| ! |
| ! SYS_SIZE is the number of clicks (16 bytes) to be loaded. |
| ! 0x3000 is 0x30000 bytes = 196kB, more than enough for current |
| ! versions of linux |
| ! |
| #include <linux/config.h> |
| SYSSIZE = DEF_SYSSIZE |
| ! |
| ! bootsect.s Copyright (C) 1991, 1992 Linus Torvalds |
| ! modified by Drew Eckhardt |
| ! modified by Bruce Evans (bde) |
| ! |
| ! bootsect.s is loaded at 0x7c00 by the bios-startup routines, and moves |
| ! itself out of the way to address 0x90000, and jumps there. |
| ! |
| ! bde - should not jump blindly, there may be systems with only 512K low |
| ! memory. Use int 0x12 to get the top of memory, etc. |
| ! |
| ! It then loads 'setup' directly after itself (0x90200), and the system |
| ! at 0x10000, using BIOS interrupts. |
| ! |
| ! NOTE! currently system is at most 8*65536 bytes long. This should be no |
| ! problem, even in the future. I want to keep it simple. This 512 kB |
| ! kernel size should be enough, especially as this doesn't contain the |
| ! buffer cache as in minix |
| ! |
| ! The loader has been made as simple as possible, and continuos |
| ! read errors will result in a unbreakable loop. Reboot by hand. It |
| ! loads pretty fast by getting whole tracks at a time whenever possible. |
| |
| .text |
| |
| SETUPSECS = 4 ! nr of setup-sectors |
| BOOTSEG = 0x07C0 ! original address of boot-sector |
| INITSEG = DEF_INITSEG ! we move boot here - out of the way |
| SETUPSEG = DEF_SETUPSEG ! setup starts here |
| SYSSEG = DEF_SYSSEG ! system loaded at 0x10000 (65536). |
| |
| ! ROOT_DEV & SWAP_DEV are now written by "build". |
| ROOT_DEV = 0 |
| SWAP_DEV = 0 |
| #ifndef SVGA_MODE |
| #define SVGA_MODE ASK_VGA |
| #endif |
| #ifndef RAMDISK |
| #define RAMDISK 0 |
| #endif |
| #ifndef CONFIG_ROOT_RDONLY |
| #define CONFIG_ROOT_RDONLY 0 |
| #endif |
| |
| ! ld86 requires an entry symbol. This may as well be the usual one. |
| .globl _main |
| _main: |
| #if 0 /* hook for debugger, harmless unless BIOS is fussy (old HP) */ |
| int 3 |
| #endif |
| mov ax,#BOOTSEG |
| mov ds,ax |
| mov ax,#INITSEG |
| mov es,ax |
| mov cx,#256 |
| sub si,si |
| sub di,di |
| cld |
| rep |
| movsw |
| jmpi go,INITSEG |
| |
| go: mov ax,cs |
| mov dx,#0x4000-12 ! 0x4000 is arbitrary value >= length of |
| ! bootsect + length of setup + room for stack |
| ! 12 is disk parm size |
| |
| ! bde - changed 0xff00 to 0x4000 to use debugger at 0x6400 up (bde). We |
| ! wouldn't have to worry about this if we checked the top of memory. Also |
| ! my BIOS can be configured to put the wini drive tables in high memory |
| ! instead of in the vector table. The old stack might have clobbered the |
| ! drive table. |
| |
| mov ds,ax |
| mov es,ax |
| mov ss,ax ! put stack at INITSEG:0x4000-12. |
| mov sp,dx |
| /* |
| * Many BIOS's default disk parameter tables will not |
| * recognize multi-sector reads beyond the maximum sector number |
| * specified in the default diskette parameter tables - this may |
| * mean 7 sectors in some cases. |
| * |
| * Since single sector reads are slow and out of the question, |
| * we must take care of this by creating new parameter tables |
| * (for the first disk) in RAM. We will set the maximum sector |
| * count to 18 - the most we will encounter on an HD 1.44. |
| * |
| * High doesn't hurt. Low does. |
| * |
| * Segments are as follows: ds=es=ss=cs - INITSEG, |
| * fs = 0, gs = parameter table segment |
| */ |
| |
| push #0 |
| pop fs |
| mov bx,#0x78 ! fs:bx is parameter table address |
