Basic ringbuf event statistics

This adds a new structure `ebpf_event_stats` where we accumulate stats, right
now it only counts lost events vs non-lost events, but we can grow this in the
future, like adding per type events if it's interesting enough.

The print in EventsTrace is quite primitive as I believe this will only be used
for debugging there, so heh.

Choosing a name for `ebpf_ringbuf_write` was a bit tricky, I wanted to keep the
same parameters but it had to be "different enough" that we could spot it with a
naked eye.

While here, adjust the enum of ebpf events to not skip that precious first bit.

GPL/Events/EbpfEventProto.h

@@ -19,26 +19,27 @@
 #endif
 
 enum ebpf_event_type {
-    EBPF_EVENT_PROCESS_FORK                 = (1 << 1),
-    EBPF_EVENT_PROCESS_EXEC                 = (1 << 2),
-    EBPF_EVENT_PROCESS_EXIT                 = (1 << 3),
-    EBPF_EVENT_PROCESS_SETSID               = (1 << 4),
-    EBPF_EVENT_PROCESS_SETUID               = (1 << 5),
-    EBPF_EVENT_PROCESS_SETGID               = (1 << 6),
-    EBPF_EVENT_PROCESS_TTY_WRITE            = (1 << 7),
-    EBPF_EVENT_FILE_DELETE                  = (1 << 8),
-    EBPF_EVENT_FILE_CREATE                  = (1 << 9),
-    EBPF_EVENT_FILE_RENAME                  = (1 << 10),
-    EBPF_EVENT_FILE_MODIFY                  = (1 << 11),
-    EBPF_EVENT_FILE_MEMFD_OPEN              = (1 << 12),
-    EBPF_EVENT_FILE_SHMEM_OPEN              = (1 << 13),
-    EBPF_EVENT_NETWORK_CONNECTION_ACCEPTED  = (1 << 14),
-    EBPF_EVENT_NETWORK_CONNECTION_ATTEMPTED = (1 << 15),
-    EBPF_EVENT_NETWORK_CONNECTION_CLOSED    = (1 << 16),
-    EBPF_EVENT_PROCESS_MEMFD_CREATE         = (1 << 17),
-    EBPF_EVENT_PROCESS_SHMGET               = (1 << 18),
-    EBPF_EVENT_PROCESS_PTRACE               = (1 << 19),
-    EBPF_EVENT_PROCESS_LOAD_MODULE          = (1 << 20),
+    EBPF_EVENT_PROCESS_INVALID              = 0,
+    EBPF_EVENT_PROCESS_FORK                 = (1 << 0),
+    EBPF_EVENT_PROCESS_EXEC                 = (1 << 1),
+    EBPF_EVENT_PROCESS_EXIT                 = (1 << 2),
+    EBPF_EVENT_PROCESS_SETSID               = (1 << 3),
+    EBPF_EVENT_PROCESS_SETUID               = (1 << 4),
+    EBPF_EVENT_PROCESS_SETGID               = (1 << 5),
+    EBPF_EVENT_PROCESS_TTY_WRITE            = (1 << 6),
+    EBPF_EVENT_FILE_DELETE                  = (1 << 7),
+    EBPF_EVENT_FILE_CREATE                  = (1 << 8),
+    EBPF_EVENT_FILE_RENAME                  = (1 << 9),
+    EBPF_EVENT_FILE_MODIFY                  = (1 << 10),
+    EBPF_EVENT_FILE_MEMFD_OPEN              = (1 << 11),
+    EBPF_EVENT_FILE_SHMEM_OPEN              = (1 << 12),
+    EBPF_EVENT_NETWORK_CONNECTION_ACCEPTED  = (1 << 13),
+    EBPF_EVENT_NETWORK_CONNECTION_ATTEMPTED = (1 << 14),
+    EBPF_EVENT_NETWORK_CONNECTION_CLOSED    = (1 << 15),
+    EBPF_EVENT_PROCESS_MEMFD_CREATE         = (1 << 16),
+    EBPF_EVENT_PROCESS_SHMGET               = (1 << 17),
+    EBPF_EVENT_PROCESS_PTRACE               = (1 << 18),
+    EBPF_EVENT_PROCESS_LOAD_MODULE          = (1 << 19),
 };
 
 struct ebpf_event_header {
@@ -378,4 +379,10 @@ struct ebpf_net_event {
     char comm[TASK_COMM_LEN];
 } __attribute__((packed));
 
