feat: add Rust userspace support; fix TLS layout for p_align < 16; kill whole process on sibling-thread faults

programs/rust/montauk-rt/src/env.rs

@@ -0,0 +1,48 @@
+//! Command-line arguments, captured from crt1.o's argv by [`crate::entry!`].
+
+use core::ffi::CStr;
+use core::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
+
+static ARGC: AtomicUsize = AtomicUsize::new(0);
+static ARGV: AtomicPtr<*const u8> = AtomicPtr::new(core::ptr::null_mut());
+
+/// # Safety
+/// `argv` must point to `argc` NUL-terminated strings that live forever.
+#[doc(hidden)]
+pub unsafe fn init(argc: i32, argv: *const *const u8) {
+    ARGV.store(argv as *mut *const u8, Ordering::Relaxed);
+    ARGC.store(argc.max(0) as usize, Ordering::Release);
+}
+
+/// Iterator over the program arguments; argv[0] is the executable path.
+/// Arguments that are not valid UTF-8 are yielded lossily as `"?"`.
+pub fn args() -> Args {
+    Args { next: 0 }
+}
+
+pub struct Args {
+    next: usize,
+}
+
+impl Iterator for Args {
+    type Item = &'static str;
+
+    fn next(&mut self) -> Option<&'static str> {
+        let argc = ARGC.load(Ordering::Acquire);
+        if self.next >= argc {
+            return None;
+        }
+        let argv = ARGV.load(Ordering::Relaxed);
+        // SAFETY: init() guarantees argc valid, immortal C strings.
+        let s = unsafe { CStr::from_ptr(*argv.add(self.next) as *const core::ffi::c_char) };
+        self.next += 1;
+        Some(s.to_str().unwrap_or("?"))
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let left = ARGC.load(Ordering::Acquire).saturating_sub(self.next);
+        (left, Some(left))
+    }
+}
+
+impl ExactSizeIterator for Args {}