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, 89 insertions, 0 deletions

diff --git a/drivers/android/binder/stats.rs b/drivers/android/binder/stats.rs
new file mode 100644
index 000000000..ec81dc774
--- /dev/null
+++ b/drivers/android/binder/stats.rs
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2025 Google LLC.
+
+//! Keep track of statistics for binder_logs.
+
+use crate::defs::*;
+use kernel::sync::atomic::{ordering::Relaxed, Atomic};
+use kernel::{ioctl::_IOC_NR, seq_file::SeqFile, seq_print};
+
+const BC_COUNT: usize = _IOC_NR(BC_FREEZE_NOTIFICATION_DONE) as usize + 1;
+const BR_COUNT: usize = _IOC_NR(BR_CLEAR_FREEZE_NOTIFICATION_DONE) as usize + 1;
+
+pub(crate) static GLOBAL_STATS: BinderStats = BinderStats::new();
+
+pub(crate) struct BinderStats {
+    bc: [Atomic<u32>; BC_COUNT],
+    br: [Atomic<u32>; BR_COUNT],
+}
+
+impl BinderStats {
+    pub(crate) const fn new() -> Self {
+        #[expect(clippy::declare_interior_mutable_const)]
+        const ZERO: Atomic<u32> = Atomic::new(0);
+
+        Self {
+            bc: [ZERO; BC_COUNT],
+            br: [ZERO; BR_COUNT],
+        }
+    }
+
+    pub(crate) fn inc_bc(&self, bc: u32) {
+        let idx = _IOC_NR(bc) as usize;
+        if let Some(bc_ref) = self.bc.get(idx) {
+            bc_ref.fetch_add(1, Relaxed);
+        }
+    }
+
+    pub(crate) fn inc_br(&self, br: u32) {
+        let idx = _IOC_NR(br) as usize;
+        if let Some(br_ref) = self.br.get(idx) {
+            br_ref.fetch_add(1, Relaxed);
+        }
+    }
+
+    pub(crate) fn debug_print(&self, prefix: &str, m: &SeqFile) {
+        for (i, cnt) in self.bc.iter().enumerate() {
+            let cnt = cnt.load(Relaxed);
+            if cnt > 0 {
+                seq_print!(m, "{}{}: {}\n", prefix, command_string(i), cnt);
+            }
+        }
+        for (i, cnt) in self.br.iter().enumerate() {
+            let cnt = cnt.load(Relaxed);
+            if cnt > 0 {
+                seq_print!(m, "{}{}: {}\n", prefix, return_string(i), cnt);
+            }
+        }
+    }
+}
+
+mod strings {
+    use core::str::from_utf8_unchecked;
+    use kernel::str::{CStr, CStrExt as _};
+
+    extern "C" {
+        static binder_command_strings: [*const u8; super::BC_COUNT];
+        static binder_return_strings: [*const u8; super::BR_COUNT];
+    }
+
+    pub(super) fn command_string(i: usize) -> &'static str {
+        // SAFETY: Accessing `binder_command_strings` is always safe.
+        let c_str_ptr = unsafe { binder_command_strings[i] };
+        // SAFETY: The `binder_command_strings` array only contains nul-terminated strings.
+        let bytes = unsafe { CStr::from_char_ptr(c_str_ptr) }.to_bytes();
+        // SAFETY: The `binder_command_strings` array only contains strings with ascii-chars.
+        unsafe { from_utf8_unchecked(bytes) }
+    }
+
+    pub(super) fn return_string(i: usize) -> &'static str {
+        // SAFETY: Accessing `binder_return_strings` is always safe.
+        let c_str_ptr = unsafe { binder_return_strings[i] };
+        // SAFETY: The `binder_command_strings` array only contains nul-terminated strings.
+        let bytes = unsafe { CStr::from_char_ptr(c_str_ptr) }.to_bytes();
+        // SAFETY: The `binder_command_strings` array only contains strings with ascii-chars.
+        unsafe { from_utf8_unchecked(bytes) }
+    }
+}
+use strings::{command_string, return_string};