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, 293 insertions, 0 deletions

diff --git a/rust/syn/group.rs b/rust/syn/group.rs
new file mode 100644
index 000000000..57586c58f
--- /dev/null
+++ b/rust/syn/group.rs
@@ -0,0 +1,293 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::error::Result;
+use crate::parse::ParseBuffer;
+use crate::token;
+use proc_macro2::extra::DelimSpan;
+use proc_macro2::Delimiter;
+
+// Not public API.
+#[doc(hidden)]
+pub struct Parens<'a> {
+    #[doc(hidden)]
+    pub token: token::Paren,
+    #[doc(hidden)]
+    pub content: ParseBuffer<'a>,
+}
+
+// Not public API.
+#[doc(hidden)]
+pub struct Braces<'a> {
+    #[doc(hidden)]
+    pub token: token::Brace,
+    #[doc(hidden)]
+    pub content: ParseBuffer<'a>,
+}
+
+// Not public API.
+#[doc(hidden)]
+pub struct Brackets<'a> {
+    #[doc(hidden)]
+    pub token: token::Bracket,
+    #[doc(hidden)]
+    pub content: ParseBuffer<'a>,
+}
+
+// Not public API.
+#[cfg(any(feature = "full", feature = "derive"))]
+#[doc(hidden)]
+pub struct Group<'a> {
+    #[doc(hidden)]
+    pub token: token::Group,
+    #[doc(hidden)]
+    pub content: ParseBuffer<'a>,
+}
+
+// Not public API.
+#[doc(hidden)]
+pub fn parse_parens<'a>(input: &ParseBuffer<'a>) -> Result<Parens<'a>> {
+    parse_delimited(input, Delimiter::Parenthesis).map(|(span, content)| Parens {
+        token: token::Paren(span),
+        content,
+    })
+}
+
+// Not public API.
+#[doc(hidden)]
+pub fn parse_braces<'a>(input: &ParseBuffer<'a>) -> Result<Braces<'a>> {
+    parse_delimited(input, Delimiter::Brace).map(|(span, content)| Braces {
+        token: token::Brace(span),
+        content,
+    })
+}
+
+// Not public API.
+#[doc(hidden)]
+pub fn parse_brackets<'a>(input: &ParseBuffer<'a>) -> Result<Brackets<'a>> {
+    parse_delimited(input, Delimiter::Bracket).map(|(span, content)| Brackets {
+        token: token::Bracket(span),
+        content,
+    })
+}
+
+#[cfg(any(feature = "full", feature = "derive"))]
+pub(crate) fn parse_group<'a>(input: &ParseBuffer<'a>) -> Result<Group<'a>> {
+    parse_delimited(input, Delimiter::None).map(|(span, content)| Group {
+        token: token::Group(span.join()),
+        content,
+    })
+}
+
+fn parse_delimited<'a>(
+    input: &ParseBuffer<'a>,
+    delimiter: Delimiter,
+) -> Result<(DelimSpan, ParseBuffer<'a>)> {
+    input.step(|cursor| {
+        if let Some((content, span, rest)) = cursor.group(delimiter) {
+            let scope = span.close();
+            let nested = crate::parse::advance_step_cursor(cursor, content);
+            let unexpected = crate::parse::get_unexpected(input);
+            let content = crate::parse::new_parse_buffer(scope, nested, unexpected);
+            Ok(((span, content), rest))
+        } else {
+            let message = match delimiter {
+                Delimiter::Parenthesis => "expected parentheses",
+                Delimiter::Brace => "expected curly braces",
+                Delimiter::Bracket => "expected square brackets",
+                Delimiter::None => "expected invisible group",
+            };
+            Err(cursor.error(message))
+        }
+    })
+}
+
+/// Parse a set of parentheses and expose their content to subsequent parsers.
