[PATCH] Implement kasprintf

Implement kasprintf, a kernel version of asprintf.  This allocates the
memory required for the formatted string, including the trailing '\0'.
Returns NULL on allocation failure.
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NChris Wright <chrisw@sous-sol.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

include/linux/kernel.h

@@ -117,6 +117,8 @@ extern int scnprintf(char * buf, size_t size, const char * fmt, ...)
 	__attribute__ ((format (printf, 3, 4)));
 extern int vscnprintf(char *buf, size_t size, const char *fmt, va_list args)
 	__attribute__ ((format (printf, 3, 0)));
+extern char *kasprintf(gfp_t gfp, const char *fmt, ...)
+	__attribute__ ((format (printf, 2, 3)));
 
 extern int sscanf(const char *, const char *, ...)
 	__attribute__ ((format (scanf, 2, 3)));

lib/vsprintf.c

@@ -849,3 +849,26 @@ int sscanf(const char * buf, const char * fmt, ...)
 }
 
 EXPORT_SYMBOL(sscanf);
+
+
+/* Simplified asprintf. */
+char *kasprintf(gfp_t gfp, const char *fmt, ...)
+{
+	va_list ap;
+	unsigned int len;
+	char *p;
+
+	va_start(ap, fmt);
+	len = vsnprintf(NULL, 0, fmt, ap);
+	va_end(ap);
+
+	p = kmalloc(len+1, gfp);
+	if (!p)
+		return NULL;
+	va_start(ap, fmt);
+	vsnprintf(p, len+1, fmt, ap);
+	va_end(ap);
+	return p;
+}
+
+EXPORT_SYMBOL(kasprintf);