x86: introduce __ASM_REG macro.

There are situations in which the architecture wants to use the
register that represents its word-size, whatever it is. For those,
introduce __ASM_REG in asm.h, along with the first users _ASM_AX
and _ASM_DX. They have users waiting for it, namely the getuser
functions.

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/lib/getuser_32.S

@@ -11,6 +11,7 @@
 #include <linux/linkage.h>
 #include <asm/dwarf2.h>
 #include <asm/thread_info.h>
+#include <asm/asm.h>
 
 
 /*
@@ -28,36 +29,36 @@
 .text
 ENTRY(__get_user_1)
 	CFI_STARTPROC
-	GET_THREAD_INFO(%edx)
-	cmp TI_addr_limit(%edx),%eax
+	GET_THREAD_INFO(%_ASM_DX)
+	cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
 	jae bad_get_user
-1:	movzb (%eax),%edx
+1:	movzb (%_ASM_AX),%edx
 	xor %eax,%eax
 	ret
 	CFI_ENDPROC
 ENDPROC(__get_user_1)
 
 ENTRY(__get_user_2)
 	CFI_STARTPROC
-	add $1,%eax
+	add $1,%_ASM_AX
 	jc bad_get_user
-	GET_THREAD_INFO(%edx)
-	cmp TI_addr_limit(%edx),%eax
+	GET_THREAD_INFO(%_ASM_DX)
+	cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
 	jae bad_get_user
-2:	movzwl -1(%eax),%edx
+2:	movzwl -1(%_ASM_AX),%edx
 	xor %eax,%eax
 	ret
 	CFI_ENDPROC
 ENDPROC(__get_user_2)
 
 ENTRY(__get_user_4)
 	CFI_STARTPROC
-	add $3,%eax
+	add $3,%_ASM_AX
 	jc bad_get_user
-	GET_THREAD_INFO(%edx)
-	cmp TI_addr_limit(%edx),%eax
+	GET_THREAD_INFO(%_ASM_DX)
+	cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
 	jae bad_get_user
-3:	mov -3(%eax),%edx
+3:	mov -3(%_ASM_AX),%edx
 	xor %eax,%eax
 	ret
 	CFI_ENDPROC
@@ -66,7 +67,7 @@ ENDPROC(__get_user_4)
 bad_get_user:
 	CFI_STARTPROC
 	xor %edx,%edx
-	mov $-14,%eax
+	mov $-14,%_ASM_AX
 	ret
 	CFI_ENDPROC
 END(bad_get_user)

arch/x86/lib/getuser_64.S

@@ -13,14 +13,13 @@
 /*
  * __get_user_X
  *
- * Inputs:	%rcx contains the address.
+ * Inputs:	%rax contains the address.
  *		The register is modified, but all changes are undone
  *		before returning because the C code doesn't know about it.
  *
  * Outputs:	%rax is error code (0 or -EFAULT)
  *		%rdx contains zero-extended value
  * 
- * %r8 is destroyed.
  *
  * These functions should not modify any other registers,
  * as they get called from within inline assembly.
@@ -32,53 +31,54 @@
 #include <asm/errno.h>
 #include <asm/asm-offsets.h>
 #include <asm/thread_info.h>
+#include <asm/asm.h>
 
 	.text
 ENTRY(__get_user_1)
 	CFI_STARTPROC
-	GET_THREAD_INFO(%rdx)
-	cmp TI_addr_limit(%rdx),%rax
+	GET_THREAD_INFO(%_ASM_DX)
+	cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
 	jae bad_get_user
-1:	movzb (%rax),%edx
+1:	movzb (%_ASM_AX),%edx
 	xor %eax,%eax
 	ret
 	CFI_ENDPROC
 ENDPROC(__get_user_1)
 
 ENTRY(__get_user_2)
 	CFI_STARTPROC
-	add $1,%rax
+	add $1,%_ASM_AX
 	jc bad_get_user
-	GET_THREAD_INFO(%rdx)
-	cmp TI_addr_limit(%rdx),%rax
+	GET_THREAD_INFO(%_ASM_DX)
+	cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
 	jae bad_get_user
-2:	movzwl -1(%rax),%edx
+2:	movzwl -1(%_ASM_AX),%edx
 	xor %eax,%eax
 	ret
 	CFI_ENDPROC
 ENDPROC(__get_user_2)
 
 ENTRY(__get_user_4)
 	CFI_STARTPROC
-	add $3,%rax
+	add $3,%_ASM_AX
 	jc bad_get_user
-	GET_THREAD_INFO(%rdx)
-	cmp TI_addr_limit(%rdx),%rax
+	GET_THREAD_INFO(%_ASM_DX)
+	cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
 	jae bad_get_user
-3:	mov -3(%rax),%edx
+3:	mov -3(%_ASM_AX),%edx
 	xor %eax,%eax
 	ret
 	CFI_ENDPROC
 ENDPROC(__get_user_4)
 
 ENTRY(__get_user_8)
 	CFI_STARTPROC
-	add $7,%rax
+	add $7,%_ASM_AX
 	jc bad_get_user
-	GET_THREAD_INFO(%rdx)
-	cmp TI_addr_limit(%rdx),%rax
+	GET_THREAD_INFO(%_ASM_DX)
+	cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
 	jae	bad_get_user
-4:	movq -7(%rax),%rdx
+4:	movq -7(%_ASM_AX),%_ASM_DX
 	xor %eax,%eax
 	ret
 	CFI_ENDPROC
@@ -87,7 +87,7 @@ ENDPROC(__get_user_8)
 bad_get_user:
 	CFI_STARTPROC
 	xor %edx,%edx
-	mov $(-EFAULT),%rax
+	mov $(-EFAULT),%_ASM_AX
 	ret
 	CFI_ENDPROC
 END(bad_get_user)

include/asm-x86/asm.h

@@ -14,6 +14,7 @@
 #endif
 
 #define __ASM_SIZE(inst)	__ASM_SEL(inst##l, inst##q)
+#define __ASM_REG(reg)		__ASM_SEL(e##reg, r##reg)
 
 #define _ASM_PTR	__ASM_SEL(.long, .quad)
 #define _ASM_ALIGN	__ASM_SEL(.balign 4, .balign 8)
@@ -24,6 +25,8 @@
 #define _ASM_ADD	__ASM_SIZE(add)
 #define _ASM_SUB	__ASM_SIZE(sub)
 #define _ASM_XADD	__ASM_SIZE(xadd)
+#define _ASM_AX		__ASM_REG(ax)
+#define _ASM_DX		__ASM_REG(dx)
 
 /* Exception table entry */
 # define _ASM_EXTABLE(from,to) \