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, 139 insertions, 0 deletions

diff --git a/tools/perf/util/mem2node.c b/tools/perf/util/mem2node.c
new file mode 100644
index 000000000..51a2292cb
--- /dev/null
+++ b/tools/perf/util/mem2node.c
@@ -0,0 +1,139 @@
+#include <errno.h>
+#include <inttypes.h>
+#include <asm/bug.h>
+#include <linux/bitmap.h>
+#include <linux/kernel.h>
+#include <linux/zalloc.h>
+#include "debug.h"
+#include "env.h"
+#include "mem2node.h"
+
+struct phys_entry {
+	struct rb_node	rb_node;
+	u64	start;
+	u64	end;
+	u64	node;
+};
+
+static void phys_entry__insert(struct phys_entry *entry, struct rb_root *root)
+{
+	struct rb_node **p = &root->rb_node;
+	struct rb_node *parent = NULL;
+	struct phys_entry *e;
+
+	while (*p != NULL) {
+		parent = *p;
+		e = rb_entry(parent, struct phys_entry, rb_node);
+
+		if (entry->start < e->start)
+			p = &(*p)->rb_left;
+		else
+			p = &(*p)->rb_right;
+	}
+
+	rb_link_node(&entry->rb_node, parent, p);
+	rb_insert_color(&entry->rb_node, root);
+}
+
+static void
+phys_entry__init(struct phys_entry *entry, u64 start, u64 bsize, u64 node)
+{
+	entry->start = start;
+	entry->end   = start + bsize;
+	entry->node  = node;
+	RB_CLEAR_NODE(&entry->rb_node);
+}
+
+int mem2node__init(struct mem2node *map, struct perf_env *env)
+{
+	struct memory_node *n, *nodes = &env->memory_nodes[0];
+	struct phys_entry *entries, *tmp_entries;
+	u64 bsize = env->memory_bsize;
+	int i, j = 0, max = 0;
+
+	memset(map, 0x0, sizeof(*map));
+	map->root = RB_ROOT;
+
+	for (i = 0; i < env->nr_memory_nodes; i++) {
+		n = &nodes[i];
+		max += bitmap_weight(n->set, n->size);
+	}
+
+	entries = calloc(max, sizeof(*entries));
+	if (!entries)
+		return -ENOMEM;
+
+	for (i = 0; i < env->nr_memory_nodes; i++) {
+		u64 bit;
+
+		n = &nodes[i];
+
+		for (bit = 0; bit < n->size; bit++) {
+			u64 start;
+
+			if (!test_bit(bit, n->set))
+				continue;
+
+			start = bit * bsize;
+
+			/*
+			 * Merge nearby areas, we walk in order
+			 * through the bitmap, so no need to sort.
+			 */
+			if (j > 0) {
+				struct phys_entry *prev = &entries[j - 1];
+
+				if ((prev->end == start) &&
+				    (prev->node == n->node)) {
+					prev->end += bsize;
+					continue;
+				}
+			}
+
+			phys_entry__init(&entries[j++], start, bsize, n->node);
+		}
+	}
+
+	/* Cut unused entries, due to merging. */
+	tmp_entries = realloc(entries, sizeof(*entries) * j);
+	if (tmp_entries ||
+	    WARN_ONCE(j == 0, "No memory nodes, is CONFIG_MEMORY_HOTPLUG enabled?\n"))
+		entries = tmp_entries;
+
+	for (i = 0; i < j; i++) {
+		pr_debug("mem2node %03" PRIu64 " [0x%016" PRIx64 "-0x%016" PRIx64 "]\n",
+			 entries[i].node, entries[i].start, entries[i].end);
+
+		phys_entry__insert(&entries[i], &map->root);
+	}
+
+	map->entries = entries;
+	return 0;
+}
+
+void mem2node__exit(struct mem2node *map)
+{
+	zfree(&map->entries);
+}
+
+int mem2node__node(struct mem2node *map, u64 addr)
+{
+	struct rb_node **p, *parent = NULL;
+	struct phys_entry *entry;
+
+	p = &map->root.rb_node;
+	while (*p != NULL) {
+		parent = *p;
+		entry = rb_entry(parent, struct phys_entry, rb_node);
+		if (addr < entry->start)
+			p = &(*p)->rb_left;
+		else if (addr >= entry->end)
+			p = &(*p)->rb_right;
+		else
+			goto out;
+	}
+
+	entry = NULL;
+out:
+	return entry ? (int) entry->node : -1;
+}