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Diffstat (limited to 'boot/entry.asm')
| -rw-r--r-- | boot/entry.asm | 564 |
1 files changed, 0 insertions, 564 deletions
diff --git a/boot/entry.asm b/boot/entry.asm deleted file mode 100644 index fa6f0ef..0000000 --- a/boot/entry.asm +++ /dev/null @@ -1,564 +0,0 @@ -; Melvin's awesome ext2 bootloader -; I'm not really good at assembly, there are MANY ways to improve this! -; MIT License, Copyright (c) 2020 Marvin Borner - -; Definitions - -; General configurations -; TODO: Find out why 2560x1600 doesn't work -%define VIDEO_WIDTH 1920 -%define VIDEO_HEIGHT 1200 -%define VIDEO_BPP 4 - -; Boot constants -%define LOCATION 0x7c00 ; Bootloader location -%define SECTOR_END 0xaa55 ; Bootsector end signature -%define SECTOR_SIZE 510 ; 512 bytes minus signature - -; Interrupts -%define VIDEO_INT 0x10 ; Video BIOS Interrupt -%define DISK_INT 0x13 ; Disk BIOS Interrupt -%define MISC_INT 0x15 ; Miscellaneous services BIOS Interrupt - -; Characters -%define NEWLINE 0x0A ; Newline character (\n) -%define RETURN 0x0D ; Return character (\r) -%define NULL 0x00 ; NULL character (\0) - -; Video commands (VGA) -%define VIDEO_CLEAR 0x03 ; Clear screen command -%define VIDEO_OUT 0x0e ; Teletype output command - -; Disk commands -%define DISK_EXT_CHECK 0x41 ; Disk extension check command -%define DISK_EXT_CHECK_SIG1 0x55aa ; First extension check signature -%define DISK_EXT_CHECK_SIG2 0xaa55 ; Second extension check signature -%define DISK_ZERO 0x80 ; First disk - TODO: Disk detection -%define DISK_READ 0x42 ; Disk extended read command - -; EXT2 constants -%define EXT2_SB_SIZE 0x400 ; Superblock size -%define EXT2_SIG_OFFSET 0x38 ; Signature offset in superblock -%define EXT2_TABLE_OFFSET 0x08 ; Inode table offset after superblock -%define EXT2_INODE_TABLE_LOC 0x1000 ; New inode table location in memory -%define EXT2_ROOT_INODE 0x02 ; Root inode -%define EXT2_INODE_SIZE 0x80 ; Single inode size -%define EXT2_GET_ADDRESS(inode) (EXT2_INODE_TABLE_LOC + (inode - 1) * EXT2_INODE_SIZE) -%define EXT2_COUNT_OFFSET 0x1c ; Inode offset of number of data blocks -%define EXT2_POINTER_OFFSET 0x28 ; Inode offset of first data pointer -%define EXT2_IND_POINTER_OFFSET 0x2c ; Inode offset of singly indirect data pointer -%define EXT2_DIRECT_POINTER_COUNT 0x0c ; Direct pointer count -%define EXT2_ENTRY_LENGTH_OFFSET 0x04 ; Dirent offset of entry length -%define EXT2_FILENAME_OFFSET 0x08 ; Dirent offset of filename -%define EXT2_INODE_OFFSET 0x00 ; Dirent offset of inode number -%define EXT2_SIG 0xef53 ; Signature - -; Video constants (VESA) -%define VESA_START 0x2000 ; Struct starts at 0x2000 -%define VESA_END 0x3000 ; Struct ends at 0x3000 -%define VESA_GET_MODES 0x4f00 ; Get video modes (via 10h) -%define VESA_GET_INFO 0x4f01 ; Get video mode info (via 10h) -%define VESA_SET_MODE 0x4f02 ; Set video mode (via 10h) -%define VESA_SUCCESS_SIG 0x004f ; Returns if VBE call succeeded -%define VESA_MODE_OFFSET 0xe ; Offset to mode pointer -%define VESA_MODE_SEGMENT 0x10 ; Mode pointer segment -%define VESA_LIST_END 0xffff ; End of mode list -%define VESA_PITCH_OFFSET 0x10 ; Pitch offset in mode info -%define VESA_WIDTH_OFFSET 0x12 ; Width offset in mode info -%define VESA_HEIGHT_OFFSET 0x14 ; Height offset