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, 332 insertions, 0 deletions

diff --git a/tools/perf/util/block-range.c b/tools/perf/util/block-range.c
new file mode 100644
index 000000000..7c559fcfd
--- /dev/null
+++ b/tools/perf/util/block-range.c
@@ -0,0 +1,332 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "block-range.h"
+#include "annotate.h"
+#include <assert.h>
+#include <stdlib.h>
+
+static struct {
+	struct rb_root root;
+	u64 blocks;
+} block_ranges;
+
+static void block_range__debug(void)
+{
+#ifndef NDEBUG
+	struct rb_node *rb;
+	u64 old = 0; /* NULL isn't executable */
+
+	for (rb = rb_first(&block_ranges.root); rb; rb = rb_next(rb)) {
+		struct block_range *entry = rb_entry(rb, struct block_range, node);
+
+		assert(old < entry->start);
+		assert(entry->start <= entry->end); /* single instruction block; jump to a jump */
+
+		old = entry->end;
+	}
+#endif
+}
+
+struct block_range *block_range__find(u64 addr)
+{
+	struct rb_node **p = &block_ranges.root.rb_node;
+	struct rb_node *parent = NULL;
+	struct block_range *entry;
+
+	while (*p != NULL) {
+		parent = *p;
+		entry = rb_entry(parent, struct block_range, node);
+
+		if (addr < entry->start)
+			p = &parent->rb_left;
+		else if (addr > entry->end)
+			p = &parent->rb_right;
+		else
+			return entry;
+	}
+
+	return NULL;
+}
+
+static inline void rb_link_left_of_node(struct rb_node *left, struct rb_node *node)
+{
+	struct rb_node **p = &node->rb_left;
+	while (*p) {
+		node = *p;
+		p = &node->rb_right;
+	}
+	rb_link_node(left, node, p);
+}
+
+static inline void rb_link_right_of_node(struct rb_node *right, struct rb_node *node)
+{
+	struct rb_node **p = &node->rb_right;
+	while (*p) {
+		node = *p;
+		p = &node->rb_left;
+	}
+	rb_link_node(right, node, p);
+}
+
+/**
+ * block_range__create
+ * @start: branch target starting this basic block
+ * @end:   branch ending this basic block
+ *
+ * Create all the required block ranges to precisely span the given range.
+ */
+struct block_range_iter block_range__create(u64 start, u64 end)
+{
+	struct rb_node **p = &block_ranges.root.rb_node;
+	struct rb_node *n, *parent = NULL;
+	struct block_range *next, *entry = NULL;
+	struct block_range_iter iter = { NULL, NULL };
+
+	while (*p != NULL) {
+		parent = *p;
+		entry = rb_entry(parent, struct block_range, node);
+
+		if (start < entry->start)
+			p = &parent->rb_left;
+		else if (start > entry->end)
+			p = &parent->rb_right;
+		else
+			break;
+	}
+
+	/*
+	 * Didn't find anything.. there's a hole at @start, however @end might
+	 * be inside/behind the next range.
+	 */
+	if (!*p) {
+		if (!entry) /* tree empty */
+			goto do_whole;
+
+		/*
+		 * If the last node is before, advance one to find the next.
+		 */
+		n = parent;
+		if (entry->end < start) {
+			n = rb_next(n);
+			if (!n)
+				goto do_whole;
+		}
+		next = rb_entry(n, struct block_range, node);
+
+		if (next->start <= end) { /* add head: [start...][n->start...] */
+			struct block_range *head = malloc(sizeof(struct block_range));
+			if (!head)
+				return iter;
+
+			*head = (struct block_range){
+				.start		= start,
+				.end		= next->start - 1,
+				.is_target	= 1,
+				.is_branch	= 0,
+			};
+
+			rb_link_left_of_node(&head->node, &next->node);
+			rb_insert_color(&head->node, &block_ranges.root);
+			block_range__debug();
+
+			iter.start = head;
+			goto do_tail;
+		}
+
+do_whole:
+		/*
+		 * The whole [start..end] range is non-overlapping.
+		 */
+		entry = malloc(sizeof(struct block_range));
+		if (!entry)
+			return iter;
+
+		*entry = (struct block_range){
+			.start		= start,
+			.end		= end,
+			.is_target	= 1,
+			.is_branch	= 1,
+		};
+
+		rb_link_node(&entry->node, parent, p);
+		rb_insert_color(&entry->node, &block_ranges.root);
+		block_range__debug();
+
+		iter.start = entry;
+		iter.end   = entry;
+		goto done;
+	}
+
+	/*
+	 * We found a range that overlapped with ours, split if needed.
