lib/vsprintf.c: reduce stack use in number()

At least since the initial git commit, when base was passed as a separate parameter, number() has only been called with bases 8, 10 and 16. I'm guessing that 66 was to accommodate 64 0/1, a sign and a '\0', but the buffer is only used for the actual digits. Octal digits carry 3 bits of information, so 24 is enough. Spell that 3*sizeof(num) so one less place needs to be changed should long long ever be 128 bits. Also remove the commented-out code that would handle an arbitrary base. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lemonadeer · Apr 15, 2015 · e26c12c · e26c12c
1 parent 51be17d
commit e26c12c
Showing 1 changed file with 1 addition and 6 deletions.
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
@@ -386,7 +386,7 @@ char *number(char *buf, char *end, unsigned long long num,
 	/* we are called with base 8, 10 or 16, only, thus don't need "G..."  */
 	static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
 
-	char tmp[66];
+	char tmp[3 * sizeof(num)];
 	char sign;
 	char locase;
 	int need_pfx = ((spec.flags & SPECIAL) && spec.base != 10);
@@ -423,11 +423,6 @@ char *number(char *buf, char *end, unsigned long long num,
 	i = 0;
 	if (num < spec.base)
 		tmp[i++] = digits[num] | locase;
-	/* Generic code, for any base:
-	else do {
-		tmp[i++] = (digits[do_div(num,base)] | locase);
-	} while (num != 0);
-	*/
 	else if (spec.base != 10) { /* 8 or 16 */
 		int mask = spec.base - 1;
 		int shift = 3;