| Current Path : /sys/boot/i386/boot2/ |
FreeBSD hs32.drive.ne.jp 9.1-RELEASE FreeBSD 9.1-RELEASE #1: Wed Jan 14 12:18:08 JST 2015 root@hs32.drive.ne.jp:/sys/amd64/compile/hs32 amd64 |
| Current File : //sys/boot/i386/boot2/boot1.S |
/* * Copyright (c) 1998 Robert Nordier * All rights reserved. * * Redistribution and use in source and binary forms are freely * permitted provided that the above copyright notice and this * paragraph and the following disclaimer are duplicated in all * such forms. * * This software is provided "AS IS" and without any express or * implied warranties, including, without limitation, the implied * warranties of merchantability and fitness for a particular * purpose. * * $FreeBSD: release/9.1.0/sys/boot/i386/boot2/boot1.S 215285 2010-11-14 08:31:02Z brucec $ */ /* Memory Locations */ .set MEM_REL,0x700 # Relocation address .set MEM_ARG,0x900 # Arguments .set MEM_ORG,0x7c00 # Origin .set MEM_BUF,0x8c00 # Load area .set MEM_BTX,0x9000 # BTX start .set MEM_JMP,0x9010 # BTX entry point .set MEM_USR,0xa000 # Client start .set BDA_BOOT,0x472 # Boot howto flag /* Partition Constants */ .set PRT_OFF,0x1be # Partition offset .set PRT_NUM,0x4 # Partitions .set PRT_BSD,0xa5 # Partition type /* Flag Bits */ .set FL_PACKET,0x80 # Packet mode /* Misc. Constants */ .set SIZ_PAG,0x1000 # Page size .set SIZ_SEC,0x200 # Sector size .set NSECT,0x10 .globl start .globl xread .code16 start: jmp main # Start recognizably /* * This is the start of a standard BIOS Parameter Block (BPB). Most bootable * FAT disks have this at the start of their MBR. While normal BIOS's will * work fine without this section, IBM's El Torito emulation "fixes" up the * BPB by writing into the memory copy of the MBR. Rather than have data * written into our xread routine, we'll define a BPB to work around it. * The data marked with (T) indicates a field required for a ThinkPad to * recognize the disk and (W) indicates fields written from IBM BIOS code. * The use of the BPB is based on what OpenBSD and NetBSD implemented in * their boot code but the required fields were determined by trial and error. * * Note: If additional space is needed in boot1, one solution would be to * move the "prompt" message data (below) to replace the OEM ID. */ .org 0x03, 0x00 oemid: .space 0x08, 0x00 # OEM ID .org 0x0b, 0x00 bpb: .word 512 # sector size (T) .byte 0 # sectors/clustor .word 0 # reserved sectors .byte 0 # number of FATs .word 0 # root entries .word 0 # small sectors .byte 0 # media type (W) .word 0 # sectors/fat .word 18 # sectors per track (T) .word 2 # number of heads (T) .long 0 # hidden sectors (W) .long 0 # large sectors .org 0x24, 0x00 ebpb: .byte 0 # BIOS physical drive number (W) .org 0x25,0x90 /* * Trampoline used by boot2 to call read to read data from the disk via * the BIOS. Call with: * * %cx:%ax - long - LBA to read in * %es:(%bx) - caddr_t - buffer to read data into * %dl - byte - drive to read from * %dh - byte - num sectors to read */ xread: push %ss # Address pop %ds # data /* * Setup an EDD disk packet and pass it to read */ xread.1: # Starting pushl $0x0 # absolute push %cx # block push %ax # number push %es # Address of push %bx # transfer buffer xor %ax,%ax # Number of movb %dh,%al # blocks to push %ax # transfer push $0x10 # Size of packet mov %sp,%bp # Packet pointer callw read # Read from disk lea 0x10(%bp),%sp # Clear stack lret # To far caller /* * Load the rest of boot2 and BTX up, copy the parts to the right locations, * and start it all up. */ /* * Setup the segment registers to flat addressing (segment 0) and setup the * stack to end just below the start of our code. */ main: cld # String ops inc xor %cx,%cx # Zero mov %cx,%es # Address mov %cx,%ds # data mov %cx,%ss # Set up mov $start,%sp # stack /* * Relocate ourself to MEM_REL. Since %cx == 0, the inc %ch sets * %cx == 0x100. */ mov %sp,%si # Source mov $MEM_REL,%di # Destination incb %ch # Word count rep # Copy movsw # code /* * If we are on a hard drive, then load the MBR and look for the first * FreeBSD slice. We use the fake partition entry below that points to * the MBR when we call nread. The first pass looks for the first active * FreeBSD slice. The second pass looks for the first non-active FreeBSD * slice if the first one fails. */ mov $part4,%si # Partition cmpb $0x80,%dl # Hard drive? jb main.4 # No movb $0x1,%dh # Block count callw nread # Read MBR mov $0x1,%cx # Two passes main.1: mov $MEM_BUF+PRT_OFF,%si # Partition table movb $0x1,%dh # Partition main.2: cmpb $PRT_BSD,0x4(%si) # Our partition type? jne main.3 # No jcxz main.5 # If second pass testb $0x80,(%si) # Active? jnz main.5 # Yes main.3: add $0x10,%si # Next entry incb %dh # Partition cmpb $0x1+PRT_NUM,%dh # In table? jb main.2 # Yes dec %cx # Do two jcxz main.1 # passes /* * If we get here, we didn't find any FreeBSD slices at all, so print an * error message and die. */ mov $msg_part,%si # Message jmp error # Error /* * Floppies use partition 0 of drive 0. */ main.4: xor %dx,%dx # Partition:drive /* * Ok, we have a slice and drive in %dx now, so use that to locate and load * boot2. %si references the start of the slice we are looking for, so go * ahead and load up the first 16 sectors (boot1 + boot2) from that. When * we read it in, we conveniently use 0x8c00 as our transfer buffer. Thus, * boot1 ends up at 0x8c00, and boot2 starts at 0x8c00 + 0x200 = 0x8e00. * The first part of boot2 is the disklabel, which is 0x200 bytes long. * The second part is BTX, which is thus loaded into 0x9000, which is where * it also runs from. The boot2.bin binary starts right after the end of * BTX, so we have to figure out where the start of it is and then move the * binary to 0xc000. Normally, BTX clients start at MEM_USR, or 0xa000, but * when we use btxld to create boot2, we use an entry point of 0x2000. That * entry point is relative to MEM_USR; thus boot2.bin starts at 0xc000. */ main.5: mov %dx,MEM_ARG # Save args movb $NSECT,%dh # Sector count callw nread # Read disk mov $MEM_BTX,%bx # BTX mov 0xa(%bx),%si # Get BTX length and set add %bx,%si # %si to start of boot2.bin mov $MEM_USR+SIZ_PAG*2,%di # Client page 2 mov $MEM_BTX+(NSECT-1)*SIZ_SEC,%cx # Byte sub %si,%cx # count rep # Relocate movsb # client /* * Enable A20 so we can access memory above 1 meg. * Use the zero-valued %cx as a timeout for embedded hardware which do not * have a keyboard controller. */ seta20: cli # Disable interrupts seta20.1: dec %cx # Timeout? jz seta20.3 # Yes inb $0x64,%al # Get status testb $0x2,%al # Busy? jnz seta20.1 # Yes movb $0xd1,%al # Command: Write outb %al,$0x64 # output port seta20.2: inb $0x64,%al # Get status testb $0x2,%al # Busy? jnz seta20.2 # Yes movb $0xdf,%al # Enable outb %al,$0x60 # A20 seta20.3: sti # Enable interrupts jmp start+MEM_JMP-MEM_ORG # Start BTX /* * Trampoline used to call read from within boot1. */ nread: mov $MEM_BUF,%bx # Transfer buffer mov 0x8(%si),%ax # Get mov 0xa(%si),%cx # LBA push %cs # Read from callw xread.1 # disk jnc return # If success, return mov $msg_read,%si # Otherwise, set the error # message and fall through to # the error routine /* * Print