[PATCH 02/26] perf: Introduce mmap3 version of mmap event

Jiri Olsa
2020-09-13T21:03:44Z

Add new version of mmap event. The MMAP3 record is an
augmented version of MMAP2, it adds build id value to
identify the exact binary object behind memory map:

struct {
struct perf_event_header header;

u32 pid, tid;
u64 addr;
u64 len;
u64 pgoff;
u32 maj;
u32 min;
u64 ino;
u64 ino_generation;
u32 prot, flags;
u32 reserved;
u8 buildid[20];
char filename[];
struct sample_id sample_id;
};

Adding 4 bytes reserved field to align buildid data to 8 bytes,
so sample_id data is properly aligned.

The mmap3 event is enabled by new mmap3 bit in perf_event_attr
struct. When set for an event, it enables the build id retrieval
and will use mmap3 format for the event.

Keeping track of mmap3 events and calling build_id_parse
in perf_event_mmap_event only if we have any defined.

Having build id attached directly to the mmap event will help
tool like perf to skip final search through perf data for
binaries that are needed in the report time. Also it prevents
possible race when the binary could be removed or replaced
during profiling.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
include/uapi/linux/perf_event.h | 27 ++++++++++++++++++++++-
kernel/events/core.c | 38 +++++++++++++++++++++++++++------
2 files changed, 57 insertions(+), 8 deletions(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 077e7ee69e3d..facfc3c673ed 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -384,7 +384,8 @@ struct perf_event_attr {
aux_output : 1, /* generate AUX records instead of events */
cgroup : 1, /* include cgroup events */
text_poke : 1, /* include text poke events */
- __reserved_1 : 30;
+ mmap3 : 1, /* include bpf events */
+ __reserved_1 : 29;

union {
__u32 wakeup_events; /* wakeup every n events */
@@ -1060,6 +1061,30 @@ enum perf_event_type {
*/
PERF_RECORD_TEXT_POKE = 20,

+ /*
+ * The MMAP3 records are an augmented version of MMAP2, they add
+ * build id value to identify the exact binary behind map
+ *
+ * struct {
+ * struct perf_event_header header;
+ *
+ * u32 pid, tid;
+ * u64 addr;
+ * u64 len;
+ * u64 pgoff;
+ * u32 maj;
+ * u32 min;
+ * u64 ino;
+ * u64 ino_generation;
+ * u32 prot, flags;
+ * u32 reserved;
+ * u8 buildid[20];
+ * char filename[];
+ * struct sample_id sample_id;
+ * };
+ */
+ PERF_RECORD_MMAP3 = 21,
+
PERF_RECORD_MAX, /* non-ABI */
};

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 7ed5248f0445..719894492dac 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -51,6 +51,7 @@
#include <linux/proc_ns.h>
#include <linux/mount.h>
#include <linux/min_heap.h>
+#include <linux/buildid.h>

#include "internal.h"

@@ -386,6 +387,7 @@ static DEFINE_PER_CPU(int, perf_sched_cb_usages);
static DEFINE_PER_CPU(struct pmu_event_list, pmu_sb_events);

static atomic_t nr_mmap_events __read_mostly;
+static atomic_t nr_mmap3_events __read_mostly;
static atomic_t nr_comm_events __read_mostly;
static atomic_t nr_namespaces_events __read_mostly;
static atomic_t nr_task_events __read_mostly;
@@ -4588,7 +4590,7 @@ static bool is_sb_event(struct perf_event *event)
return false;

if (attr->mmap || attr->mmap_data || attr->mmap2 ||
- attr->comm || attr->comm_exec ||
+ attr->mmap3 || attr->comm || attr->comm_exec ||
attr->task || attr->ksymbol ||
attr->context_switch || attr->text_poke ||
attr->bpf_event)
@@ -4644,6 +4646,8 @@ static void unaccount_event(struct perf_event *event)
dec = true;
if (event->attr.mmap || event->attr.mmap_data)
atomic_dec(&nr_mmap_events);
+ if (event->attr.mmap3)
+ atomic_dec(&nr_mmap3_events);
if (event->attr.comm)
atomic_dec(&nr_comm_events);
if (event->attr.namespaces)
@@ -7465,7 +7469,7 @@ static void perf_pmu_output_stop(struct perf_event *event)
/*
* task tracking -- fork/exit
*
- * enabled by: attr.comm | attr.mmap | attr.mmap2 | attr.mmap_data | attr.task
+ * enabled by: attr.comm | attr.mmap | attr.mmap2 | attr.mmap3 | attr.mmap_data | attr.task
*/

