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, 283 insertions, 0 deletions

diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs
new file mode 100644
index 000000000..3bf296581
--- /dev/null
+++ b/scripts/generate_rust_target.rs
@@ -0,0 +1,283 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! The custom target specification file generator for `rustc`.
+//!
+//! To configure a target from scratch, a JSON-encoded file has to be passed
+//! to `rustc` (introduced in [RFC 131]). These options and the file itself are
+//! unstable. Eventually, `rustc` should provide a way to do this in a stable
+//! manner. For instance, via command-line arguments. Therefore, this file
+//! should avoid using keys which can be set via `-C` or `-Z` options.
+//!
+//! [RFC 131]: https://rust-lang.github.io/rfcs/0131-target-specification.html
+
+use std::{
+    collections::HashMap,
+    fmt::{Display, Formatter, Result},
+    io::BufRead,
+};
+
+enum Value {
+    Boolean(bool),
+    Number(i32),
+    String(String),
+    Array(Vec<Value>),
+    Object(Object),
+}
+
+type Object = Vec<(String, Value)>;
+
+fn comma_sep<T>(
+    seq: &[T],
+    formatter: &mut Formatter<'_>,
+    f: impl Fn(&mut Formatter<'_>, &T) -> Result,
+) -> Result {
+    if let [ref rest @ .., ref last] = seq[..] {
+        for v in rest {
+            f(formatter, v)?;
+            formatter.write_str(",")?;
+        }
+        f(formatter, last)?;
+    }
+    Ok(())
+}
+
+/// Minimal "almost JSON" generator (e.g. no `null`s, no escaping),
+/// enough for this purpose.
+impl Display for Value {
+    fn fmt(&self, formatter: &mut Formatter<'_>) -> Result {
+        match self {
+            Value::Boolean(boolean) => write!(formatter, "{}", boolean),
+            Value::Number(number) => write!(formatter, "{}", number),
+            Value::String(string) => write!(formatter, "\"{}\"", string),
+            Value::Array(values) => {
+                formatter.write_str("[")?;
+                comma_sep(&values[..], formatter, |formatter, v| v.fmt(formatter))?;
+                formatter.write_str("]")
+            }
+            Value::Object(object) => {
+                formatter.write_str("{")?;
+                comma_sep(&object[..], formatter, |formatter, v| {
+                    write!(formatter, "\"{}\": {}", v.0, v.1)
+                })?;
+                formatter.write_str("}")
+            }
+        }
+    }
+}
+
+impl From<bool> for Value {
+    fn from(value: bool) -> Self {
+        Self::Boolean(value)
+    }
+}
+
+impl From<i32> for Value {
+    fn from(value: i32) -> Self {
+        Self::Number(value)
+    }
+}
+
+impl From<String> for Value {
+    fn from(value: String) -> Self {
+        Self::String(value)
+    }
+}
+
+impl From<&str> for Value {
+    fn from(value: &str) -> Self {
+        Self::String(value.to_string())
+    }
+}
+
+impl From<Object> for Value {
+    fn from(object: Object) -> Self {
+        Self::Object(object)
+    }
+}
+
+impl<T: Into<Value>, const N: usize> From<[T; N]> for Value {
+    fn from(i: [T; N]) -> Self {
+        Self::Array(i.into_iter().map(|v| v.into()).collect())
+    }
+}
+
+struct TargetSpec(Object);
+
+impl TargetSpec {
+    fn new() -> TargetSpec {
+        TargetSpec(Vec::new())
+    }
+
+    fn push(&mut self, key: &str, value: impl Into<Value>) {
+        self.0.push((key.to_string(), value.into()));
+    }
+}
+
+impl Display for TargetSpec {
+    fn fmt(&self, formatter: &mut Formatter<'_>) -> Result {
+        // We add some newlines for clarity.
+        formatter.write_str("{\n")?;
+        if let [ref rest @ .., ref last] = self.0[..] {
+            for (key, value) in rest {
+                write!(formatter, "    \"{}\": {},\n", key, value)?;
+            }
+            write!(formatter, "    \"{}\": {}\n", last.0, last.1)?;
+        }
+        formatter.write_str("}")
+    }
+}
+
+struct KernelConfig(HashMap<String, String>);
+
+impl KernelConfig {
+    /// Parses `include/config/auto.conf` from `stdin`.
+    fn from_stdin() -> KernelConfig {
+        let mut result = HashMap::new();
+
+        let stdin = std::io::stdin();
+        let mut handle = stdin.lock();
+        let mut line = String::new();
+
+        loop {
+            line.clear();
+
+            if handle.read_line(&mut line).unwrap() == 0 {
+                break;
+            }
+
+            if line.starts_with('#') {
+                continue;
+            }
+
+            let (key, value) = line.split_once('=').expect("Missing `=` in line.");
+            result.insert(key.to_string(), value.trim_end_matches('\n').to_string());
+        }
+
+        KernelConfig(result)
+    }
+
+    /// Does the option exist in the configuration (any value)?
+    ///
+    /// The argument must be passed without the `CONFIG_` prefix.
+    /// This avoids repetition and it also avoids `fixdep` making us
+    /// depend on it.
