ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 369 insertions, 0 deletions

diff --git a/lib/interval_tree_test.c b/lib/interval_tree_test.c
new file mode 100644
index 000000000..b0b07270c
--- /dev/null
+++ b/lib/interval_tree_test.c
@@ -0,0 +1,369 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/interval_tree.h>
+#include <linux/prandom.h>
+#include <linux/slab.h>
+#include <linux/printk.h>
+#include <asm/timex.h>
+#include <linux/bitmap.h>
+#include <linux/maple_tree.h>
+
+#define __param(type, name, init, msg)		\
+	static type name = init;		\
+	module_param(name, type, 0444);		\
+	MODULE_PARM_DESC(name, msg);
+
+__param(int, nnodes, 100, "Number of nodes in the interval tree");
+__param(int, perf_loops, 1000, "Number of iterations modifying the tree");
+
+__param(int, nsearches, 100, "Number of searches to the interval tree");
+__param(int, search_loops, 1000, "Number of iterations searching the tree");
+__param(bool, search_all, false, "Searches will iterate all nodes in the tree");
+
+__param(uint, max_endpoint, ~0, "Largest value for the interval's endpoint");
+__param(ullong, seed, 3141592653589793238ULL, "Random seed");
+
+static struct rb_root_cached root = RB_ROOT_CACHED;
+static struct interval_tree_node *nodes = NULL;
+static u32 *queries = NULL;
+
+static struct rnd_state rnd;
+
+static inline unsigned long
+search(struct rb_root_cached *root, unsigned long start, unsigned long last)
+{
+	struct interval_tree_node *node;
+	unsigned long results = 0;
+
+	for (node = interval_tree_iter_first(root, start, last); node;
+	     node = interval_tree_iter_next(node, start, last))
+		results++;
+	return results;
+}
+
+static void init(void)
+{
+	int i;
+
+	for (i = 0; i < nnodes; i++) {
+		u32 b = (prandom_u32_state(&rnd) >> 4) % max_endpoint;
+		u32 a = (prandom_u32_state(&rnd) >> 4) % b;
+
+		nodes[i].start = a;
+		nodes[i].last = b;
+	}
+
+	/*
+	 * Limit the search scope to what the user defined.
+	 * Otherwise we are merely measuring empty walks,
+	 * which is pointless.
+	 */
+	for (i = 0; i < nsearches; i++)
+		queries[i] = (prandom_u32_state(&rnd) >> 4) % max_endpoint;
+}
+
+static int basic_check(void)
+{
+	int i, j;
+	cycles_t time1, time2, time;
+
+	printk(KERN_ALERT "interval tree insert/remove");
+
+	init();
+
+	time1 = get_cycles();
+
+	for (i = 0; i < perf_loops; i++) {
+		for (j = 0; j < nnodes; j++)
+			interval_tree_insert(nodes + j, &root);
+		for (j = 0; j < nnodes; j++)
+			interval_tree_remove(nodes + j, &root);
+	}
+
+	time2 = get_cycles();
+	time = time2 - time1;
+
+	time = div_u64(time, perf_loops);
+	printk(" -> %llu cycles\n", (unsigned long long)time);
+
+	return 0;
+}
+
+static int search_check(void)
+{
+	int i, j;
+	unsigned long results;
+	cycles_t time1, time2, time;
+
+	printk(KERN_ALERT "interval tree search");
+
+	init();
+
+	for (j = 0; j < nnodes; j++)
+		interval_tree_insert(nodes + j, &root);
+
