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 <mmull...@fb.com>
---
v1->v2:
* avoid taking the mutex in bpf_event_notify when op is neither COMING nor
GOING.
* check that kzalloc actually succeeded
I didn't try to check list_empty before taking the mutex since I want to avoid
races between bpf_event_notify and bpf_get_raw_tracepoint. Additionally,
list_for_each_entry_safe is not strictly necessary upon MODULE_STATE_GOING, but
Alexei suggested I use it to protect against fragility if the subsequent break;
eventually disappears.
include/linux/module.h | 4 ++
include/linux/trace_events.h | 8 ++-
kernel/bpf/syscall.c | 11 ++--
kernel/module.c | 5 ++
kernel/trace/bpf_trace.c | 99 +++++++++++++++++++++++++++++++++++-
5 files changed, 120 insertions(+), 7 deletions(-)
diff --git a/include/linux/module.h b/include/linux/module.h
index fce6b4335e36..5f147dd5e709 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -432,6 +432,10 @@ struct module {
unsigned int num_tracepoints;
tracepoint_ptr_t *tracepoints_ptrs;
#endif
+#ifdef CONFIG_BPF_EVENTS
+ unsigned int num_bpf_raw_events;
+ struct bpf_raw_event_map *bpf_raw_events;
+#endif
#ifdef HAVE_JUMP_LABEL
struct jump_entry *jump_entries;
unsigned int num_jump_entries;
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 4130a5497d40..8a62731673f7 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -471,7 +471,8 @@ void perf_event_detach_bpf_prog(struct perf_event *event);
int perf_event_query_prog_array(struct perf_event *event, void __user *info);
int bpf_probe_register(struct bpf_raw_event_map *btp, struct bpf_prog *prog);
int bpf_probe_unregister(struct bpf_raw_event_map *btp, struct bpf_prog *prog);
-struct bpf_raw_event_map *bpf_find_raw_tracepoint(const char *name);
+struct bpf_raw_event_map *bpf_get_raw_tracepoint(const char *name);
+void bpf_put_raw_tracepoint(struct bpf_raw_event_map *btp);
int bpf_get_perf_event_info(const struct perf_event *event, u32 *prog_id,
u32 *fd_type, const char **buf,
u64 *probe_offset, u64 *probe_addr);
@@ -502,10 +503,13 @@ static inline int bpf_probe_unregister(struct
bpf_raw_event_map *btp, struct bpf
{
return -EOPNOTSUPP;
}
-static inline struct bpf_raw_event_map *bpf_find_raw_tracepoint(const char
*name)
+static inline struct bpf_raw_event_map *bpf_get_raw_tracepoint(const char
*name)
{
return NULL;
}
+static inline void bpf_put_raw_tracepoint(struct bpf_raw_event_map *btp)
+{
+}
static inline int bpf_get_perf_event_info(const struct perf_event *event,
u32 *prog_id, u32 *fd_type,
const char **buf, u64 *probe_offset,
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 70fb11106fc2..754370e3155e 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1609,6 +1609,7 @@ static int bpf_raw_tracepoint_release(struct inode
*inode, struct file *filp)
bpf_probe_unregister(raw_tp->btp, raw_tp->prog);
bpf_prog_put(raw_tp->prog);
}
+ bpf_put_raw_tracepoint(raw_tp->btp);
kfree(raw_tp);
return 0;
}
@@ -1634,13 +1635,15 @@ static int bpf_raw_tracepoint_open(const union bpf_attr
*attr)
return -EFAULT;
tp_name[sizeof(tp_name) - 1] = 0;
- btp = bpf_find_raw_tracepoint(tp_name);
+ btp = bpf_get_raw_tracepoint(tp_name);
if (!btp)
return -ENOENT;
raw_tp = kzalloc(sizeof(*raw_tp), GFP_USER);
- if (!raw_tp)
- return -ENOMEM;
+ if (!raw_tp) {
+ err = -ENOMEM;
+ goto out_put_btp;
+ }
raw_tp->btp = btp;
prog = bpf_prog_get_type(attr->raw_tracepoint.prog_fd,
@@ -1668,6 +1671,8 @@ static int bpf_raw_tracepoint_open(const union bpf_attr
*attr)
bpf_prog_put(prog);
out_free_tp:
kfree(raw_tp);
+out_put_btp:
+ bpf_put_raw_tracepoint(btp);
return err;
}
diff --git a/kernel/module.c b/kernel/module.c
index 49a405891587..06ec68f08387 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3093,6 +3093,11 @@ static int find_module_sections(struct module *mod,
struct load_info *info)
sizeof(*mod->tracepoints_ptrs),
&mod->num_tracepoints);
#endif
+#ifdef CONFIG_BPF_EVENTS
+ mod->bpf_raw_events = section_objs(info, "__bpf_raw_tp_map",
+ sizeof(*mod->bpf_raw_events),
+ &mod->num_bpf_raw_events);
+#endif
#ifdef HAVE_JUMP_LABEL
mod->jump_entries = section_objs(info, "__jump_table",
sizeof(*mod->jump_entries),
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 */
--
2.17.1