+///
+/// # Example
+///
+/// ```
+/// # use quote::quote;
+/// #
+/// use syn::{parenthesized, token, Ident, Result, Token, Type};
+/// use syn::parse::{Parse, ParseStream};
+/// use syn::punctuated::Punctuated;
+///
+/// // Parse a simplified tuple struct syntax like:
+/// //
+/// //     struct S(A, B);
+/// struct TupleStruct {
+///     struct_token: Token![struct],
+///     ident: Ident,
+///     paren_token: token::Paren,
+///     fields: Punctuated<Type, Token![,]>,
+///     semi_token: Token![;],
+/// }
+///
+/// impl Parse for TupleStruct {
+///     fn parse(input: ParseStream) -> Result<Self> {
+///         let content;
+///         Ok(TupleStruct {
+///             struct_token: input.parse()?,
+///             ident: input.parse()?,
+///             paren_token: parenthesized!(content in input),
+///             fields: content.parse_terminated(Type::parse, Token![,])?,
+///             semi_token: input.parse()?,
+///         })
+///     }
+/// }
+/// #
+/// # fn main() {
+/// #     let input = quote! {
+/// #         struct S(A, B);
+/// #     };
+/// #     syn::parse2::<TupleStruct>(input).unwrap();
+/// # }
+/// ```
+#[macro_export]
+#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+macro_rules! parenthesized {
+    ($content:ident in $cursor:expr) => {
+        match $crate::__private::parse_parens(&$cursor) {
+            $crate::__private::Ok(parens) => {
+                $content = parens.content;
+                parens.token
+            }
+            $crate::__private::Err(error) => {
+                return $crate::__private::Err(error);
+            }
+        }
+    };
+}
+
+/// Parse a set of curly braces and expose their content to subsequent parsers.
+///
+/// # Example
+///
+/// ```
+/// # use quote::quote;
+/// #
+/// use syn::{braced, token, Ident, Result, Token, Type};
+/// use syn::parse::{Parse, ParseStream};
+/// use syn::punctuated::Punctuated;
+///
+/// // Parse a simplified struct syntax like:
+/// //
+/// //     struct S {
+/// //         a: A,
+/// //         b: B,
+/// //     }
+/// struct Struct {
+///     struct_token: Token![struct],
+///     ident: Ident,
+///     brace_token: token::Brace,
+///     fields: Punctuated<Field, Token![,]>,
+/// }
+///
+/// struct Field {
+///     name: Ident,
+///     colon_token: Token![:],
+///     ty: Type,
+/// }
+///
+/// impl Parse for Struct {
+///     fn parse(input: ParseStream) -> Result<Self> {
+///         let content;
+///         Ok(Struct {
+///             struct_token: input.parse()?,
+///             ident: input.parse()?,
+///             brace_token: braced!(content in input),
+///             fields: content.parse_terminated(Field::parse, Token![,])?,
+///         })
+///     }
+/// }
+///
+/// impl Parse for Field {
+///     fn parse(input: ParseStream) -> Result<Self> {
+///         Ok(Field {
+///             name: input.parse()?,
+///             colon_token: input.parse()?,
+///             ty: input.parse()?,
+///         })
+///     }
+/// }
+/// #
+/// # fn main() {
+/// #     let input = quote! {
+/// #         struct S {
+/// #             a: A,
+/// #             b: B,
+/// #         }
+/// #     };
+/// #     syn::parse2::<Struct>(input).unwrap();
+/// # }
+/// ```
+#[macro_export]
+#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+macro_rules! braced {
+    ($content:ident in $cursor:expr) => {
+        match $crate::__private::parse_braces(&$cursor) {
+            $crate::__private::Ok(braces) => {
+                $content = braces.content;
+                braces.token
+            }
+            $crate::__private::Err(error) => {
+                return $crate::__private::Err(error);
+            }
+        }
+    };
+}
+
+/// Parse a set of square brackets and expose their content to subsequent
+/// parsers.
+///
+/// # Example
+///
+/// ```
+/// # use quote::quote;
+/// #
+/// use proc_macro2::TokenStream;
+/// use syn::{bracketed, token, Result, Token};
+/// use syn::parse::{Parse, ParseStream};
+///
+/// // Parse an outer attribute like:
+/// //
+/// //     #[repr(C, packed)]
+/// struct OuterAttribute {
+///     pound_token: Token![#],
+///     bracket_token: token::Bracket,
+///     content: TokenStream,
+/// }
+///
+/// impl Parse for OuterAttribute {
+///     fn parse(input: ParseStream) -> Result<Self> {
+///         let content;
+///         Ok(OuterAttribute {
+///             pound_token: input.parse()?,
+///             bracket_token: bracketed!(content in input),
+///             content: content.parse()?,
+///         })
+///     }
+/// }
+/// #
+/// # fn main() {
+/// #     let input = quote! {
+/// #         #[repr(C, packed)]
+/// #     };
+/// #     syn::parse2::<OuterAttribute>(input).unwrap();
+/// # }
+/// ```
+#[macro_export]
+#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+macro_rules! bracketed {
+    ($content:ident in $cursor:expr) => {
+        match $crate::__private::parse_brackets(&$cursor) {
+            $crate::__private::Ok(brackets) => {
+                $content = brackets.content;
+                brackets.token
+            }
+            $crate::__private::Err(error) => {
+                return $crate::__private::Err(error);
+            }
+        }
+    };
+}