bpf: introduce bpf_get_current_task() helper

over time there were multiple requests to access different data structures and fields of task_struct current, so finally add the helper to access 'current' as-is. Tracing bpf programs will do the rest of walking the pointers via bpf_probe_read(). Note that current can be null and bpf program has to deal it with, but even dumb passing null into bpf_probe_read() is still safe. Suggested-by: Brendan Gregg <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Daniel Borkmann <[email protected]> Signed-off-by: David S. Miller <[email protected]>
torvalds · Jul 9, 2016 · 606274c · 606274c
1 parent d390238
commit 606274c
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diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
@@ -357,6 +357,13 @@ enum bpf_func_id {
  */
  BPF_FUNC_get_hash_recalc,
 
+ /**
+ * u64 bpf_get_current_task(void)
+ * Returns current task_struct
+ * Return: current
+ */
+ BPF_FUNC_get_current_task,
+
  __BPF_FUNC_MAX_ID,
 };
 

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
@@ -312,6 +312,17 @@ const struct bpf_func_proto *bpf_get_event_output_proto(void)
  return &bpf_event_output_proto;
 }
 
+static u64 bpf_get_current_task(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+ return (long) current;
+}
+
+static const struct bpf_func_proto bpf_get_current_task_proto = {
+ .func = bpf_get_current_task,
+ .gpl_only = true,
+ .ret_type = RET_INTEGER,
+};
+
 static const struct bpf_func_proto *tracing_func_proto(enum bpf_func_id func_id)
 {
  switch (func_id) {
@@ -329,6 +340,8 @@ static const struct bpf_func_proto *tracing_func_proto(enum bpf_func_id func_id)
  return &bpf_tail_call_proto;
  case BPF_FUNC_get_current_pid_tgid:
  return &bpf_get_current_pid_tgid_proto;
+ case BPF_FUNC_get_current_task:
+ return &bpf_get_current_task_proto;
  case BPF_FUNC_get_current_uid_gid:
  return &bpf_get_current_uid_gid_proto;
  case BPF_FUNC_get_current_comm: