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, 114 insertions, 0 deletions

diff --git a/include/trace/perf.h b/include/trace/perf.h
new file mode 100644
index 000000000..348ad1d9b
--- /dev/null
+++ b/include/trace/perf.h
@@ -0,0 +1,114 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#undef TRACE_SYSTEM_VAR
+
+#ifdef CONFIG_PERF_EVENTS
+
+#include "stages/stage6_event_callback.h"
+
+#undef __perf_count
+#define __perf_count(c)	(__count = (c))
+
+#undef __perf_task
+#define __perf_task(t)	(__task = (t))
+
+#undef __DECLARE_EVENT_CLASS
+#define __DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print) \
+static notrace void							\
+do_perf_trace_##call(void *__data, proto)				\
+{									\
+	struct trace_event_call *event_call = __data;			\
+	struct trace_event_data_offsets_##call __maybe_unused __data_offsets;\
+	struct trace_event_raw_##call *entry;				\
+	struct pt_regs *__regs;						\
+	u64 __count = 1;						\
+	struct task_struct *__task = NULL;				\
+	struct hlist_head *head;					\
+	int __entry_size;						\
+	int __data_size;						\
+	int rctx;							\
+									\
+	__data_size = trace_event_get_offsets_##call(&__data_offsets, args); \
+									\
+	head = this_cpu_ptr(event_call->perf_events);			\
+	if (!bpf_prog_array_valid(event_call) &&			\
+	    __builtin_constant_p(!__task) && !__task &&			\
+	    hlist_empty(head))						\
+		return;							\
+									\
+	__entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),\
+			     sizeof(u64));				\
+	__entry_size -= sizeof(u32);					\
+									\
+	entry = perf_trace_buf_alloc(__entry_size, &__regs, &rctx);	\
+	if (!entry)							\
+		return;							\
+									\
+	perf_fetch_caller_regs(__regs);					\
+									\
+	tstruct								\
+									\
+	{ assign; }							\
+									\
+	perf_trace_run_bpf_submit(entry, __entry_size, rctx,		\
+				  event_call, __count, __regs,		\
+				  head, __task);			\
+}
+
+/*
+ * Define unused __count and __task variables to use @args to pass
+ * arguments to do_perf_trace_##call. This is needed because the
+ * macros __perf_count and __perf_task introduce the side-effect to
+ * store copies into those local variables.
+ */
+#undef DECLARE_EVENT_CLASS
+#define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print)	\
+__DECLARE_EVENT_CLASS(call, PARAMS(proto), PARAMS(args), PARAMS(tstruct), \
+		      PARAMS(assign), PARAMS(print))			\
+static notrace void							\
+perf_trace_##call(void *__data, proto)					\
+{									\
+	u64 __count __attribute__((unused));				\
+	struct task_struct *__task __attribute__((unused));		\
+									\
+	guard(preempt_notrace)();					\
+	do_perf_trace_##call(__data, args);				\
+}
+
+#undef DECLARE_EVENT_SYSCALL_CLASS
+#define DECLARE_EVENT_SYSCALL_CLASS(call, proto, args, tstruct, assign, print) \
+__DECLARE_EVENT_CLASS(call, PARAMS(proto), PARAMS(args), PARAMS(tstruct), \
+		      PARAMS(assign), PARAMS(print))			\
+static notrace void							\
+perf_trace_##call(void *__data, proto)					\
+{									\
+	u64 __count __attribute__((unused));				\
+	struct task_struct *__task __attribute__((unused));		\
+									\
+	might_fault();							\
+	guard(preempt_notrace)();					\
+	do_perf_trace_##call(__data, args);				\
+}
+
+/*
+ * This part is compiled out, it is only here as a build time check
+ * to make sure that if the tracepoint handling changes, the
+ * perf probe will fail to compile unless it too is updated.
+ */
+#undef DEFINE_EVENT
+#define DEFINE_EVENT(template, call, proto, args)			\
+static inline void perf_test_probe_##call(void)				\
+{									\
+	check_trace_callback_type_##call(perf_trace_##template);	\
+}
+
+
+#undef DEFINE_EVENT_PRINT
+#define DEFINE_EVENT_PRINT(template, name, proto, args, print)	\
+	DEFINE_EVENT(template, name, PARAMS(proto), PARAMS(args))
+
+#include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
+
+#undef __DECLARE_EVENT_CLASS
+
+#endif /* CONFIG_PERF_EVENTS */