[PATCH v4 bpf-next 0/4] libbpf: add perf buffer abstraction and API

[PATCH v4 bpf-next 0/4] libbpf: add perf buffer abstraction and API

[Andrii Nakryiko]

This patchset adds a high-level API for setting up and polling perf buffers
associated with BPF_MAP_TYPE_PERF_EVENT_ARRAY map. Details of APIs are
described in corresponding commit.

Patch #1 adds a set of APIs to set up and work with perf buffer.
Patch #2 enhances libbpf to support auto-setting PERF_EVENT_ARRAY map size.
Patch #3 adds test.
Patch #4 converts bpftool map event_pipe to new API.

v3->v4:
- fixed bpftool event_pipe cmd error handling (Jakub);

v2->v3:
- added perf_buffer__new_raw for more low-level control;
- converted bpftool map event_pipe to new API (Daniel);
- fixed bug with error handling in create_maps (Song);

v1->v2:
- add auto-sizing of PERF_EVENT_ARRAY maps;

Andrii Nakryiko (4):
  libbpf: add perf buffer API
  libbpf: auto-set PERF_EVENT_ARRAY size to number of CPUs
  selftests/bpf: test perf buffer API
  tools/bpftool: switch map event_pipe to libbpf's perf_buffer

 tools/bpf/bpftool/map_perf_ring.c             | 201 +++------
 tools/lib/bpf/libbpf.c                        | 397 +++++++++++++++++-
 tools/lib/bpf/libbpf.h                        |  49 +++
 tools/lib/bpf/libbpf.map                      |   4 +
 .../selftests/bpf/prog_tests/perf_buffer.c    |  94 +++++
 .../selftests/bpf/progs/test_perf_buffer.c    |  29 ++
 6 files changed, 630 insertions(+), 144 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_buffer.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_perf_buffer.c

-- 
2.17.1

[PATCH v4 bpf-next 1/4] libbpf: add perf buffer API

[Andrii Nakryiko]

BPF_MAP_TYPE_PERF_EVENT_ARRAY map is often used to send data from BPF program
to user space for additional processing. libbpf already has very low-level API
to read single CPU perf buffer, bpf_perf_event_read_simple(), but it's hard to
use and requires a lot of code to set everything up. This patch adds
perf_buffer abstraction on top of it, abstracting setting up and polling
per-CPU logic into simple and convenient API, similar to what BCC provides.

perf_buffer__new() sets up per-CPU ring buffers and updates corresponding BPF
map entries. It accepts two user-provided callbacks: one for handling raw
samples and one for get notifications of lost samples due to buffer overflow.

perf_buffer__new_raw() is similar, but provides more control over how
perf events are set up (by accepting user-provided perf_event_attr), how
they are handled (perf_event_header pointer is passed directly to
user-provided callback), and on which CPUs ring buffers are created
(it's possible to provide a list of CPUs and corresponding map keys to
update). This API allows advanced users fuller control.

perf_buffer__poll() is used to fetch ring buffer data across all CPUs,
utilizing epoll instance.

perf_buffer__free() does corresponding clean up and unsets FDs from BPF map.

All APIs are not thread-safe. User should ensure proper locking/coordination if
used in multi-threaded set up.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/lib/bpf/libbpf.c   | 366 +++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h   |  49 ++++++
 tools/lib/bpf/libbpf.map |   4 +
 3 files changed, 419 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index f8c7a7ecb35e..e2bf3eedd0ae 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -32,7 +32,9 @@
 #include <linux/limits.h>
 #include <linux/perf_event.h>
 #include <linux/ring_buffer.h>
+#include <sys/epoll.h>
 #include <sys/ioctl.h>
+#include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/vfs.h>
@@ -4348,6 +4350,370 @@ bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
 	return ret;
 }
 
