Date: Fri, 20 Jun 2014 20:18:59 +0400
From: Stanislav Fomichev <stfomichev@yandex-team.ru>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: a.p.zijlstra@chello.nl, paulus@samba.org, mingo@redhat.com,
        dsahern@gmail.com, jolsa@redhat.com, xiaoguangrong@linux.vnet.ibm.com,
        yangds.fnst@cn.fujitsu.com, adrian.hunter@intel.com,
        namhyung@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/7] perf trace pagefaults
Message-ID: <20140620161859.GN15620@stfomichev-desktop.yandex.net>
References: <1403261389-13423-1-git-send-email-stfomichev@yandex-team.ru>
 <20140620132105.GE31524@kernel.org>
 <20140620150318.GK15620@stfomichev-desktop.yandex.net>
 <20140620152449.GH31524@kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org

> Hey, haven't you seen the vfs_getname probe? Idea is to hook on where
> the relevant copy_from_user is done and insert that into the ring
> buffer, as we already do for mapping fd -> pathname.
I saw it but didn't actually try because it needs all the debugging
stuff enabled and in place.

> I.e. no need for actual tracepoints from day one, just wannabe
> tracepoints using whatever probe inserting gizmo the kprobes_tracer used
> by 'perf probe' now thinks its best to use.
But we then need to predefine many probes for decoding to work in the form of
func:offset, and then play catch-up with all the kernel changes.
Or I miss something important here?

> For now try:
> 
>   perf probe 'vfs_getname=getname_flags:65 pathname=result->name:string'
>   trace
> 
> And look at how it manages to decode fds.
I will try, but does 65 still work after c4ad8f98bef77c7356aa6a9ad9188a6acc6b849d? :-)
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