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    Subject[tip:perf/probes] tracing/kprobes: Add probe handler dispatcher to support perf and ftrace concurrent use
    Commit-ID:  50d780560785b068c358675c5f0bf6c83b5c373e
    Gitweb: http://git.kernel.org/tip/50d780560785b068c358675c5f0bf6c83b5c373e
    Author: Masami Hiramatsu <mhiramat@redhat.com>
    AuthorDate: Mon, 14 Sep 2009 16:49:20 -0400
    Committer: Frederic Weisbecker <fweisbec@gmail.com>
    CommitDate: Thu, 17 Sep 2009 04:03:54 +0200

    tracing/kprobes: Add probe handler dispatcher to support perf and ftrace concurrent use

    Add kprobe_dispatcher and kretprobe_dispatcher to dispatch event
    in both profile and tracing handlers.

    This allows simultaneous kprobe uses by ftrace and perf.

    Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
    Acked-by: Steven Rostedt <rostedt@goodmis.org>
    Cc: Jim Keniston <jkenisto@us.ibm.com>
    Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: Christoph Hellwig <hch@infradead.org>
    Cc: Frank Ch. Eigler <fche@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Jason Baron <jbaron@redhat.com>
    Cc: K.Prasad <prasad@linux.vnet.ibm.com>
    Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
    Cc: Li Zefan <lizf@cn.fujitsu.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    Cc: Tom Zanussi <tzanussi@gmail.com>
    LKML-Reference: <20090914204920.18779.57555.stgit@dhcp-100-2-132.bos.redhat.com>
    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    ---
    kernel/trace/trace_kprobe.c | 85 ++++++++++++++++++++++++++++++++-----------
    1 files changed, 63 insertions(+), 22 deletions(-)

    diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
    index ea0db8e..70b632c 100644
    --- a/kernel/trace/trace_kprobe.c
    +++ b/kernel/trace/trace_kprobe.c
    @@ -185,10 +185,15 @@ struct probe_arg {
    const char *name;
    };

    +/* Flags for trace_probe */
    +#define TP_FLAG_TRACE 1
    +#define TP_FLAG_PROFILE 2
    +
    struct trace_probe {
    struct list_head list;
    struct kretprobe rp; /* Use rp.kp for kprobe use */
    unsigned long nhit;
    + unsigned int flags; /* For TP_FLAG_* */
    const char *symbol; /* symbol name */
    struct ftrace_event_call call;
    struct trace_event event;
    @@ -200,10 +205,6 @@ struct trace_probe {
    (offsetof(struct trace_probe, args) + \
    (sizeof(struct probe_arg) * (n)))

    -static int kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs);
    -static int kretprobe_trace_func(struct kretprobe_instance *ri,
    - struct pt_regs *regs);
    -
    static __kprobes int probe_is_return(struct trace_probe *tp)
    {
    return tp->rp.handler != NULL;
    @@ -263,6 +264,10 @@ static void unregister_probe_event(struct trace_probe *tp);
    static DEFINE_MUTEX(probe_lock);
    static LIST_HEAD(probe_list);

    +static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs);
    +static int kretprobe_dispatcher(struct kretprobe_instance *ri,
    + struct pt_regs *regs);
    +
    /*
    * Allocate new trace_probe and initialize it (including kprobes).
    */
    @@ -288,11 +293,10 @@ static struct trace_probe *alloc_trace_probe(const char *group,
    } else
    tp->rp.kp.addr = addr;

    - /* Set handler here for checking whether this probe is return or not. */
    if (is_return)
    - tp->rp.handler = kretprobe_trace_func;
    + tp->rp.handler = kretprobe_dispatcher;
    else
    - tp->rp.kp.pre_handler = kprobe_trace_func;
    + tp->rp.kp.pre_handler = kprobe_dispatcher;

    if (!event)
    goto error;
    @@ -379,6 +383,7 @@ static int register_trace_probe(struct trace_probe *tp)
    goto end;
    }

