Add an example kernel that can be used to try the bootloader

Author: phil-opp

azure-pipelines.yml

@@ -106,3 +106,6 @@ steps:
     if [ $? -eq 123 ]; then (exit 0); else (exit 1); fi
   displayName: 'Test Bootloader'
 
+- script: cargo xbuild
+  workingDirectory: example-kernel
+  displayName: 'Build Example Kernel'

example-kernel/.cargo/config

@@ -0,0 +1,2 @@
+[build]
+target = "x86_64-example-kernel.json"

example-kernel/.gitignore

@@ -0,0 +1,2 @@
+/target/
+**/*.rs.bk

example-kernel/Cargo.lock

@@ -0,0 +1,8 @@
+[package]
+name = "example-kernel"
+version = "0.1.0"
+authors = ["Philipp Oppermann <[email protected]>"]
+edition = "2018"
+
+[dependencies]
+x86_64 = "0.3.4"

example-kernel/Cargo.toml

@@ -0,0 +1,31 @@
+#![no_std] // don't link the Rust standard library
+#![no_main] // disable all Rust-level entry points
+
+use core::panic::PanicInfo;
+
+static HELLO: &[u8] = b"Hello World!";
+
+#[no_mangle] // don't mangle the name of this function
+pub extern "C" fn _start() -> ! {
+    // this function is the entry point, since the linker looks for a function
+    // named `_start` by default
+
+    let vga_buffer = 0xb8000 as *mut u8;
+    
+    // print `HELLO` to the screen (see
+    // https://os.phil-opp.com/minimal-rust-kernel/#printing-to-screen)
+    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 {}
+}
+
+/// This function is called on panic.
+#[panic_handler]
+fn panic(_info: &PanicInfo) -> ! {
+    loop {}
+}

example-kernel/src/main.rs

@@ -0,0 +1,15 @@
+{
+    "llvm-target": "x86_64-unknown-none",
+    "data-layout": "e-m:e-i64:64-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"
+  }