+	 */
+	if (entry->start < start) { /* split: [e->start...][start...] */
+		struct block_range *head = malloc(sizeof(struct block_range));
+		if (!head)
+			return iter;
+
+		*head = (struct block_range){
+			.start		= entry->start,
+			.end		= start - 1,
+			.is_target	= entry->is_target,
+			.is_branch	= 0,
+
+			.coverage	= entry->coverage,
+			.entry		= entry->entry,
+		};
+
+		entry->start		= start;
+		entry->is_target	= 1;
+		entry->entry		= 0;
+
+		rb_link_left_of_node(&head->node, &entry->node);
+		rb_insert_color(&head->node, &block_ranges.root);
+		block_range__debug();
+
+	} else if (entry->start == start)
+		entry->is_target = 1;
+
+	iter.start = entry;
+
+do_tail:
+	/*
+	 * At this point we've got: @iter.start = [@start...] but @end can still be
+	 * inside or beyond it.
+	 */
+	entry = iter.start;
+	for (;;) {
+		/*
+		 * If @end is inside @entry, split.
+		 */
+		if (end < entry->end) { /* split: [...end][...e->end] */
+			struct block_range *tail = malloc(sizeof(struct block_range));
+			if (!tail)
+				return iter;
+
+			*tail = (struct block_range){
+				.start		= end + 1,
+				.end		= entry->end,
+				.is_target	= 0,
+				.is_branch	= entry->is_branch,
+
+				.coverage	= entry->coverage,
+				.taken		= entry->taken,
+				.pred		= entry->pred,
+			};
+
+			entry->end		= end;
+			entry->is_branch	= 1;
+			entry->taken		= 0;
+			entry->pred		= 0;
+
+			rb_link_right_of_node(&tail->node, &entry->node);
+			rb_insert_color(&tail->node, &block_ranges.root);
+			block_range__debug();
+
+			iter.end = entry;
+			goto done;
+		}
+
+		/*
+		 * If @end matches @entry, done
+		 */
+		if (end == entry->end) {
+			entry->is_branch = 1;
+			iter.end = entry;
+			goto done;
+		}
+
+		next = block_range__next(entry);
+		if (!next)
+			goto add_tail;
+
+		/*
+		 * If @end is in beyond @entry but not inside @next, add tail.
+		 */
+		if (end < next->start) { /* add tail: [...e->end][...end] */
+			struct block_range *tail;
+add_tail:
+			tail = malloc(sizeof(struct block_range));
+			if (!tail)
+				return iter;
+
+			*tail = (struct block_range){
+				.start		= entry->end + 1,
+				.end		= end,
+				.is_target	= 0,
+				.is_branch	= 1,
+			};
+
+			rb_link_right_of_node(&tail->node, &entry->node);
+			rb_insert_color(&tail->node, &block_ranges.root);
+			block_range__debug();
+
+			iter.end = tail;
+			goto done;
+		}
+
+		/*
+		 * If there is a hole between @entry and @next, fill it.
+		 */
+		if (entry->end + 1 != next->start) {
+			struct block_range *hole = malloc(sizeof(struct block_range));
+			if (!hole)
+				return iter;
+
+			*hole = (struct block_range){
+				.start		= entry->end + 1,
+				.end		= next->start - 1,
+				.is_target	= 0,
+				.is_branch	= 0,
+			};
+
+			rb_link_left_of_node(&hole->node, &next->node);
+			rb_insert_color(&hole->node, &block_ranges.root);
+			block_range__debug();
+		}
+
+		entry = next;
+	}
+
+done:
+	assert(iter.start->start == start && iter.start->is_target);
+	assert(iter.end->end == end && iter.end->is_branch);
+
+	block_ranges.blocks++;
+
+	return iter;
+}
+
+
+/*
+ * Compute coverage as:
+ *
+ *    br->coverage / br->sym->max_coverage
+ *
+ * This ensures each symbol has a 100% spot, to reflect that each symbol has a
+ * most covered section.
+ *
+ * Returns [0-1] for coverage and -1 if we had no data what so ever or the
+ * symbol does not exist.
+ */
+double block_range__coverage(struct block_range *br)
+{
+	struct symbol *sym;
+	struct annotated_branch *branch;
+
+	if (!br) {
+		if (block_ranges.blocks)
+			return 0;
+
+		return -1;
+	}
+
+	sym = br->sym;
+	if (!sym)
+		return -1;
+
+	branch = symbol__annotation(sym)->branch;
+	if (!branch)
+		return -1;
+
+	return (double)br->coverage / branch->max_coverage;
+}