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@redhat.com>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/4da092094cd78734384ac31e0d4ec1d8f69145a2.1424989793.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index b567056..6dcd372 100644 (file)
--- 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)