lib/kasprintf.c: introduce kvasprintf_const
This adds kvasprintf_const which tries to use kstrdup_const if possible:
If the format string contains no % characters, or if the format string is
exactly "%s", we delegate to kstrdup_const. Otherwise, we fall back to
kvasprintf.
Just as for kstrdup_const, the main motivation is to save memory by
reusing .rodata when possible.
The return value should be freed by kfree_const, just like for
kstrdup_const.
There is deliberately no kasprintf_const: In the vast majority of cases,
the format string argument is a literal, so one can determine statically
whether one could instead use kstrdup_const directly (which would also
require one to change all corresponding kfree calls to kfree_const).
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/kasprintf.c b/lib/kasprintf.c
index 32f1215..f194e6e 100644
--- a/lib/kasprintf.c
+++ b/lib/kasprintf.c
@@ -31,6 +31,22 @@
}
EXPORT_SYMBOL(kvasprintf);
+/*
+ * If fmt contains no % (or is exactly %s), use kstrdup_const. If fmt
+ * (or the sole vararg) points to rodata, we will then save a memory
+ * allocation and string copy. In any case, the return value should be
+ * freed using kfree_const().
+ */
+const char *kvasprintf_const(gfp_t gfp, const char *fmt, va_list ap)
+{
+ if (!strchr(fmt, '%'))
+ return kstrdup_const(fmt, gfp);
+ if (!strcmp(fmt, "%s"))
+ return kstrdup_const(va_arg(ap, const char*), gfp);
+ return kvasprintf(gfp, fmt, ap);
+}
+EXPORT_SYMBOL(kvasprintf_const);
+
char *kasprintf(gfp_t gfp, const char *fmt, ...)
{
va_list ap;