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Message-ID: <20090320002435.GA6895@nowhere> Date: Fri, 20 Mar 2009 01:24:36 +0100 From: Frederic Weisbecker <fweisbec@...il.com> To: Masami Hiramatsu <mhiramat@...hat.com> Cc: Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>, Ananth N Mavinakayanahalli <ananth@...ibm.com>, LKML <linux-kernel@...r.kernel.org>, systemtap-ml <systemtap@...rces.redhat.com> Subject: Re: [RFC][PATCH -tip 0/9] tracing: kprobe-based event tracer On Thu, Mar 19, 2009 at 05:09:56PM -0400, Masami Hiramatsu wrote: > Hi, > > This is a series of patches which introduce a proof-of concept of > kprobe-based event tracer to ftrace. I think that we could port some > tracing features from systemtap on this vehicle. > This can be applied on the linux-2.6-tip tree. > > This patchset includes following changes: > - Add kprobe-tracer plugin > - Add kernel_trap_sp() on x86, ia64, power, s390, arm which are > ported from systemtap runtime. > - Add module_*probe api for repawning/removing kprobes when target > module is coming/going. > > It's still not unclear that the last module_*probe would better be > provided as APIs or just embed it in trace_kprobe.c. > > Future items: > - Use binary print. > - Add kernel_trap_sp() on other archs. > - Support symbol-based memory fetching (for global variables) > - Support primitive types(long, ulong, int, uint, etc) for args. > - Support indirect memory fetch from register etc. > - Check insertion point safety by using instruction decoder. > > kprobe-based event tracer > --------------------------- > > This tracer is similar to the events tracer which is based on Tracepoint > infrastructure. Instead of Tracepoint, this tracer is based on kprobes(kprobe > and kretprobe). It probes anywhere where kprobes can probe(this means, all > functions body except for __kprobes functions). > > Unlike the function tracer, this tracer can probe instructions inside of > kernel functions. It allows you to check which instruction has been executed. > > Unlike the Tracepoint based events tracer, this tracer can add new probe points > on the fly. > > Similar to the events tracer, this tracer doesn't need to be activated via > current_tracer, instead of that, just set probe points via > /debug/tracing/kprobe_probes. > > Synopsis of kprobe_probes: > p SYMBOL[+offs|-offs]|MEMADDR [FETCHARGS] : set a probe Ahh, I see this is not only about parameters but also about very low level debugging, such as registers dumps. This is very powerful. > r SYMBOL[+0] [FETCHARGS] : set a return probe > > FETCHARGS: > rN : Fetch Nth register (N >= 0) Ah, it would be useful to have a per arch register naming here. So that one don't have to feel dizzy when he have to resolve, say edi register, to a number. > sN : Fetch Nth entry of stack (N >= 0) > mADDR : Fetch memory at ADDR (ADDR should be in kernel) > aN : Fetch function argument. (N >= 1)(*) > rv : Fetch return value.(**) > rp : Fetch return address.(**) > > (*) aN may not correct on asmlinkaged functions and at function body. > (**) only for return probe. > > E.g. > echo p do_sys_open a1 a2 a3 a4 > /debug/tracing/kprobe_probes > > This sets a kprobe on the top of do_sys_open() function with recording > 1st to 3rd arguments. > > echo r do_sys_open rv rp >> /debug/tracing/kprobe_probes > > This sets a kretprobe on the return point of do_sys_open() function with > recording return value and return address. > > echo > /debug/tracing/kprobe_probes > > This clears all probe points. and you can see the traced information via > /debug/tracing/trace. > > echo /debug/tracing/trace > # tracer: nop > # > # TASK-PID CPU# TIMESTAMP FUNCTION > # | | | | | > <...>-2376 [001] 262.389131: do_sys_open: @do_sys_open+0 0xffffff9c 0x98db83e 0x8880 0x0 > <...>-2376 [001] 262.391166: sys_open: <-do_sys_open+0 0x5 0xc06e8ebb > <...>-2376 [001] 264.384876: do_sys_open: @do_sys_open+0 0xffffff9c 0x98db83e 0x8880 0x0 > <...>-2376 [001] 264.386880: sys_open: <-do_sys_open+0 0x5 0xc06e8ebb > <...>-2084 [001] 265.380330: do_sys_open: @do_sys_open+0 0xffffff9c 0x804be3e 0x0 0x1b6 > <...>-2084 [001] 265.380399: sys_open: <-do_sys_open+0 0x3 0xc06e8ebb > > @SYMBOL means that kernel hits a probe, and <-SYMBOL means kernel returns > from SYMBOL(e.g. "sysenter_do_call: <-sys_open+0" means kernel returns from > sys_open to sysenter_do_call). Nice :-) Frederic. > > Documentation/ftrace.txt | 66 ++++ > arch/arm/include/asm/ptrace.h | 3 +- > arch/ia64/include/asm/ptrace.h | 6 + > arch/powerpc/include/asm/ptrace.h | 1 + > arch/s390/include/asm/ptrace.h | 5 +- > arch/x86/include/asm/ptrace.h | 4 +- > include/linux/kprobes.h | 39 ++ > kernel/kprobes.c | 250 ++++++++++++++ > kernel/trace/Kconfig | 9 + > kernel/trace/Makefile | 1 + > kernel/trace/trace_kprobe.c | 688 +++++++++++++++++++++++++++++++++++++ > 11 files changed, 1067 insertions(+), 5 deletions(-) > > > Thank you, > > -- > Masami Hiramatsu > > Software Engineer > Hitachi Computer Products (America) Inc. > Software Solutions Division > > e-mail: mhiramat@...hat.com > > > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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