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Message-ID: <49C30EA5.5040707@redhat.com> Date: Thu, 19 Mar 2009 23:33:57 -0400 From: Masami Hiramatsu <mhiramat@...hat.com> To: Frederic Weisbecker <fweisbec@...il.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 Frederic Weisbecker wrote: > 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. Please take care, don't shot your foot :) This tracer doesn't have a safety lever(e.g. instruction boundary checker) yet. So, currently, we need to use this with objdump -d. > >> 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. Yeah, that should be a good enhancement idea. This patchset just focuses on implementing the basic functionality. >> 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 :-) Thanks ;) > > 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/ > -- 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/
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