Messages in this thread | | | Date | Wed, 25 Jan 2012 09:54:14 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH 5/9] perf: Add sysfs format attribute for pmu device |
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On Tue, Jan 24, 2012 at 11:40:28AM -0800, Eric W. Biederman wrote: > Peter Zijlstra <a.p.zijlstra@chello.nl> writes: > > > On Mon, 2012-01-23 at 16:33 +0100, Jiri Olsa wrote: > >> > >> > > +static ssize_t perf_default_event_format(struct pmu *pmu, char *page) > >> > > +{ > >> > > + ssize_t ret; > >> > > + > >> > > + ret = sprintf(page, "config config:0-63\n"); > >> > > + ret += sprintf(page + ret, "config1 config1:0-63\n"); > >> > > + ret += sprintf(page + ret, "config2 config2:0-63\n"); > >> > > >> > This looks like abuse of sysfs. The rule is one value per file. > >> > When you start adding newlines I can't see how this format attribute can > >> > be considered one value. > >> > >> ops, missed that rule.. I think we can carry the syntax files > >> within perf, or have it builtin somehow.. or procfs? :) PeterZ? > > > > There's plenty of exceptions to this rule though and touching procfs is > > even less appreciated. > > There may be exceptions but certainly not plenty of exceptions. > > There is also a practical scaling problem. You have to be careful > with how big you make that value before you have problems. > > Perhaps what you want is a directory with a bunch of sysfs attributes? > yep, Peter outlined this possibility in here https://lkml.org/lkml/2012/1/24/206
> All I know is I see buffer overflows waiting to happen whenever I look > at the code snippet above.
from this point of view, the above data should always be static/hardcoded for given pmu.. so we will be fine with the page size buffer, it could be valifated with some sort of BUILD_BUG_ON(data_size < pagesize)
jirka
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