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    Subject[PATCH 7/9] ftrace, perf: Add support to use function tracepoint in perf
    From: Jiri Olsa <jolsa@redhat.com>

    Adding perf registration support for the ftrace function event,
    so it is now possible to register it via perf interface.

    The perf_event struct statically contains ftrace_ops as a handle
    for function tracer. The function tracer is registered/unregistered
    in open/close actions.

    To be efficient, we enable/disable ftrace_ops each time the traced
    process is scheduled in/out (via TRACE_REG_PERF_(ADD|DELL) handlers).
    This way tracing is enabled only when the process is running.
    Intentionally using this way instead of the event's hw state
    PERF_HES_STOPPED, which would not disable the ftrace_ops.

    It is now possible to use function trace within perf commands
    like:

    perf record -e ftrace:function ls
    perf stat -e ftrace:function ls

    Allowed only for root.

    Link: http://lkml.kernel.org/r/1329317514-8131-6-git-send-email-jolsa@redhat.com

    Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
    Signed-off-by: Jiri Olsa <jolsa@redhat.com>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    ---
    include/linux/perf_event.h | 3 +
    kernel/trace/trace.h | 11 +++++
    kernel/trace/trace_entries.h | 6 ++-
    kernel/trace/trace_event_perf.c | 86 +++++++++++++++++++++++++++++++++++++++
    kernel/trace/trace_export.c | 5 ++
    5 files changed, 109 insertions(+), 2 deletions(-)

    diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
    index 412b790..92a056f 100644
    --- a/include/linux/perf_event.h
    +++ b/include/linux/perf_event.h
    @@ -859,6 +859,9 @@ struct perf_event {
    #ifdef CONFIG_EVENT_TRACING
    struct ftrace_event_call *tp_event;
    struct event_filter *filter;
    +#ifdef CONFIG_FUNCTION_TRACER
    + struct ftrace_ops ftrace_ops;
    +#endif
    #endif

    #ifdef CONFIG_CGROUP_PERF
    diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
    index 638476a..76a1c50 100644
    --- a/kernel/trace/trace.h
    +++ b/kernel/trace/trace.h
    @@ -595,6 +595,8 @@ static inline int ftrace_trace_task(struct task_struct *task)
    static inline int ftrace_is_dead(void) { return 0; }
    #endif

    +int ftrace_event_is_function(struct ftrace_event_call *call);
    +
    /*
    * struct trace_parser - servers for reading the user input separated by spaces
    * @cont: set if the input is not complete - no final space char was found
    @@ -832,4 +834,13 @@ extern const char *__stop___trace_bprintk_fmt[];
    FTRACE_ENTRY(call, struct_name, id, PARAMS(tstruct), PARAMS(print))
    #include "trace_entries.h"

    +#ifdef CONFIG_PERF_EVENTS
    +#ifdef CONFIG_FUNCTION_TRACER
    +int perf_ftrace_event_register(struct ftrace_event_call *call,
    + enum trace_reg type, void *data);
    +#else
    +#define perf_ftrace_event_register NULL
    +#endif /* CONFIG_FUNCTION_TRACER */
    +#endif /* CONFIG_PERF_EVENTS */
    +
    #endif /* _LINUX_KERNEL_TRACE_H */
    diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
    index 9336590..47db7ed 100644
    --- a/kernel/trace/trace_entries.h
    +++ b/kernel/trace/trace_entries.h
    @@ -55,7 +55,7 @@
    /*
    * Function trace entry - function address and parent function address:
    */
    -FTRACE_ENTRY(function, ftrace_entry,
    +FTRACE_ENTRY_REG(function, ftrace_entry,

    TRACE_FN,

    @@ -64,7 +64,9 @@ FTRACE_ENTRY(function, ftrace_entry,
    __field( unsigned long, parent_ip )
    ),

    - F_printk(" %lx <-- %lx", __entry->ip, __entry->parent_ip)
    + F_printk(" %lx <-- %lx", __entry->ip, __entry->parent_ip),
    +
    + perf_ftrace_event_register
    );

