[PATCH v3 05/10] libperf: Add libperf_evsel__mmap()

Rob Herring
2020-09-11T21:52:17Z

In order to support usersapce access, an event must be mmapped. While
there's already mmap support for evlist, the usecase is a bit different
than the self monitoring with userspace access. So let's add a new
perf_evsel__mmap() function to mmap an evsel. This allows implementing
userspace access as a fastpath for perf_evsel__read().

The mmapped address is returned by perf_evsel__mmap() primarily for
users/tests to check if userspace access is enabled.

Signed-off-by: Rob Herring <robh@kernel.org>
---
v3:
- New patch split out from user access patch
---
tools/lib/perf/Documentation/libperf.txt | 1 +
tools/lib/perf/evsel.c | 31 ++++++++++++++++++++++++
tools/lib/perf/include/internal/evsel.h | 2 ++
tools/lib/perf/include/perf/evsel.h | 2 ++
tools/lib/perf/libperf.map | 1 +
5 files changed, 37 insertions(+)

diff --git a/tools/lib/perf/Documentation/libperf.txt b/tools/lib/perf/Documentation/libperf.txt
index 0c74c30ed23a..0b4694ce42b9 100644
--- a/tools/lib/perf/Documentation/libperf.txt
+++ b/tools/lib/perf/Documentation/libperf.txt
@@ -136,6 +136,7 @@ SYNOPSIS
struct perf_thread_map *threads);
void perf_evsel__close(struct perf_evsel *evsel);
void perf_evsel__close_cpu(struct perf_evsel *evsel, int cpu);
+ void *perf_evsel__mmap(struct perf_evsel *evsel, size_t length);
int perf_evsel__read(struct perf_evsel *evsel, int cpu, int thread,
struct perf_counts_values *count);
int perf_evsel__enable(struct perf_evsel *evsel);
diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
index 4dc06289f4c7..99fa53dc0887 100644
--- a/tools/lib/perf/evsel.c
+++ b/tools/lib/perf/evsel.c
@@ -11,10 +11,12 @@
#include <stdlib.h>
#include <internal/xyarray.h>
#include <internal/cpumap.h>
+#include <internal/mmap.h>
#include <internal/threadmap.h>
#include <internal/lib.h>
#include <linux/string.h>
#include <sys/ioctl.h>
+#include <sys/mman.h>

void perf_evsel__init(struct perf_evsel *evsel, struct perf_event_attr *attr)
{
@@ -156,6 +158,35 @@ void perf_evsel__close_cpu(struct perf_evsel *evsel, int cpu)
perf_evsel__close_fd_cpu(evsel, cpu);
}

+void *perf_evsel__mmap(struct perf_evsel *evsel, size_t length)
+{
+ int ret;
+ struct perf_mmap *map;
+ struct perf_mmap_param mp = {
+ .prot = PROT_READ | PROT_WRITE,
+ };
+
+ if (FD(evsel, 0, 0) < 0)
+ return NULL;
+
+ mp.mask = length - page_size - 1;
+
+ map = zalloc(sizeof(*map));
+ if (!map)
+ return NULL;
+
+ perf_mmap__init(map, NULL, false, NULL);
+
+ ret = perf_mmap__mmap(map, &mp, FD(evsel, 0, 0), 0);
+ if (ret) {
+ free(map);
+ return NULL;
+ }
+
+ evsel->mmap = map;
+ return map->base;
+}
+
int perf_evsel__read_size(struct perf_evsel *evsel)
{
u64 read_format = evsel->attr.read_format;
diff --git a/tools/lib/perf/include/internal/evsel.h b/tools/lib/perf/include/internal/evsel.h
index 1ffd083b235e..a7985dbb68ff 100644
--- a/tools/lib/perf/include/internal/evsel.h
+++ b/tools/lib/perf/include/internal/evsel.h
@@ -9,6 +9,7 @@

struct perf_cpu_map;
struct perf_thread_map;
+struct perf_mmap;
struct xyarray;

/*
@@ -40,6 +41,7 @@ struct perf_evsel {
struct perf_cpu_map *cpus;
struct perf_cpu_map *own_cpus;
struct perf_thread_map *threads;
+ struct perf_mmap *mmap;
struct xyarray *fd;
struct xyarray *sample_id;
u64 *id;
diff --git a/tools/lib/perf/include/perf/evsel.h b/tools/lib/perf/include/perf/evsel.h
index c82ec39a4ad0..28f1354e52df 100644
--- a/tools/lib/perf/include/perf/evsel.h
+++ b/tools/lib/perf/include/perf/evsel.h
@@ -3,6 +3,7 @@
#define __LIBPERF_EVSEL_H

#include <stdint.h>
+#include <stddef.h>
#include <perf/core.h>

struct perf_evsel;
@@ -27,6 +28,7 @@ LIBPERF_API int perf_evsel__open(struct perf_evsel *evsel, struct perf_cpu_map *
struct perf_thread_map *threads);
LIBPERF_API void perf_evsel__close(struct perf_evsel *evsel);
LIBPERF_API void perf_evsel__close_cpu(struct perf_evsel *evsel, int cpu);
+LIBPERF_API void *perf_evsel__mmap(struct perf_evsel *evsel, size_t length);
LIBPERF_API int perf_evsel__read(struct perf_evsel *evsel, int cpu, int thread,
struct perf_counts_values *count);
LIBPERF_API int perf_evsel__enable(struct perf_evsel *evsel);
diff --git a/tools/lib/perf/libperf.map b/tools/lib/perf/libperf.map
index 7be1af8a546c..733a0647be8b 100644
--- a/tools/lib/perf/libperf.map
+++ b/tools/lib/perf/libperf.map
@@ -23,6 +23,7 @@ LIBPERF_0.0.1 {
perf_evsel__disable;
perf_evsel__open;
perf_evsel__close;
+ perf_evsel__mmap;
perf_evsel__read;
perf_evsel__cpus;
perf_evsel__threads;
--
2.25.1