Merge tag 'trace-v6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing updates from Steven Rostedt:

 - User events are finally ready!

   After lots of collaboration between various parties, we finally
   locked down on a stable interface for user events that can also work
   with user space only tracing.

   This is implemented by telling the kernel (or user space library, but
   that part is user space only and not part of this patch set), where
   the variable is that the application uses to know if something is
   listening to the trace.

   There's also an interface to tell the kernel about these events,
   which will show up in the /sys/kernel/tracing/events/user_events/
   directory, where it can be enabled.

   When it's enabled, the kernel will update the variable, to tell the
   application to start writing to the kernel.

   See https://lwn.net/Articles/927595/

 - Cleaned up the direct trampolines code to simplify arm64 addition of
   direct trampolines.

   Direct trampolines use the ftrace interface but instead of jumping to
   the ftrace trampoline, applications (mostly BPF) can register their
   own trampoline for performance reasons.

 - Some updates to the fprobe infrastructure. fprobes are more efficient
   than kprobes, as it does not need to save all the registers that
   kprobes on ftrace do. More work needs to be done before the fprobes
   will be exposed as dynamic events.

 - More updates to references to the obsolete path of
   /sys/kernel/debug/tracing for the new /sys/kernel/tracing path.

 - Add a seq_buf_do_printk() helper to seq_bufs, to print a large buffer
   line by line instead of all at once.

   There are users in production kernels that have a large data dump
   that originally used printk() directly, but the data dump was larger
   than what printk() allowed as a single print.

   Using seq_buf() to do the printing fixes that.

 - Add /sys/kernel/tracing/touched_functions that shows all functions
   that was every traced by ftrace or a direct trampoline. This is used
   for debugging issues where a traced function could have caused a
   crash by a bpf program or live patching.

 - Add a "fields" option that is similar to "raw" but outputs the fields
   of the events. It's easier to read by humans.

 - Some minor fixes and clean ups.

* tag 'trace-v6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (41 commits)
  ring-buffer: Sync IRQ works before buffer destruction
  tracing: Add missing spaces in trace_print_hex_seq()
  ring-buffer: Ensure proper resetting of atomic variables in ring_buffer_reset_online_cpus
  recordmcount: Fix memory leaks in the uwrite function
  tracing/user_events: Limit max fault-in attempts
  tracing/user_events: Prevent same address and bit per process
  tracing/user_events: Ensure bit is cleared on unregister
  tracing/user_events: Ensure write index cannot be negative
  seq_buf: Add seq_buf_do_printk() helper
  tracing: Fix print_fields() for __dyn_loc/__rel_loc
  tracing/user_events: Set event filter_type from type
  ring-buffer: Clearly check null ptr returned by rb_set_head_page()
  tracing: Unbreak user events
  tracing/user_events: Use print_format_fields() for trace output
  tracing/user_events: Align structs with tabs for readability
  tracing/user_events: Limit global user_event count
  tracing/user_events: Charge event allocs to cgroups
  tracing/user_events: Update documentation for ABI
  tracing/user_events: Use write ABI in example
  tracing/user_events: Add ABI self-test
  ...

1 files changed, 46 insertions, 5 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 08155f652554..76973a70ab9d 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -45,6 +45,9 @@
 #include "trace_output.h"
 #include "trace_stat.h"
 
+/* Flags that do not get reset */
+#define FTRACE_NOCLEAR_FLAGS	(FTRACE_FL_DISABLED | FTRACE_FL_TOUCHED)
+
 #define FTRACE_INVALID_FUNCTION		"__ftrace_invalid_address__"
 
