linux-kernel - [PATCH 3/3] x86: do not save callee-preserved registers around lockdep_sys_exit

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Message-Id: <1427314468-12763-4-git-send-email-dvlasenk@redhat.com>
Date:	Wed, 25 Mar 2015 21:14:28 +0100
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] x86: do not save callee-preserved registers around lockdep_sys_exit_thunk

Internally, lockdep_sys_exit_thunk saves callee-clobbered registers,
and calls a C function, lockdep_sys_exit. Thus, callee-preserved registers
won't be mangled, there is no need to save them.

Patch was run-tested.

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
CC: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Steven Rostedt <rostedt@...dmis.org>
CC: Ingo Molnar <mingo@...nel.org>
CC: Borislav Petkov <bp@...en8.de>
CC: "H. Peter Anvin" <hpa@...or.com>
CC: Andy Lutomirski <luto@...capital.net>
CC: Oleg Nesterov <oleg@...hat.com>
CC: Frederic Weisbecker <fweisbec@...il.com>
CC: Alexei Starovoitov <ast@...mgrid.com>
CC: Will Drewry <wad@...omium.org>
CC: Kees Cook <keescook@...omium.org>
CC: x86@...nel.org
CC: linux-kernel@...r.kernel.org
---
 arch/x86/include/asm/irqflags.h | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
index 19355f3..9a63eae 100644
--- a/arch/x86/include/asm/irqflags.h
+++ b/arch/x86/include/asm/irqflags.h
@@ -179,9 +179,7 @@ static inline int arch_irqs_disabled(void)
 #    define LOCKDEP_SYS_EXIT_IRQ \
 	TRACE_IRQS_ON; \
 	sti; \
-	SAVE_EXTRA_REGS; \
 	call lockdep_sys_exit_thunk; \
-	RESTORE_EXTRA_REGS; \
 	cli; \
 	TRACE_IRQS_OFF;
 #  else
-- 
1.8.1.4

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