| seg fs |
| lgs si,(bx) ! gs:si is source |
| |
| mov di,dx ! es:di is destination |
| mov cx,#6 ! copy 12 bytes |
| cld |
| |
| rep |
| seg gs |
| movsw |
| |
| mov di,dx |
| movb 4(di),*18 ! patch sector count |
| |
| seg fs |
| mov (bx),di |
| seg fs |
| mov 2(bx),es |
| |
| mov ax,cs |
| mov fs,ax |
| mov gs,ax |
| |
| xor ah,ah ! reset FDC |
| xor dl,dl |
| int 0x13 |
| |
| ! load the setup-sectors directly after the bootblock. |
| ! Note that 'es' is already set up. |
| |
| load_setup: |
| xor dx, dx ! drive 0, head 0 |
| mov cx,#0x0002 ! sector 2, track 0 |
| mov bx,#0x0200 ! address = 512, in INITSEG |
| mov ax,#0x0200+SETUPSECS ! service 2, nr of sectors |
| ! (assume all on head 0, track 0) |
| int 0x13 ! read it |
| jnc ok_load_setup ! ok - continue |
| |
| push ax ! dump error code |
| call print_nl |
| mov bp, sp |
| call print_hex |
| pop ax |
| |
| xor dl, dl ! reset FDC |
| xor ah, ah |
| int 0x13 |
| jmp load_setup |
| |
| ok_load_setup: |
| |
| ! Get disk drive parameters, specifically nr of sectors/track |
| |
| #if 0 |
| |
| ! bde - the Phoenix BIOS manual says function 0x08 only works for fixed |
| ! disks. It doesn't work for one of my BIOS's (1987 Award). It was |
| ! fatal not to check the error code. |
| |
| xor dl,dl |
| mov ah,#0x08 ! AH=8 is get drive parameters |
| int 0x13 |
| xor ch,ch |
| #else |
| |
| ! It seems that there is no BIOS call to get the number of sectors. Guess |
| ! 18 sectors if sector 18 can be read, 15 if sector 15 can be read. |
| ! Otherwise guess 9. |
| |
| xor dx, dx ! drive 0, head 0 |
| mov cx,#0x0012 ! sector 18, track 0 |
| mov bx,#0x0200+SETUPSECS*0x200 ! address after setup (es = cs) |
| mov ax,#0x0201 ! service 2, 1 sector |
| int 0x13 |
| jnc got_sectors |
| mov cl,#0x0f ! sector 15 |
| mov ax,#0x0201 ! service 2, 1 sector |
| int 0x13 |
| jnc got_sectors |
| mov cl,#0x09 |
| |
| #endif |
| |
| got_sectors: |
| seg cs |
| mov sectors,cx |
| mov ax,#INITSEG |
| mov es,ax |
| |
| ! Print some inane message |
| |
| mov ah,#0x03 ! read cursor pos |
| xor bh,bh |
| int 0x10 |
| |
| mov cx,#9 |
| mov bx,#0x0007 ! page 0, attribute 7 (normal) |
| mov bp,#msg1 |
| mov ax,#0x1301 ! write string, move cursor |
| int 0x10 |
| |
| ! ok, we've written the message, now |
| ! we want to load the system (at 0x10000) |
| |
| mov ax,#SYSSEG |
| mov es,ax ! segment of 0x010000 |
| call read_it |
| call kill_motor |
| call print_nl |
| |
| ! After that we check which root-device to use. If the device is |
| ! defined (!= 0), nothing is done and the given device is used. |
| ! Otherwise, either /dev/PS0 (2,28) or /dev/at0 (2,8), depending |
| ! on the number of sectors that the BIOS reports currently. |
| |
| seg cs |
| mov ax,root_dev |
| or ax,ax |
| jne root_defined |
| seg cs |
| mov bx,sectors |
| mov ax,#0x0208 ! /dev/ps0 - 1.2Mb |
| cmp bx,#15 |
| je root_defined |
| mov ax,#0x021c ! /dev/PS0 - 1.44Mb |
| cmp bx,#18 |
| je root_defined |
| mov ax,#0x0200 ! /dev/fd0 - autodetect |
| root_defined: |
| seg cs |
| mov root_dev,ax |
| |
| ! after that (everyting loaded), we jump to |
| ! the setup-routine loaded directly after |
| ! the bootblock: |
| |
| jmpi 0,SETUPSEG |
| |
| ! This routine loads the system at address 0x10000, making sure |
| ! no 64kB boundaries are crossed. We try to load it as fast as |
| ! possible, loading whole tracks whenever we can. |
| ! |
| ! in: es - starting address segment (normally 0x1000) |
| ! |
