Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752308AbaJPSFd (ORCPT ); Thu, 16 Oct 2014 14:05:33 -0400 Received: from mho-02-ewr.mailhop.org ([204.13.248.72]:15011 "EHLO mho-02-ewr.mailhop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752102AbaJPSFb (ORCPT ); Thu, 16 Oct 2014 14:05:31 -0400 X-Mail-Handler: Dyn Standard SMTP by Dyn X-Originating-IP: 96.249.243.124 X-Report-Abuse-To: abuse@dyndns.com (see http://www.dyndns.com/services/sendlabs/outbound_abuse.html for abuse reporting information) X-MHO-User: U2FsdGVkX19bHzd5zPK2eva3LS+/TbzPWsF0vA0QfAY= X-DKIM: OpenDKIM Filter v2.0.1 titan 7A043600913 Date: Thu, 16 Oct 2014 14:05:17 -0400 From: Jason Cooper To: Joe Perches Cc: Rickard Strandqvist , Matt Mackall , Herbert Xu , Torsten Duwe , "Theodore Ts'o" , Amit Shah , Stephen Boyd , Paul Gortmaker , Kees Cook , Dan Carpenter , linux-kernel@vger.kernel.org Subject: Re: [PATCH 3v] char: hw_random: core.c: Changed from using strncat to strlcat Message-ID: <20141016180517.GO17447@titan.lakedaemon.net> References: <1413479722-29247-1-git-send-email-rickard_strandqvist@spectrumdigital.se> <1413480303.6702.7.camel@perches.com> <20141016174823.GM17447@titan.lakedaemon.net> <1413482157.8915.3.camel@perches.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1413482157.8915.3.camel@perches.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 16, 2014 at 10:55:57AM -0700, Joe Perches wrote: > On Thu, 2014-10-16 at 13:48 -0400, Jason Cooper wrote: > > On Thu, Oct 16, 2014 at 10:25:03AM -0700, Joe Perches wrote: > > > On Thu, 2014-10-16 at 19:15 +0200, Rickard Strandqvist wrote: > > > > The buf is used to hold the list of hwrng devices registered. > > > > The old code ensures we don't walk off the end of buf as we > > > > fill it, but it's unnecessarily complicated and thus difficult > > > > to maintain. Simplify it by using strlcat. > > > > We also ensure the string within buf is NULL terminated > > > > so the final strlen is ok. > > > [] > > > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > > > [] > > > > @@ -289,16 +288,13 @@ static ssize_t hwrng_attr_available_show(struct device *dev, > > > > return -ERESTARTSYS; > > > > buf[0] = '\0'; > > > > list_for_each_entry(rng, &rng_list, list) { > > > > - strncat(buf, rng->name, PAGE_SIZE - ret - 1); > > > > - ret += strlen(rng->name); > > > > - strncat(buf, " ", PAGE_SIZE - ret - 1); > > > > - ret++; > > > > + strlcat(buf, rng->name, PAGE_SIZE); > > > > + strlcat(buf, " ", PAGE_SIZE); > > > > } > > > > - strncat(buf, "\n", PAGE_SIZE - ret - 1); > > > > - ret++; > > > > + strlcat(buf, "\n", PAGE_SIZE); > > > > mutex_unlock(&rng_mutex); > > > > > > > > - return ret; > > > > + return strlen(buf); > > > > } > > > > > > > > static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR, > > > > > > Rickard, can you please use some optimizations here > > > (and elsewhere) so that strlcat doesn't always have > > > to strlen the first string and the return doesn't > > > have to do the strlen too? > > > > Joe, is further optimization worth the effort? This function is only > > called when the end user reads the sysfs file rng_available... > > It's unlikely that it matters much here. > > I just don't like the repeated and unnecessary strlen. > > I do imagine this pattern being repeated though where > it does matter. Agreed. Back to why I like to see descriptions from the author demonstrating they grok the code they are changing :) thx, Jason. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/