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Commit f42d24a1 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes/perf: Teach trace_uprobe/perf code to use UPROBE_HANDLER_REMOVE 



Change uprobe_trace_func() and uprobe_perf_func() to return "int". Change
uprobe_dispatcher() to return "trace_ret | perf_ret" although this is not
needed, currently TP_FLAG_TRACE/TP_FLAG_PROFILE are mutually exclusive.

The only functional change is that uprobe_perf_func() checks the filtering
too and returns UPROBE_HANDLER_REMOVE if nobody wants to trace current.

Testing:

	# perf probe -x /lib/libc.so.6 syscall

	# perf record -e probe_libc:syscall -i perl -e 'fork; syscall -1 for 1..10; wait'

	# perf report --show-total-period
		100.00%            10     perl  libc-2.8.so    [.] syscall

Before this patch:

	# cat /sys/kernel/debug/tracing/uprobe_profile
		/lib/libc.so.6 syscall				20

A child process doesn't have a counter, but still it hits this breakoint
"copied" by dup_mmap().

After the patch:

	# cat /sys/kernel/debug/tracing/uprobe_profile
		/lib/libc.so.6 syscall				11

The child process hits this int3 only once and does unapply_uprobe().

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
parent 31ba3348

kernel/trace/trace_uprobe.c

+14 −7
Original line number Diff line number Diff line
@@ -486,7 +486,7 @@ static const struct file_operations uprobe_profile_ops = { 
};



/* uprobe handler */

static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)

static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)

{

	struct uprobe_trace_entry_head *entry;

	struct ring_buffer_event *event;
@@ -504,7 +504,7 @@ static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs) 
	event = trace_current_buffer_lock_reserve(&buffer, call->event.type,

						  size, irq_flags, pc);

	if (!event)

		return;

		return 0;



	entry = ring_buffer_event_data(event);

	entry->ip = instruction_pointer(task_pt_regs(current));
@@ -514,6 +514,8 @@ static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs) 


	if (!filter_current_check_discard(buffer, call, entry, event))

		trace_buffer_unlock_commit(buffer, event, irq_flags, pc);



	return 0;

}



/* Event entry printers */
@@ -721,7 +723,7 @@ static bool uprobe_perf_filter(struct uprobe_consumer *uc, 
}



/* uprobe profile handler */

static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)

static int uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)

{

	struct ftrace_event_call *call = &tu->call;

	struct uprobe_trace_entry_head *entry;
@@ -730,11 +732,14 @@ static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs) 
	int size, __size, i;

	int rctx;



	if (!uprobe_perf_filter(&tu->consumer, 0, current->mm))

		return UPROBE_HANDLER_REMOVE;



	__size = sizeof(*entry) + tu->size;

	size = ALIGN(__size + sizeof(u32), sizeof(u64));

	size -= sizeof(u32);

	if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, "profile buffer not large enough"))

		return;

		return 0;



	preempt_disable();
@@ -752,6 +757,7 @@ static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs) 


 out:

	preempt_enable();

	return 0;

}

#endif	/* CONFIG_PERF_EVENTS */
@@ -792,18 +798,19 @@ int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type, 
static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs)

{

	struct trace_uprobe *tu;

	int ret = 0;



	tu = container_of(con, struct trace_uprobe, consumer);

	tu->nhit++;



	if (tu->flags & TP_FLAG_TRACE)

		uprobe_trace_func(tu, regs);

		ret |= uprobe_trace_func(tu, regs);



#ifdef CONFIG_PERF_EVENTS

	if (tu->flags & TP_FLAG_PROFILE)

		uprobe_perf_func(tu, regs);

		ret |= uprobe_perf_func(tu, regs);

#endif

	return 0;

	return ret;

}



static struct trace_event_functions uprobe_funcs = {