+struct perf_buffer;
+
+struct perf_buffer_params {
+	struct perf_event_attr *attr;
+	/* if event_cb is specified, it takes precendence */
+	perf_buffer_event_fn event_cb;
+	/* sample_cb and lost_cb are higher-level common-case callbacks */
+	perf_buffer_sample_fn sample_cb;
+	perf_buffer_lost_fn lost_cb;
+	void *ctx;
+	int cpu_cnt;
+	int *cpus;
+	int *map_keys;
+};
+
+struct perf_cpu_buf {
+	struct perf_buffer *pb;
+	void *base; /* mmap()'ed memory */
+	void *buf; /* for reconstructing segmented data */
+	size_t buf_size;
+	int fd;
+	int cpu;
+	int map_key;
+};
+
+struct perf_buffer {
+	perf_buffer_event_fn event_cb;
+	perf_buffer_sample_fn sample_cb;
+	perf_buffer_lost_fn lost_cb;
+	void *ctx; /* passed into callbacks */
+
+	size_t page_size;
+	size_t mmap_size;
+	struct perf_cpu_buf **cpu_bufs;
+	struct epoll_event *events;
+	int cpu_cnt;
+	int epoll_fd; /* perf event FD */
+	int map_fd; /* BPF_MAP_TYPE_PERF_EVENT_ARRAY BPF map FD */
+};
+
+static void perf_buffer__free_cpu_buf(struct perf_buffer *pb,
+				      struct perf_cpu_buf *cpu_buf)
+{
+	if (!cpu_buf)
+		return;
+	if (cpu_buf->base &&
+	    munmap(cpu_buf->base, pb->mmap_size + pb->page_size))
+		pr_warning("failed to munmap cpu_buf #%d\n", cpu_buf->cpu);
+	if (cpu_buf->fd >= 0) {
+		ioctl(cpu_buf->fd, PERF_EVENT_IOC_DISABLE, 0);
+		close(cpu_buf->fd);
+	}
+	free(cpu_buf->buf);
+	free(cpu_buf);
+}
+
+void perf_buffer__free(struct perf_buffer *pb)
+{
+	int i;
+
+	if (!pb)
+		return;
+	if (pb->cpu_bufs) {
+		for (i = 0; i < pb->cpu_cnt && pb->cpu_bufs[i]; i++) {
+			struct perf_cpu_buf *cpu_buf = pb->cpu_bufs[i];
+
+			bpf_map_delete_elem(pb->map_fd, &cpu_buf->map_key);
+			perf_buffer__free_cpu_buf(pb, cpu_buf);
+		}
+		free(pb->cpu_bufs);
+	}
+	if (pb->epoll_fd >= 0)
+		close(pb->epoll_fd);
+	free(pb->events);
+	free(pb);
+}
+
+static struct perf_cpu_buf *
+perf_buffer__open_cpu_buf(struct perf_buffer *pb, struct perf_event_attr *attr,
+			  int cpu, int map_key)
+{
+	struct perf_cpu_buf *cpu_buf;
+	char msg[STRERR_BUFSIZE];
+	int err;
+
+	cpu_buf = calloc(1, sizeof(*cpu_buf));
+	if (!cpu_buf)
+		return ERR_PTR(-ENOMEM);
+
+	cpu_buf->pb = pb;
+	cpu_buf->cpu = cpu;
+	cpu_buf->map_key = map_key;
+
+	cpu_buf->fd = syscall(__NR_perf_event_open, attr, -1 /* pid */, cpu,
+			      -1, PERF_FLAG_FD_CLOEXEC);
+	if (cpu_buf->fd < 0) {
+		err = -errno;
+		pr_warning("failed to open perf buffer event on cpu #%d: %s\n",
+			   cpu, libbpf_strerror_r(err, msg, sizeof(msg)));
+		goto error;
+	}
+
+	cpu_buf->base = mmap(NULL, pb->mmap_size + pb->page_size,
+			     PROT_READ | PROT_WRITE, MAP_SHARED,
+			     cpu_buf->fd, 0);
+	if (cpu_buf->base == MAP_FAILED) {
+		cpu_buf->base = NULL;
+		err = -errno;
+		pr_warning("failed to mmap perf buffer on cpu #%d: %s\n",
+			   cpu, libbpf_strerror_r(err, msg, sizeof(msg)));
+		goto error;
+	}
+
+	if (ioctl(cpu_buf->fd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
+		err = -errno;
+		pr_warning("failed to enable perf buffer event on cpu #%d: %s\n",
+			   cpu, libbpf_strerror_r(err, msg, sizeof(msg)));
+		goto error;
+	}
+
+	return cpu_buf;
+
+error:
+	perf_buffer__free_cpu_buf(pb, cpu_buf);
+	return (struct perf_cpu_buf *)ERR_PTR(err);
+}
+
+static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt,
+					      struct perf_buffer_params *p);
+
+struct perf_buffer *perf_buffer__new(int map_fd, size_t page_cnt,
+				     const struct perf_buffer_opts *opts)
+{
+	struct perf_buffer_params p = {};
+	struct perf_event_attr attr = {
+		.config = PERF_COUNT_SW_BPF_OUTPUT,
+		.type = PERF_TYPE_SOFTWARE,
+		.sample_type = PERF_SAMPLE_RAW,
+		.sample_period = 1,
+		.wakeup_events = 1,
+	};
+
+	p.attr = &attr;
+	p.sample_cb = opts ? opts->sample_cb : NULL;
+	p.lost_cb = opts ? opts->lost_cb : NULL;
+	p.ctx = opts ? opts->ctx : NULL;
+
+	return __perf_buffer__new(map_fd, page_cnt, &p);
+}
+
+struct perf_buffer *
+perf_buffer__new_raw(int map_fd, size_t page_cnt,
+		     const struct perf_buffer_raw_opts *opts)
+{
+	struct perf_buffer_params p = {};
+
+	p.attr = opts->attr;
+	p.event_cb = opts->event_cb;
+	p.ctx = opts->ctx;
+	p.cpu_cnt = opts->cpu_cnt;
+	p.cpus = opts->cpus;
+	p.map_keys = opts->map_keys;
+
+	return __perf_buffer__new(map_fd, page_cnt, &p);
+}
+
+static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt,
+					      struct perf_buffer_params *p)
+{
+	struct bpf_map_info map = {};
+	char msg[STRERR_BUFSIZE];
+	struct perf_buffer *pb;
+	__u32 map_info_len;
+	int err, i;
+
+	if (page_cnt & (page_cnt - 1)) {
+		pr_warning("page count should be power of two, but is %zu\n",
+			   page_cnt);
+		return ERR_PTR(-EINVAL);
+	}
+
+	map_info_len = sizeof(map);
+	err = bpf_obj_get_info_by_fd(map_fd, &map, &map_info_len);
+	if (err) {
+		err = -errno;
+		pr_warning("failed to get map info for map FD %d: %s\n",
+			   map_fd, libbpf_strerror_r(err, msg, sizeof(msg)));