out the error message pointed to by %ds:(%si) followed * by a prompt, wait for a keypress, and then reboot the machine. */ error: callw putstr # Display message mov $prompt,%si # Display callw putstr # prompt xorb %ah,%ah # BIOS: Get int $0x16 # keypress movw $0x1234, BDA_BOOT # Do a warm boot ljmp $0xf000,$0xfff0 # reboot the machine /* * Display a null-terminated string using the BIOS output. */ putstr.0: mov $0x7,%bx # Page:attribute movb $0xe,%ah # BIOS: Display int $0x10 # character putstr: lodsb # Get char testb %al,%al # End of string? jne putstr.0 # No /* * Overused return code. ereturn is used to return an error from the * read function. Since we assume putstr succeeds, we (ab)use the * same code when we return from putstr. */ ereturn: movb $0x1,%ah # Invalid stc # argument return: retw # To caller /* * Reads sectors from the disk. If EDD is enabled, then check if it is * installed and use it if it is. If it is not installed or not enabled, then * fall back to using CHS. Since we use a LBA, if we are using CHS, we have to * fetch the drive parameters from the BIOS and divide it out ourselves. * Call with: * * %dl - byte - drive number * stack - 10 bytes - EDD Packet */ read: testb $FL_PACKET,%cs:MEM_REL+flags-start # LBA support enabled? jz read.1 # No, use CHS cmpb $0x80,%dl # Hard drive? jb read.1 # No, use CHS mov $0x55aa,%bx # Magic push %dx # Save movb $0x41,%ah # BIOS: Check int $0x13 # extensions present pop %dx # Restore jc read.1 # If error, use CHS cmp $0xaa55,%bx # Magic? jne read.1 # No, so use CHS testb $0x1,%cl # Packet interface? jz read.1 # No, so use CHS mov %bp,%si # Disk packet movb $0x42,%ah # BIOS: Extended int $0x13 # read retw # To caller read.1: push %dx # Save movb $0x8,%ah # BIOS: Get drive int $0x13 # parameters movb %dh,%ch # Max head number pop %dx # Restore jc return # If error andb $0x3f,%cl # Sectors per track jz ereturn # If zero cli # Disable interrupts mov 0x8(%bp),%eax # Get LBA push %dx # Save movzbl %cl,%ebx # Divide by xor %edx,%edx # sectors div %ebx # per track movb %ch,%bl # Max head number movb %dl,%ch # Sector number inc %bx # Divide by xorb %dl,%dl # number div %ebx # of heads movb %dl,%bh # Head number pop %dx # Restore cmpl $0x3ff,%eax # Cylinder number supportable? sti # Enable interrupts ja ereturn # No, return an error xchgb %al,%ah # Set up cylinder rorb $0x2,%al # number orb %ch,%al # Merge inc %ax # sector xchg %ax,%cx # number movb %bh,%dh # Head number subb %ah,%al # Sectors this track mov 0x2(%bp),%ah # Blocks to read cmpb %ah,%al # To read jb read.2 # this #ifdef TRACK_AT_A_TIME movb %ah,%al # track #else movb $1,%al # one sector #endif read.2: mov $0x5,%di # Try count read.3: les 0x4(%bp),%bx # Transfer buffer push %ax # Save movb $0x2,%ah # BIOS: Read int $0x13 # from disk pop %bx # Restore jnc read.4 # If success dec %di # Retry? jz read.6 # No xorb %ah,%ah # BIOS: Reset int $0x13 # disk system xchg %bx,%ax # Block count jmp read.3 # Continue read.4: movzbw %bl,%ax # Sectors read add %ax,0x8(%bp) # Adjust jnc read.5 # LBA, incw 0xa(%bp) # transfer read.5: shlb %bl # buffer add %bl,0x5(%bp) # pointer, sub %al,0x2(%bp) # block count ja read.1 # If not done read.6: retw # To caller /* Messages */ msg_read: .asciz "Read" msg_part: .asciz "Boot" prompt: .asciz " error\r\n" flags: .byte FLAGS # Flags .org PRT_OFF,0x90 /* Partition table */ .fill 0x30,0x1,0x0 part4: .byte 0x80, 0x00, 0x01, 0x00 .byte 0xa5, 0xfe, 0xff, 0xff .byte 0x00, 0x00, 0x00, 0x00 .byte 0x50, 0xc3, 0x00, 0x00 # 50000 sectors long, bleh .word 0xaa55 # Magic number