/* $OpenBSD: biosboot.S,v 1.8 1997/04/29 00:10:05 mickey Exp $ */ .file "bootbios.S" #include #include #define _LOCORE #include #undef _LOCORE #define addr32 .byte 0x67 #define data32 .byte 0x66 /* Better use 32, 48 does not seem to compile */ #define BLKCNT 20 /* Max without colliding with the partition table */ #define BOOTSEG 0x07c0 /* boot loaded here */ #define BOOTSTACK 0xfffc /* stack starts here */ #define ZMAGIC 0x0b01 /* ZMAGIC */ /* * Partition table values */ BOOTABLE= 0x80 # value of boot_ind, means bootable partition OPENBSDPART= 0xA6 # OpenBSD partition type #ifdef DEBUG #define DBGMSG(msg) \ movb $msg, %al; \ data32; \ call chr #define GO_RELOC 'R' /* running relocated code */ #define REAL2PROT 'P' /* switch to protected mode */ #else /* !DEBUG */ #define DBGMSG(msg) #endif /* !DEBUG */ .text .globl start start: /* set up stack (%ss:%esp) */ cli /* disable interrupts w/o stack */ # movw $BOOTREL, %ax .byte 0xb8 .word BOOTREL movl %ax, %ss movl %ax, %es /* relocate there */ data32 movl $BOOTSTACK, %esp sti /* we have stack, do ints */ # movw $BOOTSEG, %ax /* we are here */ .byte 0xb8 .word BOOTSEG movl %ax, %ds xorl %si, %si xorl %di, %di # movw $0x100, %cx /* 512 bytes to move */ .byte 0xb9 .word 0x100 cld rep; movsl /* jump to relocated code */ data32 ljmp $BOOTREL, $2f 1: .asciz "loading /boot" 2: DBGMSG(GO_RELOC) /* set up %ds */ pushl %cs popl %ds /* set up %es, (where we will load /boot to) */ # movw $(START >> 4), %ax .byte 0xb8 .word START >> 4 movl %ax, %es #ifdef SERIAL # Initialize the serial port to 9600 baud, 8N1. pushl %dx # movw $0x00e3, %ax .byte 0xb8 .word 0x00e3 # movw SERIAL, %dx .byte 0xba .word SERIAL int $0x14 popl %dx #endif data32 movl $1b, %esi data32 call message data32 xorl %ebx, %ebx /* put it at %es:0 */ addr32 movb _block_count, %cl /* how many to read */ movzbl %cl, %ecx # movw $_block_table, %si .byte 0xbe .word _block_table 1: pushl %cx cld lodsl /* word */ /* cylinder/sector */ movl %ax, %cx lodsb /* head */ movb %al, %dh lodsb /* # of sectors to load */ movb $0x2, %ah pushl %ax int $0x13 jnc 3f /* read error */ data32 movl $2f, %esi jmp halt 2: .asciz "\r\nRead error\r\n" 3: /* read next block */ movb $'.', %al data32 call chr /* show progress indicator */ popl %ax movzbl %al, %ax shll $9, %ax /* 512 bytes sectors */ addl %ax, %bx popl %cx loop 1b data32 movl $2f, %esi /* new line */ data32 call message xorl %si, %si cld /* check /boot magic */ es;lodsl;es;lodsl /* no need for high word */ # cmpw $ZMAGIC, %ax .byte 0x3d .word ZMAGIC je 3f data32 movl $1f, %esi halt: data32 call message cli hlt 1: .ascii "Bad magic" 2: .asciz "\r\n" 3: #if notdef data32;es;lodsl /* text size */ data32;es;lodsl /* data size */ data32;es;lodsl /* bss size */ data32;es;lodsl /* syms size */ #endif data32 addl 16(%esi), %edi /* entry */ DBGMSG(REAL2PROT) /* change to protected mode */ /* guarantee that interrupts are disabled when in prot mode */ cli /* load the gdtr */ addr32 data32 lgdt Gdtr /* set the PE bit of CR0 */ movl %cr0, %eax data32 orl $CR0_PE, %eax movl %eax, %cr0 /* * make intrasegment jump to flush the processor pipeline and * reload CS register */ data32 ljmp $8, $1f+(BOOTREL << 4) 1: /* * 32bit mode * set up %ds, %ss, %es */ movw $0x10, %eax movl %ax, %ds movl %ax, %ss movl $BOOTSTACK, %esp #ifdef DEBUG movl $0xb8004, %ebx movl $0x074f0747, (%ebx) #endif movzbl %dl, %eax /* drive number is in the lowest byte */ pushl %eax pushl $BOOTMAGIC /* use some magic */ /* jmp /boot */ ljmp $8, $(START + 0x20) /* not reached */ # # chr: write the character in %al to console # chr: data32 pushl %eax #ifndef SERIAL data32 pushl %ebx movb $0x0e, %ah xorl %bx, %bx incl %bx /* movw $0x01, %bx */ int $0x10 data32 popl %ebx #else data32 pushl %edx movb $0x01, %ah xorl %dx, %dx movb SERIAL, %dl int $0x14 data32 popl %edx #endif data32 popl %eax data32 ret /* * Display string */ message: data32 pushl %eax cld 1: lodsb # load a byte into %al testb %al, %al jz 1f data32 call chr jmp 1b 1: data32 popl %eax data32 ret .align 3 gdt: /* 0x00 : null */ .long 0, 0 /* 0x08 : flat code */ .word 0xFFFF # lolimit .word 0 # lobase .byte 0 # midbase .byte SDT_MEMERAC | 0 | 0x80 # RWXAC, dpl = 0, present .byte 0xf | 0 | 0x40 | 0x80 # hilimit, xx, 32bit, 4k granularity .byte 0 # hibase /* 0x10 : flat data */ .word 0xFFFF # lolimit .word 0 # lobase .byte 0 # midbase .byte SDT_MEMRWA | 0 | 0x80 # RWA, dpl = 0, present .byte 0xf | 0 | 0x40 | 0x80 # hilimit, xx, 32bit, 4k granularity .byte 0 # hibase Gdtr: .word . - gdt .long (BOOTREL << 4) + gdt .globl _block_table _block_table: .word 0 /* cyllinder/sector */ .byte 0 /* head */ .byte 0 /* nsect */ . = _block_table + BLKCNT*4 .globl _block_count _block_count: .byte BLKCNT /* entries in _block_table */ . = 446 .globl _partitions /* throw in a partition in case we are block0 as well */ /* flag, head, sec, cyl, typ, ehead, esect, ecyl, start, len */ _partitions: .byte BOOTABLE, 0, 1, 0,OPENBSDPART, 255, 255, 255 .long 0,50000 .byte 0,0,0,0,0,0,0,0 .long 0,0 .byte 0,0,0,0,0,0,0,0 .long 0,0 .byte 0,0,0,0,0,0,0,0 .long 0,0 . = 0x200 - 2 /* a little signature */ .word 0xaa55