tracing cleanups for v6.10:

- Removed unused ftrace_direct_funcs variables
 
 - Fix a possible NULL pointer dereference race in eventfs
 
 - Update do_div() usage in trace event benchmark test
 
 - Speedup direct function registration with asynchronous RCU callback.
   The synchronization was done in the registration code and this
   caused delays when registering direct callbacks. Move the freeing
   to a call_rcu() that will prevent delaying of the registering.
 
 - Replace simple_strtoul() usage with kstrtoul()
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Merge tag 'trace-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing updates from Steven Rostedt:

 - Remove unused ftrace_direct_funcs variables

 - Fix a possible NULL pointer dereference race in eventfs

 - Update do_div() usage in trace event benchmark test

 - Speedup direct function registration with asynchronous RCU callback.

   The synchronization was done in the registration code and this caused
   delays when registering direct callbacks. Move the freeing to a
   call_rcu() that will prevent delaying of the registering.

 - Replace simple_strtoul() usage with kstrtoul()

* tag 'trace-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  eventfs: Fix a possible null pointer dereference in eventfs_find_events()
  ftrace: Fix possible use-after-free issue in ftrace_location()
  ftrace: Remove unused global 'ftrace_direct_func_count'
  ftrace: Remove unused list 'ftrace_direct_funcs'
  tracing: Improve benchmark test performance by using do_div()
  ftrace: Use asynchronous grace period for register_ftrace_direct()
  ftrace: Replaces simple_strtoul in ftrace

fs/tracefs/event_inode.c

@@ -345,10 +345,9 @@ static struct eventfs_inode *eventfs_find_events(struct dentry *dentry)
 		 * If the ei is being freed, the ownership of the children
 		 * doesn't matter.
 		 */
-		if (ei->is_freed) {
-			ei = NULL;
-			break;
-		}
+		if (ei->is_freed)
+			return NULL;
+
 		// Walk upwards until you find the events inode
 	} while (!ei->is_events);
 

include/linux/ftrace.h

@@ -83,7 +83,6 @@ static inline void early_trace_init(void) { }
 
 struct module;
 struct ftrace_hash;
-struct ftrace_direct_func;
 
 #if defined(CONFIG_FUNCTION_TRACER) && defined(CONFIG_MODULES) && \
 	defined(CONFIG_DYNAMIC_FTRACE)
@@ -414,7 +413,6 @@ struct ftrace_func_entry {
 };
 
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
-extern int ftrace_direct_func_count;
 unsigned long ftrace_find_rec_direct(unsigned long ip);
 int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr);
 int unregister_ftrace_direct(struct ftrace_ops *ops, unsigned long addr,
@@ -426,7 +424,6 @@ void ftrace_stub_direct_tramp(void);
 
 #else
 struct ftrace_ops;
-# define ftrace_direct_func_count 0
 static inline unsigned long ftrace_find_rec_direct(unsigned long ip)
 {
 	return 0;

kernel/trace/fgraph.c

@@ -125,17 +125,6 @@ int function_graph_enter(unsigned long ret, unsigned long func,
 {
 	struct ftrace_graph_ent trace;
 
-#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
-	/*
-	 * Skip graph tracing if the return location is served by direct trampoline,
-	 * since call sequence and return addresses are unpredictable anyway.
-	 * Ex: BPF trampoline may call original function and may skip frame
-	 * depending on type of BPF programs attached.
-	 */
-	if (ftrace_direct_func_count &&
-	    ftrace_find_rec_direct(ret - MCOUNT_INSN_SIZE))
-		return -EBUSY;
-#endif
 	trace.func = func;
 	trace.depth = ++current->curr_ret_depth;
 

kernel/trace/ftrace.c

@@ -1595,12 +1595,15 @@ static struct dyn_ftrace *lookup_rec(unsigned long start, unsigned long end)
 unsigned long ftrace_location_range(unsigned long start, unsigned long end)
 {
 	struct dyn_ftrace *rec;
+	unsigned long ip = 0;
 
+	rcu_read_lock();
 	rec = lookup_rec(start, end);
 	if (rec)
-		return rec->ip;
+		ip = rec->ip;
+	rcu_read_unlock();
 
-	return 0;
+	return ip;
 }
 
 /**
@@ -1614,25 +1617,22 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end)
  */
 unsigned long ftrace_location(unsigned long ip)
 {
-	struct dyn_ftrace *rec;
+	unsigned long loc;
 	unsigned long offset;
 	unsigned long size;
 
-	rec = lookup_rec(ip, ip);
-	if (!rec) {
+	loc = ftrace_location_range(ip, ip);
+	if (!loc) {
 		if (!kallsyms_lookup_size_offset(ip, &size, &offset))
 			goto out;
 
 		/* map sym+0 to __fentry__ */
 		if (!offset)
-			rec = lookup_rec(ip, ip + size - 1);
+			loc = ftrace_location_range(ip, ip + size - 1);
 	}
 
-	if (rec)
-		return rec->ip;
-
 out:
-	return 0;
+	return loc;
 }
 
 /**
@@ -2538,7 +2538,6 @@ ftrace_find_unique_ops(struct dyn_ftrace *rec)
 /* Protected by rcu_tasks for reading, and direct_mutex for writing */
 static struct ftrace_hash __rcu *direct_functions = EMPTY_HASH;
 static DEFINE_MUTEX(direct_mutex);
-int ftrace_direct_func_count;
 