+    fn has(&self, option: &str) -> bool {
+        let option = "CONFIG_".to_owned() + option;
+        self.0.contains_key(&option)
+    }
+
+    /// Is the rustc version at least `major.minor.patch`?
+    fn rustc_version_atleast(&self, major: u32, minor: u32, patch: u32) -> bool {
+        let check_version = 100000 * major + 100 * minor + patch;
+        let actual_version = self
+            .0
+            .get("CONFIG_RUSTC_VERSION")
+            .unwrap()
+            .parse::<u32>()
+            .unwrap();
+        check_version <= actual_version
+    }
+}
+
+fn main() {
+    let cfg = KernelConfig::from_stdin();
+    let mut ts = TargetSpec::new();
+
+    // `llvm-target`s are taken from `scripts/Makefile.clang`.
+    if cfg.has("ARM") {
+        panic!("arm uses the builtin rustc target");
+    } else if cfg.has("ARM64") {
+        panic!("arm64 uses the builtin rustc aarch64-unknown-none target");
+    } else if cfg.has("RISCV") {
+        if cfg.has("64BIT") {
+            panic!("64-bit RISC-V uses the builtin rustc riscv64-unknown-none-elf target");
+        } else {
+            panic!("32-bit RISC-V is an unsupported architecture");
+        }
+    } else if cfg.has("X86_64") {
+        ts.push("arch", "x86_64");
+        if cfg.rustc_version_atleast(1, 98, 0) {
+            ts.push("rustc-abi", "softfloat");
+        } else if cfg.rustc_version_atleast(1, 86, 0) {
+            ts.push("rustc-abi", "x86-softfloat");
+        }
+        ts.push(
+            "data-layout",
+            "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
+        );
+        let mut features = "-mmx,+soft-float".to_string();
+        if cfg.has("MITIGATION_RETPOLINE") {
+            // The kernel uses `-mretpoline-external-thunk` (for Clang), which Clang maps to the
+            // target feature of the same name plus the other two target features in
+            // `clang/lib/Driver/ToolChains/Arch/X86.cpp`. These should be eventually enabled via
+            // `-Ctarget-feature` when `rustc` starts recognizing them (or via a new dedicated
+            // flag); see <https://github.com/rust-lang/rust/issues/116852>.
+            features += ",+retpoline-external-thunk";
+            features += ",+retpoline-indirect-branches";
+            features += ",+retpoline-indirect-calls";
+        }
+        if cfg.has("MITIGATION_SLS") {
+            // The kernel uses `-mharden-sls=all`, which Clang maps to both these target features in
+            // `clang/lib/Driver/ToolChains/Arch/X86.cpp`. These should be eventually enabled via
+            // `-Ctarget-feature` when `rustc` starts recognizing them (or via a new dedicated
+            // flag); see <https://github.com/rust-lang/rust/issues/116851>.
+            features += ",+harden-sls-ijmp";
+            features += ",+harden-sls-ret";
+        }
+        ts.push("features", features);
+        ts.push("llvm-target", "x86_64-linux-gnu");
+        ts.push("supported-sanitizers", ["kcfi", "kernel-address"]);
+        if cfg.rustc_version_atleast(1, 91, 0) {
+            ts.push("target-pointer-width", 64);
+        } else {
+            ts.push("target-pointer-width", "64");
+        }
+    } else if cfg.has("X86_32") {
+        // This only works on UML, as i386 otherwise needs regparm support in rustc
+        if !cfg.has("UML") {
+            panic!("32-bit x86 only works under UML");
+        }
+        ts.push("arch", "x86");
+        if cfg.rustc_version_atleast(1, 98, 0) {
+            ts.push("rustc-abi", "softfloat");
+        } else if cfg.rustc_version_atleast(1, 86, 0) {
+            ts.push("rustc-abi", "x86-softfloat");
+        }
+        ts.push(
+            "data-layout",
+            "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-i128:128-f64:32:64-f80:32-n8:16:32-S128",
+        );
+        let mut features = "-mmx,+soft-float".to_string();
+        if cfg.has("MITIGATION_RETPOLINE") {
+            features += ",+retpoline-external-thunk";
+        }
+        ts.push("features", features);
+        ts.push("llvm-target", "i386-unknown-linux-gnu");
+        if cfg.rustc_version_atleast(1, 91, 0) {
+            ts.push("target-pointer-width", 32);
+        } else {
+            ts.push("target-pointer-width", "32");
+        }
+    } else if cfg.has("LOONGARCH") {
+        panic!("loongarch uses the builtin rustc loongarch64-unknown-none-softfloat target");
+    } else if cfg.has("S390") {
+        panic!("s390 uses the builtin rustc s390x-unknown-none-softfloat target");
+    } else {
+        panic!("Unsupported architecture");
+    }
+
+    ts.push("emit-debug-gdb-scripts", false);
+    ts.push("frame-pointer", "may-omit");
+    ts.push(
+        "stack-probes",
+        vec![("kind".to_string(), Value::String("none".to_string()))],
+    );
+
+    // Everything else is LE, whether `CPU_LITTLE_ENDIAN` is declared or not
+    // (e.g. x86). It is also `rustc`'s default.
+    if cfg.has("CPU_BIG_ENDIAN") {
+        ts.push("target-endian", "big");
+    }
+
+    println!("{}", ts);
+}