Merge tag 'trace-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing updates from Steven Rostedt:

 - Deprecate auto-mounting tracefs to /sys/kernel/debug/tracing

   When tracefs was first introduced back in 2014, the directory
   /sys/kernel/tracing was added and is the designated location to mount
   tracefs. To keep backward compatibility, tracefs was auto-mounted in
   /sys/kernel/debug/tracing as well.

   All distros now mount tracefs on /sys/kernel/tracing. Having it seen
   in two different locations has lead to various issues and
   inconsistencies.

   The VFS folks have to also maintain debugfs_create_automount() for
   this single user.

   It's been over 10 years. Tooling and scripts should start replacing
   the debugfs location with the tracefs one. The reason tracefs was
   created in the first place was to allow access to the tracing
   facilities without the need to configure debugfs into the kernel.
   Using tracefs should now be more robust.

   A new config is created: CONFIG_TRACEFS_AUTOMOUNT_DEPRECATED which is
   default y, so that the kernel is still built with the automount. This
   config allows those that want to remove the automount from debugfs to
   do so.

   When tracefs is accessed from /sys/kernel/debug/tracing, the
   following printk is triggerd:

     pr_warn("NOTICE: Automounting of tracing to debugfs is deprecated and will be removed in 2030\n");

   This gives users another 5 years to fix their scripts.

 - Use queue_rcu_work() instead of call_rcu() for freeing event filters

   The number of filters to be free can be many depending on the number
   of events within an event system. Freeing them from softirq context
   can potentially cause undesired latency. Use the RCU workqueue to
   free them instead.

 - Remove pointless memory barriers in latency code

   Memory barriers were added to some of the latency code a long time
   ago with the idea of "making them visible", but that's not what
   memory barriers are for. They are to synchronize access between
   different variables. There was no synchronization here making them
   pointless.

 - Remove "__attribute__()" from the type field of event format

   When LLVM is used to compile the kernel with CONFIG_DEBUG_INFO_BTF=y
   and PAHOLE_HAS_BTF_TAG=y, some of the format fields get expanded with
   the following:

     field:const char * filename;      offset:24;      size:8; signed:0;

   Turns into:

     field:const char __attribute__((btf_type_tag("user"))) * filename;      offset:24;      size:8; signed:0;

   This confuses parsers. Add code to strip these tags from the strings.

 - Add eprobe config option CONFIG_EPROBE_EVENTS

   Eprobes were added back in 5.15 but were only enabled when another
   probe was enabled (kprobe, fprobe, uprobe, etc). The eprobes had no
   config option of their own. Add one as they should be a separate
   entity.

   It's default y to keep with the old kernels but still has
   dependencies on TRACING and HAVE_REGS_AND_STACK_ACCESS_API.

 - Add eprobe documentation

   When eprobes were added back in 5.15 no documentation was added to
   describe them. This needs to be rectified.

 - Replace open coded cpumask_next_wrap() in move_to_next_cpu()

 - Have preemptirq_delay_run() use off-stack CPU mask

 - Remove obsolete comment about pelt_cfs event

   DECLARE_TRACE() appends "_tp" to trace events now, but the comment
   above pelt_cfs still mentioned appending it manually.

 - Remove EVENT_FILE_FL_SOFT_MODE flag

   The SOFT_MODE flag was required when the soft enabling and disabling
   of trace events was first introduced. But there was a bug with this
   approach as it only worked for a single instance. When multiple users
   required soft disabling and disabling the code was changed to have a
   ref count. The SOFT_MODE flag is now set iff the ref count is non
   zero. This is redundant and just reading the ref count is good
   enough.

 - Fix typo in comment

* tag 'trace-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  Documentation: tracing: Add documentation about eprobes
  tracing: Have eprobes have their own config option
  tracing: Remove "__attribute__()" from the type field of event format
  tracing: Deprecate auto-mounting tracefs in debugfs
  tracing: Fix comment in trace_module_remove_events()
  tracing: Remove EVENT_FILE_FL_SOFT_MODE flag
  tracing: Remove pointless memory barriers
  tracing/sched: Remove obsolete comment on suffixes
  kernel: trace: preemptirq_delay_test: use offstack cpu mask
  tracing: Use queue_rcu_work() to free filters
  tracing: Replace opencoded cpumask_next_wrap() in move_to_next_cpu()

1 files changed, 28 insertions, 21 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7996f26c3f46..b9716178f728 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -936,7 +936,6 @@ int tracing_is_enabled(void)
 	 * return the mirror variable of the state of the ring buffer.
 	 * It's a little racy, but we don't really care.
 	 */
-	smp_rmb();
 	return !global_trace.buffer_disabled;
 }
 
@@ -1107,8 +1106,6 @@ void tracer_tracing_on(struct trace_array *tr)
 	 * important to be fast than accurate.
 	 */
 	tr->buffer_disabled = 0;
-	/* Make the flag seen by readers */
-	smp_wmb();
 }
 
 /**
@@ -1640,8 +1637,6 @@ void tracer_tracing_off(struct trace_array *tr)
 	 * important to be fast than accurate.
 	 */
 	tr->buffer_disabled = 1;
-	/* Make the flag seen by readers */
-	smp_wmb();
 }
 
 /**
@@ -2710,8 +2705,6 @@ void trace_buffered_event_enable(void)
 
 static void enable_trace_buffered_event(void *data)
 {
-	/* Probably not needed, but do it anyway */
-	smp_rmb();
 	this_cpu_dec(trace_buffered_event_cnt);
 }
 
@@ -5931,17 +5924,27 @@ static inline void trace_insert_eval_map_file(struct module *mod,
 			      struct trace_eval_map **start, int len) { }
 #endif /* !CONFIG_TRACE_EVAL_MAP_FILE */
 
-static void trace_insert_eval_map(struct module *mod,
-				  struct trace_eval_map **start, int len)
+static void
+trace_event_update_with_eval_map(struct module *mod,
+				 struct trace_eval_map **start,
+				 int len)
 {
 	struct trace_eval_map **map;
 
-	if (len <= 0)
-		return;
+	/* Always run sanitizer only if btf_type_tag attr exists. */
+	if (len <= 0) {
+		if (!(IS_ENABLED(CONFIG_DEBUG_INFO_BTF) &&
+		      IS_ENABLED(CONFIG_PAHOLE_HAS_BTF_TAG) &&
+		      __has_attribute(btf_type_tag)))
+			return;
+	}
 
 	map = start;
 
-	trace_event_eval_update(map, len);
+	trace_event_update_all(map, len);
+
+	if (len <= 0)
+		return;
 
 	trace_insert_eval_map_file(mod, start, len);
 }
@@ -6297,7 +6300,7 @@ static bool tracer_options_updated;
 static void add_tracer_options(struct trace_array *tr, struct tracer *t)
 {
 	/* Only enable if the directory has been created already. */
-	if (!tr->dir)
+	if (!tr->dir && !(tr->flags & TRACE_ARRAY_FL_GLOBAL))
 		return;
 
 	/* Only create trace option files after update_tracer_options finish */
@@ -8978,13 +8981,13 @@ static inline __init int register_snapshot_cmd(void) { return 0; }
 
 static struct dentry *tracing_get_dentry(struct trace_array *tr)
 {
-	if (WARN_ON(!tr->dir))
-		return ERR_PTR(-ENODEV);
-
 	/* Top directory uses NULL as the parent */
 	if (tr->flags & TRACE_ARRAY_FL_GLOBAL)
 		return NULL;
 
+	if (WARN_ON(!tr->dir))
+		return ERR_PTR(-ENODEV);
+
 	/* All sub buffers have a descriptor */
 	return tr->dir;
 }
@@ -10250,6 +10253,7 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
 	ftrace_init_tracefs(tr, d_tracer);
 }
 
+#ifdef CONFIG_TRACEFS_AUTOMOUNT_DEPRECATED
 static struct vfsmount *trace_automount(struct dentry *mntpt, void *ingore)
 {
 	struct vfsmount *mnt;
@@ -10271,6 +10275,8 @@ static struct vfsmount *trace_automount(struct dentry *mntpt, void *ingore)
 	if (IS_ERR(fc))
 		return ERR_CAST(fc);
 
+	pr_warn("NOTICE: Automounting of tracing to debugfs is deprecated and will be removed in 2030\n");
+
 	ret = vfs_parse_fs_string(fc, "source",
 				  "tracefs", strlen("tracefs"));
 	if (!ret)
@@ -10281,6 +10287,7 @@ static struct vfsmount *trace_automount(struct dentry *mntpt, void *ingore)
 	put_fs_context(fc);
 	return mnt;
 }
+#endif
 
 /**
  * tracing_init_dentry - initialize top level trace array
@@ -10305,6 +10312,7 @@ int tracing_init_dentry(void)
 	if (WARN_ON(!tracefs_initialized()))
 		return -ENODEV;
 
+#ifdef CONFIG_TRACEFS_AUTOMOUNT_DEPRECATED
 	/*
 	 * As there may still be users that expect the tracing
 	 * files to exist in debugfs/tracing, we must automount
@@ -10313,6 +10321,7 @@ int tracing_init_dentry(void)
 	 */
 	tr->dir = debugfs_create_automount("tracing", NULL,
 					   trace_automount, NULL);
+#endif
 
 	return 0;
 }
@@ -10329,7 +10338,7 @@ static void __init eval_map_work_func(struct work_struct *work)
 	int len;
 
 	len = __stop_ftrace_eval_maps - __start_ftrace_eval_maps;
-	trace_insert_eval_map(NULL, __start_ftrace_eval_maps, len);
+	trace_event_update_with_eval_map(NULL, __start_ftrace_eval_maps, len);
 }
 
 static int __init trace_eval_init(void)
@@ -10382,9 +10391,6 @@ bool module_exists(const char *module)
 
 static void trace_module_add_evals(struct module *mod)
 {
-	if (!mod->num_trace_evals)
-		return;
-
 	/*
 	 * Modules with bad taint do not have events created, do
 	 * not bother with enums either.
@@ -10392,7 +10398,8 @@ static void trace_module_add_evals(struct module *mod)
 	if (trace_module_has_bad_taint(mod))
 		return;
 
-	trace_insert_eval_map(mod, mod->trace_evals, mod->num_trace_evals);
+	/* Even if no trace_evals, this need to sanitize field types. */
+	trace_event_update_with_eval_map(mod, mod->trace_evals, mod->num_trace_evals);
 }
 
 #ifdef CONFIG_TRACE_EVAL_MAP_FILE