Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [Cocci] [PATCH] usb: atm: don't use snprintf() for sysfs attrs | From | Joe Perches <> | Date | Fri, 28 Aug 2020 01:22:23 -0700 |
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On Fri, 2020-08-28 at 01:10 -0700, Joe Perches wrote: > On Fri, 2020-08-28 at 00:58 -0700, Kees Cook wrote: > > On Thu, Aug 27, 2020 at 09:12:06PM -0700, Joe Perches wrote: > > > Perhaps something like the below with a sample conversion > > > that uses single and multiple sysfs_emit uses. > > > > On quick review, I like it. :) > > > > > [...] > > > +int sysfs_emit(char *buf, char *pos, const char *fmt, ...) > > > +{ > > > + int len; > > > + va_list args; > > > + > > > + WARN(pos < buf, "pos < buf\n"); > > > + WARN(pos - buf >= PAGE_SIZE, "pos >= PAGE_SIZE (%tu > %lu)\n", > > > + pos - buf, PAGE_SIZE); > > > + if (pos < buf || pos - buf >= PAGE_SIZE) > > > + return 0; > > > > This can be: > > > > if (WARN(pos < buf, "pos < buf\n") || > > WARN(pos - buf >= PAGE_SIZE, "pos >= PAGE_SIZE (%tu > %lu)\n", > > pos - buf, PAGE_SIZE)) > > return 0; > > I have some vague recollection that WARN could be compiled > away to nothing somehow. True or false? > > If false, sure, of course, it'd be faster too.
I can't find an instance where WARN doesn't return the condition.
And likely even faster would be to just show "invalid pos" instead of specific messages.
if (WARN(pos < buf || (pos - buf) >= PAGE_SIZE, "Invalid pos\n"); return 0;
or maybe use WARN_ONCE or no WARN at all.
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