remove 64 bit for now

makefile

@@ -1,7 +1,7 @@
-CC = x86_64-elf-gcc
-LD = x86_64-elf-ld
+CC = i386-elf-gcc
+LD = i386-elf-ld
 
-CFLAGS = -ffreestanding -m64
+CFLAGS = -ffreestanding -m32
 
 all: .build/nub-os.iso
 
@@ -27,4 +27,4 @@ build-dir:
 	$(CC) $(CFLAGS) -c -o .build/print.o src/print.c
 
 .build/boot.o: build-dir src/boot.asm
-	nasm -f elf64 -o .build/boot.o src/boot.asm
+	nasm -f elf32 -o .build/boot.o src/boot.asm

src/boot.asm

@@ -14,14 +14,6 @@ align 4
 header_end:
 
 section .bss
-align 4096
-page_table_l4:
-    resb 4096
-page_table_l3:
-    resb 4096
-page_table_l2:
-    resb 4096
-
 align 16
     resb 16384
 stack_top:
@@ -29,129 +21,11 @@ stack_top:
 extern kernel_main
 
 section .text
-bits 32
 global _start
 _start:
     mov esp, stack_top
-
-    call check_cpuid
-    call check_long_mode
-
-    call setup_page_tables
-    call enable_paging
-
-    lgdt [gdt64.pointer]
-
-    jmp gdt64.kernel_code:long_mode_start
-
-check_cpuid:
-    pushfd
-    pop eax
-    mov ecx, eax
-    xor eax, 1 << 21
-    push eax
-    popfd
-    pushfd
-    pop eax
-    push ecx
-    popfd
-    xor eax, ecx
-    jz .no_cpuid
-    ret
-.no_cpuid:
-    mov al, 'I'
-    jmp error
-
-check_long_mode:
-    mov eax, 0x80000000
-    cpuid
-    cmp eax, 0x80000001
-    jb .no_long_mode
-
-    mov eax, 0x80000001
-    cpuid
-    test edx, 1 << 29
-    jz .no_long_mode
-    ret
-.no_long_mode:
-    mov al, 'L'
-    jmp error
-
-setup_page_tables:
-    mov edi, page_table_l4
-    mov ecx, 4096 * 3 / 4
-    xor eax, eax
-    rep stosd
-
-    mov eax, page_table_l3
-    or eax, 0b11
-    mov [page_table_l4], eax
-
-    mov eax, page_table_l2
-    or eax, 0b11
-    mov [page_table_l3], eax
-
-    mov ecx, 0
-.map_p2_table:
-    mov eax, 0x200000
-    mul ecx
-    or eax, 0b10000011
-    mov [page_table_l2 + ecx * 8], eax
-    inc ecx
-    cmp ecx, 512
-    jne .map_p2_table
-    ret
-
-enable_paging:
-    mov eax, page_table_l4
-    mov cr3, eax
-
-    mov eax, cr4
-    or eax, 1 << 5
-    mov cr4, eax
-
-    mov ecx, 0xC0000080
-    rdmsr
-    or eax, 1 << 8
-    wrmsr
-
-    mov eax, cr0
-    or eax, 1 << 31
-    mov cr0, eax
-    ret
-
-bits 64
-long_mode_start:
-    mov ax, gdt64.kernel_data
-    mov ss, ax
-    mov ds, ax
-    mov es, ax
-    mov fs, ax
-    mov gs, ax
-
-    mov rsp, stack_top
-
     call kernel_main
-
-    cli
 hang:
+    cli
     hlt
     jmp hang
-
-error:
-    mov dword [0xb8000], 0x4f524f45
-    mov dword [0xb8004], 0x4f3a4f52
-    mov dword [0xb8008], 0x4f204f20
-    mov byte  [0xb800a], al
-    hlt
-
-section .rodata
-gdt64:
-    dq 0
-.kernel_code: equ $ - gdt64
-    dq (1<<44) | (1<<47) | (1<<41) | (1<<43) | (1<<53)
-.kernel_data: equ $ - gdt64
-    dq (1<<44) | (1<<47) | (1<<41)
-.pointer:
-    dw $ - gdt64 - 1
-    dq gdt64

src/kernel.c

@@ -2,5 +2,5 @@
 
 void kernel_main(void)
 {
-    print("Starting nub-os\n");
+    print("Welcome to nub OS\n");
 }

src/print.c

@@ -8,38 +8,6 @@
 #define BUF_START 0xb8000
 #define BUF_END (BUF_START + BUF_SIZE)
 