+	time1 = get_cycles();
+
+	results = 0;
+	for (i = 0; i < search_loops; i++)
+		for (j = 0; j < nsearches; j++) {
+			unsigned long start = search_all ? 0 : queries[j];
+			unsigned long last = search_all ? max_endpoint : queries[j];
+
+			results += search(&root, start, last);
+		}
+
+	time2 = get_cycles();
+	time = time2 - time1;
+
+	time = div_u64(time, search_loops);
+	results = div_u64(results, search_loops);
+	printk(" -> %llu cycles (%lu results)\n",
+	       (unsigned long long)time, results);
+
+	for (j = 0; j < nnodes; j++)
+		interval_tree_remove(nodes + j, &root);
+
+	return 0;
+}
+
+static int intersection_range_check(void)
+{
+	int i, j, k;
+	unsigned long start, last;
+	struct interval_tree_node *node;
+	unsigned long *intxn1;
+	unsigned long *intxn2;
+
+	printk(KERN_ALERT "interval tree iteration\n");
+
+	intxn1 = bitmap_alloc(nnodes, GFP_KERNEL);
+	if (!intxn1) {
+		WARN_ONCE(1, "Failed to allocate intxn1\n");
+		return -ENOMEM;
+	}
+
+	intxn2 = bitmap_alloc(nnodes, GFP_KERNEL);
+	if (!intxn2) {
+		WARN_ONCE(1, "Failed to allocate intxn2\n");
+		bitmap_free(intxn1);
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < search_loops; i++) {
+		/* Initialize interval tree for each round */
+		init();
+		for (j = 0; j < nnodes; j++)
+			interval_tree_insert(nodes + j, &root);
+
+		/* Let's try nsearches different ranges */
+		for (k = 0; k < nsearches; k++) {
+			/* Try whole range once */
+			if (!k) {
+				start = 0UL;
+				last = ULONG_MAX;
+			} else {
+				last = (prandom_u32_state(&rnd) >> 4) % max_endpoint;
+				start = (prandom_u32_state(&rnd) >> 4) % last;
+			}
+
+			/* Walk nodes to mark intersection nodes */
+			bitmap_zero(intxn1, nnodes);
+			for (j = 0; j < nnodes; j++) {
+				node = nodes + j;
+
+				if (start <= node->last && last >= node->start)
+					bitmap_set(intxn1, j, 1);
+			}
+
+			/* Iterate tree to clear intersection nodes */
+			bitmap_zero(intxn2, nnodes);
+			for (node = interval_tree_iter_first(&root, start, last); node;
+			     node = interval_tree_iter_next(node, start, last))
+				bitmap_set(intxn2, node - nodes, 1);
+
+			WARN_ON_ONCE(!bitmap_equal(intxn1, intxn2, nnodes));
+		}
+
+		for (j = 0; j < nnodes; j++)
+			interval_tree_remove(nodes + j, &root);
+	}
+
+	bitmap_free(intxn1);
+	bitmap_free(intxn2);
+	return 0;
+}
+
+#ifdef CONFIG_INTERVAL_TREE_SPAN_ITER
+/*
+ * Helper function to get span of current position from maple tree point of
+ * view.
+ */
+static void mas_cur_span(struct ma_state *mas, struct interval_tree_span_iter *state)
+{
+	unsigned long cur_start;
+	unsigned long cur_last;
+	int is_hole;
+
+	if (mas->status == ma_overflow)
+		return;
+
+	/* walk to current position */
+	state->is_hole = mas_walk(mas) ? 0 : 1;
+
+	cur_start = mas->index < state->first_index ?
+			state->first_index : mas->index;
+
+	/* whether we have followers */
+	do {
+
+		cur_last = mas->last > state->last_index ?
