[POWERPC] Add hand-coded assembly strcmp

We have an assembly version of strncmp for the bootwrapper, but not
for the kernel, so we end up using the C version in the kernel.  This
takes the strncmp code from the bootup and copies it to the kernel
proper, adding two instructions so it copes correctly with len==0.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/ppc_ksyms.c

@@ -78,6 +78,7 @@ EXPORT_SYMBOL(strncpy);
 EXPORT_SYMBOL(strcat);
 EXPORT_SYMBOL(strlen);
 EXPORT_SYMBOL(strcmp);
+EXPORT_SYMBOL(strncmp);
 
 EXPORT_SYMBOL(csum_partial);
 EXPORT_SYMBOL(csum_partial_copy_generic);

arch/powerpc/lib/string.S

@@ -75,6 +75,20 @@ _GLOBAL(strcmp)
 	beq	1b
 	blr
 
+_GLOBAL(strncmp)
+	PPC_LCMPI r5,0
+	beqlr
+	mtctr	r5
+	addi	r5,r3,-1
+	addi	r4,r4,-1
+1:	lbzu	r3,1(r5)
+	cmpwi	1,r3,0
+	lbzu	r0,1(r4)
+	subf.	r3,r0,r3
+	beqlr	1
+	bdnzt	eq,1b
+	blr
+
 _GLOBAL(strlen)
 	addi	r4,r3,-1
 1:	lbzu	r0,1(r4)

include/asm-powerpc/string.h

@@ -7,6 +7,7 @@
 #define __HAVE_ARCH_STRNCPY
 #define __HAVE_ARCH_STRLEN
 #define __HAVE_ARCH_STRCMP
+#define __HAVE_ARCH_STRNCMP
 #define __HAVE_ARCH_STRCAT
 #define __HAVE_ARCH_MEMSET
 #define __HAVE_ARCH_MEMCPY
@@ -18,6 +19,7 @@ extern char * strcpy(char *,const char *);
 extern char * strncpy(char *,const char *, __kernel_size_t);
 extern __kernel_size_t strlen(const char *);
 extern int strcmp(const char *,const char *);
+extern int strncmp(const char *, const char *, __kernel_size_t);
 extern char * strcat(char *, const char *);
 extern void * memset(void *,int,__kernel_size_t);
 extern void * memcpy(void *,const void *,__kernel_size_t);