+		return ERR_PTR(err);
+	}
+
+	if (map.type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) {
+		pr_warning("map '%s' should be BPF_MAP_TYPE_PERF_EVENT_ARRAY\n",
+			   map.name);
+		return ERR_PTR(-EINVAL);
+	}
+
+	pb = calloc(1, sizeof(*pb));
+	if (!pb)
+		return ERR_PTR(-ENOMEM);
+
+	pb->event_cb = p->event_cb;
+	pb->sample_cb = p->sample_cb;
+	pb->lost_cb = p->lost_cb;
+	pb->ctx = p->ctx;
+
+	pb->page_size = getpagesize();
+	pb->mmap_size = pb->page_size * page_cnt;
+	pb->map_fd = map_fd;
+
+	pb->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
+	if (pb->epoll_fd < 0) {
+		err = -errno;
+		pr_warning("failed to create epoll instance: %s\n",
+			   libbpf_strerror_r(err, msg, sizeof(msg)));
+		goto error;
+	}
+
+	if (p->cpu_cnt > 0) {
+		pb->cpu_cnt = p->cpu_cnt;
+	} else {
+		pb->cpu_cnt = libbpf_num_possible_cpus();
+		if (pb->cpu_cnt < 0) {
+			err = pb->cpu_cnt;
+			goto error;
+		}
+		if (map.max_entries < pb->cpu_cnt)
+			pb->cpu_cnt = map.max_entries;
+	}
+
+	pb->events = calloc(pb->cpu_cnt, sizeof(*pb->events));
+	if (!pb->events) {
+		err = -ENOMEM;
+		pr_warning("failed to allocate events: out of memory\n");
+		goto error;
+	}
+	pb->cpu_bufs = calloc(pb->cpu_cnt, sizeof(*pb->cpu_bufs));
+	if (!pb->cpu_bufs) {
+		err = -ENOMEM;
+		pr_warning("failed to allocate buffers: out of memory\n");
+		goto error;
+	}
+
+	for (i = 0; i < pb->cpu_cnt; i++) {
+		struct perf_cpu_buf *cpu_buf;
+		int cpu, map_key;
+
+		cpu = p->cpu_cnt > 0 ? p->cpus[i] : i;
+		map_key = p->cpu_cnt > 0 ? p->map_keys[i] : i;
+
+		cpu_buf = perf_buffer__open_cpu_buf(pb, p->attr, cpu, map_key);
+		if (IS_ERR(cpu_buf)) {
+			err = PTR_ERR(cpu_buf);
+			goto error;
+		}
+
+		pb->cpu_bufs[i] = cpu_buf;
+
+		err = bpf_map_update_elem(pb->map_fd, &map_key,
+					  &cpu_buf->fd, 0);
+		if (err) {
+			err = -errno;
+			pr_warning("failed to set cpu #%d, key %d -> perf FD %d: %s\n",
+				   cpu, map_key, cpu_buf->fd,
+				   libbpf_strerror_r(err, msg, sizeof(msg)));
+			goto error;
+		}
+
+		pb->events[i].events = EPOLLIN;
+		pb->events[i].data.ptr = cpu_buf;
+		if (epoll_ctl(pb->epoll_fd, EPOLL_CTL_ADD, cpu_buf->fd,
+			      &pb->events[i]) < 0) {
+			err = -errno;
+			pr_warning("failed to epoll_ctl cpu #%d perf FD %d: %s\n",
+				   cpu, cpu_buf->fd,
+				   libbpf_strerror_r(err, msg, sizeof(msg)));
+			goto error;
+		}
+	}
+
+	return pb;
+
+error:
+	if (pb)
+		perf_buffer__free(pb);
+	return ERR_PTR(err);
+}
+
+struct perf_sample_raw {
+	struct perf_event_header header;
+	uint32_t size;
+	char data[0];
+};
+
+struct perf_sample_lost {
+	struct perf_event_header header;
+	uint64_t id;
+	uint64_t lost;
+	uint64_t sample_id;
+};
+
+static enum bpf_perf_event_ret
+perf_buffer__process_record(struct perf_event_header *e, void *ctx)
+{
+	struct perf_cpu_buf *cpu_buf = ctx;
+	struct perf_buffer *pb = cpu_buf->pb;
+	void *data = e;
+
+	/* user wants full control over parsing perf event */
+	if (pb->event_cb)
+		return pb->event_cb(pb->ctx, cpu_buf->cpu, e);
+
+	switch (e->type) {
+	case PERF_RECORD_SAMPLE: {
+		struct perf_sample_raw *s = data;
+
+		if (pb->sample_cb)
+			pb->sample_cb(pb->ctx, cpu_buf->cpu, s->data, s->size);
+		break;
+	}
+	case PERF_RECORD_LOST: {
+		struct perf_sample_lost *s = data;
+
+		if (pb->lost_cb)
+			pb->lost_cb(pb->ctx, cpu_buf->cpu, s->lost);
+		break;
+	}
+	default:
+		pr_warning("unknown perf sample type %d\n", e->type);
+		return LIBBPF_PERF_EVENT_ERROR;
+	}
+	return LIBBPF_PERF_EVENT_CONT;
+}
+
+static int perf_buffer__process_records(struct perf_buffer *pb,
+					struct perf_cpu_buf *cpu_buf)
+{
+	enum bpf_perf_event_ret ret;
+
+	ret = bpf_perf_event_read_simple(cpu_buf->base, pb->mmap_size,
+					 pb->page_size, &cpu_buf->buf,
+					 &cpu_buf->buf_size,
+					 perf_buffer__process_record, cpu_buf);
+	if (ret != LIBBPF_PERF_EVENT_CONT)
+		return ret;
+	return 0;
+}
+
+int perf_buffer__poll(struct perf_buffer *pb, int timeout_ms)
+{
+	int cnt, err;
+
+	cnt = epoll_wait(pb->epoll_fd, pb->events, pb->cpu_cnt, timeout_ms);
+	for (int i = 0; i < cnt; i++) {
+		struct perf_cpu_buf *cpu_buf = pb->events[i].data.ptr;
+
+		err = perf_buffer__process_records(pb, cpu_buf);
+		if (err) {
+			pr_warning("error while processing records: %d\n", err);
+			return err;
+		}
+	}
+	return cnt < 0 ? -errno : cnt;
+}
+
 struct bpf_prog_info_array_desc {
 	int	array_offset;	/* e.g. offset of jited_prog_insns */
 	int	count_offset;	/* e.g. offset of jited_prog_len */
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index f55933784f95..5cbf459ece0b 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -358,6 +358,26 @@ LIBBPF_API int bpf_prog_load(const char *file, enum bpf_prog_type type,
 LIBBPF_API int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags);
 LIBBPF_API int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags);
 
