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Subject[PATCH 06/16] x86: code shrink in paranoid_exit
Date
From: Denys Vlasenko <dvlasenk@redhat.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@redhat.com>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Borislav Petkov <bp@alien8.de>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Frederic Weisbecker <fweisbec@gmail.com>
CC: X86 ML <x86@kernel.org>
CC: Alexei Starovoitov <ast@plumgrid.com>
CC: Will Drewry <wad@chromium.org>
CC: Kees Cook <keescook@chromium.org>
CC: linux-kernel@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@amacapital.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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