 /*
  * Search the direct_functions hash to see if the given instruction pointer
@@ -4201,12 +4200,12 @@ static int
 add_rec_by_index(struct ftrace_hash *hash, struct ftrace_glob *func_g,
 		 int clear_filter)
 {
-	long index = simple_strtoul(func_g->search, NULL, 0);
+	long index;
 	struct ftrace_page *pg;
 	struct dyn_ftrace *rec;
 
 	/* The index starts at 1 */
-	if (--index < 0)
+	if (kstrtoul(func_g->search, 0, &index) || --index < 0)
 		return 0;
 
 	do_for_each_ftrace_rec(pg, rec) {
@@ -5317,14 +5316,6 @@ ftrace_set_addr(struct ftrace_ops *ops, unsigned long *ips, unsigned int cnt,
 
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 
-struct ftrace_direct_func {
-	struct list_head	next;
-	unsigned long		addr;
-	int			count;
-};
-
-static LIST_HEAD(ftrace_direct_funcs);
-
 static int register_ftrace_function_nolock(struct ftrace_ops *ops);
 
 /*
@@ -5365,6 +5356,13 @@ static void remove_direct_functions_hash(struct ftrace_hash *hash, unsigned long
 	}
 }
 
+static void register_ftrace_direct_cb(struct rcu_head *rhp)
+{
+	struct ftrace_hash *fhp = container_of(rhp, struct ftrace_hash, rcu);
+
+	free_ftrace_hash(fhp);
+}
+
 /**
  * register_ftrace_direct - Call a custom trampoline directly
  * for multiple functions registered in @ops
@@ -5463,10 +5461,8 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
  out_unlock:
 	mutex_unlock(&direct_mutex);
 
-	if (free_hash && free_hash != EMPTY_HASH) {
-		synchronize_rcu_tasks();
-		free_ftrace_hash(free_hash);
-	}
+	if (free_hash && free_hash != EMPTY_HASH)
+		call_rcu_tasks(&free_hash->rcu, register_ftrace_direct_cb);
 
 	if (new_hash)
 		free_ftrace_hash(new_hash);
@@ -5816,9 +5812,8 @@ __setup("ftrace_graph_notrace=", set_graph_notrace_function);
 
 static int __init set_graph_max_depth_function(char *str)
 {
-	if (!str)
+	if (!str || kstrtouint(str, 0, &fgraph_max_depth))
 		return 0;
-	fgraph_max_depth = simple_strtoul(str, NULL, 0);
 	return 1;
 }
 __setup("ftrace_graph_max_depth=", set_graph_max_depth_function);
@@ -6595,6 +6590,8 @@ static int ftrace_process_locs(struct module *mod,
 	/* We should have used all pages unless we skipped some */
 	if (pg_unuse) {
 		WARN_ON(!skipped);
+		/* Need to synchronize with ftrace_location_range() */
+		synchronize_rcu();
 		ftrace_free_pages(pg_unuse);
 	}
 	return ret;
@@ -6808,6 +6805,9 @@ void ftrace_release_mod(struct module *mod)
  out_unlock:
 	mutex_unlock(&ftrace_lock);
 
+	/* Need to synchronize with ftrace_location_range() */
+	if (tmp_page)
+		synchronize_rcu();
 	for (pg = tmp_page; pg; pg = tmp_page) {
 
 		/* Needs to be called outside of ftrace_lock */
@@ -7141,6 +7141,7 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr)
 	unsigned long start = (unsigned long)(start_ptr);
 	unsigned long end = (unsigned long)(end_ptr);
 	struct ftrace_page **last_pg = &ftrace_pages_start;
+	struct ftrace_page *tmp_page = NULL;
 	struct ftrace_page *pg;
 	struct dyn_ftrace *rec;
 	struct dyn_ftrace key;
@@ -7182,12 +7183,8 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr)
 		ftrace_update_tot_cnt--;
 		if (!pg->index) {
 			*last_pg = pg->next;
-			if (pg->records) {
-				free_pages((unsigned long)pg->records, pg->order);
-				ftrace_number_of_pages -= 1 << pg->order;
-			}
-			ftrace_number_of_groups--;
-			kfree(pg);
+			pg->next = tmp_page;
+			tmp_page = pg;
 			pg = container_of(last_pg, struct ftrace_page, next);
 			if (!(*last_pg))
 				ftrace_pages = pg;
@@ -7204,6 +7201,11 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr)
 		clear_func_from_hashes(func);
 		kfree(func);
 	}
+	/* Need to synchronize with ftrace_location_range() */
+	if (tmp_page) {
+		synchronize_rcu();
+		ftrace_free_pages(tmp_page);
+	}
 }
 
 void __init ftrace_free_init_mem(void)

kernel/trace/trace_benchmark.c

@@ -104,7 +104,7 @@ static void trace_do_benchmark(void)
 		stddev = 0;
 
 	delta = bm_total;
-	delta = div64_u64(delta, bm_cnt);
+	do_div(delta, (u32)bm_cnt);
 	avg = delta;
 
 	if (stddev > 0) {