 #define FTRACE_WARN_ON(cond)			\
@@ -2256,7 +2259,7 @@ static int ftrace_check_record(struct dyn_ftrace *rec, bool enable, bool update)
 		flag ^= rec->flags & FTRACE_FL_ENABLED;
 
 		if (update) {
-			rec->flags |= FTRACE_FL_ENABLED;
+			rec->flags |= FTRACE_FL_ENABLED | FTRACE_FL_TOUCHED;
 			if (flag & FTRACE_FL_REGS) {
 				if (rec->flags & FTRACE_FL_REGS)
 					rec->flags |= FTRACE_FL_REGS_EN;
@@ -2326,7 +2329,7 @@ static int ftrace_check_record(struct dyn_ftrace *rec, bool enable, bool update)
 	if (update) {
 		/* If there's no more users, clear all flags */
 		if (!ftrace_rec_count(rec))
-			rec->flags &= FTRACE_FL_DISABLED;
+			rec->flags &= FTRACE_NOCLEAR_FLAGS;
 		else
 			/*
 			 * Just disable the record, but keep the ops TRAMP
@@ -3147,7 +3150,7 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command)
 		struct dyn_ftrace *rec;
 
 		do_for_each_ftrace_rec(pg, rec) {
-			if (FTRACE_WARN_ON_ONCE(rec->flags & ~FTRACE_FL_DISABLED))
+			if (FTRACE_WARN_ON_ONCE(rec->flags & ~FTRACE_NOCLEAR_FLAGS))
 				pr_warn("  %pS flags:%lx\n",
 					(void *)rec->ip, rec->flags);
 		} while_for_each_ftrace_rec();
@@ -3598,7 +3601,10 @@ t_func_next(struct seq_file *m, loff_t *pos)
 		     !ftrace_lookup_ip(iter->hash, rec->ip)) ||
 
 		    ((iter->flags & FTRACE_ITER_ENABLED) &&
-		     !(rec->flags & FTRACE_FL_ENABLED))) {
+		     !(rec->flags & FTRACE_FL_ENABLED)) ||
+
+		    ((iter->flags & FTRACE_ITER_TOUCHED) &&
+		     !(rec->flags & FTRACE_FL_TOUCHED))) {
 
 			rec = NULL;
 			goto retry;
@@ -3857,7 +3863,7 @@ static int t_show(struct seq_file *m, void *v)
 		return 0;
 	}
 
-	if (iter->flags & FTRACE_ITER_ENABLED) {
+	if (iter->flags & (FTRACE_ITER_ENABLED | FTRACE_ITER_TOUCHED)) {
 		struct ftrace_ops *ops;
 
 		seq_printf(m, " (%ld)%s%s%s%s",
@@ -3959,6 +3965,31 @@ ftrace_enabled_open(struct inode *inode, struct file *file)
 	return 0;
 }
 
+static int
+ftrace_touched_open(struct inode *inode, struct file *file)
+{
+	struct ftrace_iterator *iter;
+
+	/*
+	 * This shows us what functions have ever been enabled
+	 * (traced, direct, patched, etc). Not sure if we want lockdown
+	 * to hide such critical information for an admin.
+	 * Although, perhaps it can show information we don't
+	 * want people to see, but if something had traced
+	 * something, we probably want to know about it.
+	 */
+
+	iter = __seq_open_private(file, &show_ftrace_seq_ops, sizeof(*iter));
+	if (!iter)
+		return -ENOMEM;
+
+	iter->pg = ftrace_pages_start;
+	iter->flags = FTRACE_ITER_TOUCHED;
+	iter->ops = &global_ops;
+
+	return 0;
+}
+
 /**
  * ftrace_regex_open - initialize function tracer filter files
  * @ops: The ftrace_ops that hold the hash filters
@@ -5872,6 +5903,13 @@ static const struct file_operations ftrace_enabled_fops = {
 	.release = seq_release_private,
 };
 
+static const struct file_operations ftrace_touched_fops = {
+	.open = ftrace_touched_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = seq_release_private,
+};
+
 static const struct file_operations ftrace_filter_fops = {
 	.open = ftrace_filter_open,
 	.read = seq_read,
@@ -6336,6 +6374,9 @@ static __init int ftrace_init_dyn_tracefs(struct dentry *d_tracer)
 	trace_create_file("enabled_functions", TRACE_MODE_READ,
 			d_tracer, NULL, &ftrace_enabled_fops);
 
+	trace_create_file("touched_functions", TRACE_MODE_READ,
+			d_tracer, NULL, &ftrace_touched_fops);
+
 	ftrace_create_filter_files(&global_ops, d_tracer);
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER