5 files changed, 73 insertions, 0 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e55e4255a210..f812ac508e9f 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -254,6 +254,7 @@ typedef unsigned long (*bpf_ctx_copy_t)(void *dst, const void *src,
 
 u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
                      void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy);
+int bpf_event_query_prog_array(struct perf_event *event, void __user *info);
 
 int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
                           union bpf_attr __user *uattr);
@@ -285,6 +286,9 @@ int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs,
 
 void bpf_prog_array_delete_safe(struct bpf_prog_array __rcu *progs,
                                 struct bpf_prog *old_prog);
+int bpf_prog_array_copy_info(struct bpf_prog_array __rcu *array,
+                             __u32 __user *prog_ids, u32 request_cnt,
+                             __u32 __user *prog_cnt);
 int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array,
                         struct bpf_prog *exclude_prog,
                         struct bpf_prog *include_prog,
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index b9a4953018ed..769533696483 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -418,6 +418,27 @@ struct perf_event_attr {
         __u16   __reserved_2;   /* align to __u64 */
 };
 
+/*
+ * Structure used by below PERF_EVENT_IOC_QUERY_BPF command
+ * to query bpf programs attached to the same perf tracepoint
+ * as the given perf event.
+ */
+struct perf_event_query_bpf {
+        /*
+         * The below ids array length
+         */
+        __u32   ids_len;
+        /*
+         * Set by the kernel to indicate the number of
+         * available programs
+         */
+        __u32   prog_cnt;
+        /*
+         * User provided buffer to store program ids
+         */
+        __u32   ids[0];
+};
+
 #define perf_flags(attr)        (*(&(attr)->read_format + 1))
 
 /*
@@ -433,6 +454,7 @@ struct perf_event_attr {
 #define PERF_EVENT_IOC_ID               _IOR('$', 7, __u64 *)
 #define PERF_EVENT_IOC_SET_BPF          _IOW('$', 8, __u32)
 #define PERF_EVENT_IOC_PAUSE_OUTPUT     _IOW('$', 9, __u32)
+#define PERF_EVENT_IOC_QUERY_BPF        _IOWR('$', 10, struct perf_event_query_bpf *)
 
 enum perf_event_ioc_flags {
         PERF_IOC_FLAG_GROUP             = 1U << 0,
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 86b50aa26ee8..b16c6f8f42b6 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1462,6 +1462,8 @@ int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs,
         rcu_read_lock();
         prog = rcu_dereference(progs)->progs;
         for (; *prog; prog++) {
+                if (*prog == &dummy_bpf_prog.prog)
+                        continue;
                 id = (*prog)->aux->id;
                 if (copy_to_user(prog_ids + i, &id, sizeof(id))) {
                         rcu_read_unlock();
@@ -1545,6 +1547,25 @@ int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array,
         return 0;
 }
 
+int bpf_prog_array_copy_info(struct bpf_prog_array __rcu *array,
+                             __u32 __user *prog_ids, u32 request_cnt,
+                             __u32 __user *prog_cnt)
+{
+        u32 cnt = 0;
+
+        if (array)
+                cnt = bpf_prog_array_length(array);
+
+        if (copy_to_user(prog_cnt, &cnt, sizeof(cnt)))
+                return -EFAULT;
+
+        /* return early if user requested only program count or nothing to copy */
+        if (!request_cnt || !cnt)
+                return 0;
+
+        return bpf_prog_array_copy_to_user(array, prog_ids, request_cnt);
+}
+
 static void bpf_prog_free_deferred(struct work_struct *work)
 {
         struct bpf_prog_aux *aux;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 16beab4767e1..f10609e539d4 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4723,6 +4723,9 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
                 rcu_read_unlock();
                 return 0;
         }
+
+        case PERF_EVENT_IOC_QUERY_BPF:
+                return bpf_event_query_prog_array(event, (void __user *)arg);
         default:
                 return -ENOTTY;
         }
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0ce99c379c30..b143f2a05aff 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -820,3 +820,26 @@ void perf_event_detach_bpf_prog(struct perf_event *event)
 unlock:
         mutex_unlock(&bpf_event_mutex);
 }
+
+int bpf_event_query_prog_array(struct perf_event *event, void __user *info)
+{
+        struct perf_event_query_bpf __user *uquery = info;
+        struct perf_event_query_bpf query = {};
+        int ret;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+        if (event->attr.type != PERF_TYPE_TRACEPOINT)
+                return -EINVAL;
+        if (copy_from_user(&query, uquery, sizeof(query)))
+                return -EFAULT;
+
+        mutex_lock(&bpf_event_mutex);
+        ret = bpf_prog_array_copy_info(event->tp_event->prog_array,
+                                       uquery->ids,
+                                       query.ids_len,
+                                       &uquery->prog_cnt);
+        mutex_unlock(&bpf_event_mutex);
+
+        return ret;
+}