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Subject[PATCH 10/11] x86: ia32entry.S: fold IA32_ARG_FIXUP macro into its callers
Date
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 IA32_ARG_FIXUP macro into its callers.

No code changes.

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
---
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 ed58fe1..55b785c 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
@@ -177,7 +166,12 @@ 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)
@@ -359,7 +353,12 @@ 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)
@@ -476,7 +475,12 @@ 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)
--
1.8.1.4


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