[PATCH 1/2] x86/asm/entry/32: Open-code CLEAR_RREGS. No code changes.

[Denys Vlasenko]

This macro is small, has only four callsites, and one of them is
slightly different using a conditional parameter.

A few saved lines aren't worth the resulting obfuscation.

Generated machine code is identical.

Signed-off-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxxxxx>
CC: Borislav Petkov <bp@xxxxxxxxx>
CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
CC: Oleg Nesterov <oleg@xxxxxxxxxx>
CC: Frederic Weisbecker <fweisbec@xxxxxxxxx>
CC: Alexei Starovoitov <ast@xxxxxxxxxxxx>
CC: Will Drewry <wad@xxxxxxxxxxxx>
CC: Kees Cook <keescook@xxxxxxxxxxxx>
CC: x86@xxxxxxxxxx
CC: linux-kernel@xxxxxxxxxxxxxxx
---

These two patches are on top of "Simplify zeroing of pt_regs->r8..r11" patch.

 arch/x86/ia32/ia32entry.S | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 2801cbe..86cbfe6 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -29,15 +29,6 @@
 
 	.section .entry.text, "ax"
 
-	/* clobbers %rax */
-	.macro  CLEAR_RREGS _r9=rax
-	xorl 	%eax,%eax
-	movq	%rax,R11(%rsp)
-	movq	%rax,R10(%rsp)
-	movq	%\_r9,R9(%rsp)
-	movq	%rax,R8(%rsp)
-	.endm
-
 	/*
 	 * Reload arg registers from stack in case ptrace changed them.
 	 * We don't reload %eax because syscall_trace_enter() returned
@@ -243,7 +234,11 @@ sysexit_from_sys_call:
 	TRACE_IRQS_OFF
 	testl %edi, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
 	jz \exit
-	CLEAR_RREGS
+	xorl	%eax, %eax
+	movq	%rax, R11(%rsp)
+	movq	%rax, R10(%rsp)
+	movq	%rax, R9(%rsp)
+	movq	%rax, R8(%rsp)
 	jmp int_with_check
 	.endm
 
@@ -267,7 +262,11 @@ sysenter_tracesys:
 	jz	sysenter_auditsys
 #endif
 	SAVE_EXTRA_REGS
-	CLEAR_RREGS
+	xorl	%eax, %eax
+	movq	%rax, R11(%rsp)
+	movq	%rax, R10(%rsp)
+	movq	%rax, R9(%rsp)
+	movq	%rax, R8(%rsp)
 	movq	%rsp,%rdi        /* &pt_regs -> arg1 */
 	call	syscall_trace_enter
 	LOAD_ARGS32  /* reload args from stack in case ptrace changed it */
@@ -407,7 +406,11 @@ cstar_tracesys:
 #endif
 	xchgl %r9d,%ebp
 	SAVE_EXTRA_REGS
-	CLEAR_RREGS r9
+	xorl	%eax, %eax
+	movq	%rax, R11(%rsp)
+	movq	%rax, R10(%rsp)
+	movq	%r9, R9(%rsp)
+	movq	%rax, R8(%rsp)
 	movq %rsp,%rdi        /* &pt_regs -> arg1 */
 	call syscall_trace_enter
 	LOAD_ARGS32 1	/* reload args from stack in case ptrace changed it */
@@ -422,7 +425,11 @@ ia32_badarg:
 	jmp ia32_sysret
 
 ia32_ret_from_sys_call:
-	CLEAR_RREGS
+	xorl	%eax, %eax
+	movq	%rax, R11(%rsp)
+	movq	%rax, R10(%rsp)
+	movq	%rax, R9(%rsp)
+	movq	%rax, R8(%rsp)
 	jmp int_ret_from_sys_call
 
 /*
-- 
1.8.1.4

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