[tip:x86/asm] x86/asm/entry/64/compat: Fold the IA32_ARG_FIXUP macro into its callers

From: tip-bot for Denys Vlasenko
Date: Wed Mar 04 2015 - 17:56:27 EST


Commit-ID: 14f6e9532dda399a7b789f744dc045f8865a9e42
Gitweb: http://git.kernel.org/tip/14f6e9532dda399a7b789f744dc045f8865a9e42
Author: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
AuthorDate: Thu, 26 Feb 2015 14:40:35 -0800
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 4 Mar 2015 22:50:52 +0100

x86/asm/entry/64/compat: Fold the IA32_ARG_FIXUP macro into its callers

Use of a small macro - one with conditional expansion - does
more harm than good. It obfuscates code, with minimal code
reuse.

For example, because of obfuscation it's not obvious that
in 'ia32_sysenter_target', we can optimize loading of r9 -
currently it is loaded with a detour through ebp.

This patch folds the IA32_ARG_FIXUP macro into its callers.

No code changes.

Signed-off-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Will Drewry <wad@xxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/4da092094cd78734384ac31e0d4ec1d8f69145a2.1424989793.git.luto@xxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/ia32/ia32entry.S | 32 ++++++++++++++++++--------------
1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index b567056..6dcd372 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -30,17 +30,6 @@

.section .entry.text, "ax"

- .macro IA32_ARG_FIXUP noebp=0
- movl %edi,%r8d
- .if \noebp
- .else
- movl %ebp,%r9d
- .endif
- xchg %ecx,%esi
- movl %ebx,%edi
- movl %edx,%edx /* zero extension */
- .endm
-
/* clobbers %rax */
.macro CLEAR_RREGS _r9=rax
xorl %eax,%eax
@@ -178,7 +167,12 @@ sysenter_flags_fixed:
cmpq $(IA32_NR_syscalls-1),%rax
ja ia32_badsys
sysenter_do_call:
- IA32_ARG_FIXUP
+ /* 32bit syscall -> 64bit C ABI argument conversion */
+ movl %edi,%r8d /* arg5 */
+ movl %ebp,%r9d /* arg6 */
+ xchg %ecx,%esi /* rsi:arg2, rcx:arg4 */
+ movl %ebx,%edi /* arg1 */
+ movl %edx,%edx /* arg3 (zero extension) */
sysenter_dispatch:
call *ia32_sys_call_table(,%rax,8)
movq %rax,RAX(%rsp)
@@ -360,7 +354,12 @@ ENTRY(ia32_cstar_target)
cmpq $IA32_NR_syscalls-1,%rax
ja ia32_badsys
cstar_do_call:
- IA32_ARG_FIXUP 1
+ /* 32bit syscall -> 64bit C ABI argument conversion */
+ movl %edi,%r8d /* arg5 */
+ /* r9 already loaded */ /* arg6 */
+ xchg %ecx,%esi /* rsi:arg2, rcx:arg4 */
+ movl %ebx,%edi /* arg1 */
+ movl %edx,%edx /* arg3 (zero extension) */
cstar_dispatch:
call *ia32_sys_call_table(,%rax,8)
movq %rax,RAX(%rsp)
@@ -477,7 +476,12 @@ ENTRY(ia32_syscall)
cmpq $(IA32_NR_syscalls-1),%rax
ja ia32_badsys
ia32_do_call:
- IA32_ARG_FIXUP
+ /* 32bit syscall -> 64bit C ABI argument conversion */
+ movl %edi,%r8d /* arg5 */
+ movl %ebp,%r9d /* arg6 */
+ xchg %ecx,%esi /* rsi:arg2, rcx:arg4 */
+ movl %ebx,%edi /* arg1 */
+ movl %edx,%edx /* arg3 (zero extension) */
call *ia32_sys_call_table(,%rax,8) # xxx: rip relative
ia32_sysret:
movq %rax,RAX(%rsp)
--
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