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Message-ID: <20100518204944.GA6959@Krystal> Date: Tue, 18 May 2010 16:49:44 -0400 From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com> To: Srikar Dronamraju <srikar@...ux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>, Masami Hiramatsu <mhiramat@...hat.com>, Mel Gorman <mel@....ul.ie>, Steven Rostedt <rostedt@...dmis.org>, Randy Dunlap <rdunlap@...otime.net>, Linus Torvalds <torvalds@...ux-foundation.org>, "H. Peter Anvin" <hpa@...or.com>, Roland McGrath <roland@...hat.com>, Christoph Hellwig <hch@...radead.org>, Ananth N Mavinakayanahalli <ananth@...ibm.com>, Oleg Nesterov <oleg@...hat.com>, Mark Wielaard <mjw@...hat.com>, LKML <linux-kernel@...r.kernel.org>, Jim Keniston <jkenisto@...ux.vnet.ibm.com>, Frederic Weisbecker <fweisbec@...il.com>, "Rafael J. Wysocki" <rjw@...k.pl>, "Frank Ch. Eigler" <fche@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> Subject: Re: [PATCH v4 0/13] Uprobes v4 * Srikar Dronamraju (srikar@...ux.vnet.ibm.com) wrote: > Uprobes Patches > > Changelog from v3: > - Reverted to background page replacement as suggested by Peter Zijlstra. Why ? I'm not sure we reached any concensus about the need for a background page replacement. Thanks, Mathieu > - Dso in 'perf probe' can be either be a short name or a absolute path. > - Addressed comments from Masami, Frederic, Steven on traceevents and perf > > Changelog from v2: > - Addressed comments from Oleg, including removal of interrupt context > handlers, reverting background page replacement in favour of > access_process_vm(). > > - Provides perf interface for uprobes. > > Changelog from v1: > - Added trace_event interface for uprobes. > - Addressed comments from Andrew Morton and Randy Dunlap. > > For previous postings: please refer: http://lkml.org/lkml/2010/5/6/273 > and http://lkml.org/lkml/2010/3/20/107 > > This patchset implements Uprobes which enables you to dynamically break > into any routine in a user space application and collect information > non-disruptively. > > This patchset is a rework based on suggestions from discussions on lkml > in January and March this year (http://lkml.org/lkml/2010/1/11/92, > http://lkml.org/lkml/2010/1/27/19, http://lkml.org/lkml/2010/3/20/107 > and http://lkml.org/lkml/2010/3/31/199 ). This implementation of > uprobes doesnt depend on utrace. > > When a uprobe is registered, Uprobes makes a copy of the probed > instruction, replaces the first byte(s) of the probed instruction with a > breakpoint instruction. (Uprobes uses background page replacement > mechanism and ensures that the breakpoint affects only that process.) > > When a CPU hits the breakpoint instruction, Uprobes gets notified of > trap and finds the associated uprobe. It then executes the associated > handler. Uprobes single-steps its copy of the probed instruction and > resumes execution of the probed process at the instruction following the > probepoint. Instruction copies to be single-stepped are stored in a > per-process "execution out of line (XOL) area". Currently XOL area is > allocated as one page vma. > > Advantages of uprobes over conventional debugging include: > > 1. Non-disruptive. > Unlike current ptrace based mechanisms, uprobes tracing wouldnt > involve signals, stopping threads and context switching between the > tracer and tracee. > > 2. Much better handling of multithreaded programs because of XOL. > Current ptrace based mechanisms use single stepping inline, i.e they > copy back the original instruction on hitting a breakpoint. In such > mechanisms tracers have to stop all the threads on a breakpoint hit or > tracers will not be able to handle all hits to the location of > interest. Uprobes uses execution out of line, where the instruction to > be traced is analysed at the time of breakpoint insertion and a