+struct perf_buffer;
+
+typedef void (*perf_buffer_sample_fn)(void *ctx, int cpu,
+				      void *data, __u32 size);
+typedef void (*perf_buffer_lost_fn)(void *ctx, int cpu, __u64 cnt);
+
+/* common use perf buffer options */
+struct perf_buffer_opts {
+	/* if specified, sample_cb is called for each sample */
+	perf_buffer_sample_fn sample_cb;
+	/* if specified, lost_cb is called for each batch of lost samples */
+	perf_buffer_lost_fn lost_cb;
+	/* ctx is provided to sample_cb and lost_cb */
+	void *ctx;
+};
+
+LIBBPF_API struct perf_buffer *
+perf_buffer__new(int map_fd, size_t page_cnt,
+		 const struct perf_buffer_opts *opts);
+
 enum bpf_perf_event_ret {
 	LIBBPF_PERF_EVENT_DONE	= 0,
 	LIBBPF_PERF_EVENT_ERROR	= -1,
@@ -365,6 +385,35 @@ enum bpf_perf_event_ret {
 };
 
 struct perf_event_header;
+
+typedef enum bpf_perf_event_ret
+(*perf_buffer_event_fn)(void *ctx, int cpu, struct perf_event_header *event);
+
+/* raw perf buffer options, giving most power and control */
+struct perf_buffer_raw_opts {
+	/* perf event attrs passed directly into perf_event_open() */
+	struct perf_event_attr *attr;
+	/* raw event callback */
+	perf_buffer_event_fn event_cb;
+	/* ctx is provided to event_cb */
+	void *ctx;
+	/* if cpu_cnt == 0, open all on all possible CPUs (up to the number of
+	 * max_entries of given PERF_EVENT_ARRAY map)
+	 */
+	int cpu_cnt;
+	/* if cpu_cnt > 0, cpus is an array of CPUs to open ring buffers on */
+	int *cpus;
+	/* if cpu_cnt > 0, map_keys specify map keys to set per-CPU FDs for */
+	int *map_keys;
+};
+
+LIBBPF_API struct perf_buffer *
+perf_buffer__new_raw(int map_fd, size_t page_cnt,
+		     const struct perf_buffer_raw_opts *opts);
+
+LIBBPF_API void perf_buffer__free(struct perf_buffer *pb);
+LIBBPF_API int perf_buffer__poll(struct perf_buffer *pb, int timeout_ms);
+
 typedef enum bpf_perf_event_ret
 	(*bpf_perf_event_print_t)(struct perf_event_header *hdr,
 				  void *private_data);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index e6b7d4edbc93..f9d316e873d8 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -179,4 +179,8 @@ LIBBPF_0.0.4 {
 		btf_dump__new;
 		btf__parse_elf;
 		libbpf_num_possible_cpus;
+		perf_buffer__free;
+		perf_buffer__new;
+		perf_buffer__new_raw;
+		perf_buffer__poll;
 } LIBBPF_0.0.3;
-- 
2.17.1

[PATCH v4 bpf-next 2/4] libbpf: auto-set PERF_EVENT_ARRAY size to number of CPUs

[Andrii Nakryiko]

For BPF_MAP_TYPE_PERF_EVENT_ARRAY typically correct size is number of
possible CPUs. This is impossible to specify at compilation time. This
change adds automatic setting of PERF_EVENT_ARRAY size to number of
system CPUs, unless non-zero size is specified explicitly. This allows
to adjust size for advanced specific cases, while providing convenient
and logical defaults.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
 tools/lib/bpf/libbpf.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e2bf3eedd0ae..a5ae7207d19a 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2118,6 +2118,7 @@ static int
 bpf_object__create_maps(struct bpf_object *obj)
 {
 	struct bpf_create_map_attr create_attr = {};
+	int nr_cpus = 0;
 	unsigned int i;
 	int err;
 
@@ -2140,7 +2141,22 @@ bpf_object__create_maps(struct bpf_object *obj)
 		create_attr.map_flags = def->map_flags;
 		create_attr.key_size = def->key_size;
 		create_attr.value_size = def->value_size;
-		create_attr.max_entries = def->max_entries;
+		if (def->type == BPF_MAP_TYPE_PERF_EVENT_ARRAY &&
+		    !def->max_entries) {
+			if (!nr_cpus)
+				nr_cpus = libbpf_num_possible_cpus();
+			if (nr_cpus < 0) {
+				pr_warning("failed to determine number of system CPUs: %d\n",
+					   nr_cpus);
+				err = nr_cpus;
+				goto err_out;
+			}
+			pr_debug("map '%s': setting size to %d\n",
+				 map->name, nr_cpus);
+			create_attr.max_entries = nr_cpus;
+		} else {
+			create_attr.max_entries = def->max_entries;
+		}
 		create_attr.btf_fd = 0;
 		create_attr.btf_key_type_id = 0;
 		create_attr.btf_value_type_id = 0;
@@ -2157,9 +2173,10 @@ bpf_object__create_maps(struct bpf_object *obj)
 		*pfd = bpf_create_map_xattr(&create_attr);
 		if (*pfd < 0 && (create_attr.btf_key_type_id ||
 				 create_attr.btf_value_type_id)) {
-			cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
+			err = -errno;
+			cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
 			pr_warning("Error in bpf_create_map_xattr(%s):%s(%d). Retrying without BTF.\n",
-				   map->name, cp, errno);
+				   map->name, cp, err);
 			create_attr.btf_fd = 0;
 			create_attr.btf_key_type_id = 0;
 			create_attr.btf_value_type_id = 0;
@@ -2171,11 +2188,11 @@ bpf_object__create_maps(struct bpf_object *obj)
 		if (*pfd < 0) {
 			size_t j;
 
