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>

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 318d583..98f1ce9 100644 (file)
--- 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;