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, 143 insertions, 0 deletions

diff --git a/tools/perf/util/lock-contention.c b/tools/perf/util/lock-contention.c
new file mode 100644
index 000000000..119a7206f
--- /dev/null
+++ b/tools/perf/util/lock-contention.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "debug.h"
+#include "env.h"
+#include "lock-contention.h"
+#include "machine.h"
+#include "symbol.h"
+
+#include <limits.h>
+#include <string.h>
+
+#include <linux/hash.h>
+#include <linux/zalloc.h>
+
+#define __lockhashfn(key)	hash_long((unsigned long)key, LOCKHASH_BITS)
+#define lockhashentry(key)	(lockhash_table + __lockhashfn((key)))
+
+struct callstack_filter {
+	struct list_head list;
+	char name[];
+};
+
+static LIST_HEAD(callstack_filters);
+struct hlist_head *lockhash_table;
+
+int parse_call_stack(const struct option *opt __maybe_unused, const char *str,
+		     int unset __maybe_unused)
+{
+	char *s, *tmp, *tok;
+	int ret = 0;
+
+	s = strdup(str);
+	if (s == NULL)
+		return -1;
+
+	for (tok = strtok_r(s, ", ", &tmp); tok; tok = strtok_r(NULL, ", ", &tmp)) {
+		struct callstack_filter *entry;
+
+		entry = malloc(sizeof(*entry) + strlen(tok) + 1);
+		if (entry == NULL) {
+			pr_err("Memory allocation failure\n");
+			free(s);
+			return -1;
+		}
+
+		strcpy(entry->name, tok);
+		list_add_tail(&entry->list, &callstack_filters);
+	}
+
+	free(s);
+	return ret;
+}
+
+bool needs_callstack(void)
+{
+	return !list_empty(&callstack_filters);
+}
+
+struct lock_stat *lock_stat_find(u64 addr)
+{
+	struct hlist_head *entry = lockhashentry(addr);
+	struct lock_stat *ret;
+
+	hlist_for_each_entry(ret, entry, hash_entry) {
+		if (ret->addr == addr)
+			return ret;
+	}
+	return NULL;
+}
+
+struct lock_stat *lock_stat_findnew(u64 addr, const char *name, int flags)
+{
+	struct hlist_head *entry = lockhashentry(addr);
+	struct lock_stat *ret, *new;
+
+	hlist_for_each_entry(ret, entry, hash_entry) {
+		if (ret->addr == addr)
+			return ret;
+	}
+
+	new = zalloc(sizeof(struct lock_stat));
+	if (!new)
+		goto alloc_failed;
+
+	new->addr = addr;
+	new->name = strdup(name);
+	if (!new->name) {
+		free(new);
+		goto alloc_failed;
+	}
+
+	new->flags = flags;
+	new->wait_time_min = ULLONG_MAX;
+
+	hlist_add_head(&new->hash_entry, entry);
+	return new;
+
+alloc_failed:
+	pr_err("memory allocation failed\n");
+	return NULL;
+}
+
+bool match_callstack_filter(struct machine *machine, u64 *callstack, int max_stack_depth)
+{
+	struct map *kmap;
+	struct symbol *sym;
+	u64 ip;
+	uint16_t e_machine = perf_env__e_machine(machine->env, /*e_flags=*/NULL);
+	bool is_powerpc = e_machine == EM_PPC64 || e_machine == EM_PPC;
+
+	if (list_empty(&callstack_filters))
+		return true;
+
+	for (int i = 0; i < max_stack_depth; i++) {
+		struct callstack_filter *filter;
+
+		/*
+		 * In powerpc, the callchain saved by kernel always includes
+		 * first three entries as the NIP (next instruction pointer),
+		 * LR (link register), and the contents of LR save area in the
+		 * second stack frame. In certain scenarios its possible to have
+		 * invalid kernel instruction addresses in either LR or the second
+		 * stack frame's LR. In that case, kernel will store that address as
+		 * zero.
+		 *
+		 * The below check will continue to look into callstack,
+		 * incase first or second callstack index entry has 0
+		 * address for powerpc.
+		 */
+		if (!callstack || (!callstack[i] && (!is_powerpc || (i != 1 && i != 2))))
+			break;
+
+		ip = callstack[i];
+		sym = machine__find_kernel_symbol(machine, ip, &kmap);
+		if (sym == NULL)
+			continue;
+
+		list_for_each_entry(filter, &callstack_filters, list) {
+			if (strstr(sym->name, filter->name))
+				return true;
+		}
+	}
+	return false;
+}