+// Basic event statistics
+struct ebpf_event_stats {
+    uint64_t lost; // lost events due to a full ringbuffer
+    uint64_t sent; // events sent through the ringbuffer
+};
+
 #endif // EBPF_EVENTPROBE_EBPFEVENTPROTO_H

GPL/Events/File/Probe.bpf.c

@@ -155,7 +155,7 @@ static int vfs_unlink__exit(int ret)
     size  = ebpf_resolve_pids_ss_cgroup_path_to_string(field->data, task);
     ebpf_vl_field__set_size(&event->vl_fields, field, size);
 
-    bpf_ringbuf_output(&ringbuf, event, EVENT_SIZE(event), 0);
+    ebpf_ringbuf_write(&ringbuf, event, EVENT_SIZE(event), 0);
 
     // Certain filesystems (eg. overlayfs) call vfs_unlink twice during the same
     // execution context.
@@ -263,10 +263,10 @@ static void prepare_and_send_file_event(struct file *f,
     if (path_prefix) {
         if ((path_prefix_len > 0) && (size >= path_prefix_len)) {
             if (is_equal_prefix(field->data, path_prefix, path_prefix_len))
-                bpf_ringbuf_output(&ringbuf, event, EVENT_SIZE(event), 0);
+                ebpf_ringbuf_write(&ringbuf, event, EVENT_SIZE(event), 0);
         }
     } else {
-        bpf_ringbuf_output(&ringbuf, event, EVENT_SIZE(event), 0);
+        ebpf_ringbuf_write(&ringbuf, event, EVENT_SIZE(event), 0);
     }
 }
 
@@ -516,7 +516,7 @@ static int vfs_rename__exit(int ret)
     size  = ebpf_resolve_pids_ss_cgroup_path_to_string(field->data, task);
     ebpf_vl_field__set_size(&event->vl_fields, field, size);
 
-    bpf_ringbuf_output(&ringbuf, event, EVENT_SIZE(event), 0);
+    ebpf_ringbuf_write(&ringbuf, event, EVENT_SIZE(event), 0);
 
     // Certain filesystems (eg. overlayfs) call vfs_rename twice during the same
     // execution context.
@@ -588,7 +588,7 @@ static void file_modify_event__emit(enum ebpf_file_change_type typ, struct path
     size  = ebpf_resolve_pids_ss_cgroup_path_to_string(field->data, task);
     ebpf_vl_field__set_size(&event->vl_fields, field, size);
 
-    bpf_ringbuf_output(&ringbuf, event, EVENT_SIZE(event), 0);
+    ebpf_ringbuf_write(&ringbuf, event, EVENT_SIZE(event), 0);
 
 out:
     return;

GPL/Events/Helpers.h

@@ -295,6 +295,27 @@ static void ebpf_comm__fill(char *comm, size_t len, const struct task_struct *ta
     read_kernel_str_or_empty_str(comm, len, BPF_CORE_READ(task, comm));
 }
 
+struct {
+    __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+    __type(key, u32);
+    __type(value, struct ebpf_event_stats);
+    __uint(max_entries, 1);
+} ringbuf_stats SEC(".maps");
+
+static long ebpf_ringbuf_write(void *ringbuf, void *data, u64 size, u64 flags)
+{
+    long r;
+    struct ebpf_event_stats *ees;
+    u32 zero = 0;
+
+    r   = bpf_ringbuf_output(ringbuf, data, size, flags);
+    ees = bpf_map_lookup_elem(&ringbuf_stats, &zero);
+    if (ees != NULL)
+        r == 0 ? ees->sent++ : ees->lost++;
+
+    return (r);
+}
+
 static bool is_kernel_thread(const struct task_struct *task)
 {
     // All kernel threads are children of kthreadd, which always has pid 2

