[PATCH 2/5] x86/asm/entry/64: simplify retint_kernel label usage, make retint_restore_args label local

Denys Vlasenko
2015-03-30T18:10:08Z

Get rid of #define obfuscation of retint_kernel in CONFIG_PREEMPT case
by defining retint_kernel label always, not only for CONFIG_PREEMPT.

Strip retint_kernel of .global-ness (ENTRY macro) - it has no users
outside of this file.

This looks like cosmetics, but it is not:
"je LABEL" can be optimized to short jump by assember
only if LABEL is not global, for global labels jump is always
a near one with relocation.

Convert retint_restore_args to a local numeric label, making it clearer
that it is not used elsewhere in the file.

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 | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 34d60c3..4d723ed 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -57,10 +57,6 @@
.section .entry.text, "ax"

-#ifndef CONFIG_PREEMPT
-#define retint_kernel retint_restore_args
-#endif
-
#ifdef CONFIG_PARAVIRT
ENTRY(native_usergs_sysret64)
swapgs
@@ -741,18 +737,18 @@ opportunistic_sysret_failed:
jmp restore_args

/* Returning to kernel space */
+retint_kernel:
#ifdef CONFIG_PREEMPT
/* Interrupts are off */
/* Check if we need preemption */
-ENTRY(retint_kernel)
cmpl $0,PER_CPU_VAR(__preempt_count)
- jnz retint_restore_args
+ jnz 1f
bt $9,EFLAGS(%rsp) /* interrupts were off? */
- jnc retint_restore_args
+ jnc 1f
call preempt_schedule_irq
jmp exit_intr
+1:
#endif
-retint_restore_args:
DISABLE_INTERRUPTS(CLBR_ANY)
/*
* The iretq could re-enable interrupts:
--
1.8.1.4