in mode info -%define VESA_BPP_OFFSET 0x19 ; Bytes Per Pixel (BPP) offset in mode info -%define VESA_FRAMEBUFFER_OFFSET 0x2a ; Framebuffer offset in mode info -%define VESA_LFB_FLAG 0x4000 ; Enable LFB flag - -; MMAP constants -%define MMAP_START 0x500 ; Starts at 0x500, ends at 0x600 -%define MMAP_SIZE 0x18 ; Struct size -%define MMAP_SIG 0x0534d4150 ; Signature ("SMAP") -%define MMAP_BIOS_MAGIC 0xe820 ; BIOS int 15h code to get address map - -; A20 constants -%define A20_GATE 0x92 ; Fast A20 gate -%define A20_ENABLED 0b10 ; Bit 1 defines whether A20 is enabled -%define A20_EXCLUDE_BIT 0xfe ; Bit 0 may be write-only, causing a crash - -; GDT constants (bitmap) -%define GDT_MAX_LIMIT 0xffff ; I just use the max limit lel -%define GDT_PRESENT 0b10000000 ; Is present -%define GDT_RING3 0b01100000 ; Privilege level 3 -%define GDT_DESCRIPTOR 0b00010000 ; Descriptor type, set for code/data -%define GDT_EXECUTABLE 0b00001000 ; Can be executed -%define GDT_READWRITE 0b00000010 ; Read/write access for code/data -%define GDT_ACCESSED 0b00000001 ; Whether segment is accessed -%define GDT_GRANULARITY (0x80 | 0x00) ; Page granularity (4KiB) -%define GDT_SIZE (0x40 | 0x00) ; Use 32 bit selectors -%define GDT_DATA_OFFSET 0x10 ; Offset to GDT data segment - -; Kernel loader constants -%define STACK_POINTER 0x00500000 ; The initial stack pointer in kernel mode -%define LOADER_POSITION 0x00009000 ; Kernel loader position in protected mode - -; ENOUGH, let's go! - -bits 16 -org LOCATION - -; This is the first stage. It prints some things, checks some things -; and jumps to the second stage. Nothing special. -global _start -_start: - ; Clear screen - mov ax, VIDEO_CLEAR - int VIDEO_INT - - ; Check LBA support - mov ah, DISK_EXT_CHECK - mov bx, DISK_EXT_CHECK_SIG1 - int DISK_INT - jc lba_error - cmp bx, DISK_EXT_CHECK_SIG2 - jnz lba_error - - ; Check disk and move dl - and dl, DISK_ZERO ; Use disk 0 - jz disk_error - mov [drive], dl - - ; Load stage two - mov bx, stage_two - mov [dest], bx - call disk_read - - ; JUMP - jmp stage_two - -print: - push bx - push ax - mov ah, VIDEO_OUT - xor bh, bh - print_ch: - lodsb - test al, al - jz print_end - int VIDEO_INT - jmp print_ch - print_end: - pop ax - pop bx - ret - -disk_read: - mov si, packet ; Address of dap - mov ah, DISK_READ ; Extended read - mov dl, [drive] ; Drive number - int DISK_INT - jc disk_error - ret - -; Errors -disk_error: - mov si, disk_error_msg - call print - jmp $ -lba_error: - mov si, lba_error_msg - call print - jmp $ - -; Now put some data and routines just before the end of the boot sector because -; we've still got some space left :) - -; Video map routine -video_map: - mov bx, VESA_START ; Set load address - mov di, bx - mov ax, VESA_GET_MODES ; Get video modes - int VIDEO_INT ; Ask BIOS for data! - - cmp ax, VESA_SUCCESS_SIG ; Check VBE support in response - jne .error ; Not supported :( - - mov si, [bx + VESA_MODE_OFFSET] ; Mode pointer offset - mov ax, [bx + VESA_MODE_SEGMENT] ; Mode pointer segment - mov es, ax - - mov di, VESA_END ; End of VBE struct -.loop: - mov bx, [es:si] ; Load bx with video mode - cmp bx, VESA_LIST_END ; Is this the end? - jae .done ; Yes, there aren't any modes left - - add si, 2 - mov [.mode], bx - - mov ax, VESA_GET_INFO ; Get mode information - mov cx, [.mode] ; Save in here - int VIDEO_INT ; BIOS interrupt! - cmp ax, VESA_SUCCESS_SIG ; Check if call succeeded - jne .error ; Nope, jump to error! - - mov ax, [es:di + VESA_FRAMEBUFFER_OFFSET] ; Save framebuffer - mov [.framebuffer], ax ; Move fb address to struct - - mov ax, [es:di + VESA_PITCH_OFFSET] ; Save pitch - mov bx, [es:di + VESA_WIDTH_OFFSET] ; Save width - mov cx, [es:di + VESA_HEIGHT_OFFSET] ; Save height - mov dx, [es:di + VESA_BPP_OFFSET] ; Save BPP - - mov [.bpp], dx ; Move bpp to struct (bigger bpp is always desired) - add di, 0x100 - - cmp ax, [.pitch] ; Compare with desired pitch - jne .loop ; Not equal, continue search! - cmp bx, [.width] ; Compare with desired height - jne .loop ; Not equal, continue search! - cmp cx, [.height] ; Compare with desired height - jne .loop ; Not equal, continue search! - - lea ax, [es:di - 0x100] - mov [vid_info.array], ax -.set_mode: - mov ax, VESA_SET_MODE ; Set VBE mode - mov bx, [.mode] ; Set mode address - mov [vid_info], bx ; Move mode information to array - or bx, VESA_LFB_FLAG ; Enable LFB - int VIDEO_INT ; SET! - cmp ax, VESA_SUCCESS_SIG ; Check if set succeeded - jne .error ; Nope, jump to error! -.done: - ret ; Finished loop and set! -.error: ; Something failed - print message and loop! - mov si, video_error_msg - call print - jmp $ - -; Video default data -.mode dw 0 -.width dw VIDEO_WIDTH -.height dw VIDEO_HEIGHT -.pitch dw (VIDEO_WIDTH * VIDEO_BPP) -.bpp dw VIDEO_BPP -.framebuffer dd 0 - -; Tries to load a memory map using BIOS INT 15h and e820h -memory_map: - xor ebx, ebx ; Must be 0 by spec - xor bp, bp - mov edx, MMAP_SIG ; "SMAP" in hex - mov eax, MMAP_BIOS_MAGIC ; Specify MMAP information - mov [es:di + 20], dword 1 ; Force a valid ACPI entry - mov ecx, MMAP_SIZE ; Request struct size - int MISC_INT ; BIOS interrupt - jc .fail ; Carry means "unsupported function" - mov edx, MMAP_SIG ; Mov for verification - cmp eax, edx ; Verification: Must be "SMAP" - jne .fail ; Result wasn't correct signature - test ebx, ebx ; Is size >1 - je .fail ; Nope, worthless :( - jmp .loop -.next: - mov eax, MMAP_BIOS_MAGIC ; Re-move because 0x15 clears or sth - mov [es:di + 20], dword 1 ; Force a valid ACPI entry - mov ecx, MMAP_SIZE ; Request struct size - int MISC_INT ; BIOS interrupt - jc .done ; Carry means "end of list already reached" - mov edx, MMAP_SIG ; Repair register (safety first!) -.loop: - jcxz .skip ; Skip 0-length entries - cmp cl, 20 ; Is the response correct ACPI spec (24 byte)? - jbe .notext ; Nope? Jump! - test byte [es:di + 20], 1 ; Is the "ignore this data" bit clear? - je .skip ; Yep? Skip! -.notext: - mov ecx, [es:di + 8] ; Get lower 32 bits of region - or ecx, [es:di + 12] ; "Or" with upper 32 bits to test for zero - jz .skip ; It's zero, skip! - inc bp - add di, MMAP_SIZE ; Else, next! -.skip: - test ebx, ebx ; If ebx is 0, list is complete - jne .next ; Else, next! -.done: - mov [mmap_cnt], bp - clc ; Clear carry - ret ; Finished! -.fail: - stc ; Set "unsupported function" - ret ; Finished! - -mmap_cnt: dd 0 - -; Variables -disk_error_msg db "Disk error!", NEWLINE, RETURN, NULL -lba_error_msg db "LBA error!", NEWLINE, RETURN, NULL -video_error_msg db "Video error!", NEWLINE, RETURN, NULL -found_msg db "Found file!", NEWLINE, RETURN, NULL - -; Filenames -loader_name db "load.bin" -loader_name_len equ $ - loader_name - -drive db 0 - -; Video info struct -vid_info: -.mode dd 0 ; Mode info pointer -.array dd 0 ; Mode array pointer - -; Data -packet: - db 0x10 ; Packet size - db 0 ; Always 0 -count: - dw 4 ; Number of sectors to transfer -dest: - dw 0 ; Destination offset - dw 0 ; Destination segment -lba: - dd 1 ; LBA number - dd 0 ; More storage bytes - -; End of boot sector -times SECTOR_SIZE - ($ - $$) db 0 -dw SECTOR_END - -; This is the second stage. It tries to load the kernel loader into memory. -; To do this, it first checks the integrity of the ext2 fs. Then it has to find -; the address of the root inode (2), find the filename in it and load its contents into memory. -; After this is finished, the stage can jump into the protected mode, enable the -; A20 line and finally jump to the kernel loader! ez -stage_two: - ; Verify signature - mov ax, [superblock + EXT2_SIG_OFFSET] - cmp ax, EXT2_SIG - jne disk_error - - ; Load inode table - mov ax, [superblock + EXT2_SB_SIZE + EXT2_TABLE_OFFSET] ; Inode table - shl ax, 1 ; Multiply ax by 2 - mov [lba], ax ; Sector - ; TODO: This might only work with smaller inodes - ;mov ax, 4 - ;mov [count], ax ; Read 4kb - mov bx, EXT2_INODE_TABLE_LOC ; Copy data to 0x1000 - mov [dest], bx - call disk_read - - ; Load root directory - mov bx, EXT2_GET_ADDRESS(EXT2_ROOT_INODE) ; First block - mov ax, [bx + EXT2_POINTER_OFFSET] ; Address of first block pointer - shl ax, 1 ; Multiply ax by 2 - mov [lba], ax - mov bx, 0x3500 ; Load to this address - mov [dest], bx - call disk_read - -.search_loop: - lea si, [bx + EXT2_FILENAME_OFFSET] ; First comparison string - mov di, loader_name ; Second comparison string - mov cx, loader_name_len ; String length - rep cmpsb ; Compare strings - je .found ; Found loader! - add bx, EXT2_ENTRY_LENGTH_OFFSET ; Add dirent struct size - jmp .search_loop ; Next dirent! -.found: - mov si, found_msg - call print ; Print success message - mov ax, [bx + EXT2_INODE_OFFSET] ; Get inode number from dirent - ; Calculate address: (EXT2_INODE_TABLE_LOC + (inode - 1) * EXT2_INODE_SIZE) - dec ax ; (inode - 1) - mov cx, EXT2_INODE_SIZE ; Prepare for multiplication - mul cx ; Multiply inode number - mov bx, ax ; Transfer calculation - add bx, EXT2_INODE_TABLE_LOC ; bx is at the start of the inode now! - mov cx, [bx + EXT2_COUNT_OFFSET] ; Number of blocks for inode - cmp cx, 0 - je disk_error - cmp cx, 256 + 12 ; BLOCK_SIZE / sizeof(u32) = 256 - jge disk_error - lea di, [bx + EXT2_POINTER_OFFSET] ; Address of first block pointer - mov bx, 0x900 ; Load to this address (LOADER_POSITION >> 4) - mov [dest + 2], bx - mov bx, 0 ; Inode location = 0xF0000 - mov [dest], bx - call inode_load - - ; Load mmap - xor eax, eax - mov es, eax - mov edi, MMAP_START - push edi - call memory_map - push edi - - ; Set video mode - call video_map - - jmp protected_mode_enter - -inode_load: - mov ax, [di] ; Set ax = block pointer - shl ax, 1 ; Multiply ax by 2 - mov [lba], ax - mov [dest], bx - call disk_read - jmp .end - -.end: - add bx, 0x400 ; 1kb increase - add di, 0x4 ; Move to next block pointer - sub cx, 0x2 ; Read 2 blocks - jnz inode_load - ret - -protected_mode_enter: - cli ; Turn off interrupts - - ; TODO: Check A20 support? - ; TODO: 0x92 method may not work on every device - in al, A20_GATE - test al, A20_ENABLED - jnz .a20_enabled - or al, A20_ENABLED - and al, A20_EXCLUDE_BIT - out A20_GATE, al - .a20_enabled: - - lgdt [gdt_desc] ; Load GDT - - ; Set protected mode via cr0 - mov eax, cr0 - or eax, 1 ; Set bit 0 - mov cr0, eax - - jmp (gdt_code - gdt):protected_mode ; JUMP! - -bits 32 ; Woah, so big! -protected_mode: - mov ecx, [mmap_cnt] ; Get mmap entry count - mov [mem_info + 8], ecx ; Count of maps - pop ecx ; End of memory map - mov [mem_info + 4], ecx ; Ending boundary of struct - pop ecx ; Start of memory map - mov [mem_info], ecx ; Starting boundary of struct - - mov ax, GDT_DATA_OFFSET ; Data segment offset of GDT - mov ds, ax - mov es, ax - mov fs, ax - mov gs, ax - mov ss, ax ; Stack segment - - mov esp, STACK_POINTER ; Move stack pointer - - mov ax, (gdt_tss - gdt) | 0b11 ; Load TSS in ring 3 - ltr ax - - mov [boot_info], dword vid_info - mov [boot_info + 4], dword mem_info - mov [boot_info + 8], dword tss_entry - mov [boot_info + 12], dword drive - - mov eax, boot_info ; Pass boot_info to kernel loader - push eax ; Push as first kernel parameter - - mov edx, LOADER_POSITION - lea eax, [edx] - call eax - -; Memory map -align 16 -mem_info: - dd 0 ; Start address - dd 0 ; End address - dd 0 ; Count - -align 16 -boot_info: - dd 0 ; VBE - dd 0 ; MMAP - dd 0 ; TSS - dd 0 ; Drive - -; GDT -align 32 -gdt: ; GDTs start -gdt_null: ; Must be null - dd 0 - dd 0 -gdt_code: ; Code segment - dw GDT_MAX_LIMIT ; Limit - dw 0 ; First base - db 0 ; Second base - db (GDT_PRESENT | GDT_DESCRIPTOR | GDT_EXECUTABLE | GDT_READWRITE) ; Configuration - db (GDT_GRANULARITY | GDT_SIZE) ; Flags - db 0 ; Third base -gdt_data: ; Data segment - dw GDT_MAX_LIMIT ; Limit - dw 0 ; First base - db 0 ; Second base - db (GDT_PRESENT | GDT_DESCRIPTOR | GDT_READWRITE) ; Configuration - db (GDT_GRANULARITY | GDT_SIZE) ; Flags - db 0 ; Third base -gdt_user_code: ; User code segment - dw GDT_MAX_LIMIT ; Limit - dw 0 ; First base - db 0 ; Second base - db (GDT_PRESENT | GDT_RING3 | GDT_DESCRIPTOR | GDT_EXECUTABLE | GDT_READWRITE) ; Configuration - db (GDT_GRANULARITY | GDT_SIZE) ; Flags - db 0 ; Third base -gdt_user_data: ; Data segment - dw GDT_MAX_LIMIT ; Limit - dw 0 ; First base - db 0 ; Second base - db (GDT_PRESENT | GDT_RING3 | GDT_DESCRIPTOR | GDT_READWRITE) ; Configuration - db (GDT_GRANULARITY | GDT_SIZE) ; Flags - db 0 ; Third base -gdt_tss: ; TSS segment - dw tss_entry + (tss_entry_end - tss_entry) ; Limit - dw tss_entry ; First base - db 0 ; Second base - db (GDT_PRESENT | GDT_RING3 | GDT_EXECUTABLE | GDT_ACCESSED) ; Configuration - db GDT_SIZE ; Flags - db 0 ; Third base -gdt_end: -gdt_desc: - dw gdt_end - gdt - 1 - dd gdt - -; TSS -align 4 -tss_entry: - dd 0 ; Previous TSS - dd STACK_POINTER ; esp0 - dd gdt_data - gdt ; ss0 (data offset) - dd 0 ; esp1 - dd 0 ; ss1 - dd 0 ; esp2 - dd 0 ; ss2 - dd 0 ; cr3 - dd 0 ; eip - dd 0 ; eflags - dd 0 ; eax - dd 0 ; ecx - dd 0 ; edx - dd 0 ; ebx - dd 0 ; esp - dd 0 ; ebp - dd 0 ; esi - dd 0 ; edi - dd 0 ; es - dd 0 ; cs - dd 0 ; ss - dd 0 ; ds - dd 0 ; fs - dd 0 ; gs - dd 0 ; ldt - dw 0 ; trap - dw -1 ; iomap base -tss_entry_end: - -times 1024 - ($ - $$) db 0 - -; Start at LBA 2 -superblock: |