GPL/Events/Process/Probe.bpf.c

@@ -75,7 +75,7 @@ int BPF_PROG(sched_process_fork, const struct task_struct *parent, const struct
     size  = ebpf_resolve_path_to_string(field->data, &child->fs->pwd, child);
     ebpf_vl_field__set_size(&event->vl_fields, field, size);
 
-    bpf_ringbuf_output(&ringbuf, event, EVENT_SIZE(event), 0);
+    ebpf_ringbuf_write(&ringbuf, event, EVENT_SIZE(event), 0);
 
 out:
     return 0;
@@ -165,7 +165,7 @@ int BPF_PROG(sched_process_exec,
     size  = read_kernel_str_or_empty_str(field->data, PATH_MAX, binprm->filename);
     ebpf_vl_field__set_size(&event->vl_fields, field, size);
 
-    bpf_ringbuf_output(&ringbuf, event, EVENT_SIZE(event), 0);
+    ebpf_ringbuf_write(&ringbuf, event, EVENT_SIZE(event), 0);
 
 out:
     return 0;
@@ -219,7 +219,7 @@ static int taskstats_exit__enter(const struct task_struct *task, int group_dead)
     size  = ebpf_resolve_pids_ss_cgroup_path_to_string(field->data, task);
     ebpf_vl_field__set_size(&event->vl_fields, field, size);
 
-    bpf_ringbuf_output(&ringbuf, event, EVENT_SIZE(event), 0);
+    ebpf_ringbuf_write(&ringbuf, event, EVENT_SIZE(event), 0);
 
 out:
     return 0;
@@ -315,7 +315,7 @@ int BPF_PROG(module_load, struct module *mod)
     size  = read_kernel_str_or_empty_str(field->data, PATH_MAX, mod->srcversion);
     ebpf_vl_field__set_size(&event->vl_fields, field, size);
 
-    bpf_ringbuf_output(&ringbuf, event, EVENT_SIZE(event), 0);
+    ebpf_ringbuf_write(&ringbuf, event, EVENT_SIZE(event), 0);
 
 out:
     return 0;
@@ -448,7 +448,7 @@ int tracepoint_syscalls_sys_enter_memfd_create(struct trace_event_raw_sys_enter
         goto out;
     ebpf_vl_field__set_size(&event->vl_fields, field, size);
 
-    bpf_ringbuf_output(&ringbuf, event, EVENT_SIZE(event), 0);
+    ebpf_ringbuf_write(&ringbuf, event, EVENT_SIZE(event), 0);
 
 out:
     return 0;
@@ -562,7 +562,7 @@ static int output_tty_event(struct ebpf_tty_dev *slave, const void *base, size_t
     }
 
     ebpf_vl_field__set_size(&event->vl_fields, field, len_cap);
-    bpf_ringbuf_output(&ringbuf, event, EVENT_SIZE(event), 0);
+    ebpf_ringbuf_write(&ringbuf, event, EVENT_SIZE(event), 0);
 out:
     return ret;
 }

GPL/Events/Varlen.h

@@ -17,7 +17,7 @@
 // We can't use the ringbuf reserve/commit API if we want to output an event
 // with variable length fields as we won't know the event size in advance, so
 // we create events on the event_buffer_map if this is the case and output them
-// with bpf_ringbuf_output.
+// with ebpf_ringbuf_write.
 //
 // If the event has no variable length parameters (i.e. is always a fixed
 // size). bpf_ringbuf_reserve/bpf_ringbuf_submit should be used instead to

non-GPL/Events/EventsTrace/EventsTrace.c

@@ -35,7 +35,7 @@ const char argp_program_doc[] =
     "[--process-setgid] [--process-tty-write] [--process-memfd_create] [--process-shmget] "
     "[--process-ptrace] [--process-load_module]\n"
     "[--net-conn-accept] [--net-conn-attempt] [--net-conn-closed]\n"
-    "[--print-features-on-init] [--unbuffer-stdout] [--libbpf-verbose]\n";
+    "[--print-features-on-init] [--stats|-s] [--unbuffer-stdout] [--libbpf-verbose]\n";
 
