From mboxrd@z Thu Jan 1 00:00:00 1970 From: Masami Hiramatsu Subject: Re: [PATCH -tip v5 0/7] tracing: kprobe-based event tracer and x86 instruction decoder Date: Mon, 11 May 2009 10:40:38 -0400 Message-ID: <4A0838E6.2000309@redhat.com> References: <20090509004829.5505.38720.stgit@localhost.localdomain> <20090509044302.GH8007@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Steven Rostedt , lkml , Avi Kivity , "H. Peter Anvin" , Frederic Weisbecker , Ananth N Mavinakayanahalli , Andrew Morton , Andi Kleen , Jim Keniston , "K.Prasad" , KOSAKI Motohiro , systemtap , kvm , Tom Zanussi To: Ingo Molnar Return-path: Received: from mx2.redhat.com ([66.187.237.31]:60634 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752661AbZEKOkT (ORCPT ); Mon, 11 May 2009 10:40:19 -0400 In-Reply-To: <20090509044302.GH8007@elte.hu> Sender: kvm-owner@vger.kernel.org List-ID: Ingo Molnar wrote: > * Masami Hiramatsu wrote: > >> Hi, >> >> Here are the patches of kprobe-based event tracer for x86, version >> 5, which allows you to probe various kernel events through ftrace >> interface. >> >> This version supports only x86(-32/-64) (but porting it on other >> arch just needs kprobes/kretprobes and register and stack access >> APIs). >> >> This patchset also includes x86(-64) instruction decoder which >> supports non-SSE/FP opcodes and includes x86 opcode map. I think >> it will be possible to share this opcode map with KVM's decoder. >> >> This series can be applied on the latest linux-2.6-tip tree. >> >> This patchset includes following changes: >> - Add x86 instruction decoder [1/7] >> - Check insertion point safety in kprobe [2/7] >> - Cleanup fix_riprel() with insn decoder [3/7] >> - Add kprobe-tracer plugin [4/7] >> - Fix kernel_trap_sp() on x86 according to systemtap runtime. [5/7] >> - Add arch-dep register and stack fetching functions [6/7] >> - Support fetching various status (register/stack/memory/etc.) [7/7] >> >> Future items: >> - .init function tracing support. >> - Support primitive types(long, ulong, int, uint, etc) for args. > > Ok, this looks pretty complete already. > > Two high-level comments: > > - There's no self-test - would it be possible to add one? See > trace_selftest* in kernel/trace/ I'm not so sure. Currently, it seems that those self-tests are only for tracers which define new event-entry on ring-buffer. Since this tracer just use ftrace_bprintk, it might need another kind of selftest. e.g. comparing outputs with expected patterns. In that case, would it be better to make a user-space self test including filters and tracepoints? > - No generic integration. Right, this just rides on the ftrace's printk :-) > > It would be nice if these ops: > >> E.g. >> echo p do_sys_open a0 a1 a2 a3 > /debug/tracing/kprobe_events >> >> This sets a kprobe on the top of do_sys_open() function with recording >> 1st to 4th arguments. >> >> echo r do_sys_open rv rp >> /debug/tracing/kprobe_events > > were just generally available in just about any other tracer - a bit > like the event tracer. > > It would also be nice to use the 'function attributes' facilities of > the function tracer, combined with a new special syntax of the > function-filter regex parser, to enable the recovery of return > values (or the call arguments), for selected set of functions. > > For example, today we can already do things like: > > echo 'sys_read:traceon:4' > /debug/tracing/set_ftrace_filter > > for 'trace triggers': the above will trigger tracing to be enabled > on the entry of sys_read(), 4 times. > > Likewise, something like: > > echo 'sys_read:args' > /debug/tracing/set_ftrace_filter > echo 'sys_read:return' > /debug/tracing/set_ftrace_filter > > Could activate kprobes based argument and return-value tracing. Ah, that's a good idea. And also, I have another idea for using filters with kprobes, which is adding new kprobe-entry as a new trace-event when user defines a new probe via kprobe_events. Thus, user can use it as a dynamic-defined tracepoint. Thank you, -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America) Inc. Software Solutions Division e-mail: mhiramat@redhat.com