Initial bootstrap into ‘main’.

1 files changed, 38 insertions, 0 deletions

diff --git a/src/main.rs b/src/main.rs
new file mode 100755
index 0000000..0f77639
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,38 @@
+#![feature(naked_functions)]
+
+#![no_std]
+#![no_main]
+
+use core::arch::asm;
+
+#[no_mangle]
+fn main(_hartid: usize) -> ! {
+    loop {}
+}
+
+#[naked]
+#[link_section = ".text.init"]
+#[export_name = "_start"]
+unsafe extern "C" fn _start() -> ! {
+    // At boot, the hart is in privilege mode M, mstatus fields MIE
+    // and MPRV are 0, the pc is set to a reset vector, the mcause
+    // register specifies why the reset occurred.
+    // c.f.: [^super::rism2] § 3.4 (Reset)
+    asm!(
+        ".option push",
+        ".option norelax",
+        "la gp, __global_pointer$",
+        ".option pop",
+
+        "csrr a0, mhartid",
+        "la sp, _stack_top",
+
+        "j main",
+        options(noreturn)
+    )
+}
+
+#[panic_handler]
+fn panic(_info: &core::panic::PanicInfo) -> ! {
+    loop {}
+}