bpf: support raw tracepoints in modules

Distributions build drivers as modules, including network and filesystem
drivers which export numerous tracepoints.  This enables
bpf(BPF_RAW_TRACEPOINT_OPEN) to attach to those tracepoints.

Signed-off-by: Matt Mullins <mmullins@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 97 insertions, 2 deletions

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 9864a35c8bb5..9ddb6fddb4e0 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -17,6 +17,43 @@
 #include "trace_probe.h"
 #include "trace.h"
 
+#ifdef CONFIG_MODULES
+struct bpf_trace_module {
+	struct module *module;
+	struct list_head list;
+};
+
+static LIST_HEAD(bpf_trace_modules);
+static DEFINE_MUTEX(bpf_module_mutex);
+
+static struct bpf_raw_event_map *bpf_get_raw_tracepoint_module(const char *name)
+{
+	struct bpf_raw_event_map *btp, *ret = NULL;
+	struct bpf_trace_module *btm;
+	unsigned int i;
+
+	mutex_lock(&bpf_module_mutex);
+	list_for_each_entry(btm, &bpf_trace_modules, list) {
+		for (i = 0; i < btm->module->num_bpf_raw_events; ++i) {
+			btp = &btm->module->bpf_raw_events[i];
+			if (!strcmp(btp->tp->name, name)) {
+				if (try_module_get(btm->module))
+					ret = btp;
+				goto out;
+			}
+		}
+	}
+out:
+	mutex_unlock(&bpf_module_mutex);
+	return ret;
+}
+#else
+static struct bpf_raw_event_map *bpf_get_raw_tracepoint_module(const char *name)
+{
+	return NULL;
+}
+#endif /* CONFIG_MODULES */
+
 u64 bpf_get_stackid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
 u64 bpf_get_stack(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
 
@@ -1076,7 +1113,7 @@ int perf_event_query_prog_array(struct perf_event *event, void __user *info)
 extern struct bpf_raw_event_map __start__bpf_raw_tp[];
 extern struct bpf_raw_event_map __stop__bpf_raw_tp[];
 
-struct bpf_raw_event_map *bpf_find_raw_tracepoint(const char *name)
+struct bpf_raw_event_map *bpf_get_raw_tracepoint(const char *name)
 {
 	struct bpf_raw_event_map *btp = __start__bpf_raw_tp;
 
@@ -1084,7 +1121,16 @@ struct bpf_raw_event_map *bpf_find_raw_tracepoint(const char *name)
 		if (!strcmp(btp->tp->name, name))
 			return btp;
 	}
-	return NULL;
+
+	return bpf_get_raw_tracepoint_module(name);
+}
+
+void bpf_put_raw_tracepoint(struct bpf_raw_event_map *btp)
+{
+	struct module *mod = __module_address((unsigned long)btp);
+
+	if (mod)
+		module_put(mod);
 }
 
 static __always_inline
@@ -1222,3 +1268,52 @@ int bpf_get_perf_event_info(const struct perf_event *event, u32 *prog_id,
 
 	return err;
 }
+
+#ifdef CONFIG_MODULES
+int bpf_event_notify(struct notifier_block *nb, unsigned long op, void *module)
+{
+	struct bpf_trace_module *btm, *tmp;
+	struct module *mod = module;
+
+	if (mod->num_bpf_raw_events == 0 ||
+	    (op != MODULE_STATE_COMING && op != MODULE_STATE_GOING))
+		return 0;
+
+	mutex_lock(&bpf_module_mutex);
+
+	switch (op) {
+	case MODULE_STATE_COMING:
+		btm = kzalloc(sizeof(*btm), GFP_KERNEL);
+		if (btm) {
+			btm->module = module;
+			list_add(&btm->list, &bpf_trace_modules);
+		}
+		break;
+	case MODULE_STATE_GOING:
+		list_for_each_entry_safe(btm, tmp, &bpf_trace_modules, list) {
+			if (btm->module == module) {
+				list_del(&btm->list);
+				kfree(btm);
+				break;
+			}
+		}
+		break;
+	}
+
+	mutex_unlock(&bpf_module_mutex);
+
+	return 0;
+}
+
+static struct notifier_block bpf_module_nb = {
+	.notifier_call = bpf_event_notify,
+};
+
+int __init bpf_event_init(void)
+{
+	register_module_notifier(&bpf_module_nb);
+	return 0;
+}
+
+fs_initcall(bpf_event_init);
+#endif /* CONFIG_MODULES */