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    Subject[PATCH v5 3.1.0-rc4-tip 0/26] Uprobes patchset with perf probe support

    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 resolves most of the comments on the previous posting
    (https://lkml.org/lkml/2011/6/7/232) patchset applies on top of tip
    commit e467f18f945c83e66

    Uprobes Patches
    This patchset implements inode based uprobes which are specified as
    <file>:<offset> where offset is the offset from start of the map.

    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-mm "execution out of line (XOL) area". Currently XOL area is
    allocated as one page vma.

    For previous postings: please refer: https://lkml.org/lkml/2011/4/1/176
    http://lkml.org/lkml/2011/3/14/171/ http://lkml.org/lkml/2010/12/16/65
    http://lkml.org/lkml/2010/8/25/165 http://lkml.org/lkml/2010/7/27/121
    http://lkml.org/lkml/2010/7/12/67 http://lkml.org/lkml/2010/7/8/239
    http://lkml.org/lkml/2010/6/29/299 http://lkml.org/lkml/2010/6/14/41
    http://lkml.org/lkml/2010/3/20/107 and http://lkml.org/lkml/2010/5/18/307

    This patchset is a rework based on suggestions from discussions on lkml
    in September, March and January 2010 (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.

    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.

    Changes from last patchset:
    - mmap_uprobe doesnt drop mmap_sem anymore
    - Introduced uprobes_mmap_mutex to serialize mmap_uprobes.
    - Uses i_mutex instead of uprobes_mutex.
    - Introduces munmap_uprobes
    - Change in perf probe interface as recommended by Masami.
    - Doesnt depend on get_user_pages to do the COW.
    - Slot allocation changed from per-task to shared slot allocation mechanism.

    Here is the list of TODO Items.

    - Prefiltering (i.e filtering at the time of probe insertion)
    - Return probes.
    - Support for other architectures.
    - Uprobes booster.
    - replace macro W with bits in inat table.

    Please refer "[RFC] [PATCH 3.1-rc4-tip 21/26] tracing: tracing: Uprobe
    tracer documentation" on how to use uprobe_tracer.

    Please refer "[RFC] [PATCH 3.1-rc4-tip 25/26] perf: Documentation for perf
    uprobes" on how to use uprobe_tracer.

    Please do provide your valuable comments.

    Thanks in advance.
    Srikar
    ---
    0 files changed, 0 insertions(+), 0 deletions(-)


    Srikar Dronamraju (26)
    0: Uprobes patchset with perf probe support
    1: uprobes: Auxillary routines to insert, find, delete uprobes
    2: Uprobes: Allow multiple consumers for an uprobe.
    3: Uprobes: register/unregister probes.
    4: uprobes: Define hooks for mmap/munmap.
    5: Uprobes: copy of the original instruction.
    6: Uprobes: define fixups.
    7: Uprobes: uprobes arch info
    8: x86: analyze instruction and determine fixups.
    9: Uprobes: Background page replacement.
    10: x86: Set instruction pointer.
    11: x86: Introduce TIF_UPROBE FLAG.
    12: Uprobes: Handle breakpoint and Singlestep
    13: x86: define a x86 specific exception notifier.
    14: uprobe: register exception notifier
    15: x86: Define x86_64 specific uprobe_task_arch_info structure
    16: uprobes: Introduce uprobe_task_arch_info structure.
    17: x86: arch specific hooks for pre/post singlestep handling.
    18: uprobes: slot allocation.
    19: tracing: Extract out common code for kprobes/uprobes traceevents.
    20: tracing: uprobes trace_event interface
    21: tracing: uprobes Documentation
    22: perf: rename target_module to target
    23: perf: perf interface for uprobes
    24: perf: show possible probes in a given executable file or library.
    25: perf: Documentation for perf uprobes
    26: uprobes: queue signals while thread is singlestepping.


    Documentation/trace/uprobetracer.txt | 94 ++
    arch/Kconfig | 4 +
    arch/x86/Kconfig | 3 +
    arch/x86/include/asm/thread_info.h | 2 +
    arch/x86/include/asm/uprobes.h | 54 ++
    arch/x86/kernel/Makefile | 1 +
    arch/x86/kernel/signal.c | 14 +
    arch/x86/kernel/uprobes.c | 562 ++++++++++++
    include/linux/mm_types.h | 5 +
    include/linux/sched.h | 3 +
    include/linux/uprobes.h | 165 ++++
    kernel/Makefile | 1 +
    kernel/fork.c | 11 +
    kernel/signal.c | 22 +-
    kernel/trace/Kconfig | 20 +
    kernel/trace/Makefile | 2 +
    kernel/trace/trace.h | 5 +
    kernel/trace/trace_kprobe.c | 894 +------------------
    kernel/trace/trace_probe.c | 784 ++++++++++++++++
    kernel/trace/trace_probe.h | 162 ++++
    kernel/trace/trace_uprobe.c | 770 ++++++++++++++++
    kernel/uprobes.c | 1475 +++++++++++++++++++++++++++++++
    mm/memory.c | 4 +
    mm/mmap.c | 6 +
    tools/perf/Documentation/perf-probe.txt | 14 +
    tools/perf/builtin-probe.c | 49 +-
    tools/perf/util/probe-event.c | 410 +++++++--
    tools/perf/util/probe-event.h | 12 +-
    tools/perf/util/symbol.c | 10 +-
    tools/perf/util/symbol.h | 1 +
    30 files changed, 4581 insertions(+), 978 deletions(-)


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