feat(userspace-rt): add runtime crate with entry point, panic handler, and allocator re-export

Snake and hello apps now use extern crate userspace_rt — no more boilerplate assembly or panic handlers in app code.

crates/apps/snake/src/main.rs

@@ -1,48 +1,31 @@
 #![no_std]
 #![no_main]
 
+extern crate userspace_rt;
+
 use snake::game::{Direction, GameState, Snake};
 use snake::renderer::{render, RenderCommand};
+use userspace_rt::syscall;
 
 const DISPLAY_EP: usize = 0;
 const INPUT_EP: usize = 1;
 const TICK_DELAY: usize = 2_000_000;
 const MAX_RENDER_COMMANDS: usize = 192;
 
-#[cfg(not(test))]
-use core::arch::global_asm;
-
-#[cfg(not(test))]
-global_asm!(
-    r#"
-.section .text.entry
-.globl _start
-_start:
-    call main
-    j _start
-"#
-);
-
-#[cfg(not(test))]
 #[unsafe(no_mangle)]
-extern "C" fn main() -> ! {
-    run_game();
-}
-
-fn run_game() -> ! {
+extern "C" fn main() {
     let mut snake = Snake::new();
     let mut commands = [RenderCommand { x: 0, y: 0, w: 0, h: 0, color: 0 }; MAX_RENDER_COMMANDS];
 
     loop {
         handle_input(&mut snake);
-
         snake.tick();
 
         let count = render(&snake, &mut commands);
         send_render_commands(&commands, count);
 
         if snake.state() == GameState::GameOver {
-            userspace::syscall::exit();
+            return;
         }
 
         wait_tick();
@@ -50,11 +33,9 @@ fn run_game() -> ! {
 }
 
 fn handle_input(snake: &mut Snake) {
-    // PollEvent request: tag=0
-    let _ = userspace::syscall::send(INPUT_EP, 0, 0, 0, 0);
-    let (tag, kind, _data, _) = userspace::syscall::receive(INPUT_EP);
+    let _ = syscall::send(INPUT_EP, 0, 0, 0, 0);
+    let (tag, kind, _, _) = syscall::receive(INPUT_EP);
 
-    // InputResponse::Event(KeyDown(key)): tag=1, key_kind in word 1
     if tag == 1 {
         match kind {
             0 => snake.set_direction(Direction::Up),
@@ -67,34 +48,25 @@ fn handle_input(snake: &mut Snake) {
 }
 
 fn send_render_commands(commands: &[RenderCommand], count: usize) {
-    // Clear: DisplayRequest tag=1
-    let _ = userspace::syscall::send(DISPLAY_EP, 1, 0, 0, 0);
-    let _ = userspace::syscall::receive(DISPLAY_EP);
+    let _ = syscall::send(DISPLAY_EP, 1, 0, 0, 0);
+    let _ = syscall::receive(DISPLAY_EP);
 
     for i in 0..count {
         let cmd = &commands[i];
-        // DrawRect: DisplayRequest tag=0, xy packed, wh packed, color
         let xy = cmd.x as usize | ((cmd.y as usize) << 16);
         let wh = cmd.w as usize | ((cmd.h as usize) << 16);
-        let _ = userspace::syscall::send(DISPLAY_EP, 0, xy, wh, cmd.color as usize);
-        let _ = userspace::syscall::receive(DISPLAY_EP);
+        let _ = syscall::send(DISPLAY_EP, 0, xy, wh, cmd.color as usize);
+        let _ = syscall::receive(DISPLAY_EP);
     }
 
-    // Flush: DisplayRequest tag=2
-    let _ = userspace::syscall::send(DISPLAY_EP, 2, 0, 0, 0);
-    let _ = userspace::syscall::receive(DISPLAY_EP);
+    let _ = syscall::send(DISPLAY_EP, 2, 0, 0, 0);
+    let _ = syscall::receive(DISPLAY_EP);
 }
 
 fn wait_tick() {
-    let start = userspace::syscall::get_time();
+    let start = syscall::get_time();
     let deadline = start + TICK_DELAY;
-    while userspace::syscall::get_time() < deadline {
-        userspace::syscall::yield_now();
+    while syscall::get_time() < deadline {
+        syscall::yield_now();
     }
 }
-
-#[cfg(not(test))]
-#[panic_handler]
-fn panic(_: &core::panic::PanicInfo) -> ! {
-    userspace::syscall::exit();
-}