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Subject[PATCH 6/8] x86/asm/entry/64: simplify jumps in ret_from_fork
Date
Replace
test
jz 1f
jmp label
1:

with
test
jnz label

Run-tested.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: Ingo Molnar <mingo@kernel.org>
CC: Borislav Petkov <bp@alien8.de>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Frederic Weisbecker <fweisbec@gmail.com>
CC: Alexei Starovoitov <ast@plumgrid.com>
CC: Will Drewry <wad@chromium.org>
CC: Kees Cook <keescook@chromium.org>
CC: x86@kernel.org
CC: linux-kernel@vger.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 7d4c7c6..9915897 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -531,18 +531,18 @@ 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)
--
1.8.1.4


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