[PATCH] x86-64: slightly shorten int_ret_from_sys_call

[PATCH] x86-64: slightly shorten int_ret_from_sys_call

[Jan Beulich]

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@suse.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)

[tip:x86/asm] x86-64: Slightly shorten int_ret_from_sys_call

[tip-bot for Jan Beulich]

Commit-ID:  70ea6855d368588a7f1b0242ab83ca6fe2e2ff16
Gitweb:     http://git.kernel.org/tip/70ea6855d368588a7f1b0242ab83ca6fe2e2ff16
Author:     Jan Beulich <JBeulich@suse.com>
AuthorDate: Tue, 29 Nov 2011 10:54:22 +0000
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 5 Dec 2011 17:24:37 +0100

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@suse.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/4ED4C7EE0200007800064028@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/kernel/entry_64.S |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index faf8d5e..ab4b7ff 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/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)