linux-kernel - [PATCH] x86-64: slightly shorten int_ret_from_sys

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Date:	Tue, 29 Nov 2011 10:54:22 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	<mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc:	<linux-kernel@...r.kernel.org>
Subject: [PATCH] x86-64: slightly shorten int_ret_from_sys_call

Testing for a return to ring 0 was necessary here solely because of the
branch out of ret_from_fork. That branch, however, can be directed to
retint_restore_args, and thus the test-and-branch can be eliminated
here.

Signed-off-by: Jan Beulich <jbeulich@...e.com>

---
 arch/x86/kernel/entry_64.S |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- 3.2-rc3/arch/x86/kernel/entry_64.S
+++ 3.2-rc3-x86_64-entry-iret-from-syscall/arch/x86/kernel/entry_64.S
@@ -411,7 +411,7 @@ ENTRY(ret_from_fork)
 	RESTORE_REST
 
 	testl $3, CS-ARGOFFSET(%rsp)		# from kernel_thread?
-	je   int_ret_from_sys_call
+	jz   retint_restore_args
 
 	testl $_TIF_IA32, TI_flags(%rcx)	# 32-bit compat task needs IRET
 	jnz  int_ret_from_sys_call
@@ -612,8 +612,6 @@ tracesys:
 GLOBAL(int_ret_from_sys_call)
 	DISABLE_INTERRUPTS(CLBR_NONE)
 	TRACE_IRQS_OFF
-	testl $3,CS-ARGOFFSET(%rsp)
-	je retint_restore_args
 	movl $_TIF_ALLWORK_MASK,%edi
 	/* edi:	mask to check */
 GLOBAL(int_with_check)



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