[PATCH v2 35/59] x86/entry: Make sync_regs() invocation a tail call

Peter Zijlstra posted 59 patches 3 years, 7 months ago
There is a newer version of this series
[PATCH v2 35/59] x86/entry: Make sync_regs() invocation a tail call
Posted by Peter Zijlstra 3 years, 7 months ago
From: Peter Zijlstra <peterz@infradead.org>

No point in having a call there. Spare the call/ret overhead.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/x86/entry/entry_64.S |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1062,11 +1062,8 @@ SYM_CODE_START_LOCAL(error_entry)
 	UNTRAIN_RET
 
 	leaq	8(%rsp), %rdi			/* arg0 = pt_regs pointer */
-.Lerror_entry_from_usermode_after_swapgs:
-
 	/* Put us onto the real thread stack. */
-	call	sync_regs
-	RET
+	jmp	sync_regs
 
 	/*
 	 * There are two places in the kernel that can potentially fault with
@@ -1124,7 +1121,7 @@ SYM_CODE_START_LOCAL(error_entry)
 	leaq	8(%rsp), %rdi			/* arg0 = pt_regs pointer */
 	call	fixup_bad_iret
 	mov	%rax, %rdi
-	jmp	.Lerror_entry_from_usermode_after_swapgs
+	jmp	sync_regs
 SYM_CODE_END(error_entry)
 
 SYM_CODE_START_LOCAL(error_return)