From: Denys Vlasenko <dvlasenk@redhat.com>
Date: Thu, 26 Feb 2015 22:40:35 +0000 (-0800)
Subject: x86/asm/entry/64/compat: Fold the IA32_ARG_FIXUP macro into its callers
X-Git-Tag: v4.13~5465^2~108
X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=14f6e9532dda399a7b789f744dc045f8865a9e42;p=mirror_ubuntu-bionic-kernel.git

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 b5670564a1fb..6dcd37256979 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)