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, 227 insertions, 0 deletions

diff --git a/rust/syn/mac.rs b/rust/syn/mac.rs
new file mode 100644
index 000000000..ce4b022b4
--- /dev/null
+++ b/rust/syn/mac.rs
@@ -0,0 +1,227 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+#[cfg(feature = "parsing")]
+use crate::error::Result;
+#[cfg(feature = "parsing")]
+use crate::parse::{Parse, ParseStream, Parser};
+use crate::path::Path;
+use crate::token::{Brace, Bracket, Paren};
+use proc_macro2::extra::DelimSpan;
+#[cfg(feature = "parsing")]
+use proc_macro2::Delimiter;
+use proc_macro2::TokenStream;
+#[cfg(feature = "parsing")]
+use proc_macro2::TokenTree;
+
+ast_struct! {
+    /// A macro invocation: `println!("{}", mac)`.
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+    pub struct Macro {
+        pub path: Path,
+        pub bang_token: Token![!],
+        pub delimiter: MacroDelimiter,
+        pub tokens: TokenStream,
+    }
+}
+
+ast_enum! {
+    /// A grouping token that surrounds a macro body: `m!(...)` or `m!{...}` or `m![...]`.
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
+    pub enum MacroDelimiter {
+        Paren(Paren),
+        Brace(Brace),
+        Bracket(Bracket),
+    }
+}
+
+impl MacroDelimiter {
+    pub fn span(&self) -> &DelimSpan {
+        match self {
+            MacroDelimiter::Paren(token) => &token.span,
+            MacroDelimiter::Brace(token) => &token.span,
+            MacroDelimiter::Bracket(token) => &token.span,
+        }
+    }
+
+    #[cfg(all(feature = "full", any(feature = "parsing", feature = "printing")))]
+    pub(crate) fn is_brace(&self) -> bool {
+        match self {
+            MacroDelimiter::Brace(_) => true,
+            MacroDelimiter::Paren(_) | MacroDelimiter::Bracket(_) => false,
+        }
+    }
+}
+
+impl Macro {
+    /// Parse the tokens within the macro invocation's delimiters into a syntax
+    /// tree.
+    ///
+    /// This is equivalent to `syn::parse2::<T>(mac.tokens)` except that it
+    /// produces a more useful span when `tokens` is empty.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use syn::{parse_quote, Expr, ExprLit, Ident, Lit, LitStr, Macro, Token};
+    /// use syn::ext::IdentExt;
+    /// use syn::parse::{Error, Parse, ParseStream, Result};
+    /// use syn::punctuated::Punctuated;
+    ///
+    /// // The arguments expected by libcore's format_args macro, and as a
+    /// // result most other formatting and printing macros like println.
+    /// //
+    /// //     println!("{} is {number:.prec$}", "x", prec=5, number=0.01)
+    /// struct FormatArgs {
+    ///     format_string: Expr,
+    ///     positional_args: Vec<Expr>,
+    ///     named_args: Vec<(Ident, Expr)>,
+    /// }
+    ///
+    /// impl Parse for FormatArgs {
+    ///     fn parse(input: ParseStream) -> Result<Self> {
+    ///         let format_string: Expr;
+    ///         let mut positional_args = Vec::new();
+    ///         let mut named_args = Vec::new();
+    ///
+    ///         format_string = input.parse()?;
+    ///         while !input.is_empty() {
+    ///             input.parse::<Token![,]>()?;
+    ///             if input.is_empty() {
+    ///                 break;
+    ///             }
+    ///             if input.peek(Ident::peek_any) && input.peek2(Token![=]) {
+    ///                 while !input.is_empty() {
+    ///                     let name: Ident = input.call(Ident::parse_any)?;
+    ///                     input.parse::<Token![=]>()?;
+    ///                     let value: Expr = input.parse()?;
+    ///                     named_args.push((name, value));
+    ///                     if input.is_empty() {
+    ///                         break;
+    ///                     }
+    ///                     input.parse::<Token![,]>()?;
+    ///                 }
+    ///                 break;
+    ///             }
+    ///             positional_args.push(input.parse()?);
+    ///         }
+    ///
+    ///         Ok(FormatArgs {
+    ///             format_string,
+    ///             positional_args,
+    ///             named_args,
+    ///         })
+    ///     }
+    /// }
+    ///
+    /// // Extract the first argument, the format string literal, from an
+    /// // invocation of a formatting or printing macro.
