Add more from the std

library/std/src/sys/exit.rs

@@ -0,0 +1,143 @@
+cfg_select! {
+    target_os = "linux" => {
+        /// Mitigation for <https://github.com/rust-lang/rust/issues/126600>
+        ///
+        /// On glibc, `libc::exit` has been observed to not always be thread-safe.
+        /// It is currently unclear whether that is a glibc bug or allowed by the standard.
+        /// To mitigate this problem, we ensure that only one
+        /// Rust thread calls `libc::exit` (or returns from `main`) by calling this function before
+        /// calling `libc::exit` (or returning from `main`).
+        ///
+        /// Technically, this is not enough to ensure soundness, since other code directly calling
+        /// `libc::exit` will still race with this.
+        ///
+        /// *This function does not itself call `libc::exit`.* This is so it can also be used
+        /// to guard returning from `main`.
+        ///
+        /// This function will return only the first time it is called in a process.
+        ///
+        /// * If it is called again on the same thread as the first call, it will abort.
+        /// * If it is called again on a different thread, it will wait in a loop
+        ///   (waiting for the process to exit).
+        pub fn unique_thread_exit() {
+            use crate::ffi::c_int;
+            use crate::ptr;
+            use crate::sync::atomic::AtomicPtr;
+            use crate::sync::atomic::Ordering::{Acquire, Relaxed};
+
+            static EXITING_THREAD_ID: AtomicPtr<c_int> = AtomicPtr::new(ptr::null_mut());
+
+            // We use the address of `errno` as a cheap and safe way to identify
+            // threads. As the C standard mandates that `errno` must have thread
+            // storage duration, we can rely on its address not changing over the
+            // lifetime of the thread. Additionally, accesses to `errno` are
+            // async-signal-safe, so this function is available in all imaginable
+            // circumstances.
+            let this_thread_id = crate::sys::io::errno_location();
+            match EXITING_THREAD_ID.compare_exchange(ptr::null_mut(), this_thread_id, Acquire, Relaxed) {
+                Ok(_) => {
+                    // This is the first thread to call `unique_thread_exit`,
+                    // and this is the first time it is called. Continue exiting.
+                }
+                Err(exiting_thread_id) if exiting_thread_id == this_thread_id => {
+                    // This is the first thread to call `unique_thread_exit`,
+                    // but this is the second time it is called.
+                    // Abort the process.
+                    core::panicking::panic_nounwind("std::process::exit called re-entrantly")
+                }
+                Err(_) => {
+                    // This is not the first thread to call `unique_thread_exit`.
+                    // Pause until the process exits.
+                    loop {
+                        // Safety: libc::pause is safe to call.
+                        unsafe { libc::pause(); }
+                    }
+                }
+            }
+        }
+    }
+    _ => {
+        /// Mitigation for <https://github.com/rust-lang/rust/issues/126600>
+        ///
+        /// Mitigation is ***NOT*** implemented on this platform, either because this platform
+        /// is not affected, or because mitigation is not yet implemented for this platform.
+        #[cfg_attr(any(test, doctest), expect(dead_code))]
+        pub fn unique_thread_exit() {
+            // Mitigation not required on platforms where `exit` is thread-safe.
+        }
+    }
+}
+
+pub fn exit(code: i32) -> ! {
+    cfg_select! {
+        target_os = "hermit" => {
+            unsafe { hermit_abi::exit(code) }
+        }
+        target_os = "linux" => {
+            unsafe {
+                unique_thread_exit();
+                libc::exit(code)
+            }
+        }
+        target_os = "motor" => {
+            moto_rt::process::exit(code)
+        }
+        all(target_vendor = "fortanix", target_env = "sgx") => {
+            crate::sys::pal::abi::exit_with_code(code as _)
+        }
+        target_os = "solid_asp3" => {
+            rtabort!("exit({}) called", code)
+        }
+        target_os = "teeos" => {
+            let _ = code;
+            panic!("TA should not call `exit`")
+        }
+        target_os = "uefi" => {
+            use r_efi::base::Status;
+
+            use crate::os::uefi::env;
+
+            if let (Some(boot_services), Some(handle)) =
+                (env::boot_services(), env::try_image_handle())
+            {
+                let boot_services = boot_services.cast::<r_efi::efi::BootServices>();
+                let _ = unsafe {
+                    ((*boot_services.as_ptr()).exit)(
+                        handle.as_ptr(),
+                        Status::from_usize(code as usize),
+                        0,
+                        crate::ptr::null_mut(),
+                    )
+                };
+            }
+            crate::intrinsics::abort()
+        }
+        any(
+            target_family = "unix",
+            target_os = "wasi",
+        ) => {
+            unsafe { libc::exit(code as crate::ffi::c_int) }
+        }
+        target_os = "vexos" => {
+            let _ = code;
+
+            unsafe {
+                vex_sdk::vexSystemExitRequest();
+
+                loop {
+                    vex_sdk::vexTasksRun();
+                }
+            }
+        }
+        target_os = "windows" => {
+            unsafe { crate::sys::pal::c::ExitProcess(code as u32) }
+        }
+        target_os = "xous" => {
+            crate::os::xous::ffi::exit(code as u32)
+        }
+        _ => {
+            let _ = code;
+            crate::intrinsics::abort()
+        }
+    }
+}