linux-kernel - [PATCH 04/24] x86/entry: Expose the address of .Lgs

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Date:   Wed,  1 Sep 2021 01:50:05 +0800
From:   Lai Jiangshan <jiangshanlai@...il.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 04/24] x86/entry: Expose the address of .Lgs_change to traps.c

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

The address of .Lgs_change will be used in traps.c in later patch when
some entry code is implemented in traps.c.  So the address of .Lgs_change
is exposed to traps.c for preparation.

The label .Lgs_change is still needed in ASM code for extable.

Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
---
 arch/x86/entry/entry_64.S | 3 ++-
 arch/x86/entry/traps.c    | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index e38a4cf795d9..9164e85b36b8 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -729,6 +729,7 @@ _ASM_NOKPROBE(common_interrupt_return)
 SYM_FUNC_START(asm_load_gs_index)
 	FRAME_BEGIN
 	swapgs
+SYM_INNER_LABEL(asm_load_gs_index_gs_change, SYM_L_GLOBAL)
 .Lgs_change:
 	movl	%edi, %gs
 2:	ALTERNATIVE "", "mfence", X86_BUG_SWAPGS_FENCE
@@ -1011,7 +1012,7 @@ SYM_CODE_START_LOCAL(error_entry)
 	movl	%ecx, %eax			/* zero extend */
 	cmpq	%rax, RIP+8(%rsp)
 	je	.Lbstep_iret
-	cmpq	$.Lgs_change, RIP+8(%rsp)
+	cmpq	$asm_load_gs_index_gs_change, RIP+8(%rsp)
 	jne	.Lerror_entry_done_lfence
 
 	/*
diff --git a/arch/x86/entry/traps.c b/arch/x86/entry/traps.c
index 7869343473b7..f71db7934f90 100644
--- a/arch/x86/entry/traps.c
+++ b/arch/x86/entry/traps.c
@@ -67,6 +67,7 @@
 #include <asm/proto.h>
 
 extern unsigned char native_irq_return_iret[];
+extern unsigned char asm_load_gs_index_gs_change[];
 
 #else
 #include <asm/processor-flags.h>
-- 
2.19.1.6.gb485710b