Hello, World!

.cargo/config.toml

@@ -1,6 +1,9 @@
 [build]
 target = "x86_64_plain_os.json"
 
+[target.'cfg(target_os = "none")']
+runner = "bootimage runner"
+
 [unstable]
 # enable implementations for memset, memcpy and memcmp etc.
 build-std-features = ["compiler-builtins-mem"]

Cargo.lock

@@ -2,6 +2,15 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "bootloader"
+version = "0.9.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "de78decc37247c7cfac5dbf3495c7298c6ac97cb355161caa7e15969c6648e6c"
+
 [[package]]
 name = "plain_os"
 version = "0.1.0"
+dependencies = [
+ "bootloader",
+]

Cargo.toml

@@ -14,3 +14,4 @@ panic = "abort" # disable stack unwinding on panic
 panic = "abort" # disable stack unwinding on panic
 
 [dependencies]
+bootloader = "0.9"

README.md

@@ -0,0 +1,21 @@
+# PlainOS, something that may operate your system
+
+This may or may not do things in the future.
+
+## Building
+
+Building the project requires Rust Nightly and the `bootimage` tool since I've yet to upgrade my `bootloader` dependency:
+
+```bash
+rustup override set nightly
+rustup component add rust-src --toolchain nightly # needed for building `core` from source
+cargo install bootimage
+rustup component add llvm-tools-preview
+```
+
+You'll need QEMU to run the kernel. To build the project and run it in `qemu`, run:
+
+```bash
+cargo run
+```
+

src/main.rs

@@ -3,15 +3,26 @@
 
 use core::panic::PanicInfo;
 
+static HELLO: &[u8] = b"Hello World!";
+
 /// This function defines the panic handler
 #[panic_handler]
 fn panic(_info: &PanicInfo) -> ! {
     loop{}
 }
 
-#[no_mangle]
-pub extern "C" fn _start() -> ! {
 // this function is the entry point, since the linker looks for a function
 // named `_start` by default
+#[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 {}
 }