Add a new bpf file to each trace event. The following commands can be written into it: attach:<fd> Attaches BPF prog fd to tracepoint detach:<fd> Detaches BPF prog fd to tracepoint
Reading the bpf file will show all the attached programs to the tracepoint.
Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org --- include/linux/bpf_trace.h | 6 ++ include/linux/trace_events.h | 1 + kernel/trace/bpf_trace.c | 169 +++++++++++++++++++++++++++++++++++ kernel/trace/trace.h | 1 + kernel/trace/trace_events.c | 9 +- 5 files changed, 184 insertions(+), 2 deletions(-)
diff --git a/include/linux/bpf_trace.h b/include/linux/bpf_trace.h index 4a593827fd87..1fe73501809c 100644 --- a/include/linux/bpf_trace.h +++ b/include/linux/bpf_trace.h @@ -9,6 +9,12 @@ struct bpf_raw_tracepoint { struct bpf_raw_event_map *btp; struct bpf_prog *prog; + /* + * Multiple programs can be attached to a tracepoint, + * All of these are linked to each other and can be reached + * from the event's bpf_attach file in tracefs. + */ + struct list_head event_attached; };
struct bpf_raw_tracepoint *bpf_raw_tracepoint_open(char *tp_name, int prog_fd); diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 8a62731673f7..525f2ac44aa3 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -371,6 +371,7 @@ struct trace_event_file { struct trace_array *tr; struct trace_subsystem_dir *system; struct list_head triggers; + struct list_head bpf_attached;
/* * 32 bit flags: diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index c4b543bc617f..28621ad88c12 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1469,3 +1469,172 @@ struct bpf_raw_tracepoint *bpf_raw_tracepoint_open(char *tp_name, int prog_fd) bpf_put_raw_tracepoint(btp); return ERR_PTR(err); } + +enum event_bpf_cmd { BPF_ATTACH, BPF_DETACH }; +#define BPF_CMD_BUF_LEN 32 + +static ssize_t +event_bpf_attach_write(struct file *filp, const char __user *ubuf, + size_t cnt, loff_t *ppos) +{ + int err, prog_fd, cmd_num, len; + struct trace_event_call *call; + struct trace_event_file *file; + struct bpf_raw_tracepoint *raw_tp, *next; + char buf[BPF_CMD_BUF_LEN], *end, *tok; + enum event_bpf_cmd cmd; + struct bpf_prog *prog; + bool prog_put = true; + + len = min((int)cnt, BPF_CMD_BUF_LEN - 1); + + err = copy_from_user(buf, ubuf, len); + if (err) + return err; + buf[len] = 0; + + /* Parse 2 arguments of format: <cmd>:<fd> */ + end = &buf[0]; + cmd_num = 1; + while (cmd_num < 3) { + tok = strsep(&end, ":"); + if (!tok) + return -EINVAL; + + switch (cmd_num) { + case 1: + if (!strncmp(tok, "attach", 6)) + cmd = BPF_ATTACH; + else if (!strncmp(tok, "detach", 6)) + cmd = BPF_DETACH; + else + return -EINVAL; + break; + case 2: + err = kstrtoint(tok, 10, &prog_fd); + if (err) + return err; + break; + } + cmd_num++; + } + if (cmd_num != 3) + return -EINVAL; + + file = event_file_data(filp); + /* Command is to attach fd to tracepoint */ + if (cmd == BPF_ATTACH) { + mutex_lock(&event_mutex); + call = file->event_call; + + raw_tp = bpf_raw_tracepoint_open((char *)call->tp->name, + prog_fd); + if (IS_ERR(raw_tp)) { + mutex_unlock(&event_mutex); + return PTR_ERR(raw_tp); + } + + list_add(&raw_tp->event_attached, &file->bpf_attached); + mutex_unlock(&event_mutex); + *ppos += cnt; + return cnt; + } + + /* Command is to detach fd from tracepoint */ + prog = bpf_prog_get(prog_fd); + if (IS_ERR(prog)) + return PTR_ERR(prog); + + mutex_lock(&event_mutex); + list_for_each_entry_safe(raw_tp, next, &file->bpf_attached, + event_attached) { + if (raw_tp->prog == prog) { + list_del(&raw_tp->event_attached); + bpf_raw_tracepoint_close(raw_tp); + prog_put = false; + break; + } + } + mutex_unlock(&event_mutex); + + if (prog_put) + bpf_prog_put(prog); + *ppos += cnt; + return cnt; +} + +static void *event_bpf_attach_next(struct seq_file *m, void *t, loff_t *pos) +{ + struct trace_event_file *file = event_file_data(m->private); + + return seq_list_next(t, &file->bpf_attached, pos); +} + +static void *event_bpf_attach_start(struct seq_file *m, loff_t *pos) +{ + struct trace_event_file *event_file; + + /* ->stop() is called even if ->start() fails */ + mutex_lock(&event_mutex); + event_file = event_file_data(m->private); + if (unlikely(!event_file)) + return ERR_PTR(-ENODEV); + + if (list_empty(&event_file->bpf_attached)) + return NULL; + + return seq_list_start(&event_file->bpf_attached, *pos); +} + +static void event_bpf_attach_stop(struct seq_file *m, void *t) +{ + mutex_unlock(&event_mutex); +} + +static int event_bpf_attach_show(struct seq_file *m, void *v) +{ + struct bpf_raw_tracepoint *raw_tp; + + raw_tp = list_entry(v, struct bpf_raw_tracepoint, event_attached); + seq_printf(m, "prog id: %u\n", raw_tp->prog->aux->id); + return 0; +} + +static const struct seq_operations event_bpf_attach_seq_ops = { + .start = event_bpf_attach_start, + .next = event_bpf_attach_next, + .stop = event_bpf_attach_stop, + .show = event_bpf_attach_show, +}; + +static int event_bpf_attach_open(struct inode *inode, struct file *file) +{ + int ret = 0; + + mutex_lock(&event_mutex); + + if (unlikely(!event_file_data(file))) { + mutex_unlock(&event_mutex); + return -ENODEV; + } + + if (file->f_mode & FMODE_READ) { + ret = seq_open(file, &event_bpf_attach_seq_ops); + if (!ret) { + struct seq_file *m = file->private_data; + + m->private = file; + } + } + + mutex_unlock(&event_mutex); + + return ret; +} + +const struct file_operations event_bpf_attach_fops = { + .open = event_bpf_attach_open, + .read = seq_read, + .write = event_bpf_attach_write, + .llseek = default_llseek, +}; diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 005f08629b8b..e33828d24eb2 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1582,6 +1582,7 @@ extern struct list_head ftrace_events;
extern const struct file_operations event_trigger_fops; extern const struct file_operations event_hist_fops; +extern const struct file_operations event_bpf_attach_fops;
#ifdef CONFIG_HIST_TRIGGERS extern int register_trigger_hist_cmd(void); diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 67851fb66b6b..79420d5efaef 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2018,8 +2018,10 @@ event_create_dir(struct dentry *parent, struct trace_event_file *file) trace_create_file("trigger", 0644, file->dir, file, &event_trigger_fops);
- trace_create_file("bpf_attach", 0644, file->dir, file, - &bpf_attach_trigger_fops); +#ifdef CONFIG_BPF_EVENTS + trace_create_file("bpf", 0644, file->dir, file, + &event_bpf_attach_fops); +#endif }
#ifdef CONFIG_HIST_TRIGGERS @@ -2267,6 +2269,9 @@ trace_create_new_event(struct trace_event_call *call, atomic_set(&file->sm_ref, 0); atomic_set(&file->tm_ref, 0); INIT_LIST_HEAD(&file->triggers); +#ifdef CONFIG_BPF_EVENTS + INIT_LIST_HEAD(&file->bpf_attached); +#endif list_add(&file->list, &tr->events);
return file;