    + tp->flags = TP_FLAG_TRACE;
    if (probe_is_return(tp))
    ret = register_kretprobe(&tp->rp);
    else
    @@ -987,23 +992,24 @@ static int probe_event_enable(struct ftrace_event_call *call)
    {
    struct trace_probe *tp = (struct trace_probe *)call->data;

    - if (probe_is_return(tp)) {
    - tp->rp.handler = kretprobe_trace_func;
    + tp->flags |= TP_FLAG_TRACE;
    + if (probe_is_return(tp))
    return enable_kretprobe(&tp->rp);
    - } else {
    - tp->rp.kp.pre_handler = kprobe_trace_func;
    + else
    return enable_kprobe(&tp->rp.kp);
    - }
    }

    static void probe_event_disable(struct ftrace_event_call *call)
    {
    struct trace_probe *tp = (struct trace_probe *)call->data;

    - if (probe_is_return(tp))
    - disable_kretprobe(&tp->rp);
    - else
    - disable_kprobe(&tp->rp.kp);
    + tp->flags &= ~TP_FLAG_TRACE;
    + if (!(tp->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE))) {
    + if (probe_is_return(tp))
    + disable_kretprobe(&tp->rp);
    + else
    + disable_kprobe(&tp->rp.kp);
    + }
    }

    static int probe_event_raw_init(struct ftrace_event_call *event_call)
    @@ -1212,22 +1218,57 @@ static int probe_profile_enable(struct ftrace_event_call *call)
    if (atomic_inc_return(&call->profile_count))
    return 0;

    - if (probe_is_return(tp)) {
    - tp->rp.handler = kretprobe_profile_func;
    + tp->flags |= TP_FLAG_PROFILE;
    + if (probe_is_return(tp))
    return enable_kretprobe(&tp->rp);
    - } else {
    - tp->rp.kp.pre_handler = kprobe_profile_func;
    + else
    return enable_kprobe(&tp->rp.kp);
    - }
    }

    static void probe_profile_disable(struct ftrace_event_call *call)
    {
    + struct trace_probe *tp = (struct trace_probe *)call->data;
    +
    if (atomic_add_negative(-1, &call->profile_count))
    - probe_event_disable(call);
    + tp->flags &= ~TP_FLAG_PROFILE;
    +
    + if (!(tp->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE))) {
    + if (probe_is_return(tp))
    + disable_kretprobe(&tp->rp);
    + else
    + disable_kprobe(&tp->rp.kp);
    + }
    }
    +#endif /* CONFIG_EVENT_PROFILE */
    +
    +
    +static __kprobes
    +int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs)
    +{
    + struct trace_probe *tp = container_of(kp, struct trace_probe, rp.kp);

    + if (tp->flags & TP_FLAG_TRACE)
    + kprobe_trace_func(kp, regs);
    +#ifdef CONFIG_EVENT_PROFILE
    + if (tp->flags & TP_FLAG_PROFILE)
    + kprobe_profile_func(kp, regs);
    #endif /* CONFIG_EVENT_PROFILE */
    + return 0; /* We don't tweek kernel, so just return 0 */
    +}
    +
    +static __kprobes
    +int kretprobe_dispatcher(struct kretprobe_instance *ri, struct pt_regs *regs)
    +{
    + struct trace_probe *tp = container_of(ri->rp, struct trace_probe, rp);
    +
    + if (tp->flags & TP_FLAG_TRACE)
    + kretprobe_trace_func(ri, regs);
    +#ifdef CONFIG_EVENT_PROFILE
    + if (tp->flags & TP_FLAG_PROFILE)
    + kretprobe_profile_func(ri, regs);
    +#endif /* CONFIG_EVENT_PROFILE */
    + return 0; /* We don't tweek kernel, so just return 0 */
    +}

    static int register_probe_event(struct trace_probe *tp)
    {

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