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, 306 insertions, 0 deletions

diff --git a/rust/syn/custom_punctuation.rs b/rust/syn/custom_punctuation.rs
new file mode 100644
index 000000000..d37c0e9c3
--- /dev/null
+++ b/rust/syn/custom_punctuation.rs
@@ -0,0 +1,306 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+/// Define a type that supports parsing and printing a multi-character symbol
+/// as if it were a punctuation token.
+///
+/// # Usage
+///
+/// ```
+/// syn::custom_punctuation!(LeftRightArrow, <=>);
+/// ```
+///
+/// The generated syntax tree node supports the following operations just like
+/// any built-in punctuation token.
+///
+/// - [Peeking] — `input.peek(LeftRightArrow)`
+///
+/// - [Parsing] — `input.parse::<LeftRightArrow>()?`
+///
+/// - [Printing] — `quote!( ... #lrarrow ... )`
+///
+/// - Construction from a [`Span`] — `let lrarrow = LeftRightArrow(sp)`
+///
+/// - Construction from multiple [`Span`] — `let lrarrow = LeftRightArrow([sp, sp, sp])`
+///
+/// - Field access to its spans — `let spans = lrarrow.spans`
+///
+/// [Peeking]: crate::parse::ParseBuffer::peek
+/// [Parsing]: crate::parse::ParseBuffer::parse
+/// [Printing]: quote::ToTokens
+/// [`Span`]: proc_macro2::Span
+///
+/// # Example
+///
+/// ```
+/// use proc_macro2::{TokenStream, TokenTree};
+/// use syn::parse::{Parse, ParseStream, Peek, Result};
+/// use syn::punctuated::Punctuated;
+/// use syn::Expr;
+///
+/// syn::custom_punctuation!(PathSeparator, </>);
+///
+/// // expr </> expr </> expr ...
+/// struct PathSegments {
+///     segments: Punctuated<Expr, PathSeparator>,
+/// }
+///
+/// impl Parse for PathSegments {
+///     fn parse(input: ParseStream) -> Result<Self> {
+///         let mut segments = Punctuated::new();
+///
+///         let first = parse_until(input, PathSeparator)?;
+///         segments.push_value(syn::parse2(first)?);
+///
+///         while input.peek(PathSeparator) {
+///             segments.push_punct(input.parse()?);
+///
+///             let next = parse_until(input, PathSeparator)?;
+///             segments.push_value(syn::parse2(next)?);
+///         }
+///
+///         Ok(PathSegments { segments })
+///     }
+/// }
+///
+/// fn parse_until<E: Peek>(input: ParseStream, end: E) -> Result<TokenStream> {
+///     let mut tokens = TokenStream::new();
+///     while !input.is_empty() && !input.peek(end) {
+///         let next: TokenTree = input.parse()?;
+///         tokens.extend(Some(next));
+///     }
+///     Ok(tokens)
+/// }
+///
+/// fn main() {
+///     let input = r#" a::b </> c::d::e "#;
+///     let _: PathSegments = syn::parse_str(input).unwrap();
+/// }
+/// ```
+#[macro_export]
+macro_rules! custom_punctuation {
+    ($ident:ident, $($tt:tt)+) => {
+        pub struct $ident {
+            #[allow(dead_code)]
+            pub spans: $crate::custom_punctuation_repr!($($tt)+),
+        }
+
+        #[doc(hidden)]
+        #[allow(dead_code, non_snake_case)]
+        pub fn $ident<__S: $crate::__private::IntoSpans<$crate::custom_punctuation_repr!($($tt)+)>>(
+            spans: __S,
+        ) -> $ident {
+            let _validate_len = 0 $(+ $crate::custom_punctuation_len!(strict, $tt))*;
+            $ident {
+                spans: $crate::__private::IntoSpans::into_spans(spans)
+            }
+        }
+
+        const _: () = {
+            impl $crate::__private::Default for $ident {
+                fn default() -> Self {
+                    $ident($crate::__private::Span::call_site())
+                }
+            }
+
+            $crate::impl_parse_for_custom_punctuation!($ident, $($tt)+);
+            $crate::impl_to_tokens_for_custom_punctuation!($ident, $($tt)+);
+            $crate::impl_clone_for_custom_punctuation!($ident, $($tt)+);
+            $crate::impl_extra_traits_for_custom_punctuation!($ident, $($tt)+);
+        };
+    };
+}
+
+// Not public API.
+#[cfg(feature = "parsing")]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_parse_for_custom_punctuation {
+    ($ident:ident, $($tt:tt)+) => {
+        impl $crate::__private::CustomToken for $ident {
+            fn peek(cursor: $crate::buffer::Cursor) -> $crate::__private::bool {
+                $crate::__private::peek_punct(cursor, $crate::stringify_punct!($($tt)+))
+            }
+
+            fn display() -> &'static $crate::__private::str {
+                $crate::__private::concat!("`", $crate::stringify_punct!($($tt)+), "`")
+            }
+        }
+
+        impl $crate::parse::Parse for $ident {
+            fn parse(input: $crate::parse::ParseStream) -> $crate::parse::Result<$ident> {
+                let spans: $crate::custom_punctuation_repr!($($tt)+) =
+                    $crate::__private::parse_punct(input, $crate::stringify_punct!($($tt)+))?;
+                Ok($ident(spans))
+            }
+        }
+    };
+}
+
+// Not public API.
+#[cfg(not(feature = "parsing"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_parse_for_custom_punctuation {
+    ($ident:ident, $($tt:tt)+) => {};
+}
+
+// Not public API.
