Add VESA initiation code feature (Issue #37)

Author: jabedude

Cargo.toml

@@ -28,6 +28,7 @@ llvm-tools = "0.1"
 [features]
 default = []
 vga_320x200 = []
+vesa_800x600 = []
 recursive_page_table = []
 map_physical_memory = []
 

src/main.rs

@@ -31,9 +31,11 @@ global_asm!(include_str!("stage_2.s"));
 global_asm!(include_str!("e820.s"));
 global_asm!(include_str!("stage_3.s"));
 
+#[cfg(feature = "vesa_800x600")]
+global_asm!(include_str!("video_mode/vesa_800x600.s"));
 #[cfg(feature = "vga_320x200")]
 global_asm!(include_str!("video_mode/vga_320x200.s"));
-#[cfg(not(feature = "vga_320x200"))]
+#[cfg(not(any(feature = "vesa_800x600", feature = "vga_320x200")))]
 global_asm!(include_str!("video_mode/vga_text_80x25.s"));
 
 unsafe fn context_switch(boot_info: VirtAddr, entry_point: VirtAddr, stack_pointer: VirtAddr) -> ! {

src/stage_1.s

@@ -35,7 +35,6 @@ enable_a20:
     out 0x92, al
 enable_a20_after:
 
-
 enter_protected_mode:
     # clear interrupts
     cli

src/video_mode/vesa_800x600.s

@@ -0,0 +1,43 @@
+.section .boot, "awx"
+.intel_syntax noprefix
+.code16
+
+# This code is responsible for enabling VESA graphics while in 
+# real mode.
+config_video_mode:
+    # Try VESA
+    mov ax, 0x9000
+    mov es, ax
+    mov di, 0
+    mov ax, 0x4f00
+    int 0x10
+    cmp ax, 0x004f
+    jne vesa_out
+    # Check VESA version 2 or 3
+    mov ax, es:[di+4]
+    cmp ax, 0x0300
+    je init_vesa
+    cmp ax, 0x0200
+    jne vesa_out
+    # Hard coded 800x600x16bit mode; this gets us the PHY-addr of the FB
+init_vesa:
+    mov ax, 0x4f01
+    mov cx, 0x114
+    mov di, VESAInfo
+    int 0x10
+
+    mov ax, 0x4f02
+    mov bx, 0x4114
+    int 0x10
+
+vesa_out:
+    ret
+
+vga_println:
+    ret
+
+vga_map_frame_buffer:
+    ret
+
+VESAInfo:
+    .space 256, 0