x86, boot: Create a separate string.h file to provide standard string functions

Create a separate arch/x86/boot/string.h file to provide declaration of
some of the common string functions.

By default memcpy, memset and memcmp functions will default to gcc
builtin functions. If code wants to use an optimized version of any
of these functions, they need to #undef the respective macro and link
against a local file providing definition of undefed function.

For example, arch/x86/boot/* code links against copy.S to get memcpy()
and memcmp() definitions. arch/86/boot/compressed/* links against
compressed/string.c.

There are quite a few places in arch/x86/ where these functions are
used. Idea is to try to consilidate  their declaration and possibly
definitions so that it can be reused.

I am planning to reuse boot/string.h in arch/x86/purgatory/ and use
gcc builtin functions for memcpy, memset and memcmp.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: http://lkml.kernel.org/r/1395170800-11059-3-git-send-email-vgoyal@redhat.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/boot/boot.h

@@ -228,11 +228,6 @@ void copy_to_fs(addr_t dst, void *src, size_t len);
 void *copy_from_fs(void *dst, addr_t src, size_t len);
 void copy_to_gs(addr_t dst, void *src, size_t len);
 void *copy_from_gs(void *dst, addr_t src, size_t len);
-void *memcpy(void *dst, void *src, size_t len);
-void *memset(void *dst, int c, size_t len);
-
-#define memcpy(d,s,l) __builtin_memcpy(d,s,l)
-#define memset(d,c,l) __builtin_memset(d,c,l)
 
 /* a20.c */
 int enable_a20(void);

arch/x86/boot/cpucheck.c

@@ -27,6 +27,7 @@
 #include <asm/processor-flags.h>
 #include <asm/required-features.h>
 #include <asm/msr-index.h>
+#include "string.h"
 
 static u32 err_flags[NCAPINTS];
 

arch/x86/boot/edd.c

@@ -15,6 +15,7 @@
 
 #include "boot.h"
 #include <linux/edd.h>
+#include "string.h"
 
 #if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
 

arch/x86/boot/main.c

@@ -14,6 +14,7 @@
  */
 
 #include "boot.h"
+#include "string.h"
 
 struct boot_params boot_params __attribute__((aligned(16)));
 

arch/x86/boot/regs.c

@@ -17,6 +17,7 @@
  */
 
 #include "boot.h"
+#include "string.h"
 
 void initregs(struct biosregs *reg)
 {

arch/x86/boot/string.h

@@ -0,0 +1,19 @@
+#ifndef BOOT_STRING_H
+#define BOOT_STRING_H
+
+/* Undef any of these macros coming from string_32.h. */
+#undef memcpy
+#undef memset
+#undef memcmp
+
+void *memcpy(void *dst, const void *src, size_t len);
+void *memset(void *dst, int c, size_t len);
+
+/*
+ * Access builtin version by default. If one needs to use optimized version,
+ * do "undef memcpy" in .c file and link against right string.c
+ */
+#define memcpy(d,s,l) __builtin_memcpy(d,s,l)
+#define memset(d,c,l) __builtin_memset(d,c,l)
+
+#endif /* BOOT_STRING_H */

arch/x86/boot/video-vesa.c

@@ -16,6 +16,7 @@
 #include "boot.h"
 #include "video.h"
 #include "vesa.h"
+#include "string.h"
 
 /* VESA information */
 static struct vesa_general_info vginfo;