copy > of instruction is stored at a different location. On breakpoint hit, > uprobes jumps to that copied location and singlesteps the same > instruction and does the necessary fixups post singlestepping. > > 3. Multiple tracers for an application. > Multiple uprobes based tracer could work in unison to trace an > application. There could one tracer that could be interested in > generic events for a particular set of process. While there could be > another tracer that is just interested in one specific event of a > particular process thats part of the previous set of process. > > 4. Corelating events from kernels and userspace. > Uprobes could be used with other tools like kprobes, tracepoints or as > part of higher level tools like perf to give a consolidated set of > events from kernel and userspace. In future we could look at a single > backtrace showing application, library and kernel calls. > > Here is the list of TODO Items. > > - Rebase to -tip tree. (targeted for v5) > - Allowing probes across fork. > - Allowing probes per-executable/per dso. > - Allow multiple probes to share a probepoint. > - Return probes. > - Support for other architectures. > - Uprobes booster. > - Merge uprobes and kprobes trace_event. > - replace macro with bits in inat table. > > The current patchset is based on 2.6.34. > > Please do provide your valuable comments. > > Thanks in advance. > Srikar > > Srikar Dronamraju (10): > 1. X86 instruction analysis: Move Macro W to insn.h > 2. mm: Move replace_page() to mm/memory.c > 3. user_bkpt: User Space Breakpoint Assistance Layer > 4. user_bkpt: X86 details for User space breakpoint assistance > 5. user_bkpt: Slot allocation for Execution out of line > 6. uprobes: Uprobes Implementation > 7. uprobes: X86 details for Uprobes > 8. samples: Uprobes samples > 9. uprobes: Uprobes Documentation patch > 10. trace: Share common code for uprobes/kprobes traceevents > 11. trace: uprobes trace_event interface > 12. perf: Dont adjust symbols if lookup is by name. > 13. perf: perf interface for uprobes. > > Documentation/uprobes.txt | 236 ++++++++++ > arch/Kconfig | 31 ++ > arch/x86/Kconfig | 2 + > arch/x86/include/asm/insn.h | 7 + > arch/x86/include/asm/thread_info.h | 2 + > arch/x86/include/asm/user_bkpt.h | 43 ++ > arch/x86/kernel/Makefile | 3 + > arch/x86/kernel/kprobes.c | 7 - > arch/x86/kernel/signal.c | 17 + > arch/x86/kernel/uprobes.c | 77 ++++ > arch/x86/kernel/user_bkpt.c | 572 ++++++++++++++++++++++++ > fs/exec.c | 4 + > include/linux/mm.h | 4 + > include/linux/mm_types.h | 4 + > include/linux/sched.h | 4 + > include/linux/uprobes.h | 169 ++++++++ > include/linux/user_bkpt.h | 305 +++++++++++++ > include/linux/user_bkpt_xol.h | 40 ++ > kernel/Makefile | 3 + > kernel/fork.c | 20 + > kernel/trace/Kconfig | 13 + > kernel/trace/Makefile | 1 + > kernel/trace/trace.h | 11 + > kernel/trace/trace_kprobe.c | 76 +---- > kernel/trace/trace_probe.h | 111 +++++ > kernel/trace/trace_uprobe.c | 839 ++++++++++++++++++++++++++++++++++++ > kernel/uprobes.c | 681 +++++++++++++++++++++++++++++ > kernel/user_bkpt.c | 589 +++++++++++++++++++++++++ > kernel/user_bkpt_xol.c | 302 +++++++++++++ > mm/ksm.c | 112 ----- > mm/memory.c | 120 +++++ > samples/Kconfig | 7 + > samples/Makefile | 2 +- > samples/uprobes/Makefile | 17 + > samples/uprobes/uprobe_example.c | 83 ++++ > tools/perf/builtin-probe.c | 38 ++- > tools/perf/builtin-top.c | 20 - > tools/perf/util/event.c | 20 + > tools/perf/util/event.h | 1 + > tools/perf/util/probe-event.c | 237 +++++++++-- > tools/perf/util/probe-event.h | 9 +- > tools/perf/util/probe-finder.h | 1 + > tools/perf/util/symbol.c | 6 +- > 43 files changed, 4576 insertions(+), 270 deletions(-) -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.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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