Messages in this thread | | | From | Rickard Strandqvist <> | Date | Thu, 16 Oct 2014 20:11:45 +0200 | Subject | Re: [PATCH 3v] char: hw_random: core.c: Changed from using strncat to strlcat |
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2014-10-16 20:05 GMT+02:00 Jason Cooper <jason@lakedaemon.net>: > 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 :) >
Hi
I will submit a new patch without return strlen.
All these features are more or less stupid really. You can also read what Linus thinks about this here.
https://plus.google.com/111049168280159033135/posts/1amLbuhWbh5
I keep on trying to get a patch that solves one of these stupid functions, but the strncpy in that case.
Kind regards Rickard Strandqvist
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