lkml.org 
[lkml]   [2012]   [Jan]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 5/9] perf: Add sysfs format attribute for pmu device
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


\
 
 \ /
  Last update: 2012-01-25 09:57    [W:0.031 / U:3.984 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site