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, 261 insertions, 0 deletions

diff --git a/rust/syn/derive.rs b/rust/syn/derive.rs
new file mode 100644
index 000000000..27fd9f12c
--- /dev/null
+++ b/rust/syn/derive.rs
@@ -0,0 +1,261 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::attr::Attribute;
+use crate::data::{Fields, FieldsNamed, Variant};
+use crate::generics::Generics;
+use crate::ident::Ident;
+use crate::punctuated::Punctuated;
+use crate::restriction::Visibility;
+use crate::token;
+
+ast_struct! {
+    /// Data structure sent to a `proc_macro_derive` macro.
+    #[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
+    pub struct DeriveInput {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub ident: Ident,
+        pub generics: Generics,
+        pub data: Data,
+    }
+}
+
+ast_enum! {
+    /// The storage of a struct, enum or union data structure.
+    ///
+    /// # Syntax tree enum
+    ///
+    /// This type is a [syntax tree enum].
+    ///
+    /// [syntax tree enum]: crate::expr::Expr#syntax-tree-enums
+    #[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
+    pub enum Data {
+        Struct(DataStruct),
+        Enum(DataEnum),
+        Union(DataUnion),
+    }
+}
+
+ast_struct! {
+    /// A struct input to a `proc_macro_derive` macro.
+    #[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
+    pub struct DataStruct {
+        pub struct_token: Token![struct],
+        pub fields: Fields,
+        pub semi_token: Option<Token![;]>,
+    }
+}
+
+ast_struct! {
+    /// An enum input to a `proc_macro_derive` macro.
+    #[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
+    pub struct DataEnum {
+        pub enum_token: Token![enum],
+        pub brace_token: token::Brace,
+        pub variants: Punctuated<Variant, Token![,]>,
+    }
+}
+
+ast_struct! {
+    /// An untagged union input to a `proc_macro_derive` macro.
+    #[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
+    pub struct DataUnion {
+        pub union_token: Token![union],
+        pub fields: FieldsNamed,
+    }
+}
+
+#[cfg(feature = "parsing")]
+pub(crate) mod parsing {
+    use crate::attr::Attribute;
+    use crate::data::{Fields, FieldsNamed, Variant};
+    use crate::derive::{Data, DataEnum, DataStruct, DataUnion, DeriveInput};
+    use crate::error::Result;
+    use crate::generics::{Generics, WhereClause};
+    use crate::ident::Ident;
+    use crate::parse::{Parse, ParseStream};
+    use crate::punctuated::Punctuated;
+    use crate::restriction::Visibility;
+    use crate::token;
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for DeriveInput {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let vis = input.parse::<Visibility>()?;
+
+            let lookahead = input.lookahead1();
+            if lookahead.peek(Token![struct]) {
+                let struct_token = input.parse::<Token![struct]>()?;
+                let ident = input.parse::<Ident>()?;
+                let generics = input.parse::<Generics>()?;
+                let (where_clause, fields, semi) = data_struct(input)?;
+                Ok(DeriveInput {
+                    attrs,
+                    vis,
+                    ident,
+                    generics: Generics {
+                        where_clause,
+                        ..generics
+                    },
+                    data: Data::Struct(DataStruct {
+                        struct_token,
+                        fields,
+                        semi_token: semi,
+                    }),
+                })
+            } else if lookahead.peek(Token![enum]) {
+                let enum_token = input.parse::<Token![enum]>()?;
+                let ident = input.parse::<Ident>()?;
+                let generics = input.parse::<Generics>()?;
+                let (where_clause, brace, variants) = data_enum(input)?;
+                Ok(DeriveInput {
+                    attrs,
+                    vis,
+                    ident,
+                    generics: Generics {
+                        where_clause,
+                        ..generics
+                    },
+                    data: Data::Enum(DataEnum {
+                        enum_token,
+                        brace_token: brace,
+                        variants,
+                    }),
+                })
+            } else if lookahead.peek(Token![union]) {
+                let union_token = input.parse::<Token![union]>()?;
+                let ident = input.parse::<Ident>()?;
+                let generics = input.parse::<Generics>()?;
+                let (where_clause, fields) = data_union(input)?;
