x86, msr: CFI annotations, cleanups for msr-reg.S

Add CFI annotations for native_{rd,wr}msr_safe_regs().
Simplify the 64-bit implementation: we don't allow the upper half
registers to be set, and so we can use them to carry state across the
operation.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Borislav Petkov <petkovbb@gmail.com>
LKML-Reference: <1251705011-18636-1-git-send-email-petkovbb@gmail.com>

arch/x86/lib/msr-reg.S

@@ -1,5 +1,6 @@
 #include <linux/linkage.h>
 #include <linux/errno.h>
+#include <asm/dwarf2.h>
 #include <asm/asm.h>
 #include <asm/msr.h>
 
@@ -12,10 +13,11 @@
  */
 .macro op_safe_regs op:req
 ENTRY(native_\op\()_safe_regs)
-	push    %rbx
-	push    %rbp
-	push    $0              /* Return value */
-	push    %rdi
+	CFI_STARTPROC
+	pushq_cfi %rbx
+	pushq_cfi %rbp
+	movq	%rdi, %r10	/* Save pointer */
+	xorl	%r11d, %r11d	/* Return value */
 	movl    (%rdi), %eax
 	movl    4(%rdi), %ecx
 	movl    8(%rdi), %edx
@@ -23,27 +25,26 @@ ENTRY(native_\op\()_safe_regs)
 	movl    20(%rdi), %ebp
 	movl    24(%rdi), %esi
 	movl    28(%rdi), %edi
+	CFI_REMEMBER_STATE
 1:	\op
-2:	movl    %edi, %r10d
-	pop     %rdi
-	movl    %eax, (%rdi)
-	movl    %ecx, 4(%rdi)
-	movl    %edx, 8(%rdi)
-	movl    %ebx, 12(%rdi)
-	movl    %ebp, 20(%rdi)
-	movl    %esi, 24(%rdi)
-	movl    %r10d, 28(%rdi)
-	pop     %rax
-	pop     %rbp
-	pop     %rbx
+2:	movl    %eax, (%r10)
+	movl	%r11d, %eax	/* Return value */
+	movl    %ecx, 4(%r10)
+	movl    %edx, 8(%r10)
+	movl    %ebx, 12(%r10)
+	movl    %ebp, 20(%r10)
+	movl    %esi, 24(%r10)
+	movl    %edi, 28(%r10)
+	popq_cfi %rbp
+	popq_cfi %rbx
 	ret
 3:
-	movq    $-EIO, 8(%rsp)
+	CFI_RESTORE_STATE
+	movl    $-EIO, %r11d
 	jmp     2b
-	.section __ex_table,"ax"
-	.balign 4
-	.quad   1b, 3b
-	.previous
+
+	_ASM_EXTABLE(1b, 3b)
+	CFI_ENDPROC
 ENDPROC(native_\op\()_safe_regs)
 .endm
 
@@ -51,12 +52,13 @@ ENDPROC(native_\op\()_safe_regs)
 
 .macro op_safe_regs op:req
 ENTRY(native_\op\()_safe_regs)
-	push    %ebx
-	push    %ebp
-	push    %esi
-	push    %edi
-	push    $0              /* Return value */
-	push    %eax
+	CFI_STARTPROC
+	pushl_cfi %ebx
+	pushl_cfi %ebp
+	pushl_cfi %esi
+	pushl_cfi %edi
+	pushl_cfi $0              /* Return value */
+	pushl_cfi %eax
 	movl    4(%eax), %ecx
 	movl    8(%eax), %edx
 	movl    12(%eax), %ebx
@@ -64,30 +66,32 @@ ENTRY(native_\op\()_safe_regs)
 	movl    24(%eax), %esi
 	movl    28(%eax), %edi
 	movl    (%eax), %eax
+	CFI_REMEMBER_STATE
 1:	\op
-2:	push    %eax
+2:	pushl_cfi %eax
 	movl    4(%esp), %eax
-	pop     (%eax)
+	popl_cfi (%eax)
 	addl    $4, %esp
+	CFI_ADJUST_CFA_OFFSET -4
 	movl    %ecx, 4(%eax)
 	movl    %edx, 8(%eax)
 	movl    %ebx, 12(%eax)
 	movl    %ebp, 20(%eax)
 	movl    %esi, 24(%eax)
 	movl    %edi, 28(%eax)
-	pop     %eax
-	pop     %edi
-	pop     %esi
-	pop     %ebp
-	pop     %ebx
+	popl_cfi %eax
+	popl_cfi %edi
+	popl_cfi %esi
+	popl_cfi %ebp
+	popl_cfi %ebx
 	ret
 3:
+	CFI_RESTORE_STATE
 	movl    $-EIO, 4(%esp)
 	jmp     2b
-	.section __ex_table,"ax"
-	.balign 4
-	.long   1b, 3b
-	.previous
+
+	_ASM_EXTABLE(1b, 3b)
+	CFI_ENDPROC
 ENDPROC(native_\op\()_safe_regs)
 .endm