Added BPB and minor changes

.gitignore

@@ -69,5 +69,6 @@ _deps
 *.bin
 *.img
 dist/
-
+obj/
+build/
 

.vscode/c_cpp_properties.json

@@ -10,7 +10,8 @@
             "compilerPath": "/usr/bin/gcc",
             "cStandard": "gnu17",
             "cppStandard": "gnu++17",
-            "intelliSenseMode": "linux-gcc-x64"
+            "intelliSenseMode": "linux-gcc-x64",
+            "configurationProvider": "ms-vscode.makefile-tools"
         }
     ],
     "version": 4

Makefile

@@ -67,6 +67,7 @@ $(OBJDIR)/%.o: prepare $(SRCDIR)/%.c
 # Compile kernel drivers
 drivers: $(DRIVERS_OBJS)
 
+
 # Compile and link the kernel
 $(BUILDDIR)/kernel.bin: $(OBJDIR)/entrypoint.o $(KERNEL_OBJS) $(DRIVERS_OBJS)
 	$(LD) -o $@ -Ttext 0x1000 $^ --oformat binary

src/boot/mbr.s

@@ -12,43 +12,82 @@
 ; See the License for the specific language governing permissions and
 ; limitations under the License.
 
-; Definition of the MBR (Master Boot Record). This is basically our bootloader and
-; is located in the first 512 bytes of the drive we're booting from. From here, we
-; do some basic setup and then call into the kernel
+; Welcome to TSBL: The Simple Bootloader
 
 [org 0x7c00]    ; Address where the code expects to be loaded in. The BIOS always loads us here
 [bits 16]       ; All x86 CPUs start in 16 bit (aka "real") mode, so we tell nasm to emit 16-bit code
 
-kernel_offset: equ 0x1000
-reserved_sectors: equ 4
-
-; This isn't needed inside the qemu emulator, but
-; real hardware is unlikely to start up with the
-; segment registers zeroed, so we do it here
-mov ax, 0
-mov ds, ax
-mov ss, ax
-mov es, ax
-xor ax, ax
-
-; We save the value of the current boot drive
-mov [boot_drive], dl
-
-; Now we setup the stack by setting the
-; base pointer to a location that's far
-; enough from where the code for the BIOS
-; is located
-mov sp, 0x9000
-mov bp, sp
-call bios_cls
-mov si, loading_stage2_msg
-call bios_println
-mov bx, stage2
-mov cl, 2
-mov dh, reserved_sectors
-mov dl, [boot_drive]
-call load_disk
-jmp stage2
+; Code copied from the limine bootloader
+
+jmp skip_bpb ; Workaround for some BIOSes that require this stub
+nop
+
+; Some BIOSes will do a funny and decide to overwrite bytes of code in
+; the section where a FAT BPB would be, potentially overwriting
+; bootsector code.
+; Avoid that by filling the BPB area with dummy values.
+; Some of the values have to be set to certain values in order
+; to boot on even quirkier machines.
+; Source: https://github.com/freebsd/freebsd-src/blob/82a21151cf1d7a3e9e95b9edbbf74ac10f386d6a/stand/i386/boot2/boot1.S
+
+bpb:
+    times 3-($-$$) db 0
+    bpb_oem_id:            db "TSBL  "
+    bpb_sector_size:       dw 512
+    bpb_sects_per_cluster: db 0
+    bpb_reserved_sects:    dw 0
+    bpb_fat_count:         db 0
+    bpb_root_dir_entries:  dw 0
+    bpb_sector_count:      dw 0
+    bpb_media_type:        db 0
+    bpb_sects_per_fat:     dw 0
+    bpb_sects_per_track:   dw 18
+    bpb_heads_count:       dw 2
+    bpb_hidden_sects:      dd 0
+    bpb_sector_count_big:  dd 0
+    bpb_drive_num:         db 0
+    bpb_reserved:          db 0
+    bpb_signature:         db 0
+    bpb_volume_id:         dd 0
+    bpb_volume_label:      db "TSBL     "
+    bpb_filesystem_type:   times 8 db 0
+
+
+kernel_offset: equ 0x1000   ; Address in memory where kernel will be loaded
+reserved_sectors: equ 4     ; How many disk sectors we reserve for our second stage
+
+
+skip_bpb:
+    cli 
+    cld
+    ; This isn't needed inside the qemu emulator, but
+    ; real hardware is unlikely to start up with the
+    ; segment registers zeroed, so we do it here
+    xor si, si
+    mov ds, si
+    mov ss, si
+    mov es, si 
+
+
+    ; We save the value of the current boot drive
+    mov [boot_drive], dl
+
+    ; Now we setup the stack by setting the
+    ; base pointer to a location that's far
+    ; enough from where the code for the BIOS
+    ; is located
+    mov sp, 0x7c00
+    mov bp, sp
+    sti
+    call bios_cls
+    mov si, loading_stage2_msg
+    call bios_println
+    mov bx, stage2
+    mov cl, 2
+    mov dh, reserved_sectors
+    mov dl, [boot_drive]
+    call load_disk
+    jmp stage2
 
 
 ; Variables needed in the boot
@@ -66,6 +105,7 @@ times 510 - ($ - $$) db 0
 dw 0xaa55
 
 [bits 16]
+
 stage2:
     ; Here we're no longer limited by the size of the
     ; boot sector, so we can perform the more complex
@@ -76,7 +116,7 @@ stage2:
     call switch_to_protected_mode
 
 
-load_kernel:    
+load_kernel:
     ; Loads the kernel into memory
     mov bx, kernel_offset
     mov cl, reserved_sectors + 1

src/kernel/drivers/vga/screen.c

@@ -59,7 +59,7 @@ void kprintAt(char* message, i32 col, i32 row) {
 }
 
 
-void kprint(char* message) {
+void inline kprint(char* message) {
     /*
     Prints a null-terminated string to the
     VGA text buffer

src/kernel/main.c

@@ -21,7 +21,8 @@ limitations under the License.
 
 i32 kmain(void) {
     /*
-    The kernel entry point of TSOS
+    The kernel entry point of TSKL: The
+    Simple Kernel
     */
 
 
@@ -29,5 +30,5 @@ i32 kmain(void) {
     // log messages like this is just awful
     kprintln("\n\n\nTSKL -  INFO: Kernel booted successfully");
     // TODO...
-    return 0x022172; // :D
+    return 0x202172; // :D
 }

src/kernel/util.c

@@ -82,6 +82,4 @@ void itoa(i32 n, char* a) {
 
     if (sign < 0) a[--i] = '-';
     a[--i] = '\0';
-
-    /* TODO: implement "reverse" */
 }