+    /// fn get_format_string(m: &Macro) -> Result<LitStr> {
+    ///     let args: FormatArgs = m.parse_body()?;
+    ///     match args.format_string {
+    ///         Expr::Lit(ExprLit { lit: Lit::Str(lit), .. }) => Ok(lit),
+    ///         other => {
+    ///             // First argument was not a string literal expression.
+    ///             // Maybe something like: println!(concat!(...), ...)
+    ///             Err(Error::new_spanned(other, "format string must be a string literal"))
+    ///         }
+    ///     }
+    /// }
+    ///
+    /// fn main() {
+    ///     let invocation = parse_quote! {
+    ///         println!("{:?}", Instant::now())
+    ///     };
+    ///     let lit = get_format_string(&invocation).unwrap();
+    ///     assert_eq!(lit.value(), "{:?}");
+    /// }
+    /// ```
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    pub fn parse_body<T: Parse>(&self) -> Result<T> {
+        self.parse_body_with(T::parse)
+    }
+
+    /// Parse the tokens within the macro invocation's delimiters using the
+    /// given parser.
+    #[cfg(feature = "parsing")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    pub fn parse_body_with<F: Parser>(&self, parser: F) -> Result<F::Output> {
+        let scope = self.delimiter.span().close();
+        crate::parse::parse_scoped(parser, scope, self.tokens.clone())
+    }
+}
+
+#[cfg(feature = "parsing")]
+pub(crate) fn parse_delimiter(input: ParseStream) -> Result<(MacroDelimiter, TokenStream)> {
+    input.step(|cursor| {
+        if let Some((TokenTree::Group(g), rest)) = cursor.token_tree() {
+            let span = g.delim_span();
+            let delimiter = match g.delimiter() {
+                Delimiter::Parenthesis => MacroDelimiter::Paren(Paren(span)),
+                Delimiter::Brace => MacroDelimiter::Brace(Brace(span)),
+                Delimiter::Bracket => MacroDelimiter::Bracket(Bracket(span)),
+                Delimiter::None => {
+                    return Err(cursor.error("expected delimiter"));
+                }
+            };
+            Ok(((delimiter, g.stream()), rest))
+        } else {
+            Err(cursor.error("expected delimiter"))
+        }
+    })
+}
+
+#[cfg(feature = "parsing")]
+pub(crate) mod parsing {
+    use crate::error::Result;
+    use crate::mac::{parse_delimiter, Macro};
+    use crate::parse::{Parse, ParseStream};
+    use crate::path::Path;
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for Macro {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let tokens;
+            Ok(Macro {
+                path: input.call(Path::parse_mod_style)?,
+                bang_token: input.parse()?,
+                delimiter: {
+                    let (delimiter, content) = parse_delimiter(input)?;
+                    tokens = content;
+                    delimiter
+                },
+                tokens,
+            })
+        }
+    }
+}
+
+#[cfg(feature = "printing")]
+mod printing {
+    use crate::mac::{Macro, MacroDelimiter};
+    use crate::path;
+    use crate::path::printing::PathStyle;
+    use crate::token;
+    use proc_macro2::{Delimiter, TokenStream};
+    use quote::ToTokens;
+
+    impl MacroDelimiter {
+        pub(crate) fn surround(&self, tokens: &mut TokenStream, inner: TokenStream) {
+            let (delim, span) = match self {
+                MacroDelimiter::Paren(paren) => (Delimiter::Parenthesis, paren.span),
+                MacroDelimiter::Brace(brace) => (Delimiter::Brace, brace.span),
+                MacroDelimiter::Bracket(bracket) => (Delimiter::Bracket, bracket.span),
+            };
+            token::printing::delim(delim, span.join(), tokens, inner);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for Macro {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            path::printing::print_path(tokens, &self.path, PathStyle::Mod);
+            self.bang_token.to_tokens(tokens);
+            self.delimiter.surround(tokens, self.tokens.clone());
+        }
+    }
+}