-			err = *pfd;
+			err = -errno;
 err_out:
-			cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
-			pr_warning("failed to create map (name: '%s'): %s\n",
-				   map->name, cp);
+			cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
+			pr_warning("failed to create map (name: '%s'): %s(%d)\n",
+				   map->name, cp, err);
 			for (j = 0; j < i; j++)
 				zclose(obj->maps[j].fd);
 			return err;
-- 
2.17.1

[PATCH v4 bpf-next 3/4] selftests/bpf: test perf buffer API

[Andrii Nakryiko]

Add test verifying perf buffer API functionality.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
 .../selftests/bpf/prog_tests/perf_buffer.c    | 94 +++++++++++++++++++
 .../selftests/bpf/progs/test_perf_buffer.c    | 29 ++++++
 2 files changed, 123 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_buffer.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_perf_buffer.c

diff --git a/tools/testing/selftests/bpf/prog_tests/perf_buffer.c b/tools/testing/selftests/bpf/prog_tests/perf_buffer.c
new file mode 100644
index 000000000000..64556ab0d1a9
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/perf_buffer.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <pthread.h>
+#include <sched.h>
+#include <sys/socket.h>
+#include <test_progs.h>
+
+static void on_sample(void *ctx, int cpu, void *data, __u32 size)
+{
+	int cpu_data = *(int *)data, duration = 0;
+	cpu_set_t *cpu_seen = ctx;
+
+	if (cpu_data != cpu)
+		CHECK(cpu_data != cpu, "check_cpu_data",
+		      "cpu_data %d != cpu %d\n", cpu_data, cpu);
+
+	CPU_SET(cpu, cpu_seen);
+}
+
+void test_perf_buffer(void)
+{
+	int err, prog_fd, nr_cpus, i, duration = 0;
+	const char *prog_name = "kprobe/sys_nanosleep";
+	const char *file = "./test_perf_buffer.o";
+	struct perf_buffer_opts pb_opts = {};
+	struct bpf_map *perf_buf_map;
+	cpu_set_t cpu_set, cpu_seen;
+	struct bpf_program *prog;
+	struct bpf_object *obj;
+	struct perf_buffer *pb;
+	struct bpf_link *link;
+
+	nr_cpus = libbpf_num_possible_cpus();
+	if (CHECK(nr_cpus < 0, "nr_cpus", "err %d\n", nr_cpus))
+		return;
+
+	/* load program */
+	err = bpf_prog_load(file, BPF_PROG_TYPE_KPROBE, &obj, &prog_fd);
+	if (CHECK(err, "obj_load", "err %d errno %d\n", err, errno))
+		return;
+
+	prog = bpf_object__find_program_by_title(obj, prog_name);
+	if (CHECK(!prog, "find_probe", "prog '%s' not found\n", prog_name))
+		goto out_close;
+
+	/* load map */
+	perf_buf_map = bpf_object__find_map_by_name(obj, "perf_buf_map");
+	if (CHECK(!perf_buf_map, "find_perf_buf_map", "not found\n"))
+		goto out_close;
+
+	/* attach kprobe */
+	link = bpf_program__attach_kprobe(prog, false /* retprobe */,
+					      "sys_nanosleep");
+	if (CHECK(IS_ERR(link), "attach_kprobe", "err %ld\n", PTR_ERR(link)))
+		goto out_close;
+
+	/* set up perf buffer */
+	pb_opts.sample_cb = on_sample;
+	pb_opts.ctx = &cpu_seen;
+	pb = perf_buffer__new(bpf_map__fd(perf_buf_map), 1, &pb_opts);
+	if (CHECK(IS_ERR(pb), "perf_buf__new", "err %ld\n", PTR_ERR(pb)))
+		goto out_detach;
+
+	/* trigger kprobe on every CPU */
+	CPU_ZERO(&cpu_seen);
+	for (i = 0; i < nr_cpus; i++) {
+		CPU_ZERO(&cpu_set);
+		CPU_SET(i, &cpu_set);
+
+		err = pthread_setaffinity_np(pthread_self(), sizeof(cpu_set),
+					     &cpu_set);
+		if (err && CHECK(err, "set_affinity", "cpu #%d, err %d\n",
+				 i, err))
+			goto out_detach;
+
+		usleep(1);
+	}
+
+	/* read perf buffer */
+	err = perf_buffer__poll(pb, 100);
+	if (CHECK(err < 0, "perf_buffer__poll", "err %d\n", err))
+		goto out_free_pb;
+
+	if (CHECK(CPU_COUNT(&cpu_seen) != nr_cpus, "seen_cpu_cnt",
+		  "expect %d, seen %d\n", nr_cpus, CPU_COUNT(&cpu_seen)))
+		goto out_free_pb;
+
+out_free_pb:
+	perf_buffer__free(pb);
+out_detach:
+	bpf_link__destroy(link);
+out_close:
+	bpf_object__close(obj);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_perf_buffer.c b/tools/testing/selftests/bpf/progs/test_perf_buffer.c
new file mode 100644
index 000000000000..8609f0031bc0
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_perf_buffer.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/ptrace.h>
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+
+struct {
+	int type;
+	int key_size;
+	int value_size;
+} perf_buf_map SEC(".maps") = {
+	.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
+	.key_size = sizeof(int),
+	.value_size = sizeof(int),
+};
+
+SEC("kprobe/sys_nanosleep")
+int handle_sys_nanosleep_entry(struct pt_regs *ctx)
+{
+	int cpu = bpf_get_smp_processor_id();
+
+	bpf_perf_event_output(ctx, &perf_buf_map, BPF_F_CURRENT_CPU,
+			      &cpu, sizeof(cpu));
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+__u32 _version SEC("version") = 1;
-- 
2.17.1

[PATCH v4 bpf-next 4/4] tools/bpftool: switch map event_pipe to libbpf's perf_buffer

[Andrii Nakryiko]

Switch event_pipe implementation to rely on new libbpf perf buffer API
(it's raw low-level variant).

