Merge tag 'trace-v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:
 "Updates for tracing and bootconfig:

   - Add support for "bool" type in synthetic events

   - Add per instance tracing for bootconfig

   - Support perf-style return probe ("SYMBOL%return") in kprobes and
     uprobes

   - Allow for kprobes to be enabled earlier in boot up

   - Added tracepoint helper function to allow testing if tracepoints
     are enabled in headers

   - Synthetic events can now have dynamic strings (variable length)

   - Various fixes and cleanups"

* tag 'trace-v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (58 commits)
  tracing: support "bool" type in synthetic trace events
  selftests/ftrace: Add test case for synthetic event syntax errors
  tracing: Handle synthetic event array field type checking correctly
  selftests/ftrace: Change synthetic event name for inter-event-combined test
  tracing: Add synthetic event error logging
  tracing: Check that the synthetic event and field names are legal
  tracing: Move is_good_name() from trace_probe.h to trace.h
  tracing: Don't show dynamic string internals in synthetic event description
  tracing: Fix some typos in comments
  tracing/boot: Add ftrace.instance.*.alloc_snapshot option
  tracing: Fix race in trace_open and buffer resize call
  tracing: Check return value of __create_val_fields() before using its result
  tracing: Fix synthetic print fmt check for use of __get_str()
  tracing: Remove a pointless assignment
  ftrace: ftrace_global_list is renamed to ftrace_ops_list
  ftrace: Format variable declarations of ftrace_allocate_records
  ftrace: Simplify the calculation of page number for ftrace_page->records
  ftrace: Simplify the dyn_ftrace->flags macro
  ftrace: Simplify the hash calculation
  ftrace: Use fls() to get the bits for dup_hash()
  ...

1 files changed, 34 insertions, 0 deletions

diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index de97450cf190..e7c2276be33e 100644
--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -53,4 +53,38 @@ struct bpf_raw_event_map {
 	u32			writable_size;
 } __aligned(32);
 
+/*
+ * If a tracepoint needs to be called from a header file, it is not
+ * recommended to call it directly, as tracepoints in header files
+ * may cause side-effects and bloat the kernel. Instead, use
+ * tracepoint_enabled() to test if the tracepoint is enabled, then if
+ * it is, call a wrapper function defined in a C file that will then
+ * call the tracepoint.
+ *
+ * For "trace_foo_bar()", you would need to create a wrapper function
+ * in a C file to call trace_foo_bar():
+ *   void do_trace_foo_bar(args) { trace_foo_bar(args); }
+ * Then in the header file, declare the tracepoint:
+ *   DECLARE_TRACEPOINT(foo_bar);
+ * And call your wrapper:
+ *   static inline void some_inlined_function() {
+ *            [..]
+ *            if (tracepoint_enabled(foo_bar))
+ *                    do_trace_foo_bar(args);
+ *            [..]
+ *   }
+ *
+ * Note: tracepoint_enabled(foo_bar) is equivalent to trace_foo_bar_enabled()
+ *   but is safe to have in headers, where trace_foo_bar_enabled() is not.
+ */
+#define DECLARE_TRACEPOINT(tp) \
+	extern struct tracepoint __tracepoint_##tp
+
+#ifdef CONFIG_TRACEPOINTS
+# define tracepoint_enabled(tp) \
+	static_key_false(&(__tracepoint_##tp).key)
+#else
+# define tracepoint_enabled(tracepoint) false
+#endif
+
 #endif