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Commit ced39002 authored by Jiri Olsa's avatar Jiri Olsa Committed by Steven Rostedt
Browse files

ftrace, perf: Add support to use function tracepoint in perf 

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: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarJiri Olsa <jolsa@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent e59a0bff

include/linux/perf_event.h

+3 −0
Original line number Diff line number Diff line
@@ -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

kernel/trace/trace.h

+11 −0
Original line number Diff line number Diff line
@@ -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 */

kernel/trace/trace_entries.h

+4 −2
Original line number Diff line number Diff line
@@ -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 */

kernel/trace/trace_event_perf.c

+86 −0
Original line number Diff line number Diff line
@@ -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 */

kernel/trace/trace_export.c

+5 −0
Original line number Diff line number Diff line
@@ -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"