Set up VESA mode properly instead of hardcoding it

Use the vesa init code from Redox. Comment out prompting the user for resolution for now (we can make it configurable later).

Author: phil-opp

Cargo.toml

@@ -65,10 +65,9 @@ serde = { version = "1.0", features = ["derive"], optional = true}
 default = []
 builder = ["argh", "thiserror", "displaydoc", "anyhow", "llvm-tools", "json", "fatfs", "gpt"]
 runner = ["anyhow"]
-bios_bin = ["binary", "vga_320x200", "rsdp"]
-uefi_bin = ["binary", "uefi", "font8x8"]
-binary = ["llvm-tools-build", "x86_64", "toml", "xmas-elf", "usize_conversions", "log", "conquer-once", "spinning_top", "serde"]
-vga_320x200 = ["font8x8"]
+bios_bin = ["binary", "rsdp"]
+uefi_bin = ["binary", "uefi"]
+binary = ["llvm-tools-build", "x86_64", "toml", "xmas-elf", "usize_conversions", "log", "conquer-once", "spinning_top", "serde", "font8x8"]
 recursive_page_table = []
 map_physical_memory = []
 

src/asm/stage_2.s

@@ -87,7 +87,7 @@ create_memory_map:
     call do_e820
 
 video_mode_config:
-    call config_video_mode
+    call vesa
 
 enter_protected_mode_again:
     cli
@@ -103,3 +103,70 @@ enter_protected_mode_again:
 
 spin32:
     jmp spin32
+
+
+
+# print a string and a newline
+# IN
+#   esi: points at zero-terminated String
+vga_println:
+    push eax
+    push ebx
+    push ecx
+    push edx
+
+    call vga_print
+
+    # newline
+    mov edx, 0
+    mov eax, vga_position
+    mov ecx, 80 * 2
+    div ecx
+    add eax, 1
+    mul ecx
+    mov vga_position, eax
+
+    pop edx
+    pop ecx
+    pop ebx
+    pop eax
+
+    ret
+
+# print a string
+# IN
+#   esi: points at zero-terminated String
+# CLOBBER
+#   ah, ebx
+vga_print:
+    cld
+vga_print_loop:
+    # note: if direction flag is set (via std)
+    # this will DECREMENT the ptr, effectively
+    # reading/printing in reverse.
+    lodsb al, BYTE PTR [esi]
+    test al, al
+    jz vga_print_done
+    call vga_print_char
+    jmp vga_print_loop
+vga_print_done:
+    ret
+
+
+# print a character
+# IN
+#   al: character to print
+# CLOBBER
+#   ah, ebx
+vga_print_char:
+    mov ebx, vga_position
+    mov ah, 0x0f
+    mov [ebx + 0xa0000], ax
+
+    add ebx, 2
+    mov [vga_position], ebx
+
+    ret
+
+vga_position:
+    .double 0

src/asm/stage_3.s

@@ -13,9 +13,6 @@ stage_3:
     mov es, bx # set extra segment
     mov ss, bx # set stack segment
 
-    mov si, offset boot_third_stage_str
-    call vga_println
-
 check_cpu:
     call check_cpuid
     call check_long_mode
@@ -168,6 +165,5 @@ gdt_64_pointer:
     .word gdt_64_pointer - gdt_64 - 1    # 16-bit Size (Limit) of GDT.
     .long gdt_64                            # 32-bit Base Address of GDT. (CPU will zero extend to 64-bit)
 
-boot_third_stage_str: .asciz "Booting (third stage)..."
 no_cpuid_str: .asciz "Error: CPU does not support CPUID"
 no_long_mode_str: .asciz "Error: CPU does not support long mode"