Booting from the code

.cargo/config.toml

@@ -0,0 +1,9 @@
+[build]
+target = "x86_64-simpleos.json"
+
+[unstable]
+build-std-features = ["compiler-builtins-mem"]
+build-std = ["core", "compiler_builtins"]
+
+[target.'cfg(target_os = "none")']
+runner = "bootimage runner"

Cargo.toml

@@ -4,3 +4,4 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+bootloader = "0.9"

src/main.rs

@@ -1,3 +1,25 @@
-fn main() {
-    println!("Hello, world!");
+#![no_std]
+#![no_main]
+
+use core::panic::PanicInfo;
+
+static HELLO: &[u8] = b"Hello World!";
+
+#[no_mangle]
+pub extern "C" fn _start() -> ! {
+    let vga_buffer = 0xb8000 as *mut u8;
+
+    for (i, &byte) in HELLO.iter().enumerate() {
+        unsafe {
+            *vga_buffer.offset(i as isize * 2) = byte;
+            *vga_buffer.offset(i as isize * 2 + 1) = 0xb;
+        }
+    }
+
+    loop {}
+}
+
+#[panic_handler]
+fn panic(_info: &PanicInfo) -> ! {
+    loop {}
 }

x86_64-simpleos.json

@@ -0,0 +1,15 @@
+{
+    "llvm-target": "x86_64-unknown-none",
+    "data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
+    "arch": "x86_64",
+    "target-endian": "little",
+    "target-pointer-width": "64",
+    "target-c-int-width": "32",
+    "os": "none",
+    "executables": true,
+    "linker-flavor": "ld.lld",
+    "linker": "rust-lld",
+    "panic-strategy": "abort",
+    "disable-redzone": true,
+    "features": "-mmx,-sse,+soft-float"
+}