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/bpf/bpftool/map_perf_ring.c | 201 ++++++++++--------------------
 1 file changed, 64 insertions(+), 137 deletions(-)

diff --git a/tools/bpf/bpftool/map_perf_ring.c b/tools/bpf/bpftool/map_perf_ring.c
index 0507dfaf7a8f..c291de8ef116 100644
--- a/tools/bpf/bpftool/map_perf_ring.c
+++ b/tools/bpf/bpftool/map_perf_ring.c
@@ -28,7 +28,7 @@
 
 #define MMAP_PAGE_CNT	16
 
-static bool stop;
+static volatile bool stop;
 
 struct event_ring_info {
 	int fd;
@@ -44,32 +44,44 @@ struct perf_event_sample {
 	unsigned char data[];
 };
 
+struct perf_event_lost {
+	struct perf_event_header header;
+	__u64 id;
+	__u64 lost;
+};
+
 static void int_exit(int signo)
 {
 	fprintf(stderr, "Stopping...\n");
 	stop = true;
 }
 
+struct event_pipe_ctx {
+	bool all_cpus;
+	int cpu;
+	int idx;
+};
+
 static enum bpf_perf_event_ret
-print_bpf_output(struct perf_event_header *event, void *private_data)
+print_bpf_output(void *private_data, int cpu, struct perf_event_header *event)
 {
-	struct perf_event_sample *e = container_of(event, struct perf_event_sample,
+	struct perf_event_sample *e = container_of(event,
+						   struct perf_event_sample,
 						   header);
-	struct event_ring_info *ring = private_data;
-	struct {
-		struct perf_event_header header;
-		__u64 id;
-		__u64 lost;
-	} *lost = (typeof(lost))event;
+	struct perf_event_lost *lost = container_of(event,
+						    struct perf_event_lost,
+						    header);
+	struct event_pipe_ctx *ctx = private_data;
+	int idx = ctx->all_cpus ? cpu : ctx->idx;
 
 	if (json_output) {
 		jsonw_start_object(json_wtr);
 		jsonw_name(json_wtr, "type");
 		jsonw_uint(json_wtr, e->header.type);
 		jsonw_name(json_wtr, "cpu");
-		jsonw_uint(json_wtr, ring->cpu);
+		jsonw_uint(json_wtr, cpu);
 		jsonw_name(json_wtr, "index");
-		jsonw_uint(json_wtr, ring->key);
+		jsonw_uint(json_wtr, idx);
 		if (e->header.type == PERF_RECORD_SAMPLE) {
 			jsonw_name(json_wtr, "timestamp");
 			jsonw_uint(json_wtr, e->time);
@@ -89,7 +101,7 @@ print_bpf_output(struct perf_event_header *event, void *private_data)
 		if (e->header.type == PERF_RECORD_SAMPLE) {
 			printf("== @%lld.%09lld CPU: %d index: %d =====\n",
 			       e->time / 1000000000ULL, e->time % 1000000000ULL,
-			       ring->cpu, ring->key);
+			       cpu, idx);
 			fprint_hex(stdout, e->data, e->size, " ");
 			printf("\n");
 		} else if (e->header.type == PERF_RECORD_LOST) {
@@ -103,87 +115,25 @@ print_bpf_output(struct perf_event_header *event, void *private_data)
 	return LIBBPF_PERF_EVENT_CONT;
 }
 
-static void
-perf_event_read(struct event_ring_info *ring, void **buf, size_t *buf_len)
-{
-	enum bpf_perf_event_ret ret;
-
-	ret = bpf_perf_event_read_simple(ring->mem,
-					 MMAP_PAGE_CNT * get_page_size(),
-					 get_page_size(), buf, buf_len,
-					 print_bpf_output, ring);
-	if (ret != LIBBPF_PERF_EVENT_CONT) {
-		fprintf(stderr, "perf read loop failed with %d\n", ret);
-		stop = true;
-	}
-}
-
-static int perf_mmap_size(void)
-{
-	return get_page_size() * (MMAP_PAGE_CNT + 1);
-}
-
-static void *perf_event_mmap(int fd)
-{
-	int mmap_size = perf_mmap_size();
-	void *base;
-
-	base = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
-	if (base == MAP_FAILED) {
-		p_err("event mmap failed: %s\n", strerror(errno));
-		return NULL;
-	}
-
-	return base;
-}
-
-static void perf_event_unmap(void *mem)
-{
-	if (munmap(mem, perf_mmap_size()))
-		fprintf(stderr, "Can't unmap ring memory!\n");
-}
-
-static int bpf_perf_event_open(int map_fd, int key, int cpu)
+int do_event_pipe(int argc, char **argv)
 {
-	struct perf_event_attr attr = {
+	struct perf_event_attr perf_attr = {
 		.sample_type = PERF_SAMPLE_RAW | PERF_SAMPLE_TIME,
 		.type = PERF_TYPE_SOFTWARE,
 		.config = PERF_COUNT_SW_BPF_OUTPUT,
+		.sample_period = 1,
+		.wakeup_events = 1,
 	};
-	int pmu_fd;
-
-	pmu_fd = sys_perf_event_open(&attr, -1, cpu, -1, 0);
-	if (pmu_fd < 0) {
-		p_err("failed to open perf event %d for CPU %d", key, cpu);
-		return -1;
-	}
-
-	if (bpf_map_update_elem(map_fd, &key, &pmu_fd, BPF_ANY)) {
-		p_err("failed to update map for event %d for CPU %d", key, cpu);
-		goto err_close;
-	}
-	if (ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0)) {
-		p_err("failed to enable event %d for CPU %d", key, cpu);
-		goto err_close;
-	}
-
-	return pmu_fd;
-
-err_close:
-	close(pmu_fd);
-	return -1;
-}
-
-int do_event_pipe(int argc, char **argv)
-{
-	int i, nfds, map_fd, index = -1, cpu = -1;
 	struct bpf_map_info map_info = {};
-	struct event_ring_info *rings;
-	size_t tmp_buf_sz = 0;
-	void *tmp_buf = NULL;
-	struct pollfd *pfds;
+	struct perf_buffer_raw_opts opts;
+	struct event_pipe_ctx ctx = {
+		.all_cpus = true,
+		.cpu = -1,
+		.idx = -1,
+	};
+	struct perf_buffer *pb;
 	__u32 map_info_len;
-	bool do_all = true;
+	int err, map_fd;
 
