From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755452AbbBTXWy (ORCPT ); Fri, 20 Feb 2015 18:22:54 -0500 Received: from mail-lb0-f178.google.com ([209.85.217.178]:34829 "EHLO mail-lb0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755369AbbBTXVu (ORCPT ); Fri, 20 Feb 2015 18:21:50 -0500 From: Rasmus Villemoes To: Andrew Morton , Rasmus Villemoes , "Peter Zijlstra (Intel)" , Tejun Heo Cc: linux-kernel@vger.kernel.org Subject: [PATCH 2/4] lib/vsprintf.c: Reduce stack use in number() Date: Sat, 21 Feb 2015 00:21:17 +0100 Message-Id: <1424474479-25543-3-git-send-email-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.1.3 In-Reply-To: <1424474479-25543-1-git-send-email-linux@rasmusvillemoes.dk> References: <1424474479-25543-1-git-send-email-linux@rasmusvillemoes.dk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- lib/vsprintf.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 318d583fe862..98f1ce907d3d 100644 --- 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; -- 2.1.3