feat(bootloader): add bootable image

Signed-off-by: Julien CLEMENT <julien.clement@epita.fr>

.cargo/config.toml

@@ -1,5 +1,9 @@
-[target.'cfg(target_os = "linux")']
+[build]
-rustflags = ["-C", "link-arg=-nostartfiles"]
+target = "x86_64-julios.json"
 
 [unstable]
+build-std-features = ["compiler-builtins-mem"]
 build-std = ["core", "compiler_builtins"]
+
+[target.'cfg(target_os = "none")']
+runner = "bootimage runner"

Cargo.lock

@@ -2,6 +2,15 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "bootloader"
+version = "0.9.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b7c452074efc3c0bfb241fb7bc87df04741c7c85e926f6a07c05f8fbd6008240"
+
 [[package]]
 name = "julios"
 version = "0.1.0"
+dependencies = [
+ "bootloader",
+]

Cargo.toml

@@ -6,4 +6,4 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-
+bootloader = "0.9.8"

src/main.rs

@@ -7,8 +7,21 @@ fn panic(_info: &core::panic::PanicInfo) -> !
     loop {}
 }
 
+static HELLO: &[u8] = b"Welcome to the JuliOS";
+
 #[no_mangle]
 pub extern "C" fn _start() -> !
 {
+    let vga_buffer: *mut u8 = 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 {}
 }