[PATCH 4/5] x86/asm/entry/32: Replace RESTORE_RSI_RDI[_RDX] with open-coded 32-bit reads

Denys Vlasenko
2015-06-09T18:55:04Z

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@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/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