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Subject[PATCH V6 27/49] x86/entry: Make paranoid_exit() callable
Date
From: Lai Jiangshan <laijs@linux.alibaba.com>

Move the last JMP out of paranoid_exit() and make it callable.

Allow paranoid_exit() to be re-written in C later and also allow
asm_exc_nmi() to call it to avoid duplicated code.

No functional change intended.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
arch/x86/entry/entry_64.S | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index dd0cb43627a3..897892dc563c 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -471,7 +471,8 @@ SYM_CODE_START(\asmsym)

call \cfunc

- jmp paranoid_exit
+ call paranoid_exit
+ jmp restore_regs_and_return_to_kernel

/* Switch to the regular task stack and use the noist entry point */
.Lfrom_usermode_switch_stack_\@:
@@ -549,7 +550,8 @@ SYM_CODE_START(\asmsym)
* identical to the stack in the IRET frame or the VC fall-back stack,
* so it is definitely mapped even with PTI enabled.
*/
- jmp paranoid_exit
+ call paranoid_exit
+ jmp restore_regs_and_return_to_kernel

/* Switch to the regular task stack */
.Lfrom_usermode_switch_stack_\@:
@@ -580,7 +582,8 @@ SYM_CODE_START(\asmsym)
movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */
call \cfunc

- jmp paranoid_exit
+ call paranoid_exit
+ jmp restore_regs_and_return_to_kernel

_ASM_NOKPROBE(\asmsym)
SYM_CODE_END(\asmsym)
@@ -972,7 +975,7 @@ SYM_CODE_END(paranoid_entry)
* Y User space GSBASE, must be restored unconditionally
*/
SYM_CODE_START_LOCAL(paranoid_exit)
- UNWIND_HINT_REGS
+ UNWIND_HINT_REGS offset=8
/*
* The order of operations is important. RESTORE_CR3 requires
* kernel GSBASE.
@@ -988,16 +991,17 @@ SYM_CODE_START_LOCAL(paranoid_exit)

/* With FSGSBASE enabled, unconditionally restore GSBASE */
wrgsbase %rbx
- jmp restore_regs_and_return_to_kernel
+ ret

.Lparanoid_exit_checkgs:
/* On non-FSGSBASE systems, conditionally do SWAPGS */
testl %ebx, %ebx
- jnz restore_regs_and_return_to_kernel
+ jnz .Lparanoid_exit_done

/* We are returning to a context with user GSBASE */
swapgs
- jmp restore_regs_and_return_to_kernel
+.Lparanoid_exit_done:
+ ret
SYM_CODE_END(paranoid_exit)

SYM_CODE_START_LOCAL(error_return)
--
2.19.1.6.gb485710b
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