1 files changed, 41 insertions, 0 deletions
diff --git a/src/startup.zig b/src/startup.zig
new file mode 100644
index 0000000..f7c7712
--- /dev/null
+++ b/src/startup.zig
@@ -0,0 +1,41 @@
+const main = @import("main.zig");
+
+extern const __data_flash: u32;
+extern const __data: u32;
+extern const __data_size: u32;
+extern const __bss: u32;
+extern const __bss_size: u32;
+
+comptime {
+    asm (
+        \\.extern _start
+        \\.extern _tstack
+        \\
+        \\.section .vector_table
+        \\.global init_vector_table
+        \\init_vector_table:
+        \\    .word _tstack
+        \\    .word _start
+        \\    .skip 4 * 14
+    );
+}
+
+inline fn zero_bss() void {
+    const bss: [*]volatile u8 = @ptrFromInt(@intFromPtr(&__bss));
+    @memset(bss[0..@intFromPtr(&__bss_size)], 0);
+}
+
+inline fn copy_data() void {
+    const data_flash: [*]volatile u8 = @ptrFromInt(@intFromPtr(&__data_flash));
+    const data: [*]volatile u8 = @ptrFromInt(@intFromPtr(&__data));
+    const data_size = @intFromPtr(&__data_size);
+    @memcpy(data[0..data_size], data_flash[0..data_size]);
+}
+
+export fn _start() callconv(.C) noreturn {
+    zero_bss();
+    copy_data();
+    main.main();
+    while (true) {}
+}
+