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: