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libbpf: add perf buffer API

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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>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Andrii Nakryiko
2019-07-06 11:06:24 -07:00
committed by Andrii Nakryiko
parent 8b82b9c82b
commit 9007494e6c
3 changed files with 419 additions and 0 deletions
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49
src/libbpf.h
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@@ -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);