[PATCH V2 09/41] x86/entry: Expose the address of .Lgs_change to entry64.c

From: Lai Jiangshan
Date: Sun Sep 26 2021 - 11:09:52 EST


From: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx>

The address of .Lgs_change will be used in traps.c in later patch when
some entry code is implemented in entry64.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 due to it
can not use asm_load_gs_index_gs_change. Otherwise:

warning: objtool: __ex_table+0x0: don't know how to handle
non-section reloc symbol asm_load_gs_index_gs_change

Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx>
---
arch/x86/entry/entry64.c | 2 ++
arch/x86/entry/entry_64.S | 3 ++-
2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/entry64.c b/arch/x86/entry/entry64.c
index 3a6d70367940..7272266a3726 100644
--- a/arch/x86/entry/entry64.c
+++ b/arch/x86/entry/entry64.c
@@ -9,3 +9,5 @@
* is PTI user CR3 or both.
*/
#include <asm/traps.h>
+
+extern unsigned char asm_load_gs_index_gs_change[];
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 95d85b16710b..291732f571a7 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
@@ -1006,7 +1007,7 @@ 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

/*
--
2.19.1.6.gb485710b