linux-kernel - [PATCH 4/5] x86/asm/entry/32: Replace RESTORE_RSI_RDI[

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Date:	Tue,  9 Jun 2015 20:54:10 +0200
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 4/5] x86/asm/entry/32: Replace RESTORE_RSI_RDI[_RDX] with open-coded 32-bit reads

This doesn't change much, but this uses shorter 32-bit insns:

	-48 8b 74 24 68         mov    0x68(%rsp),%rsi
	-48 8b 7c 24 70         mov    0x70(%rsp),%rdi
	-48 8b 54 24 60         mov    0x60(%rsp),%rdx
	+8b 74 24 68            mov    0x68(%rsp),%esi
	+8b 7c 24 70            mov    0x70(%rsp),%edi
	+8b 54 24 60            mov    0x60(%rsp),%edx

Since these are the only uses of RESTORE_RSI_RDI[_RDX], drop these macros.

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/entry/calling.h         | 6 ------
 arch/x86/entry/entry_64_compat.S | 7 +++++--
 2 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index f4e6308..519207f 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -193,12 +193,6 @@ For 32-bit we have the following conventions - kernel is built with
 	.macro RESTORE_C_REGS_EXCEPT_RCX_R11
 	RESTORE_C_REGS_HELPER 1,0,0,1,1
 	.endm
-	.macro RESTORE_RSI_RDI
-	RESTORE_C_REGS_HELPER 0,0,0,0,0
-	.endm
-	.macro RESTORE_RSI_RDI_RDX
-	RESTORE_C_REGS_HELPER 0,0,0,0,1
-	.endm
 
 	.macro REMOVE_PT_GPREGS_FROM_STACK addskip=0
 	subq $-(15*8+\addskip), %rsp
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index a0ddcb6..d83e7e3 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -140,7 +140,8 @@ sysexit_from_sys_call:
 	 */
 	andl	$~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
 	movl	RIP(%rsp), %ecx		/* User %eip */
-	RESTORE_RSI_RDI
+	movl	RSI(%rsp), %esi
+	movl	RDI(%rsp), %edi
 	xorl	%edx, %edx		/* Do not leak kernel information */
 	xorq	%r8, %r8
 	xorq	%r9, %r9
@@ -361,7 +362,9 @@ cstar_dispatch:
 
 sysretl_from_sys_call:
 	andl	$~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
-	RESTORE_RSI_RDI_RDX
+	movl	RSI(%rsp), %esi
+	movl	RDI(%rsp), %edi
+	movl	RDX(%rsp), %edx
 	movl	RIP(%rsp), %ecx
 	movl	EFLAGS(%rsp), %r11d
 	xorq	%r10, %r10
-- 
1.8.1.4

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