 	map_info_len = sizeof(map_info);
 	map_fd = map_parse_fd_and_info(&argc, &argv, &map_info, &map_info_len);
@@ -205,7 +155,7 @@ int do_event_pipe(int argc, char **argv)
 			char *endptr;
 
 			NEXT_ARG();
-			cpu = strtoul(*argv, &endptr, 0);
+			ctx.cpu = strtoul(*argv, &endptr, 0);
 			if (*endptr) {
 				p_err("can't parse %s as CPU ID", **argv);
 				goto err_close_map;
@@ -216,7 +166,7 @@ int do_event_pipe(int argc, char **argv)
 			char *endptr;
 
 			NEXT_ARG();
-			index = strtoul(*argv, &endptr, 0);
+			ctx.idx = strtoul(*argv, &endptr, 0);
 			if (*endptr) {
 				p_err("can't parse %s as index", **argv);
 				goto err_close_map;
@@ -228,45 +178,32 @@ int do_event_pipe(int argc, char **argv)
 			goto err_close_map;
 		}
 
-		do_all = false;
+		ctx.all_cpus = false;
 	}
 
-	if (!do_all) {
-		if (index == -1 || cpu == -1) {
+	if (!ctx.all_cpus) {
+		if (ctx.idx == -1 || ctx.cpu == -1) {
 			p_err("cpu and index must be specified together");
 			goto err_close_map;
 		}
-
-		nfds = 1;
 	} else {
-		nfds = min(get_possible_cpus(), map_info.max_entries);
-		cpu = 0;
-		index = 0;
+		ctx.cpu = 0;
+		ctx.idx = 0;
 	}
 
-	rings = calloc(nfds, sizeof(rings[0]));
-	if (!rings)
+	opts.attr = &perf_attr;
+	opts.event_cb = print_bpf_output;
+	opts.ctx = &ctx;
+	opts.cpu_cnt = ctx.all_cpus ? 0 : 1;
+	opts.cpus = &ctx.cpu;
+	opts.map_keys = &ctx.idx;
+
+	pb = perf_buffer__new_raw(map_fd, MMAP_PAGE_CNT, &opts);
+	err = libbpf_get_error(pb);
+	if (err) {
+		p_err("failed to create perf buffer: %s (%d)",
+		      strerror(err), err);
 		goto err_close_map;
-
-	pfds = calloc(nfds, sizeof(pfds[0]));
-	if (!pfds)
-		goto err_free_rings;
-
-	for (i = 0; i < nfds; i++) {
-		rings[i].cpu = cpu + i;
-		rings[i].key = index + i;
-
-		rings[i].fd = bpf_perf_event_open(map_fd, rings[i].key,
-						  rings[i].cpu);
-		if (rings[i].fd < 0)
-			goto err_close_fds_prev;
-
-		rings[i].mem = perf_event_mmap(rings[i].fd);
-		if (!rings[i].mem)
-			goto err_close_fds_current;
-
-		pfds[i].fd = rings[i].fd;
-		pfds[i].events = POLLIN;
 	}
 
 	signal(SIGINT, int_exit);
@@ -277,34 +214,24 @@ int do_event_pipe(int argc, char **argv)
 		jsonw_start_array(json_wtr);
 
 	while (!stop) {
-		poll(pfds, nfds, 200);
-		for (i = 0; i < nfds; i++)
-			perf_event_read(&rings[i], &tmp_buf, &tmp_buf_sz);
+		err = perf_buffer__poll(pb, 200);
+		if (err < 0 && err != -EINTR) {
+			p_err("perf buffer polling failed: %s (%d)",
+			      strerror(err), err);
+			goto err_close_pb;
+		}
 	}
-	free(tmp_buf);
 
 	if (json_output)
 		jsonw_end_array(json_wtr);
 
-	for (i = 0; i < nfds; i++) {
-		perf_event_unmap(rings[i].mem);
-		close(rings[i].fd);
-	}
-	free(pfds);
-	free(rings);
+	perf_buffer__free(pb);
 	close(map_fd);
 
 	return 0;
 
-err_close_fds_prev:
-	while (i--) {
-		perf_event_unmap(rings[i].mem);
-err_close_fds_current:
-		close(rings[i].fd);
-	}
-	free(pfds);
-err_free_rings:
-	free(rings);
+err_close_pb:
+	perf_buffer__free(pb);
 err_close_map:
 	close(map_fd);
 	return -1;
-- 
2.17.1