 // Somewhat kludgy way of ensuring argp doesn't print the EBPF_* constants that
 // happen to be valid ASCII values as short options. We pass these enum values
@@ -120,6 +120,7 @@ static const struct argp_option opts[] = {
      "Print network connection closed events", 0},
     {"print-features-on-init", 'i', NULL, false,
      "Print a message with feature information when probes have been successfully loaded", 1},
+    {"stats", 's', NULL, false, "Print event statistics", 0},
     {"unbuffer-stdout", 'u', NULL, false, "Disable userspace stdout buffering", 2},
     {"libbpf-verbose", 'v', NULL, false, "Log verbose libbpf logs to stderr", 2},
     {},
@@ -132,6 +133,7 @@ bool g_print_features_init = 0;
 bool g_features_printed    = 0;
 bool g_unbuffer_stdout     = 0;
 bool g_libbpf_verbose      = 0;
+bool g_stats               = 0;
 
 static error_t parse_arg(int key, char *arg, struct argp_state *state)
 {
@@ -148,6 +150,9 @@ static error_t parse_arg(int key, char *arg, struct argp_state *state)
     case 'a':
         g_events_env = UINT64_MAX;
         break;
+    case 's':
+        g_stats = 1;
+        break;
     case FILE_DELETE:
     case FILE_CREATE:
     case FILE_RENAME:
@@ -1179,6 +1184,14 @@ int main(int argc, char **argv)
             fprintf(stderr, "Failed to poll event context %d: %s\n", err, strerror(-err));
             break;
         }
+        if (g_stats) {
+            struct ebpf_event_stats ees;
+
+            if (ebpf_event_ctx__read_stats(ctx, &ees) == 0)
+                printf("sent %lu lost %lu\n", ees.sent, ees.lost);
+            else
+                fprintf(stderr, "Failed to read stats: %s\n", strerror(errno));
+        }
     }
 
     ebpf_event_ctx__destroy(&ctx);

non-GPL/Events/Lib/EbpfEvents.c

@@ -797,6 +797,27 @@ int ebpf_event_ctx__poll(struct ebpf_event_ctx *ctx, int timeout)
     return ring_buffer__poll(ctx->ringbuf, timeout);
 }
 
+int ebpf_event_ctx__read_stats(struct ebpf_event_ctx *ctx, struct ebpf_event_stats *ees)
+{
+    struct ebpf_event_stats pcpu_ees[libbpf_num_possible_cpus()];
+    uint32_t zero = 0;
+    int i;
+
+    if (!ctx || !ees)
+        return -1;
+    if (bpf_map__lookup_elem(ctx->probe->maps.ringbuf_stats, &zero, sizeof(zero), pcpu_ees,
+                             sizeof(pcpu_ees), 0) != 0)
+        return -1;
+
+    memset(ees, 0, sizeof(*ees));
+    for (i = 0; i < libbpf_num_possible_cpus(); i++) {
+        ees->lost += pcpu_ees[i].lost;
+        ees->sent += pcpu_ees[i].sent;
+    }
+
+    return 0;
+}
+
 int ebpf_event_ctx__consume(struct ebpf_event_ctx *ctx)
 {
     if (!ctx)

non-GPL/Events/Lib/EbpfEvents.h

@@ -54,6 +54,12 @@ int ebpf_event_ctx__next(struct ebpf_event_ctx *ctx, int timeout);
  */
 int ebpf_event_ctx__poll(struct ebpf_event_ctx *ctx, int timeout);
 
+/* Read event statistics into ees.
+ *
+ * returns 0 on success or less than 0 on failure.
+ */
+int ebpf_event_ctx__read_stats(struct ebpf_event_ctx *ctx, struct ebpf_event_stats *ees);
+
 /* Consumes as many events as possible from the event context and returns the
  * number consumed. Does not poll. This is good if you are polling outside
  * this library.