path: root/lib
diff options
authorRasmus Villemoes <linux@rasmusvillemoes.dk>2015-11-06 16:31:20 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-11-06 17:50:42 -0800
commit0a9df786a6ae2f898114bdd242b64920dedf53bd (patch)
tree2c693d2a4038f96f03f2d44dfafc6180d457affb /lib
parent2cf12f821cd4f996bfabeec23d8f25e7a2052a28 (diff)
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>
Diffstat (limited to 'lib')
1 files changed, 16 insertions, 0 deletions
diff --git a/lib/kasprintf.c b/lib/kasprintf.c
index 32f12150fc4f..f194e6e593e1 100644
--- a/lib/kasprintf.c
+++ b/lib/kasprintf.c
@@ -31,6 +31,22 @@ char *kvasprintf(gfp_t gfp, const char *fmt, va_list ap)
+ * 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);
char *kasprintf(gfp_t gfp, const char *fmt, ...)
va_list ap;