[PATCH V2] x86, boot: add missing declaration of string functions

[Nicholas Mc Guire]

Add the missing declarations of basic string functions to string.h to allow
a clean build.

Fixes: commit 5be865661516 ("String-handling functions for the new x86 setup code.")
Link: http://lkml.org/lkml/2017/1/5/109
Signed-off-by: Nicholas Mc Guire <hofrat@xxxxxxxxx>
---

V2: declare the string functions extern to "highlight the API declarations like the
    rest of the kernel does" as suggested by Ingo Molnar <mingo@xxxxxxxxxx>

sparse issues: a set of warnings about missing declarations:
arch/x86/purgatory/../boot/string.c:18:5: warning: symbol 'memcmp' was not declared. Should it be static?
arch/x86/purgatory/../boot/string.c:26:5: warning: symbol 'strcmp' was not declared. Should it be static?
arch/x86/purgatory/../boot/string.c:42:5: warning: symbol 'strncmp' was not declared. Should it be static?
arch/x86/purgatory/../boot/string.c:58:8: warning: symbol 'strnlen' was not declared. Should it be static?
arch/x86/purgatory/../boot/string.c:69:14: warning: symbol 'atou' was not declared. Should it be static?
arch/x86/purgatory/../boot/string.c:99:20: warning: symbol 'simple_strtoull' was not declared. Should it be static?
arch/x86/purgatory/../boot/string.c:128:8: warning: symbol 'strlen' was not declared. Should it be static?
arch/x86/purgatory/../boot/string.c:142:6: warning: symbol 'strstr' was not declared. Should it be static?

This patch has one checkpatch warning about the use of simple_strtoul which
is obsolete. As this is an independent implementation it is not clear if
the changes made in simple_strtoul -> _kstrtoull might also need to be
applied here ?

Patch was compile tested with: x86_64_defconfig

Patch is against 4.10-rc2 (localversion-next is next-20170106)

 arch/x86/boot/string.c |  1 +
 arch/x86/boot/string.h |  9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
index cc3bd58..9e240fc 100644
--- a/arch/x86/boot/string.c
+++ b/arch/x86/boot/string.c
@@ -14,6 +14,7 @@
 
 #include <linux/types.h>
 #include "ctype.h"
+#include "string.h"
 
 int memcmp(const void *s1, const void *s2, size_t len)
 {
diff --git a/arch/x86/boot/string.h b/arch/x86/boot/string.h
index 725e820..f6ee139 100644
--- a/arch/x86/boot/string.h
+++ b/arch/x86/boot/string.h
@@ -18,4 +18,13 @@ int memcmp(const void *s1, const void *s2, size_t len);
 #define memset(d,c,l) __builtin_memset(d,c,l)
 #define memcmp	__builtin_memcmp
 
+extern int strcmp(const char *str1, const char *str2);
+extern int strncmp(const char *cs, const char *ct, size_t count);
+extern size_t strlen(const char *s);
+extern char *strstr(const char *s1, const char *s2);
+extern size_t strnlen(const char *s, size_t maxlen);
+extern unsigned int atou(const char *s);
+extern unsigned long long simple_strtoull(const char *cp,
+				    char **endp, unsigned int base);
+
 #endif /* BOOT_STRING_H */
-- 
2.1.4