diff mbox series

[RFC,1/7] x86/entry: Move PUSH_AND_CLEAR_REGS out of paranoid_entry

Message ID 20230403140605.540512-2-jiangshanlai@gmail.com (mailing list archive)
State New, archived
Headers show
Series x86/entry: Atomic statck switching for IST | expand

Commit Message

Lai Jiangshan April 3, 2023, 2:05 p.m. UTC 
From: Lai Jiangshan <jiangshan.ljs@antgroup.com>

Prepare to call paranoid_entry() with pt_regs pushed.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
---
 arch/x86/entry/entry_64.S | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

Comments

Peter Zijlstra April 6, 2023, 8:37 p.m. UTC | #1 
On Mon, Apr 03, 2023 at 10:05:59PM +0800, Lai Jiangshan wrote:
> @@ -915,11 +922,8 @@ SYM_CODE_END(xen_failsafe_callback)
>   * R14 - old CR3
>   * R15 - old SPEC_CTRL
>   */
> -SYM_CODE_START(paranoid_entry)
> +SYM_FUNC_START(paranoid_entry)
>  	ANNOTATE_NOENDBR
> -	UNWIND_HINT_FUNC

That isn't quite equivalent. SYM_FUNC_START() gets you ENDBR, while the
SYM_CODE_START(); ANNOTATE_NOENDBR; UNWIND_HINT_FUNC is
explicitly no ENDBR.


> -	PUSH_AND_CLEAR_REGS save_ret=1
> -	ENCODE_FRAME_POINTER 8
>  
>  	/*
>  	 * Always stash CR3 in %r14.  This value will be restored,
diff mbox series

Patch

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index eccc3431e515..49ddc4dd3117 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -475,11 +475,13 @@  SYM_CODE_START(\asmsym)
 	testb	$3, CS-ORIG_RAX(%rsp)
 	jnz	.Lfrom_usermode_switch_stack_\@
 
+	PUSH_AND_CLEAR_REGS
+	UNWIND_HINT_REGS
+	ENCODE_FRAME_POINTER
+
 	/* paranoid_entry returns GS information for paranoid_exit in EBX. */
 	call	paranoid_entry
 
-	UNWIND_HINT_REGS
-
 	movq	%rsp, %rdi		/* pt_regs pointer */
 
 	call	\cfunc
@@ -530,14 +532,16 @@  SYM_CODE_START(\asmsym)
 	testb	$3, CS-ORIG_RAX(%rsp)
 	jnz	.Lfrom_usermode_switch_stack_\@
 
+	PUSH_AND_CLEAR_REGS
+	UNWIND_HINT_REGS
+	ENCODE_FRAME_POINTER
+
 	/*
 	 * paranoid_entry returns SWAPGS flag for paranoid_exit in EBX.
 	 * EBX == 0 -> SWAPGS, EBX == 1 -> no SWAPGS
 	 */
 	call	paranoid_entry
 
-	UNWIND_HINT_REGS
-
 	/*
 	 * Switch off the IST stack to make it free for nested exceptions. The
 	 * vc_switch_off_ist() function will switch back to the interrupted
@@ -587,9 +591,12 @@  SYM_CODE_START(\asmsym)
 	ASM_CLAC
 	cld
 
+	PUSH_AND_CLEAR_REGS
+	UNWIND_HINT_REGS
+	ENCODE_FRAME_POINTER
+
 	/* paranoid_entry returns GS information for paranoid_exit in EBX. */
 	call	paranoid_entry
-	UNWIND_HINT_REGS
 
 	movq	%rsp, %rdi		/* pt_regs pointer into first argument */
 	movq	ORIG_RAX(%rsp), %rsi	/* get error code into 2nd argument*/
@@ -903,8 +910,8 @@  SYM_CODE_END(xen_failsafe_callback)
 #endif /* CONFIG_XEN_PV */
 
 /*
- * Save all registers in pt_regs. Return GSBASE related information
- * in EBX depending on the availability of the FSGSBASE instructions:
+ * Return GSBASE related information in EBX depending on the availability
+ * of the FSGSBASE instructions:
  *
  * FSGSBASE	R/EBX
  *     N        0 -> SWAPGS on exit
@@ -915,11 +922,8 @@  SYM_CODE_END(xen_failsafe_callback)
  * R14 - old CR3
  * R15 - old SPEC_CTRL
  */
-SYM_CODE_START(paranoid_entry)
+SYM_FUNC_START(paranoid_entry)
 	ANNOTATE_NOENDBR
-	UNWIND_HINT_FUNC
-	PUSH_AND_CLEAR_REGS save_ret=1
-	ENCODE_FRAME_POINTER 8
 
 	/*
 	 * Always stash CR3 in %r14.  This value will be restored,
@@ -988,7 +992,7 @@  SYM_CODE_START(paranoid_entry)
 	UNTRAIN_RET_FROM_CALL
 
 	RET
-SYM_CODE_END(paranoid_entry)
+SYM_FUNC_END(paranoid_entry)
 
 /*
  * "Paranoid" exit path from exception stack.  This is invoked
@@ -1443,6 +1447,10 @@  end_repeat_nmi:
 	 */
 	pushq	$-1				/* ORIG_RAX: no syscall to restart */
 
+	PUSH_AND_CLEAR_REGS
+	UNWIND_HINT_REGS
+	ENCODE_FRAME_POINTER
+
 	/*
 	 * Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit
 	 * as we should not be calling schedule in NMI context.
@@ -1451,7 +1459,6 @@  end_repeat_nmi:
 	 * exceptions might do.
 	 */
 	call	paranoid_entry
-	UNWIND_HINT_REGS
 
 	movq	%rsp, %rdi
 	movq	$-1, %rsi