Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 0a9df786 authored by Rasmus Villemoes's avatar Rasmus Villemoes Committed by Linus Torvalds
Browse files

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: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2cf12f82

include/linux/kernel.h

+2 −0
Original line number Diff line number Diff line
@@ -413,6 +413,8 @@ extern __printf(2, 3) 
char *kasprintf(gfp_t gfp, const char *fmt, ...);

extern __printf(2, 0)

char *kvasprintf(gfp_t gfp, const char *fmt, va_list args);

extern __printf(2, 0)

const char *kvasprintf_const(gfp_t gfp, const char *fmt, va_list args);



extern __scanf(2, 3)

int sscanf(const char *, const char *, ...);

lib/kasprintf.c

+16 −0
Original line number Diff line number Diff line
@@ -31,6 +31,22 @@ char *kvasprintf(gfp_t gfp, const char *fmt, va_list ap) 
}

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;