Merge tag 'trace-v4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:

 - Rework of the kprobe/uprobe and synthetic events to consolidate all
   the dynamic event code. This will make changes in the future easier.

 - Partial rewrite of the function graph tracing infrastructure. This
   will allow for multiple users of hooking onto functions to get the
   callback (return) of the function. This is the ground work for having
   kprobes and function graph tracer using one code base.

 - Clean up of the histogram code that will facilitate adding more
   features to the histograms in the future.

 - Addition of str_has_prefix() and a few use cases. There currently is
   a similar function strstart() that is used in a few places, but only
   returns a bool and not a length. These instances will be removed in
   the future to use str_has_prefix() instead.

 - A few other various clean ups as well.

* tag 'trace-v4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (57 commits)
  tracing: Use the return of str_has_prefix() to remove open coded numbers
  tracing: Have the historgram use the result of str_has_prefix() for len of prefix
  tracing: Use str_has_prefix() instead of using fixed sizes
  tracing: Use str_has_prefix() helper for histogram code
  string.h: Add str_has_prefix() helper function
  tracing: Make function ‘ftrace_exports’ static
  tracing: Simplify printf'ing in seq_print_sym
  tracing: Avoid -Wformat-nonliteral warning
  tracing: Merge seq_print_sym_short() and seq_print_sym_offset()
  tracing: Add hist trigger comments for variable-related fields
  tracing: Remove hist trigger synth_var_refs
  tracing: Use hist trigger's var_ref array to destroy var_refs
  tracing: Remove open-coding of hist trigger var_ref management
  tracing: Use var_refs[] for hist trigger reference checking
  tracing: Change strlen to sizeof for hist trigger static strings
  tracing: Remove unnecessary hist trigger struct field
  tracing: Fix ftrace_graph_get_ret_stack() to use task and not current
  seq_buf: Use size_t for len in seq_buf_puts()
  seq_buf: Make seq_buf_puts() null-terminate the buffer
  arm64: Use ftrace_graph_get_ret_stack() instead of curr_ret_stack
  ...

include/linux/ftrace.h

@@ -389,6 +389,7 @@ enum {
 	FTRACE_UPDATE_TRACE_FUNC	= (1 << 2),
 	FTRACE_START_FUNC_RET		= (1 << 3),
 	FTRACE_STOP_FUNC_RET		= (1 << 4),
+	FTRACE_MAY_SLEEP		= (1 << 5),
 };
 
 /*
@@ -752,6 +753,11 @@ typedef int (*trace_func_graph_ent_t)(struct ftrace_graph_ent *); /* entry */
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
+struct fgraph_ops {
+	trace_func_graph_ent_t		entryfunc;
+	trace_func_graph_ret_t		retfunc;
+};
+
 /*
  * Stack of return addresses for functions
  * of a thread.
@@ -783,6 +789,9 @@ extern int
 function_graph_enter(unsigned long ret, unsigned long func,
 		     unsigned long frame_pointer, unsigned long *retp);
 
+struct ftrace_ret_stack *
+ftrace_graph_get_ret_stack(struct task_struct *task, int idx);
+
 unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
 				    unsigned long ret, unsigned long *retp);
 
@@ -793,11 +802,11 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
  */
 #define __notrace_funcgraph		notrace
 
-#define FTRACE_NOTRACE_DEPTH 65536
 #define FTRACE_RETFUNC_DEPTH 50
 #define FTRACE_RETSTACK_ALLOC_SIZE 32
-extern int register_ftrace_graph(trace_func_graph_ret_t retfunc,
-				trace_func_graph_ent_t entryfunc);
+
+extern int register_ftrace_graph(struct fgraph_ops *ops);
+extern void unregister_ftrace_graph(struct fgraph_ops *ops);
 
 extern bool ftrace_graph_is_dead(void);
 extern void ftrace_graph_stop(void);
@@ -806,17 +815,10 @@ extern void ftrace_graph_stop(void);
 extern trace_func_graph_ret_t ftrace_graph_return;
 extern trace_func_graph_ent_t ftrace_graph_entry;
 
-extern void unregister_ftrace_graph(void);
-
 extern void ftrace_graph_init_task(struct task_struct *t);
 extern void ftrace_graph_exit_task(struct task_struct *t);
 extern void ftrace_graph_init_idle_task(struct task_struct *t, int cpu);
 
-static inline int task_curr_ret_stack(struct task_struct *t)
-{
-	return t->curr_ret_stack;
-}
-
 static inline void pause_graph_tracing(void)
 {
 	atomic_inc(&current->tracing_graph_pause);
@@ -834,17 +836,9 @@ static inline void ftrace_graph_init_task(struct task_struct *t) { }
 static inline void ftrace_graph_exit_task(struct task_struct *t) { }
 static inline void ftrace_graph_init_idle_task(struct task_struct *t, int cpu) { }
 
-static inline int register_ftrace_graph(trace_func_graph_ret_t retfunc,
-			  trace_func_graph_ent_t entryfunc)
-{
-	return -1;
-}
-static inline void unregister_ftrace_graph(void) { }
-
-static inline int task_curr_ret_stack(struct task_struct *tsk)
-{
-	return -1;
-}
+/* Define as macros as fgraph_ops may not be defined */
+#define register_ftrace_graph(ops) ({ -1; })
+#define unregister_ftrace_graph(ops) do { } while (0)
 
 static inline unsigned long
 ftrace_graph_ret_addr(struct task_struct *task, int *idx, unsigned long ret,

include/linux/ring_buffer.h

@@ -97,7 +97,7 @@ __ring_buffer_alloc(unsigned long size, unsigned flags, struct lock_class_key *k
 	__ring_buffer_alloc((size), (flags), &__key);	\
 })
 
-int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full);
+int ring_buffer_wait(struct ring_buffer *buffer, int cpu, int full);
 __poll_t ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
 			  struct file *filp, poll_table *poll_table);
 
@@ -189,6 +189,8 @@ bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer);
 
 size_t ring_buffer_page_len(void *page);
 
+size_t ring_buffer_nr_pages(struct ring_buffer *buffer, int cpu);
+size_t ring_buffer_nr_dirty_pages(struct ring_buffer *buffer, int cpu);
 
 void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu);
 void ring_buffer_free_read_page(struct ring_buffer *buffer, int cpu, void *data);

include/linux/string.h

@@ -456,4 +456,24 @@ static inline void memcpy_and_pad(void *dest, size_t dest_len,
 		memcpy(dest, src, dest_len);
 }
 
+/**
+ * str_has_prefix - Test if a string has a given prefix
+ * @str: The string to test
+ * @prefix: The string to see if @str starts with
+ *
+ * A common way to test a prefix of a string is to do:
+ *  strncmp(str, prefix, sizeof(prefix) - 1)
+ *
+ * But this can lead to bugs due to typos, or if prefix is a pointer
+ * and not a constant. Instead use str_has_prefix().
+ *
+ * Returns: 0 if @str does not start with @prefix
+         strlen(@prefix) if @str does start with @prefix
+ */
+static __always_inline size_t str_has_prefix(const char *str, const char *prefix)
+{
+	size_t len = strlen(prefix);
+	return strncmp(str, prefix, len) == 0 ? len : 0;
+}
+
 #endif /* _LINUX_STRING_H_ */