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Re: [PATCH -tip 10/10] perf probe: Accessing members in data structures
- From: Mark Wielaard <mjw at redhat dot com>
- To: Masami Hiramatsu <mhiramat at redhat dot com>
- Cc: Ingo Molnar <mingo at elte dot hu>, lkml <linux-kernel at vger dot kernel dot org>, systemtap <systemtap at sources dot redhat dot com>, DLE <dle-develop at lists dot sourceforge dot net>, Frederic Weisbecker <fweisbec at gmail dot com>, Arnaldo Carvalho de Melo <acme at redhat dot com>, Paul Mackerras <paulus at samba dot org>, Mike Galbraith <efault at gmx dot de>, Peter Zijlstra <a dot p dot zijlstra at chello dot nl>
- Date: Wed, 17 Mar 2010 11:25:37 +0100
- Subject: Re: [PATCH -tip 10/10] perf probe: Accessing members in data structures
- References: <20100316220515.32050.82185.stgit@localhost6.localdomain6> <20100316220626.32050.57552.stgit@localhost6.localdomain6>
On Tue, 2010-03-16 at 18:06 -0400, Masami Hiramatsu wrote:
> Support accessing members in the data structures. With this,
> perf-probe accepts data-structure members(IOW, it now accepts
> dot '.' and arrow '->' operators) as probe arguemnts.
>
> e.g.
>
> ./perf probe --add 'schedule:44 rq->curr'
>
> ./perf probe --add 'vfs_read file->f_op->read file->f_path.dentry'
>
> Note that '>' can be interpreted as redirection in command-line.
If you find that a problem then you can do like SystemTap does and allow
'.' in place of '->'. In the code you already use the
perf_probe_arg_field ref flag only to check that the DIE gives you the
same information. So you could just drop that and use any separator.
Then you decide based on whether you see a DW_TAG_pointer_type. This
gives the user some extra flexibility by letting them not having to care
about specifying extra type information already available elsewhere.
Cheers,
Mark