perf/core: Add PERF_RECORD_CGROUP event

To support cgroup tracking, add CGROUP event to save a link between
cgroup path and id number.  This is needed since cgroups can go away
when userspace tries to read the cgroup info (from the id) later.

The attr.cgroup bit was also added to enable cgroup tracking from
userspace.

This event will be generated when a new cgroup becomes active.
Userspace might need to synthesize those events for existing cgroups.

Committer testing:

From the resulting kernel, using /sys/kernel/btf/vmlinux:

  $ pahole perf_event_attr | grep -w cgroup -B5 -A1
  	__u64                      write_backward:1;     /*    40:27  8 */
  	__u64                      namespaces:1;         /*    40:28  8 */
  	__u64                      ksymbol:1;            /*    40:29  8 */
  	__u64                      bpf_event:1;          /*    40:30  8 */
  	__u64                      aux_output:1;         /*    40:31  8 */
  	__u64                      cgroup:1;             /*    40:32  8 */
  	__u64                      __reserved_1:31;      /*    40:33  8 */
  $

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
[staticize perf_event_cgroup function]
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lore.kernel.org/lkml/20200325124536.2800725-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 397cfd65b3fe..de95f6c7b273 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -381,7 +381,8 @@ struct perf_event_attr {
 				ksymbol        :  1, /* include ksymbol events */
 				bpf_event      :  1, /* include bpf events */
 				aux_output     :  1, /* generate AUX records instead of events */
-				__reserved_1   : 32;
+				cgroup         :  1, /* include cgroup events */
+				__reserved_1   : 31;
 
 	union {
 		__u32		wakeup_events;	  /* wakeup every n events */
@@ -1012,6 +1013,16 @@ enum perf_event_type {
 	 */
 	PERF_RECORD_BPF_EVENT			= 18,
 
+	/*
+	 * struct {
+	 *	struct perf_event_header	header;
+	 *	u64				id;
+	 *	char				path[];
+	 *	struct sample_id		sample_id;
+	 * };
+	 */
+	PERF_RECORD_CGROUP			= 19,
+
 	PERF_RECORD_MAX,			/* non-ABI */
 };