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Subject[tip:x86/asm] x86/asm/entry/64: Simplify jumps in ret_from_fork
Commit-ID:  66ad4efa51805964521db03d8aa827a8dd9058b9
Gitweb: http://git.kernel.org/tip/66ad4efa51805964521db03d8aa827a8dd9058b9
Author: Denys Vlasenko <dvlasenk@redhat.com>
AuthorDate: Tue, 7 Apr 2015 22:43:42 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 9 Apr 2015 10:31:25 +0200

x86/asm/entry/64: Simplify jumps in ret_from_fork

Replace
test
jz 1f
jmp label
1:

with
test
jnz label

Run-tested.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1428439424-7258-6-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/entry_64.S | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index e8ddd51..a35e5e4 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -608,18 +608,18 @@ ENTRY(ret_from_fork)
RESTORE_EXTRA_REGS

testl $3,CS(%rsp) # from kernel_thread?
- jz 1f

/*
* By the time we get here, we have no idea whether our pt_regs,
* ti flags, and ti status came from the 64-bit SYSCALL fast path,
* the slow path, or one of the ia32entry paths.
- * Use int_ret_from_sys_call to return, since it can safely handle
+ * Use IRET code path to return, since it can safely handle
* all of the above.
*/
- jmp int_ret_from_sys_call
+ jnz int_ret_from_sys_call

-1:
+ /* We came from kernel_thread */
+ /* nb: we depend on RESTORE_EXTRA_REGS above */
movq %rbp, %rdi
call *%rbx
movl $0, RAX(%rsp)

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