linux-kernel - [PATCH 06/16] x86: code shrink in paranoid

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Date:	Thu, 26 Feb 2015 14:40:29 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Borislav Petkov <bp@...en8.de>, Oleg Nesterov <oleg@...hat.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>
Subject: [PATCH 06/16] x86: code shrink in paranoid_exit

From: Denys Vlasenko <dvlasenk@...hat.com>

RESTORE_EXTRA_REGS + RESTORE_C_REGS looks small, but it's
a lot of instructions (fourteen). Let's reuse them.

[I changed the labels.  In vda's version of this patch, paranoid_exit_restore
 was paranoid_restore1 and paranoid_exit_no_swapgs was paranoid_restore.
 This still isn't great, but I think it's a lot better.  --Andy]

Link: http://lkml.kernel.org/r/1421272101-16847-2-git-send-email-dvlasenk@redhat.com
Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
CC: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Oleg Nesterov <oleg@...hat.com>
CC: Borislav Petkov <bp@...en8.de>
CC: "H. Peter Anvin" <hpa@...or.com>
CC: Andy Lutomirski <luto@...capital.net>
CC: Frederic Weisbecker <fweisbec@...il.com>
CC: X86 ML <x86@...nel.org>
CC: Alexei Starovoitov <ast@...mgrid.com>
CC: Will Drewry <wad@...omium.org>
CC: Kees Cook <keescook@...omium.org>
CC: linux-kernel@...r.kernel.org
Signed-off-by: Andy Lutomirski <luto@...capital.net>
---
 arch/x86/kernel/entry_64.S | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index b4469ed2b30f..e5cad016cb60 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1282,15 +1282,13 @@ ENTRY(paranoid_exit)
 	DISABLE_INTERRUPTS(CLBR_NONE)
 	TRACE_IRQS_OFF_DEBUG
 	testl %ebx,%ebx				/* swapgs needed? */
-	jnz paranoid_restore
+	jnz paranoid_exit_no_swapgs
 	TRACE_IRQS_IRETQ 0
 	SWAPGS_UNSAFE_STACK
-	RESTORE_EXTRA_REGS
-	RESTORE_C_REGS
-	REMOVE_PT_GPREGS_FROM_STACK 8
-	INTERRUPT_RETURN
-paranoid_restore:
+	jmp paranoid_exit_restore
+paranoid_exit_no_swapgs:
 	TRACE_IRQS_IRETQ_DEBUG 0
+paranoid_exit_restore:
 	RESTORE_EXTRA_REGS
 	RESTORE_C_REGS
 	REMOVE_PT_GPREGS_FROM_STACK 8
-- 
2.1.0

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