From e4470bc04c0db9da783c46342efe62d6b6eded1c Mon Sep 17 00:00:00 2001
From: Sainnhe Park <sainnhe@gmail.com>
Date: Wed, 1 Dec 2021 16:47:28 +0800
Subject: [PATCH] Finish VGA Buffer

---
 .cargo/config       |  2 --
 .cargo/config.toml  |  6 ++++++
 Cargo.lock          |  9 +++++++++
 Cargo.toml          |  3 +++
 rust-toolchain.toml |  4 +---
 src/main.rs         | 14 ++++++++++++++
 x86_64-anos.json    | 15 +++++++++++++++
 7 files changed, 48 insertions(+), 5 deletions(-)
 delete mode 100644 .cargo/config
 create mode 100644 .cargo/config.toml
 create mode 100644 x86_64-anos.json

diff --git a/.cargo/config b/.cargo/config
deleted file mode 100644
index 5d10902..0000000
--- a/.cargo/config
+++ /dev/null
@@ -1,2 +0,0 @@
-[build]
-target = "thumbv7em-none-eabihf"
diff --git a/.cargo/config.toml b/.cargo/config.toml
new file mode 100644
index 0000000..098ed3e
--- /dev/null
+++ b/.cargo/config.toml
@@ -0,0 +1,6 @@
+[build]
+target = "x86_64-anos.json"
+
+[unstable]
+build-std-features = ["compiler-builtins-mem"]
+build-std = ["core", "compiler_builtins"]
diff --git a/Cargo.lock b/Cargo.lock
index 9678ac5..addcc1d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5,3 +5,12 @@ version = 3
 [[package]]
 name = "anos"
 version = "0.1.0"
+dependencies = [
+ "bootloader",
+]
+
+[[package]]
+name = "bootloader"
+version = "0.9.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b7c452074efc3c0bfb241fb7bc87df04741c7c85e926f6a07c05f8fbd6008240"
diff --git a/Cargo.toml b/Cargo.toml
index 793a53b..b9b47b9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,3 +9,6 @@ panic = "abort"         # 禁用 panic 时的栈展开
 
 [profile.release]
 panic = "abort"         # 禁用 panic 时的栈展开
+
+[dependencies]
+bootloader = "0.9.8"
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
index 39d1ac5..92e4674 100644
--- a/rust-toolchain.toml
+++ b/rust-toolchain.toml
@@ -1,6 +1,4 @@
 [toolchain]
 channel = "nightly"
-components = [ "rust-analyzer-preview" ]
-targets = [ "thumbv7em-none-eabihf" ]
+components = [ "llvm-tools-preview" ]
 profile = "minimal"
-
diff --git a/src/main.rs b/src/main.rs
index 3457e83..7529037 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,11 +3,25 @@
 
 use core::panic::PanicInfo;
 
+// 定义一个 byte string 类型的静态变量
+static HELLO: &[u8] = b"Hello World!";
+
 #[no_mangle]    // 不重整函数名，否则编译器可能会生成名为 _ZN3blog_os4_start7hb173fedf945531caE 的函数
 // extern "C" 告诉编译器这个函数应当使用 C 语言的调用约定
 // 函数名为 _start 是因为大多数系统默认用这个名字作为入口点名称
 // -> ! 代表这是一个发散函数，不允许有任何返回值，因为它不会被任何函数调用，而是将直接被 bootloader 调用
 pub extern "C" fn _start() -> ! {
+    // VGA Buffer 从 0xb8000 开始
+    let vga_buffer = 0xb8000 as *mut u8;
+
+    // 迭代 HELLO, 通过裸指针 vga_buffer 来定位待写入的缓冲区地址
+    for (i, &byte) in HELLO.iter().enumerate() {
+        unsafe {
+            *vga_buffer.offset(i as isize * 2) = byte;      // ASCII 码字节
+            *vga_buffer.offset(i as isize * 2 + 1) = 0xb;   // 颜色字节, 0xb 代表青色
+        }
+    }
+
     loop {}
 }
 
diff --git a/x86_64-anos.json b/x86_64-anos.json
new file mode 100644
index 0000000..23da62b
--- /dev/null
+++ b/x86_64-anos.json
@@ -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"
+}