Added BPB and minor changes
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parent
512f348d74
commit
946f7e72c3
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@ -69,5 +69,6 @@ _deps
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*.bin
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*.img
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dist/
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obj/
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build/
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@ -10,7 +10,8 @@
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"compilerPath": "/usr/bin/gcc",
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"cStandard": "gnu17",
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"cppStandard": "gnu++17",
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"intelliSenseMode": "linux-gcc-x64"
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"intelliSenseMode": "linux-gcc-x64",
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"configurationProvider": "ms-vscode.makefile-tools"
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}
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],
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"version": 4
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1
Makefile
1
Makefile
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@ -67,6 +67,7 @@ $(OBJDIR)/%.o: prepare $(SRCDIR)/%.c
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# Compile kernel drivers
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drivers: $(DRIVERS_OBJS)
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# Compile and link the kernel
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$(BUILDDIR)/kernel.bin: $(OBJDIR)/entrypoint.o $(KERNEL_OBJS) $(DRIVERS_OBJS)
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$(LD) -o $@ -Ttext 0x1000 $^ --oformat binary
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100
src/boot/mbr.s
100
src/boot/mbr.s
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@ -12,43 +12,82 @@
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; See the License for the specific language governing permissions and
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; limitations under the License.
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; Definition of the MBR (Master Boot Record). This is basically our bootloader and
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; is located in the first 512 bytes of the drive we're booting from. From here, we
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; do some basic setup and then call into the kernel
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; Welcome to TSBL: The Simple Bootloader
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[org 0x7c00] ; Address where the code expects to be loaded in. The BIOS always loads us here
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[bits 16] ; All x86 CPUs start in 16 bit (aka "real") mode, so we tell nasm to emit 16-bit code
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kernel_offset: equ 0x1000
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reserved_sectors: equ 4
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; Code copied from the limine bootloader
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; This isn't needed inside the qemu emulator, but
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; real hardware is unlikely to start up with the
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; segment registers zeroed, so we do it here
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mov ax, 0
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mov ds, ax
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mov ss, ax
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mov es, ax
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xor ax, ax
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jmp skip_bpb ; Workaround for some BIOSes that require this stub
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nop
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; We save the value of the current boot drive
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mov [boot_drive], dl
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; Some BIOSes will do a funny and decide to overwrite bytes of code in
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; the section where a FAT BPB would be, potentially overwriting
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; bootsector code.
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; Avoid that by filling the BPB area with dummy values.
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; Some of the values have to be set to certain values in order
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; to boot on even quirkier machines.
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; Source: https://github.com/freebsd/freebsd-src/blob/82a21151cf1d7a3e9e95b9edbbf74ac10f386d6a/stand/i386/boot2/boot1.S
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; Now we setup the stack by setting the
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; base pointer to a location that's far
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; enough from where the code for the BIOS
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; is located
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mov sp, 0x9000
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mov bp, sp
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call bios_cls
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mov si, loading_stage2_msg
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call bios_println
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mov bx, stage2
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mov cl, 2
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mov dh, reserved_sectors
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mov dl, [boot_drive]
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call load_disk
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jmp stage2
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bpb:
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times 3-($-$$) db 0
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bpb_oem_id: db "TSBL "
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bpb_sector_size: dw 512
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bpb_sects_per_cluster: db 0
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bpb_reserved_sects: dw 0
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bpb_fat_count: db 0
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bpb_root_dir_entries: dw 0
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bpb_sector_count: dw 0
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bpb_media_type: db 0
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bpb_sects_per_fat: dw 0
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bpb_sects_per_track: dw 18
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bpb_heads_count: dw 2
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bpb_hidden_sects: dd 0
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bpb_sector_count_big: dd 0
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bpb_drive_num: db 0
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bpb_reserved: db 0
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bpb_signature: db 0
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bpb_volume_id: dd 0
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bpb_volume_label: db "TSBL "
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bpb_filesystem_type: times 8 db 0
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kernel_offset: equ 0x1000 ; Address in memory where kernel will be loaded
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reserved_sectors: equ 4 ; How many disk sectors we reserve for our second stage
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skip_bpb:
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cli
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cld
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; This isn't needed inside the qemu emulator, but
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; real hardware is unlikely to start up with the
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; segment registers zeroed, so we do it here
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xor si, si
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mov ds, si
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mov ss, si
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mov es, si
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; We save the value of the current boot drive
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mov [boot_drive], dl
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; Now we setup the stack by setting the
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; base pointer to a location that's far
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; enough from where the code for the BIOS
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; is located
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mov sp, 0x7c00
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mov bp, sp
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sti
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call bios_cls
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mov si, loading_stage2_msg
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call bios_println
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mov bx, stage2
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mov cl, 2
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mov dh, reserved_sectors
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mov dl, [boot_drive]
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call load_disk
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jmp stage2
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; Variables needed in the boot
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@ -66,6 +105,7 @@ times 510 - ($ - $$) db 0
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dw 0xaa55
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[bits 16]
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stage2:
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; Here we're no longer limited by the size of the
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; boot sector, so we can perform the more complex
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@ -59,7 +59,7 @@ void kprintAt(char* message, i32 col, i32 row) {
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}
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void kprint(char* message) {
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void inline kprint(char* message) {
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/*
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Prints a null-terminated string to the
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VGA text buffer
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@ -21,7 +21,8 @@ limitations under the License.
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i32 kmain(void) {
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/*
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The kernel entry point of TSOS
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The kernel entry point of TSKL: The
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Simple Kernel
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*/
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@ -29,5 +30,5 @@ i32 kmain(void) {
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// log messages like this is just awful
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kprintln("\n\n\nTSKL - INFO: Kernel booted successfully");
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// TODO...
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return 0x022172; // :D
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return 0x202172; // :D
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}
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@ -82,6 +82,4 @@ void itoa(i32 n, char* a) {
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if (sign < 0) a[--i] = '-';
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a[--i] = '\0';
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/* TODO: implement "reverse" */
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}
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