diff --git a/src/stage2/stage2.nasm b/src/stage2/stage2.nasm index d74c65b..f27bea6 100755 --- a/src/stage2/stage2.nasm +++ b/src/stage2/stage2.nasm @@ -36,18 +36,10 @@ section .text begin_text: ; dl = byte boot_drive -; ax = word part_offset (active partition offset) -; si = ptr PartTable_t partition_table -; di = ptr FAT32_bpb_t fat32_bpb ALIGN 4, db 0x90 init: cli ; We do not want to be interrupted - - ; these 4 are stored in the .data section and are effectivly const types - mov [vbr_part_table_ptr], si ; pointer to partition_table - mov [vbr_fat32_bpb_ptr], di ; pointer to fat32_bpb - mov [boot_drive], dl ; copy boot_drive to globals - mov [partition_offset], ax ; copy partition_offset to globals + mov [boot_drive], dl ; copy boot_drive to globals mov ax, __STAGE2_SEGMENT ; set all our segments to the configured segment, except es mov ds, ax ; * @@ -129,23 +121,35 @@ main: je main.stage2_main ERROR STAGE2_SIGNATURE_MISSING .stage2_main: - ; copy partition table data to .data section in stage2 - __CDECL16_CALL_ARGS partition_table, word [vbr_part_table_ptr], PartTable_t_size - __CDECL16_CALL kmemcpy, 3 - - ; copy bpb & ebpb to memory - __CDECL16_CALL_ARGS fat32_bpb, word [vbr_fat32_bpb_ptr], (FAT32_bpb_t_size + FAT32_ebpb_t_size) - __CDECL16_CALL kmemcpy, 3 - call SetTextMode call disable_cursor_bios + ; setup the early heap + __CDECL16_CALL_ARGS early_heap_state + __CDECL16_CALL arena_init, 1 + __CDECL16_CALL_ARGS HelloPrompt_info __CDECL16_CALL PrintString, 1 - ; setup the early heap - __CDECL16_CALL_ARGS early_heap_state - + ; setup and store our vbr/mbr (e)bpb + __CDECL16_CALL_ARGS 0x200, 0x10 + __CDECL16_CALL arena_alloc, 2 + mov word [mbr_ptr], ax + + push ax ; dst + movzx ax, byte [boot_drive] + push ax ; boot_drive + __CDECL16_CALL read_mbr, 2 ; fill mbr buffer + + __CDECL16_CALL_ARGS 0x200, 0x10 + __CDECL16_CALL arena_alloc, 2 + mov word [vbr_ptr], ax + + push ax ; dst + movzx ax, byte [boot_drive] + push ax ; boot_drive + __CDECL16_CALL read_vbr, 2 ; fill vbr buffer + ; enable A20 gate call EnableA20 __CDECL16_CALL_ARGS A20_Enabled_OK_info @@ -197,55 +201,80 @@ hcf: ; destination buffer needs 512 bytes of space read_mbr: __CDECL16_PROC_ENTRY -.func: - __BOCHS_MAGIC_DEBUG +.proc: ; read mbr on boot drive to memory (for the partition table) - movzx ax, byte [bp - 4] + movzx ax, byte [bp + 4] push ax ; drive_num (2) push 0x01 ; count (2) push dword 0x0 ; lba (4) - push word [bp - 6] ; offset = dst + push word [bp + 6] ; offset = dst push __STAGE2_SEGMENT ; this segment - __CDECL16_CALL read_disk_raw, 12 + call read_disk_raw + add sp, 0xC + +.check_sig: + mov bx, [bp + 6] + cmp word [bx + 0x1FE], 0xAA55 ; check for bytes at end + jne read_mbr.error ; TODO: this needs error checking, zero checking, check the sig a bunch of stuff... -.endf: +.update_globals: + mov ax, [bp + 6] + add ax, 0x1B8 ; offset to start of PartTable + mov [part_table_ptr], ax +.endp: __CDECL16_PROC_EXIT + ret .error: ERROR STEVIA_DEBUG_ERR -; int read_vbr(int boot_drive, void* mbr, void* buf) +; int read_vbr(int boot_drive, void* buf) read_vbr: __CDECL16_PROC_ENTRY -.func: +.proc: __BOCHS_MAGIC_DEBUG ; read vbr on boot partition to memory (for fat bpb/ebpb) .calc_part_offset: - mov bx, [bp - 6] - add bx, 0x1B8 ; offset to partition table in mbr - mov cx, 4 ; only checking 4 entries + mov bx, word [part_table_ptr] ; base pointer @ partition table + mov cx, 4 ; only checking 4 entries + mov si, PartEntry_t.attributes .find_active_L0: - mov al, byte [bx + PartEntry_t.attributes] + mov al, byte [bx + si] test al, 0x80 ; 0x80 == 1000_0000b - jnz read_vbr.active_found - add bx, 0x10 ; add 16 bytes to offset + je read_vbr.active_found + add si, 0x10 ; add 16 bytes to offset (next part entry's attributes) loop read_vbr.find_active_L0 jmp read_vbr.error .active_found: - movzx ax, byte [bp - 4] + add bx, si ; update base to active part + + movzx ax, byte [bp + 4] push ax ; drive_num (2) push 0x01 ; count (2) mov eax, dword [bx + PartEntry_t.lba_start] push dword eax ; lba (4) - push word [bp - 6] ; offset = dst + push word [bp + 6] ; offset = dst push __STAGE2_SEGMENT ; this segment - __CDECL16_CALL read_disk_raw, 12 + call read_disk_raw + add sp, 0xC ; vbr (with fat bpb/ebpb) is at the buffer now -.endf: +.check_sig: + mov bx, [bp + 6] + cmp word [bx + 0x1FE], 0xAA55 ; check for bytes at end + jne read_mbr.error +.check_FAT_size: + test word [bx + FAT32_bpb_t.unused2_ZERO_word], 0 ; TotSectors16 will not be set if FAT32 + jnz read_vbr.error +.update_globals: + mov word [fat32_bpb_ptr], bx + add bx, FAT32_bpb_t_size ; offset to ebpb + mov word [fat32_ebpb_ptr], bx +.endp: __CDECL16_PROC_EXIT + ret .error: ERROR STEVIA_DEBUG_ERR @@ -386,25 +415,14 @@ BootTarget: db 'BOOT BIN' ; -; pre-bss init globals (generally const...but there are exceptions) +; pre-bss init globals ; -align 8, db 0 +; set to boot_drive passed from BIOS almost first thing in init +align 4, db 0 boot_drive: db 0x00 -align 8, db 0 -partition_offset: - dw 0x0000 - -align 8, db 0 -vbr_fat32_bpb_ptr: - dw 0x0000 - -align 8, db 0 -vbr_part_table_ptr: - dw 0x0000 - align 16, db 0 IntToHex_table: db '0123456789ABCDEF' @@ -497,8 +515,28 @@ STAGE2_SIG: dd 0xDEADBEEF ; Signature to mark the end of the stag section .bss follows=.sign begin_bss: -; structures +align 4, resb 1 +mbr_ptr: + resw 1 + +align 4, resb 1 +vbr_ptr: + resw 1 + +align 4, resb 1 +part_table_ptr: + resw 1 + +align 4, resb 1 +fat32_bpb_ptr: + resw 1 + +align 4, resb 1 +fat32_ebpb_ptr: + resw 1 + +; structures align 16, resb 1 partition_table: resb PartTable_t_size