| sread: .word 1+SETUPSECS ! sectors read of current track |
| head: .word 0 ! current head |
| track: .word 0 ! current track |
| |
| read_it: |
| mov ax,es |
| test ax,#0x0fff |
| die: jne die ! es must be at 64kB boundary |
| xor bx,bx ! bx is starting address within segment |
| rp_read: |
| mov ax,es |
| sub ax,#SYSSEG |
| cmp ax,syssize ! have we loaded all yet? |
| jbe ok1_read |
| ret |
| ok1_read: |
| seg cs |
| mov ax,sectors |
| sub ax,sread |
| mov cx,ax |
| shl cx,#9 |
| add cx,bx |
| jnc ok2_read |
| je ok2_read |
| xor ax,ax |
| sub ax,bx |
| shr ax,#9 |
| ok2_read: |
| call read_track |
| mov cx,ax |
| add ax,sread |
| seg cs |
| cmp ax,sectors |
| jne ok3_read |
| mov ax,#1 |
| sub ax,head |
| jne ok4_read |
| inc track |
| ok4_read: |
| mov head,ax |
| xor ax,ax |
| ok3_read: |
| mov sread,ax |
| shl cx,#9 |
| add bx,cx |
| jnc rp_read |
| mov ax,es |
| add ah,#0x10 |
| mov es,ax |
| xor bx,bx |
| jmp rp_read |
| |
| read_track: |
| pusha |
| pusha |
| mov ax, #0xe2e ! loading... message 2e = . |
| mov bx, #7 |
| int 0x10 |
| popa |
| |
| mov dx,track |
| mov cx,sread |
| inc cx |
| mov ch,dl |
| mov dx,head |
| mov dh,dl |
| and dx,#0x0100 |
| mov ah,#2 |
| |
| push dx ! save for error dump |
| push cx |
| push bx |
| push ax |
| |
| int 0x13 |
| jc bad_rt |
| add sp, #8 |
| popa |
| ret |
| |
| bad_rt: push ax ! save error code |
| call print_all ! ah = error, al = read |
| |
| |
| xor ah,ah |
| xor dl,dl |
| int 0x13 |
| |
| |
| add sp, #10 |
| popa |
| jmp read_track |
| |
| /* |
| * print_all is for debugging purposes. |
| * It will print out all of the registers. The assumption is that this is |
| * called from a routine, with a stack frame like |
| * dx |
| * cx |
| * bx |
| * ax |
| * error |
| * ret <- sp |
| * |
| */ |
| |
| print_all: |
| mov cx, #5 ! error code + 4 registers |
| mov bp, sp |
| |
| print_loop: |
| push cx ! save count left |
| call print_nl ! nl for readability |
| |
| cmp cl, 5 |
| jae no_reg ! see if register name is needed |
| |
| mov ax, #0xe05 + 'A - 1 |
| sub al, cl |
| int 0x10 |
| |
| mov al, #'X |
| int 0x10 |
| |
| mov al, #': |
| int 0x10 |
| |
| no_reg: |
| add bp, #2 ! next register |
| call print_hex ! print it |
| pop cx |
| loop print_loop |
| ret |
| |
| print_nl: |
| mov ax, #0xe0d ! CR |
| int 0x10 |
| mov al, #0xa ! LF |
| int 0x10 |
| ret |
| |
| /* |
| * print_hex is for debugging purposes, and prints the word |
| * pointed to by ss:bp in hexadecmial. |
| */ |
| |
| print_hex: |
| mov cx, #4 ! 4 hex digits |
| mov dx, (bp) ! load word into dx |
| print_digit: |
| rol dx, #4 ! rotate so that lowest 4 bits are used |
| mov ah, #0xe |
| mov al, dl ! mask off so we have only next nibble |
| and al, #0xf |
| add al, #'0 ! convert to 0-based digit |
| cmp al, #'9 ! check for overflow |
| jbe good_digit |
| add al, #'A - '0 - 10 |
| |
| good_digit: |
| int 0x10 |
| loop print_digit |
| ret |
| |
| |
| /* |
| * This procedure turns off the floppy drive motor, so |
| * that we enter the kernel in a known state, and |
| * don't have to worry about it later. |
| */ |
| kill_motor: |
| push dx |
| mov dx,#0x3f2 |
| xor al, al |
| outb |
| pop dx |
| ret |
| |
| sectors: |
| .word 0 |
| |
| msg1: |
| .byte 13,10 |
| .ascii "Loading" |
| |
| .org 498 |
| root_flags: |
| .word CONFIG_ROOT_RDONLY |
| syssize: |
| .word SYSSIZE |
| swap_dev: |
| .word SWAP_DEV |
| ram_size: |
| .word RAMDISK |
| vid_mode: |
| .word SVGA_MODE |
| root_dev: |
| .word ROOT_DEV |
| boot_flag: |
| .word 0xAA55 |