_START(interrupt_entry)
 	pushq	8(%rdi)			/* return address */
 
 	movq	(%rdi), %rdi
+.endm
+
+/*
+ * Interrupt entry helper function.
+ *
+ * Entry runs with interrupts off. Stack layout at entry:
+ * +----------------------------------------------------+
+ * | regs->ss						|
+ * | regs->rsp						|
+ * | regs->eflags					|
+ * | regs->cs						|
+ * | regs->ip						|
+ * +----------------------------------------------------+
+ * | regs->orig_ax = ~(interrupt number)		|
+ * +----------------------------------------------------+
+ * | return address					|
+ * +----------------------------------------------------+
+ */
+SYM_CODE_START(interrupt_entry)
+	UNWIND_HINT_IRET_REGS offset=16
+	ASM_CLAC
+	cld
+
+	testb	$3, CS-ORIG_RAX+8(%rsp)
+	jz	1f
+
+	idtentry_swapgs_and_switch_to_kernel_stack
+
 	jmp	2f
 1:
 	FENCE_SWAPGS_KERNEL_ENTRY
-- 
2.20.1