Add kvasprintf()

Add a kvasprintf() function to complement kasprintf().

No in-tree users yet, but I have some coming up.

[akpm@linux-foundation.org: EXPORT it]
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Keir Fraser <keir@xensource.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kernel.h

@@ -121,6 +121,7 @@ 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 char *kvasprintf(gfp_t gfp, const char *fmt, va_list args);
 
 extern int sscanf(const char *, const char *, ...)
 	__attribute__ ((format (scanf, 2, 3)));

lib/vsprintf.c

@@ -851,23 +851,35 @@ EXPORT_SYMBOL(sscanf);
 
 
 /* Simplified asprintf. */
-char *kasprintf(gfp_t gfp, const char *fmt, ...)
+char *kvasprintf(gfp_t gfp, const char *fmt, va_list ap)
 {
-	va_list ap;
 	unsigned int len;
 	char *p;
+	va_list aq;
 
-	va_start(ap, fmt);
-	len = vsnprintf(NULL, 0, fmt, ap);
-	va_end(ap);
+	va_copy(aq, ap);
+	len = vsnprintf(NULL, 0, fmt, aq);
+	va_end(aq);
 
 	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(kvasprintf);
 
+char *kasprintf(gfp_t gfp, const char *fmt, ...)
+{
+	va_list ap;
+	char *p;
+
+	va_start(ap, fmt);
+	p = kvasprintf(gfp, fmt, ap);
+	va_end(ap);
+
+	return p;
+}
 EXPORT_SYMBOL(kasprintf);