bpf: sync bpf.h to tools/

Fix a 'struct pt_reg' typo and clarify when bpf_trace_printk discards
lines. Affects documentation only.
Signed-off-by: Peter Wu <peter@lekensteyn.nl>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/include/uapi/linux/bpf.h

@@ -580,6 +580,8 @@ union bpf_attr {
  * 		limited to five).
  *
  * 		Each time the helper is called, it appends a line to the trace.
+ * 		Lines are discarded while *\/sys/kernel/debug/tracing/trace* is
+ * 		open, use *\/sys/kernel/debug/tracing/trace_pipe* to avoid this.
  * 		The format of the trace is customizable, and the exact output
  * 		one will get depends on the options set in
  * 		*\/sys/kernel/debug/tracing/trace_options* (see also the
@@ -1018,7 +1020,7 @@ union bpf_attr {
  * 		The realm of the route for the packet associated to *skb*, or 0
  * 		if none was found.
  *
- * int bpf_perf_event_output(struct pt_reg *ctx, struct bpf_map *map, u64 flags, void *data, u64 size)
+ * int bpf_perf_event_output(struct pt_regs *ctx, struct bpf_map *map, u64 flags, void *data, u64 size)
  * 	Description
  * 		Write raw *data* blob into a special BPF perf event held by
  * 		*map* of type **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. This perf
@@ -1080,7 +1082,7 @@ union bpf_attr {
  * 	Return
  * 		0 on success, or a negative error in case of failure.
  *
- * int bpf_get_stackid(struct pt_reg *ctx, struct bpf_map *map, u64 flags)
+ * int bpf_get_stackid(struct pt_regs *ctx, struct bpf_map *map, u64 flags)
  * 	Description
  * 		Walk a user or a kernel stack and return its id. To achieve
  * 		this, the helper needs *ctx*, which is a pointer to the context
@@ -1729,7 +1731,7 @@ union bpf_attr {
  * 	Return
  * 		0 on success, or a negative error in case of failure.
  *
- * int bpf_override_return(struct pt_reg *regs, u64 rc)
+ * int bpf_override_return(struct pt_regs *regs, u64 rc)
  * 	Description
  * 		Used for error injection, this helper uses kprobes to override
  * 		the return value of the probed function, and to set it to *rc*.