perf/core: Add PERF_SAMPLE_CGROUP feature

The PERF_SAMPLE_CGROUP bit is to save (perf_event) cgroup information in
the sample.  It will add a 64-bit id to identify current cgroup and it's
the file handle in the cgroup file system.  Userspace should use this
information with PERF_RECORD_CGROUP event to match which cgroup it
belongs.

I put it before PERF_SAMPLE_AUX for simplicity since it just needs a
64-bit word.  But if we want bigger samples, I can work on that
direction too.

Committer testing:

  $ pahole perf_sample_data | grep -w cgroup -B5 -A5
  	/* --- cacheline 4 boundary (256 bytes) was 56 bytes ago --- */
  	struct perf_regs           regs_intr;            /*   312    16 */
  	/* --- cacheline 5 boundary (320 bytes) was 8 bytes ago --- */
  	u64                        stack_user_size;      /*   328     8 */
  	u64                        phys_addr;            /*   336     8 */
  	u64                        cgroup;               /*   344     8 */

  	/* size: 384, cachelines: 6, members: 22 */
  	/* padding: 32 */
  };
  $

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>
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/20200325124536.2800725-3-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 994932d5e474..1569979c8912 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1862,6 +1862,9 @@ static void __perf_event_header_size(struct perf_event *event, u64 sample_type)
 	if (sample_type & PERF_SAMPLE_PHYS_ADDR)
 		size += sizeof(data->phys_addr);
 
+	if (sample_type & PERF_SAMPLE_CGROUP)
+		size += sizeof(data->cgroup);
+
 	event->header_size = size;
 }
 
@@ -6867,6 +6870,9 @@ void perf_output_sample(struct perf_output_handle *handle,
 	if (sample_type & PERF_SAMPLE_PHYS_ADDR)
 		perf_output_put(handle, data->phys_addr);
 
+	if (sample_type & PERF_SAMPLE_CGROUP)
+		perf_output_put(handle, data->cgroup);
+
 	if (sample_type & PERF_SAMPLE_AUX) {
 		perf_output_put(handle, data->aux_size);
 
@@ -7066,6 +7072,16 @@ void perf_prepare_sample(struct perf_event_header *header,
 	if (sample_type & PERF_SAMPLE_PHYS_ADDR)
 		data->phys_addr = perf_virt_to_phys(data->addr);
 
+#ifdef CONFIG_CGROUP_PERF
+	if (sample_type & PERF_SAMPLE_CGROUP) {
+		struct cgroup *cgrp;
+
+		/* protected by RCU */
+		cgrp = task_css_check(current, perf_event_cgrp_id, 1)->cgroup;
+		data->cgroup = cgroup_id(cgrp);
+	}
+#endif
+
 	if (sample_type & PERF_SAMPLE_AUX) {
 		u64 size;
 
@@ -11264,6 +11280,12 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
 
 	if (attr->sample_type & PERF_SAMPLE_REGS_INTR)
 		ret = perf_reg_validate(attr->sample_regs_intr);
+
+#ifndef CONFIG_CGROUP_PERF
+	if (attr->sample_type & PERF_SAMPLE_CGROUP)
+		return -EINVAL;
+#endif
+
 out:
 	return ret;