+                Ok(DeriveInput {
+                    attrs,
+                    vis,
+                    ident,
+                    generics: Generics {
+                        where_clause,
+                        ..generics
+                    },
+                    data: Data::Union(DataUnion {
+                        union_token,
+                        fields,
+                    }),
+                })
+            } else {
+                Err(lookahead.error())
+            }
+        }
+    }
+
+    pub(crate) fn data_struct(
+        input: ParseStream,
+    ) -> Result<(Option<WhereClause>, Fields, Option<Token![;]>)> {
+        let mut lookahead = input.lookahead1();
+        let mut where_clause = None;
+        if lookahead.peek(Token![where]) {
+            where_clause = Some(input.parse()?);
+            lookahead = input.lookahead1();
+        }
+
+        if where_clause.is_none() && lookahead.peek(token::Paren) {
+            let fields = input.parse()?;
+
+            lookahead = input.lookahead1();
+            if lookahead.peek(Token![where]) {
+                where_clause = Some(input.parse()?);
+                lookahead = input.lookahead1();
+            }
+
+            if lookahead.peek(Token![;]) {
+                let semi = input.parse()?;
+                Ok((where_clause, Fields::Unnamed(fields), Some(semi)))
+            } else {
+                Err(lookahead.error())
+            }
+        } else if lookahead.peek(token::Brace) {
+            let fields = input.parse()?;
+            Ok((where_clause, Fields::Named(fields), None))
+        } else if lookahead.peek(Token![;]) {
+            let semi = input.parse()?;
+            Ok((where_clause, Fields::Unit, Some(semi)))
+        } else {
+            Err(lookahead.error())
+        }
+    }
+
+    pub(crate) fn data_enum(
+        input: ParseStream,
+    ) -> Result<(
+        Option<WhereClause>,
+        token::Brace,
+        Punctuated<Variant, Token![,]>,
+    )> {
+        let where_clause = input.parse()?;
+
+        let content;
+        let brace = braced!(content in input);
+        let variants = content.parse_terminated(Variant::parse, Token![,])?;
+
+        Ok((where_clause, brace, variants))
+    }
+
+    pub(crate) fn data_union(input: ParseStream) -> Result<(Option<WhereClause>, FieldsNamed)> {
+        let where_clause = input.parse()?;
+        let fields = input.parse()?;
+        Ok((where_clause, fields))
+    }
+}
+
+#[cfg(feature = "printing")]
+mod printing {
+    use crate::attr::FilterAttrs;
+    use crate::data::Fields;
+    use crate::derive::{Data, DeriveInput};
+    use crate::print::TokensOrDefault;
+    use proc_macro2::TokenStream;
+    use quote::ToTokens;
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for DeriveInput {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            for attr in self.attrs.outer() {
+                attr.to_tokens(tokens);
+            }
+            self.vis.to_tokens(tokens);
+            match &self.data {
+                Data::Struct(d) => d.struct_token.to_tokens(tokens),
+                Data::Enum(d) => d.enum_token.to_tokens(tokens),
+                Data::Union(d) => d.union_token.to_tokens(tokens),
+            }
+            self.ident.to_tokens(tokens);
+            self.generics.to_tokens(tokens);
+            match &self.data {
+                Data::Struct(data) => match &data.fields {
+                    Fields::Named(fields) => {
+                        self.generics.where_clause.to_tokens(tokens);
+                        fields.to_tokens(tokens);
+                    }
+                    Fields::Unnamed(fields) => {
+                        fields.to_tokens(tokens);
+                        self.generics.where_clause.to_tokens(tokens);
+                        TokensOrDefault(&data.semi_token).to_tokens(tokens);
+                    }
+                    Fields::Unit => {
+                        self.generics.where_clause.to_tokens(tokens);
+                        TokensOrDefault(&data.semi_token).to_tokens(tokens);
+                    }
+                },
+                Data::Enum(data) => {
+                    self.generics.where_clause.to_tokens(tokens);
+                    data.brace_token.surround(tokens, |tokens| {
+                        data.variants.to_tokens(tokens);
+                    });
+                }
+                Data::Union(data) => {
+                    self.generics.where_clause.to_tokens(tokens);
+                    data.fields.to_tokens(tokens);
+                }
+            }
+        }
+    }
+}