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SubjectRe: [PATCH 5/7] ftrace, perf: Add support to use function tracepoint in perf
On Wed, Feb 15, 2012 at 03:51:52PM +0100, Jiri Olsa wrote:
> 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.
>
> Signed-off-by: Jiri Olsa <jolsa@redhat.com>

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>

> ---
> 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"
> --
> 1.7.1
>


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