Messages in this thread | | | Date | Thu, 16 Oct 2014 14:05:17 -0400 | From | Jason Cooper <> | Subject | Re: [PATCH 3v] char: hw_random: core.c: Changed from using strncat to strlcat |
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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.
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