+				state->last_index : mas->last;
+
+		is_hole = mas_next_range(mas, state->last_index) ? 0 : 1;
+
+	} while (mas->status != ma_overflow && is_hole == state->is_hole);
+
+	if (state->is_hole) {
+		state->start_hole = cur_start;
+		state->last_hole = cur_last;
+	} else {
+		state->start_used = cur_start;
+		state->last_used = cur_last;
+	}
+
+	/* advance position for next round */
+	if (mas->status != ma_overflow)
+		mas_set(mas, cur_last + 1);
+}
+
+static int span_iteration_check(void)
+{
+	int i, j, k;
+	unsigned long start, last;
+	struct interval_tree_span_iter span, mas_span;
+
+	DEFINE_MTREE(tree);
+
+	MA_STATE(mas, &tree, 0, 0);
+
+	printk(KERN_ALERT "interval tree span iteration\n");
+
+	for (i = 0; i < search_loops; i++) {
+		/* Initialize interval tree for each round */
+		init();
+		for (j = 0; j < nnodes; j++)
+			interval_tree_insert(nodes + j, &root);
+
+		/* Put all the range into maple tree */
+		mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE);
+		mt_set_in_rcu(&tree);
+
+		for (j = 0; j < nnodes; j++)
+			WARN_ON_ONCE(mtree_store_range(&tree, nodes[j].start,
+					nodes[j].last, nodes + j, GFP_KERNEL));
+
+		/* Let's try nsearches different ranges */
+		for (k = 0; k < nsearches; k++) {
+			/* Try whole range once */
+			if (!k) {
+				start = 0UL;
+				last = ULONG_MAX;
+			} else {
+				last = (prandom_u32_state(&rnd) >> 4) % max_endpoint;
+				start = (prandom_u32_state(&rnd) >> 4) % last;
+			}
+
+			mas_span.first_index = start;
+			mas_span.last_index = last;
+			mas_span.is_hole = -1;
+			mas_set(&mas, start);
+
+			interval_tree_for_each_span(&span, &root, start, last) {
+				mas_cur_span(&mas, &mas_span);
+
+				WARN_ON_ONCE(span.is_hole != mas_span.is_hole);
+
+				if (span.is_hole) {
+					WARN_ON_ONCE(span.start_hole != mas_span.start_hole);
+					WARN_ON_ONCE(span.last_hole != mas_span.last_hole);
+				} else {
+					WARN_ON_ONCE(span.start_used != mas_span.start_used);
+					WARN_ON_ONCE(span.last_used != mas_span.last_used);
+				}
+			}
+
+		}
+
+		WARN_ON_ONCE(mas.status != ma_overflow);
+
+		/* Cleanup maple tree for each round */
+		mtree_destroy(&tree);
+		/* Cleanup interval tree for each round */
+		for (j = 0; j < nnodes; j++)
+			interval_tree_remove(nodes + j, &root);
+	}
+	return 0;
+}
+#else
+static inline int span_iteration_check(void) {return 0; }
+#endif
+
+static int interval_tree_test_init(void)
+{
+	if (nnodes <= 0) {
+		pr_warn("nnodes must be positive\n");
+		return -EINVAL;
+	}
+	if (nsearches <= 0) {
+		pr_warn("nsearches must be positive\n");
+		return -EINVAL;
+	}
+	if (perf_loops <= 0) {
+		pr_warn("perf_loops must be positive\n");
+		return -EINVAL;
+	}
+	if (search_loops <= 0) {
+		pr_warn("search_loops must be positive\n");
+		return -EINVAL;
+	}
+	if (max_endpoint < 2) {
+		pr_warn("max_endpoint must be at least 2\n");
+		return -EINVAL;
+	}
+
+	nodes = kmalloc_objs(struct interval_tree_node, nnodes);
+	if (!nodes)
+		return -ENOMEM;
+
+	queries = kmalloc_array(nsearches, sizeof(int), GFP_KERNEL);
+	if (!queries) {
+		kfree(nodes);
+		return -ENOMEM;
+	}
+
+	prandom_seed_state(&rnd, seed);
+
+	basic_check();
+	search_check();
+	intersection_range_check();
+	span_iteration_check();
+
+	kfree(queries);
+	kfree(nodes);
+
+	return -EAGAIN; /* Fail will directly unload the module */
+}
+
+static void interval_tree_test_exit(void)
+{
+	printk(KERN_ALERT "test exit\n");
+}
+
+module_init(interval_tree_test_init)
+module_exit(interval_tree_test_exit)
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Michel Lespinasse");
+MODULE_DESCRIPTION("Interval Tree test");