Commit 97c79a38 authored by Arnaldo Carvalho de Melo's avatar Arnaldo Carvalho de Melo
Browse files

perf core: Per event callchain limit 

Additionally to being able to control the system wide maximum depth via
/proc/sys/kernel/perf_event_max_stack, now we are able to ask for
different depths per event, using perf_event_attr.sample_max_stack for
that.

This uses an u16 hole at the end of perf_event_attr, that, when
perf_event_attr.sample_type has the PERF_SAMPLE_CALLCHAIN, if
sample_max_stack is zero, means use perf_event_max_stack, otherwise
it'll be bounds checked under callchain_mutex.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lkml.kernel.org/n/tip-kolmn1yo40p7jhswxwrc7rrd@git.kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 480ca357

include/linux/perf_event.h

+1 −1
Original line number Diff line number Diff line
@@ -1076,7 +1076,7 @@ extern void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct 
extern struct perf_callchain_entry *

get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,

		   u32 max_stack, bool crosstask, bool add_mark);

extern int get_callchain_buffers(void);

extern int get_callchain_buffers(int max_stack);

extern void put_callchain_buffers(void);



extern int sysctl_perf_event_max_stack;

include/uapi/linux/perf_event.h

+5 −1
Original line number Diff line number Diff line
@@ -276,6 +276,9 @@ enum perf_event_read_format { 


/*

 * Hardware event_id to monitor via a performance monitoring event:

 *

 * @sample_max_stack: Max number of frame pointers in a callchain,

 *		      should be < /proc/sys/kernel/perf_event_max_stack

 */

struct perf_event_attr {
@@ -385,7 +388,8 @@ struct perf_event_attr { 
	 * Wakeup watermark for AUX area

	 */

	__u32	aux_watermark;

	__u32	__reserved_2;	/* align to __u64 */

	__u16	sample_max_stack;

	__u16	__reserved_2;	/* align to __u64 */

};



#define perf_flags(attr)	(*(&(attr)->read_format + 1))

kernel/bpf/stackmap.c

+1 −1
Original line number Diff line number Diff line
@@ -99,7 +99,7 @@ static struct bpf_map *stack_map_alloc(union bpf_attr *attr) 
	if (err)

		goto free_smap;



	err = get_callchain_buffers();

	err = get_callchain_buffers(sysctl_perf_event_max_stack);

	if (err)

		goto free_smap;

kernel/events/callchain.c

+12 −2
Original line number Diff line number Diff line
@@ -104,7 +104,7 @@ fail: 
	return -ENOMEM;

}



int get_callchain_buffers(void)

int get_callchain_buffers(int event_max_stack)

{

	int err = 0;

	int count;
@@ -121,6 +121,15 @@ int get_callchain_buffers(void) 
		/* If the allocation failed, give up */

		if (!callchain_cpus_entries)

			err = -ENOMEM;

		/*

		 * If requesting per event more than the global cap,

		 * return a different error to help userspace figure

		 * this out.

		 *

		 * And also do it here so that we have &callchain_mutex held.

		 */

		if (event_max_stack > sysctl_perf_event_max_stack)

			err = -EOVERFLOW;

		goto exit;

	}
@@ -174,11 +183,12 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs) 
	bool user   = !event->attr.exclude_callchain_user;

	/* Disallow cross-task user callchains. */

	bool crosstask = event->ctx->task && event->ctx->task != current;

	const u32 max_stack = event->attr.sample_max_stack;



	if (!kernel && !user)

		return NULL;



	return get_perf_callchain(regs, 0, kernel, user, sysctl_perf_event_max_stack, crosstask, true);

	return get_perf_callchain(regs, 0, kernel, user, max_stack, crosstask, true);

}



struct perf_callchain_entry *

kernel/events/core.c

+4 −1
Original line number Diff line number Diff line
@@ -8843,7 +8843,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, 


	if (!event->parent) {

		if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) {

			err = get_callchain_buffers();

			err = get_callchain_buffers(attr->sample_max_stack);

			if (err)

				goto err_addr_filters;

		}
@@ -9165,6 +9165,9 @@ SYSCALL_DEFINE5(perf_event_open, 
			return -EINVAL;

	}



	if (!attr.sample_max_stack)

		attr.sample_max_stack = sysctl_perf_event_max_stack;



	/*

	 * In cgroup mode, the pid argument is used to pass the fd

	 * opened to the cgroup directory in cgroupfs. The cpu argument

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