+#[cfg(feature = "printing")]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_to_tokens_for_custom_punctuation {
+    ($ident:ident, $($tt:tt)+) => {
+        impl $crate::__private::ToTokens for $ident {
+            fn to_tokens(&self, tokens: &mut $crate::__private::TokenStream2) {
+                $crate::__private::print_punct($crate::stringify_punct!($($tt)+), &self.spans, tokens)
+            }
+        }
+    };
+}
+
+// Not public API.
+#[cfg(not(feature = "printing"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_to_tokens_for_custom_punctuation {
+    ($ident:ident, $($tt:tt)+) => {};
+}
+
+// Not public API.
+#[cfg(feature = "clone-impls")]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_clone_for_custom_punctuation {
+    ($ident:ident, $($tt:tt)+) => {
+        impl $crate::__private::Copy for $ident {}
+
+        #[allow(clippy::expl_impl_clone_on_copy)]
+        impl $crate::__private::Clone for $ident {
+            fn clone(&self) -> Self {
+                *self
+            }
+        }
+    };
+}
+
+// Not public API.
+#[cfg(not(feature = "clone-impls"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_clone_for_custom_punctuation {
+    ($ident:ident, $($tt:tt)+) => {};
+}
+
+// Not public API.
+#[cfg(feature = "extra-traits")]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_extra_traits_for_custom_punctuation {
+    ($ident:ident, $($tt:tt)+) => {
+        impl $crate::__private::Debug for $ident {
+            fn fmt(&self, f: &mut $crate::__private::Formatter) -> $crate::__private::FmtResult {
+                $crate::__private::Formatter::write_str(f, $crate::__private::stringify!($ident))
+            }
+        }
+
+        impl $crate::__private::Eq for $ident {}
+
+        impl $crate::__private::PartialEq for $ident {
+            fn eq(&self, _other: &Self) -> $crate::__private::bool {
+                true
+            }
+        }
+
+        impl $crate::__private::Hash for $ident {
+            fn hash<__H: $crate::__private::Hasher>(&self, _state: &mut __H) {}
+        }
+    };
+}
+
+// Not public API.
+#[cfg(not(feature = "extra-traits"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_extra_traits_for_custom_punctuation {
+    ($ident:ident, $($tt:tt)+) => {};
+}
+
+// Not public API.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! custom_punctuation_repr {
+    ($($tt:tt)+) => {
+        [$crate::__private::Span; 0 $(+ $crate::custom_punctuation_len!(lenient, $tt))+]
+    };
+}
+
+// Not public API.
+#[doc(hidden)]
+#[macro_export]
+#[rustfmt::skip]
+macro_rules! custom_punctuation_len {
+    ($mode:ident, &)     => { 1 };
+    ($mode:ident, &&)    => { 2 };
+    ($mode:ident, &=)    => { 2 };
+    ($mode:ident, @)     => { 1 };
+    ($mode:ident, ^)     => { 1 };
+    ($mode:ident, ^=)    => { 2 };
+    ($mode:ident, :)     => { 1 };
+    ($mode:ident, ,)     => { 1 };
+    ($mode:ident, $)     => { 1 };
+    ($mode:ident, .)     => { 1 };
+    ($mode:ident, ..)    => { 2 };
+    ($mode:ident, ...)   => { 3 };
+    ($mode:ident, ..=)   => { 3 };
+    ($mode:ident, =)     => { 1 };
+    ($mode:ident, ==)    => { 2 };
+    ($mode:ident, =>)    => { 2 };
+    ($mode:ident, >=)    => { 2 };
+    ($mode:ident, >)     => { 1 };
+    ($mode:ident, <-)    => { 2 };
+    ($mode:ident, <=)    => { 2 };
+    ($mode:ident, <)     => { 1 };
+    ($mode:ident, -)     => { 1 };
+    ($mode:ident, -=)    => { 2 };
+    ($mode:ident, !=)    => { 2 };
+    ($mode:ident, !)     => { 1 };
+    ($mode:ident, |)     => { 1 };
+    ($mode:ident, |=)    => { 2 };
+    ($mode:ident, ||)    => { 2 };
+    ($mode:ident, ::)    => { 2 };
+    ($mode:ident, %)     => { 1 };
+    ($mode:ident, %=)    => { 2 };
+    ($mode:ident, +)     => { 1 };
+    ($mode:ident, +=)    => { 2 };
+    ($mode:ident, #)     => { 1 };
+    ($mode:ident, ?)     => { 1 };
+    ($mode:ident, ->)    => { 2 };
+    ($mode:ident, ;)     => { 1 };
+    ($mode:ident, <<)    => { 2 };
+    ($mode:ident, <<=)   => { 3 };
+    ($mode:ident, >>)    => { 2 };
+    ($mode:ident, >>=)   => { 3 };
+    ($mode:ident, /)     => { 1 };
+    ($mode:ident, /=)    => { 2 };
+    ($mode:ident, *)     => { 1 };
+    ($mode:ident, *=)    => { 2 };
+    ($mode:ident, ~)     => { 1 };
+    (lenient, $tt:tt)    => { 0 };
+    (strict, $tt:tt)     => {{ $crate::custom_punctuation_unexpected!($tt); 0 }};
+}
+
+// Not public API.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! custom_punctuation_unexpected {
+    () => {};
+}
+
+// Not public API.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! stringify_punct {
+    ($($tt:tt)+) => {
+        $crate::__private::concat!($($crate::__private::stringify!($tt)),+)
+    };
+}