-enum FG_COLOR
-{
-    FG_BLACK = 0x0,
-    FG_BLUE = 0x1,
-    FG_GREEN = 0x2,
-    FG_CYAN = 0x3,
-    FG_RED = 0x4,
-    FG_MAGENTA = 0x5,
-    FG_BROWN = 0x6,
-    FG_LIGHT_GRAY = 0x7,
-    FG_DARK_GRAY = 0x8,
-    FG_LIGHT_BLUE = 0x9,
-    FG_LIGHT_GREEN = 0xA,
-    FG_LIGHT_CYAN = 0xB,
-    FG_LIGHT_RED = 0xC,
-    FG_LIGHT_MAGENTA = 0xD,
-    FG_YELLOW = 0xE,
-    FG_WHITE = 0xF,
-};
-
-enum BG_COLOR
-{
-    BG_BLACK = 0x0,
-    BG_BLUE = 0x1,
-    BG_GREEN = 0x2,
-    BG_CYAN = 0x3,
-    BG_RED = 0x4,
-    BG_MAGENTA = 0x5,
-    BG_BROWN = 0x6,
-    BG_LIGHT_GRAY = 0x7,
-};
-
 typedef struct
 {
     uint8_t character;
@@ -66,7 +34,7 @@ void scroll(void)
     }
 }
 
-void put_char(char c, uint8_t color)
+void put_char(char c, FG_COLOR fg_color, BG_COLOR bg_color)
 {
     if (c == '\n')
     {
@@ -75,6 +43,7 @@ void put_char(char c, uint8_t color)
     }
     else
     {
+        uint8_t color = fg_color | bg_color << 4;
         vga_buffer[cursor_row * COLUMNS + cursor_col] = (vga_char){ c, color };
         cursor_col++;
     }
@@ -94,11 +63,14 @@ void put_char(char c, uint8_t color)
 
 void print(const char* string)
 {
-    uint8_t color = FG_WHITE | BG_BLACK << 4;
+    print_clr(string, FG_WHITE, BG_BLACK);
+}
 
+void print_clr(const char* string, FG_COLOR fg_color, BG_COLOR bg_color)
+{
     for (int i = 0; string[i]; i++)
     {
-        put_char(string[i], color);
+        put_char(string[i], fg_color, bg_color);
     }
 }
 

src/print.h

@@ -1,8 +1,40 @@
+#pragma once
 #include <stdint.h>
 
-void kernel_print(const char* string);
+typedef enum
+{
+    FG_BLACK = 0x0,
+    FG_BLUE = 0x1,
+    FG_GREEN = 0x2,
+    FG_CYAN = 0x3,
+    FG_RED = 0x4,
+    FG_MAGENTA = 0x5,
+    FG_BROWN = 0x6,
+    FG_LIGHT_GRAY = 0x7,
+    FG_DARK_GRAY = 0x8,
+    FG_LIGHT_BLUE = 0x9,
+    FG_LIGHT_GREEN = 0xA,
+    FG_LIGHT_CYAN = 0xB,
+    FG_LIGHT_RED = 0xC,
+    FG_LIGHT_MAGENTA = 0xD,
+    FG_YELLOW = 0xE,
+    FG_WHITE = 0xF,
+} FG_COLOR;
 
-void put_char(char c, uint8_t color);
+typedef enum
+{
+    BG_BLACK = 0x0,
+    BG_BLUE = 0x1,
+    BG_GREEN = 0x2,
+    BG_CYAN = 0x3,
+    BG_RED = 0x4,
+    BG_MAGENTA = 0x5,
+    BG_BROWN = 0x6,
+    BG_LIGHT_GRAY = 0x7,
+} BG_COLOR;
+
+void put_char(char c, FG_COLOR fg_color, BG_COLOR bg_color);
 void print(const char* string);
+void print_clr(const char* string, FG_COLOR fg_color, BG_COLOR bg_color);
 void clear_screen(void);
 void set_cursor_position(int row, int col);

src/string.c

@@ -0,0 +1,10 @@
+int strcmp(const char* a, const char* b)
+{
+    while ((*a != '\0' && *b != '\0') && *a == *b)
+    {
+        a++;
+        b++;
+    }
+
+    return (*a == *b) ? 0 : (*a > *b) ? 1 : -1;
+}

src/string.h

@@ -0,0 +1,3 @@
+#pragma once
+
+int strcmp(const char* a, const char* b);