refactor + wip bios call from protected mode

boot1/src/main.rs

@@ -8,35 +8,31 @@ const VGA_HEIGHT: usize = 25;
 const VGA_SIZE: usize = VGA_WIDTH * VGA_HEIGHT;
 const VGA_ADDR: usize = 0xb8000;
 
-const STR: &[u8] = b"the quick brown fox jumps over the lazy dog";
+const STR: &[u8] = b"sphinx of black quartz, judge my vow";
 
-// extern "C" {
-//   fn prelude() -> !;
-// }
+#[repr(C)]
+#[derive(Clone, Debug)]
+struct BiosIntr {
+  eax: u32,
+  ebx: u32,
+  ecx: u32,
+  edx: u32,
+  esi: u32,
+  edi: u32,
+  ds: u16,
+  es: u16,
+  eflags: u32,
+}
+
+unsafe extern "C" {
+  unsafe fn bios_call(intr: u32, args: *mut BiosIntr);
+}
 
 #[panic_handler]
 fn panic(_info: &PanicInfo) -> ! {
   hlt()
 }
 
-// ```asm
-// 00000000  E800000000        call 0x5      ; call / pop gadget to load eip into ecx
-// 00000005  59                pop ecx
-// 00000006  81C15F000000      add ecx,0x5f
-// 0000000C  31C0              xor eax,eax
-// 0000000E  8D89D4FFFFFF      lea ecx,[ecx-0x2c]      ; length of string is 0x2b
-// 00000014  0FB611            movzx edx,byte [ecx]
-// 00000017  81CA001F0000      or edx,0x1f00
-// 0000001D  6689940000800B00  mov [eax+eax+0xb8000],dx
-// 00000025  40                inc eax
-// 00000026  41                inc ecx
-// 00000027  83F82B            cmp eax,byte +0x2b
-// 0000002A  75E8              jnz 0x14
-// 0000002C  66C70500800B0002  mov word [dword 0xb8000],0x1f02
-//          -1F
-// 00000035  F4                hlt
-// 00000036  EBFD              jmp short 0x35
-// ```
 #[no_mangle]
 pub extern "C" fn _start() -> ! {
   let vga_buf: &'static mut [u16; VGA_SIZE] = unsafe { &mut *(VGA_ADDR as *mut [u16; VGA_SIZE]) };
@@ -45,6 +41,26 @@ pub extern "C" fn _start() -> ! {
     vga_buf[i] = 0x1f00 | u16::from(b);
   }
 
+  let mut args = BiosIntr {
+    eax: 0xe820,
+    ebx: 0,
+    ecx: 24,
+    edx: 0x534d4150,
+    esi: 0,
+    edi: 0x6a00,
+    ds: 0,
+    es: 0,
+    eflags: 0,
+  };
+
+  unsafe {
+    bios_call(0x15, &raw mut args);
+  }
+
+  for (i, b) in STR.iter().copied().enumerate() {
+    vga_buf[i + VGA_WIDTH] = 0x1f00 | u16::from(b);
+  }
+
   hlt()
 }