samples: bpf: add bpf_perf_event_output example

Performance test and example of bpf_perf_event_output().
kprobe is attached to sys_write() and trivial bpf program streams
pid+cookie into userspace via PERF_COUNT_SW_BPF_OUTPUT event.

Usage:
$ sudo ./bld_x64/samples/bpf/trace_output
recv 2968913 events per sec

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 196 insertions, 0 deletions

diff --git a/samples/bpf/trace_output_user.c b/samples/bpf/trace_output_user.c
new file mode 100644
index 000000000000..661a7d052f2c
--- /dev/null
+++ b/samples/bpf/trace_output_user.c
@@ -0,0 +1,196 @@
+/* This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <sys/ioctl.h>
+#include <linux/perf_event.h>
+#include <linux/bpf.h>
+#include <errno.h>
+#include <assert.h>
+#include <sys/syscall.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <time.h>
+#include <signal.h>
+#include "libbpf.h"
+#include "bpf_load.h"
+
+static int pmu_fd;
+
+int page_size;
+int page_cnt = 8;
+volatile struct perf_event_mmap_page *header;
+
+typedef void (*print_fn)(void *data, int size);
+
+static int perf_event_mmap(int fd)
+{
+        void *base;
+        int mmap_size;
+
+        page_size = getpagesize();
+        mmap_size = page_size * (page_cnt + 1);
+
+        base = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+        if (base == MAP_FAILED) {
+                printf("mmap err\n");
+                return -1;
+        }
+
+        header = base;
+        return 0;
+}
+
+static int perf_event_poll(int fd)
+{
+        struct pollfd pfd = { .fd = fd, .events = POLLIN };
+
+        return poll(&pfd, 1, 1000);
+}
+
+struct perf_event_sample {
+        struct perf_event_header header;
+        __u32 size;
+        char data[];
+};
+
+void perf_event_read(print_fn fn)
+{
+        __u64 data_tail = header->data_tail;
+        __u64 data_head = header->data_head;
+        __u64 buffer_size = page_cnt * page_size;
+        void *base, *begin, *end;
+        char buf[256];
+
+        asm volatile("" ::: "memory"); /* in real code it should be smp_rmb() */
+        if (data_head == data_tail)
+                return;
+
+        base = ((char *)header) + page_size;
+
+        begin = base + data_tail % buffer_size;
+        end = base + data_head % buffer_size;
+
+        while (begin != end) {
+                struct perf_event_sample *e;
+
+                e = begin;
+                if (begin + e->header.size > base + buffer_size) {
+                        long len = base + buffer_size - begin;
+
+                        assert(len < e->header.size);
+                        memcpy(buf, begin, len);
+                        memcpy(buf + len, base, e->header.size - len);
+                        e = (void *) buf;
+                        begin = base + e->header.size - len;
+                } else if (begin + e->header.size == base + buffer_size) {
+                        begin = base;
+                } else {
+                        begin += e->header.size;
+                }
+
+                if (e->header.type == PERF_RECORD_SAMPLE) {
+                        fn(e->data, e->size);
+                } else if (e->header.type == PERF_RECORD_LOST) {
+                        struct {
+                                struct perf_event_header header;
+                                __u64 id;
+                                __u64 lost;
+                        } *lost = (void *) e;
+                        printf("lost %lld events\n", lost->lost);
+                } else {
+                        printf("unknown event type=%d size=%d\n",
+                               e->header.type, e->header.size);
+                }
+        }
+
+        __sync_synchronize(); /* smp_mb() */
+        header->data_tail = data_head;
+}
+
+static __u64 time_get_ns(void)
+{
+        struct timespec ts;
+
+        clock_gettime(CLOCK_MONOTONIC, &ts);
+        return ts.tv_sec * 1000000000ull + ts.tv_nsec;
+}
+
+static __u64 start_time;
+
+#define MAX_CNT 100000ll
+
+static void print_bpf_output(void *data, int size)
+{
+        static __u64 cnt;
+        struct {
+                __u64 pid;
+                __u64 cookie;
+        } *e = data;
+
+        if (e->cookie != 0x12345678) {
+                printf("BUG pid %llx cookie %llx sized %d\n",
+                       e->pid, e->cookie, size);
+                kill(0, SIGINT);
+        }
+
+        cnt++;
+
+        if (cnt == MAX_CNT) {
+                printf("recv %lld events per sec\n",
+                       MAX_CNT * 1000000000ll / (time_get_ns() - start_time));
+                kill(0, SIGINT);
+        }
+}
+
+static void test_bpf_perf_event(void)
+{
+        struct perf_event_attr attr = {
+                .sample_type = PERF_SAMPLE_RAW,
+                .type = PERF_TYPE_SOFTWARE,
+                .config = PERF_COUNT_SW_BPF_OUTPUT,
+        };
+        int key = 0;
+
+        pmu_fd = perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0);
+
+        assert(pmu_fd >= 0);
+        assert(bpf_update_elem(map_fd[0], &key, &pmu_fd, BPF_ANY) == 0);
+        ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0);
+}
+
+int main(int argc, char **argv)
+{
+        char filename[256];
+        FILE *f;
+
+        snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+
+        if (load_bpf_file(filename)) {
+                printf("%s", bpf_log_buf);
+                return 1;
+        }
+
+        test_bpf_perf_event();
+
+        if (perf_event_mmap(pmu_fd) < 0)
+                return 1;
+
+        f = popen("taskset 1 dd if=/dev/zero of=/dev/null", "r");
+        (void) f;
+
+        start_time = time_get_ns();
+        for (;;) {
+                perf_event_poll(pmu_fd);
+                perf_event_read(print_bpf_output);
+        }
+
+        return 0;
+}