    /* Function call entry */
    diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
    index d72af0b..fdeeb5c 100644
    --- a/kernel/trace/trace_event_perf.c
    +++ b/kernel/trace/trace_event_perf.c
    @@ -24,6 +24,11 @@ static int total_ref_count;
    static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
    struct perf_event *p_event)
    {
    + /* The ftrace function trace is allowed only for root. */
    + if (ftrace_event_is_function(tp_event) &&
    + perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
    + return -EPERM;
    +
    /* No tracing, just counting, so no obvious leak */
    if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW))
    return 0;
    @@ -250,3 +255,84 @@ __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
    return raw_data;
    }
    EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);
    +
    +#ifdef CONFIG_FUNCTION_TRACER
    +static void
    +perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip)
    +{
    + struct ftrace_entry *entry;
    + struct hlist_head *head;
    + struct pt_regs regs;
    + int rctx;
    +
    +#define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \
    + sizeof(u64)) - sizeof(u32))
    +
    + BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE);
    +
    + perf_fetch_caller_regs(&regs);
    +
    + entry = perf_trace_buf_prepare(ENTRY_SIZE, TRACE_FN, NULL, &rctx);
    + if (!entry)
    + return;
    +
    + entry->ip = ip;
    + entry->parent_ip = parent_ip;
    +
    + head = this_cpu_ptr(event_function.perf_events);
    + perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0,
    + 1, &regs, head);
    +
    +#undef ENTRY_SIZE
    +}
    +
    +static int perf_ftrace_function_register(struct perf_event *event)
    +{
    + struct ftrace_ops *ops = &event->ftrace_ops;
    +
    + ops->flags |= FTRACE_OPS_FL_CONTROL;
    + ops->func = perf_ftrace_function_call;
    + return register_ftrace_function(ops);
    +}
    +
    +static int perf_ftrace_function_unregister(struct perf_event *event)
    +{
    + struct ftrace_ops *ops = &event->ftrace_ops;
    + return unregister_ftrace_function(ops);
    +}
    +
    +static void perf_ftrace_function_enable(struct perf_event *event)
    +{
    + ftrace_function_local_enable(&event->ftrace_ops);
    +}
    +
    +static void perf_ftrace_function_disable(struct perf_event *event)
    +{
    + ftrace_function_local_disable(&event->ftrace_ops);
    +}
    +
    +int perf_ftrace_event_register(struct ftrace_event_call *call,
    + enum trace_reg type, void *data)
    +{
    + switch (type) {
    + case TRACE_REG_REGISTER:
    + case TRACE_REG_UNREGISTER:
    + break;
    + case TRACE_REG_PERF_REGISTER:
    + case TRACE_REG_PERF_UNREGISTER:
    + return 0;
    + case TRACE_REG_PERF_OPEN:
    + return perf_ftrace_function_register(data);
    + case TRACE_REG_PERF_CLOSE:
    + return perf_ftrace_function_unregister(data);
    + case TRACE_REG_PERF_ADD:
    + perf_ftrace_function_enable(data);
    + return 0;
    + case TRACE_REG_PERF_DEL:
    + perf_ftrace_function_disable(data);
    + return 0;
    + }
    +
    + return -EINVAL;
    +}
    +#endif /* CONFIG_FUNCTION_TRACER */
    diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c
    index f74de86..a3dbee6 100644
    --- a/kernel/trace/trace_export.c
    +++ b/kernel/trace/trace_export.c
    @@ -184,4 +184,9 @@ __attribute__((section("_ftrace_events"))) *__event_##call = &event_##call;
    FTRACE_ENTRY_REG(call, struct_name, etype, \
    PARAMS(tstruct), PARAMS(print), NULL)

    +int ftrace_event_is_function(struct ftrace_event_call *call)
    +{
    + return call == &event_function;
    +}
    +
    #include "trace_entries.h"
    --
    1.7.8.3

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