1 files changed, 81 insertions, 0 deletions
diff --git a/cortex-m-rt/src/lib.rs b/cortex-m-rt/src/lib.rs
new file mode 100644
index 0000000..e1ec26f
--- /dev/null
+++ b/cortex-m-rt/src/lib.rs
@@ -0,0 +1,81 @@
+//! Minimal startup / runtime for Cortex-M microcontrollers
+//!
+//! Provides
+//!
+//! - Before main initialization of the `.bss` and `.data` sections
+//!
+//! - An overridable (\*) `panic_fmt` implementation that prints overs the ITM
+//!   or through semihosting depending on the enabled Cargo feature.
+//!
+//! - Minimal `start` lang item, to support vanilla `fn main()`. NOTE the
+//!   processor goes into "reactive" mode (`loop { asm!("wfi") }`) after
+//!   returning from `main`.
+//!
+//! (\*) To override the `panic_fmt` implementation, simply create a new
+//! `rust_begin_unwind` symbol:
+//!
+//! ```
+//! #[no_mangle]
+//! pub unsafe extern "C" fn rust_begin_unwind(
+//!     _args: ::core::fmt::Arguments,
+//!     _file: &'static str,
+//!     _line: u32,
+//! ) -> ! {
+//!     ..
+//! }
+//! ```
+
+#![deny(missing_docs)]
+#![deny(warnings)]
+#![feature(asm)]
+#![feature(compiler_builtins_lib)]
+#![feature(lang_items)]
+#![feature(linkage)]
+#![no_std]
+
+#[cfg(feature = "panic-over-itm")]
+#[macro_use]
+extern crate cortex_m;
+extern crate compiler_builtins;
+#[cfg(feature = "panic-over-semihosting")]
+#[macro_use]
+extern crate cortex_m_semihosting;
+extern crate r0;
+
+mod lang_items;
+
+// TODO make private and use `#[used]`
+/// The reset handler
+///
+/// This is the entry point of all programs
+#[doc(hidden)]
+#[export_name = "start"]
+pub unsafe extern "C" fn reset_handler() -> ! {
+    extern "C" {
+        static mut _ebss: u32;
+        static mut _sbss: u32;
+
+        static mut _edata: u32;
+        static mut _sdata: u32;
+
+        static _sidata: u32;
+    }
+
+    ::r0::zero_bss(&mut _sbss, &mut _ebss);
+    ::r0::init_data(&mut _sdata, &mut _edata, &_sidata);
+
+    // NOTE `rustc` forces this signature on us. See `src/lang_items.rs`
+    extern "C" {
+        fn main(argc: isize, argv: *const *const u8) -> isize;
+    }
+
+    // Neither `argc` or `argv` make sense in bare metal contexts so we just
+    // stub them
+    main(0, ::core::ptr::null());
+
+    // If `main` returns, then we go into "reactive" mode and attend interrupts
+    // as they occur.
+    loop {
+        asm!("wfi" :::: "volatile");
+    }
+}