struct perf_task_event {
@@ -7486,8 +7490,8 @@ struct perf_task_event {
static int perf_event_task_match(struct perf_event *event)
{
return event->attr.comm || event->attr.mmap ||
- event->attr.mmap2 || event->attr.mmap_data ||
- event->attr.task;
+ event->attr.mmap2 || event->attr.mmap3 ||
+ event->attr.mmap_data || event->attr.task;
}

static void perf_event_task_output(struct perf_event *event,
@@ -7913,6 +7917,7 @@ struct perf_mmap_event {
u64 ino;
u64 ino_generation;
u32 prot, flags;
+ u8 buildid[BUILD_ID_SIZE];

struct {
struct perf_event_header header;
@@ -7933,7 +7938,7 @@ static int perf_event_mmap_match(struct perf_event *event,
int executable = vma->vm_flags & VM_EXEC;

return (!executable && event->attr.mmap_data) ||
- (executable && (event->attr.mmap || event->attr.mmap2));
+ (executable && (event->attr.mmap || event->attr.mmap2 || event->attr.mmap3));
}

static void perf_event_mmap_output(struct perf_event *event,
@@ -7949,7 +7954,7 @@ static void perf_event_mmap_output(struct perf_event *event,
if (!perf_event_mmap_match(event, data))
return;

- if (event->attr.mmap2) {
+ if (event->attr.mmap2 || event->attr.mmap3) {
mmap_event->event_id.header.type = PERF_RECORD_MMAP2;
mmap_event->event_id.header.size += sizeof(mmap_event->maj);
mmap_event->event_id.header.size += sizeof(mmap_event->min);
@@ -7959,6 +7964,12 @@ static void perf_event_mmap_output(struct perf_event *event,
mmap_event->event_id.header.size += sizeof(mmap_event->flags);
}

+ if (event->attr.mmap3) {
+ mmap_event->event_id.header.type = PERF_RECORD_MMAP3;
+ mmap_event->event_id.header.size += sizeof(u32);
+ mmap_event->event_id.header.size += sizeof(mmap_event->buildid);
+ }
+
perf_event_header__init_id(&mmap_event->event_id.header, &sample, event);
ret = perf_output_begin(&handle, event,
mmap_event->event_id.header.size);
@@ -7970,7 +7981,7 @@ static void perf_event_mmap_output(struct perf_event *event,

perf_output_put(&handle, mmap_event->event_id);

- if (event->attr.mmap2) {
+ if (event->attr.mmap2 || event->attr.mmap3) {
perf_output_put(&handle, mmap_event->maj);
perf_output_put(&handle, mmap_event->min);
perf_output_put(&handle, mmap_event->ino);
@@ -7979,6 +7990,13 @@ static void perf_event_mmap_output(struct perf_event *event,
perf_output_put(&handle, mmap_event->flags);
}

+ if (event->attr.mmap3) {
+ u32 reserved = 0;
+
+ perf_output_put(&handle, reserved);
+ __output_copy(&handle, mmap_event->buildid, BUILD_ID_SIZE);
+ }
+
__output_copy(&handle, mmap_event->file_name,
mmap_event->file_size);

@@ -8098,6 +8116,9 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
mmap_event->prot = prot;
mmap_event->flags = flags;

+ if (atomic_read(&nr_mmap3_events))
+ build_id_parse(vma, mmap_event->buildid);
+
if (!(vma->vm_flags & VM_EXEC))
mmap_event->event_id.header.misc |= PERF_RECORD_MISC_MMAP_DATA;

@@ -8241,6 +8262,7 @@ void perf_event_mmap(struct vm_area_struct *vma)
/* .ino_generation (attr_mmap2 only) */
/* .prot (attr_mmap2 only) */
/* .flags (attr_mmap2 only) */
+ /* .buildid (attr_mmap3 only) */
};

perf_addr_filters_adjust(vma);
@@ -11040,6 +11062,8 @@ static void account_event(struct perf_event *event)
inc = true;
if (event->attr.mmap || event->attr.mmap_data)
atomic_inc(&nr_mmap_events);
+ if (event->attr.mmap3)
+ atomic_inc(&nr_mmap3_events);
if (event->attr.comm)
atomic_inc(&nr_comm_events);
if (event->attr.namespaces)
--
2.26.2