Commit 2e498d0a authored by Marco Elver's avatar Marco Elver Committed by Peter Zijlstra
Browse files

perf: Add support for event removal on exec 



Adds bit perf_event_attr::remove_on_exec, to support removing an event
from a task on exec.

This option supports the case where an event is supposed to be
process-wide only, and should not propagate beyond exec, to limit
monitoring to the original process image only.

Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210408103605.1676875-5-elver@google.com
parent 2b26f0aa

include/uapi/linux/perf_event.h

+2 −1
Original line number Diff line number Diff line
@@ -390,7 +390,8 @@ struct perf_event_attr { 
				text_poke      :  1, /* include text poke events */

				build_id       :  1, /* use build id in mmap2 events */

				inherit_thread :  1, /* children only inherit if cloned with CLONE_THREAD */

				__reserved_1   : 28;

				remove_on_exec :  1, /* event is removed from task on exec */

				__reserved_1   : 27;



	union {

		__u32		wakeup_events;	  /* wakeup every n events */

kernel/events/core.c

+62 −8
Original line number Diff line number Diff line
@@ -4248,6 +4248,57 @@ static void perf_event_enable_on_exec(int ctxn) 
		put_ctx(clone_ctx);

}



static void perf_remove_from_owner(struct perf_event *event);

static void perf_event_exit_event(struct perf_event *event,

				  struct perf_event_context *ctx);



/*

 * Removes all events from the current task that have been marked

 * remove-on-exec, and feeds their values back to parent events.

 */

static void perf_event_remove_on_exec(int ctxn)

{

	struct perf_event_context *ctx, *clone_ctx = NULL;

	struct perf_event *event, *next;

	LIST_HEAD(free_list);

	unsigned long flags;

	bool modified = false;



	ctx = perf_pin_task_context(current, ctxn);

	if (!ctx)

		return;



	mutex_lock(&ctx->mutex);



	if (WARN_ON_ONCE(ctx->task != current))

		goto unlock;



	list_for_each_entry_safe(event, next, &ctx->event_list, event_entry) {

		if (!event->attr.remove_on_exec)

			continue;



		if (!is_kernel_event(event))

			perf_remove_from_owner(event);



		modified = true;



		perf_event_exit_event(event, ctx);

	}



	raw_spin_lock_irqsave(&ctx->lock, flags);

	if (modified)

		clone_ctx = unclone_ctx(ctx);

	--ctx->pin_count;

	raw_spin_unlock_irqrestore(&ctx->lock, flags);



unlock:

	mutex_unlock(&ctx->mutex);



	put_ctx(ctx);

	if (clone_ctx)

		put_ctx(clone_ctx);

}



struct perf_read_data {

	struct perf_event *event;

	bool group;
@@ -7560,19 +7611,19 @@ void perf_event_exec(void) 
	struct perf_event_context *ctx;

	int ctxn;



	rcu_read_lock();

	for_each_task_context_nr(ctxn) {

		ctx = current->perf_event_ctxp[ctxn];

		if (!ctx)

			continue;



		perf_event_enable_on_exec(ctxn);

		perf_event_remove_on_exec(ctxn);



		perf_iterate_ctx(ctx, perf_event_addr_filters_exec, NULL,

				   true);

		rcu_read_lock();

		ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);

		if (ctx) {

			perf_iterate_ctx(ctx, perf_event_addr_filters_exec,

					 NULL, true);

		}

		rcu_read_unlock();

	}

}



struct remote_output {

	struct perf_buffer	*rb;
@@ -11656,6 +11707,9 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr, 
	if (!attr->inherit && attr->inherit_thread)

		return -EINVAL;



	if (attr->remove_on_exec && attr->enable_on_exec)

		return -EINVAL;



out:

	return ret;