Re: [PATCH v4 bpf-next 4/4] tools/bpftool: switch map event_pipe to libbpf's perf_buffer

[Jakub Kicinski]

On Sat, 29 Jun 2019 23:51:09 -0700, Andrii Nakryiko wrote:
> Switch event_pipe implementation to rely on new libbpf perf buffer API
> (it's raw low-level variant).
> 
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>

> -int do_event_pipe(int argc, char **argv)
> -{
> -	int i, nfds, map_fd, index = -1, cpu = -1;
>  	struct bpf_map_info map_info = {};
> -	struct event_ring_info *rings;
> -	size_t tmp_buf_sz = 0;
> -	void *tmp_buf = NULL;
> -	struct pollfd *pfds;
> +	struct perf_buffer_raw_opts opts;

I'm slightly worried we don't init the ops, but we can wait and see if
it bites us or not.

Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>

Thanks!

Re: [PATCH v4 bpf-next 0/4] libbpf: add perf buffer abstraction and API

[Daniel Borkmann]

On 06/30/2019 08:51 AM, Andrii Nakryiko wrote:
> This patchset adds a high-level API for setting up and polling perf buffers
> associated with BPF_MAP_TYPE_PERF_EVENT_ARRAY map. Details of APIs are
> described in corresponding commit.
> 
> Patch #1 adds a set of APIs to set up and work with perf buffer.
> Patch #2 enhances libbpf to support auto-setting PERF_EVENT_ARRAY map size.
> Patch #3 adds test.
> Patch #4 converts bpftool map event_pipe to new API.
> 
> v3->v4:
> - fixed bpftool event_pipe cmd error handling (Jakub);
> 
> v2->v3:
> - added perf_buffer__new_raw for more low-level control;
> - converted bpftool map event_pipe to new API (Daniel);
> - fixed bug with error handling in create_maps (Song);
> 
> v1->v2:
> - add auto-sizing of PERF_EVENT_ARRAY maps;
> 
> Andrii Nakryiko (4):
>   libbpf: add perf buffer API
>   libbpf: auto-set PERF_EVENT_ARRAY size to number of CPUs
>   selftests/bpf: test perf buffer API
>   tools/bpftool: switch map event_pipe to libbpf's perf_buffer
> 
>  tools/bpf/bpftool/map_perf_ring.c             | 201 +++------
>  tools/lib/bpf/libbpf.c                        | 397 +++++++++++++++++-
>  tools/lib/bpf/libbpf.h                        |  49 +++
>  tools/lib/bpf/libbpf.map                      |   4 +
>  .../selftests/bpf/prog_tests/perf_buffer.c    |  94 +++++
>  .../selftests/bpf/progs/test_perf_buffer.c    |  29 ++
>  6 files changed, 630 insertions(+), 144 deletions(-)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_buffer.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_perf_buffer.c

Hm, set looks good, but this does not apply cleanly. Please rebase against
bpf-next and resubmit. Please also update tools/lib/bpf/README.rst with regards
to the perf_buffer__ prefix. While at it, you could also address Jakub's comment.

Thanks,
Daniel

Re: [PATCH v4 bpf-next 0/4] libbpf: add perf buffer abstraction and API

[Andrii Nakryiko]

On Wed, Jul 3, 2019 at 2:36 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 06/30/2019 08:51 AM, Andrii Nakryiko wrote:
> > This patchset adds a high-level API for setting up and polling perf buffers
> > associated with BPF_MAP_TYPE_PERF_EVENT_ARRAY map. Details of APIs are
> > described in corresponding commit.
> >
> > Patch #1 adds a set of APIs to set up and work with perf buffer.
> > Patch #2 enhances libbpf to support auto-setting PERF_EVENT_ARRAY map size.
> > Patch #3 adds test.
> > Patch #4 converts bpftool map event_pipe to new API.
> >
> > v3->v4:
> > - fixed bpftool event_pipe cmd error handling (Jakub);
> >
> > v2->v3:
> > - added perf_buffer__new_raw for more low-level control;
> > - converted bpftool map event_pipe to new API (Daniel);
> > - fixed bug with error handling in create_maps (Song);
> >
> > v1->v2:
> > - add auto-sizing of PERF_EVENT_ARRAY maps;
> >
> > Andrii Nakryiko (4):
> >   libbpf: add perf buffer API
> >   libbpf: auto-set PERF_EVENT_ARRAY size to number of CPUs
> >   selftests/bpf: test perf buffer API
> >   tools/bpftool: switch map event_pipe to libbpf's perf_buffer
> >
> >  tools/bpf/bpftool/map_perf_ring.c             | 201 +++------
> >  tools/lib/bpf/libbpf.c                        | 397 +++++++++++++++++-
> >  tools/lib/bpf/libbpf.h                        |  49 +++
> >  tools/lib/bpf/libbpf.map                      |   4 +
> >  .../selftests/bpf/prog_tests/perf_buffer.c    |  94 +++++
> >  .../selftests/bpf/progs/test_perf_buffer.c    |  29 ++
> >  6 files changed, 630 insertions(+), 144 deletions(-)
> >  create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_buffer.c
> >  create mode 100644 tools/testing/selftests/bpf/progs/test_perf_buffer.c
>
> Hm, set looks good, but this does not apply cleanly. Please rebase against
> bpf-next and resubmit. Please also update tools/lib/bpf/README.rst with regards
> to the perf_buffer__ prefix. While at it, you could also address Jakub's comment.

Yeah, I forgot to mention that in cover letter: this patchset is using
APIs added in my other patch set (tracing APIs), so that one has to go
in first. I'll wait for it to land and will update and post v5,
updating README and initializing ops (Jakub's feedback). Thanks!

>
> Thanks,
> Daniel