1/* 2 * Copyright (c) 1998 Robert Nordier 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms are freely 6 * permitted provided that the above copyright notice and this 7 * paragraph and the following disclaimer are duplicated in all 8 * such forms. 9 * 10 * This software is provided "AS IS" and without any express or 11 * implied warranties, including, without limitation, the implied 12 * warranties of merchantability and fitness for a particular 13 * purpose. 14 * 15 * $FreeBSD$ 16 */ 17 18/* Memory Locations */ 19 .set MEM_ARG,0x900 # Arguments 20 .set MEM_ORG,0x7c00 # Origin 21 .set MEM_BUF,0x8000 # Load area 22 .set MEM_BTX,0x9000 # BTX start 23 .set MEM_JMP,0x9010 # BTX entry point 24 .set MEM_USR,0xa000 # Client start 25 .set BDA_BOOT,0x472 # Boot howto flag 26 27/* Partition Constants */ 28 .set PRT_OFF,0x1be # Partition offset 29 .set PRT_NUM,0x4 # Partitions 30 .set PRT_BSD,0xa5 # Partition type 31 32/* Misc. Constants */ 33 .set SIZ_PAG,0x1000 # Page size 34 .set SIZ_SEC,0x200 # Sector size 35 .set COPY_BLKS,0x8 # Number of blocks 36 # to copy for boot2 (<= 15) 37 .set COPY_BLK_SZ,0x8000 # Copy in 32k blocks; must be 38 # a multiple of 16 bytes 39 .set NSECT,(COPY_BLK_SZ / SIZ_SEC * COPY_BLKS) 40 .globl start 41 .code16 42 43/* 44 * Load the rest of zfsboot2 and BTX up, copy the parts to the right locations, 45 * and start it all up. 46 */ 47 48/* 49 * Setup the segment registers to flat addressing (segment 0) and setup the 50 * stack to end just below the start of our code. 51 */ 52start: cld # String ops inc 53 xor %cx,%cx # Zero 54 mov %cx,%es # Address 55 mov %cx,%ds # data 56 mov %cx,%ss # Set up 57 mov $start,%sp # stack 58/* 59 * Load the MBR and look for the first FreeBSD slice. We use the fake 60 * partition entry below that points to the MBR when we call read. 61 * The first pass looks for the first active FreeBSD slice. The 62 * second pass looks for the first non-active FreeBSD slice if the 63 * first one fails. 64 */ 65 call check_edd # Make sure EDD works 66 mov $part4,%si # Dummy partition 67 xor %eax,%eax # Read MBR 68 movl $MEM_BUF,%ebx # from first 69 call read # sector 70 mov $0x1,%cx # Two passes 71main.1: mov $MEM_BUF+PRT_OFF,%si # Partition table 72 movb $0x1,%dh # Partition 73main.2: cmpb $PRT_BSD,0x4(%si) # Our partition type? 74 jne main.3 # No 75 jcxz main.5 # If second pass 76 testb $0x80,(%si) # Active? 77 jnz main.5 # Yes 78main.3: add $0x10,%si # Next entry 79 incb %dh # Partition 80 cmpb $0x1+PRT_NUM,%dh # In table? 81 jb main.2 # Yes 82 dec %cx # Do two 83 jcxz main.1 # passes 84/* 85 * If we get here, we didn't find any FreeBSD slices at all, so print an 86 * error message and die. 87 */ 88 mov $msg_part,%si # Message 89 jmp error # Error 90 91/* 92 * Ok, we have a slice and drive in %dx now, so use that to locate and 93 * load boot2. %si references the start of the slice we are looking 94 * for, so go ahead and load up the COPY_BLKS*COPY_BLK_SZ/SIZ_SEC sectors 95 * starting at sector 1024 (i.e. after the two vdev labels). We don't 96 * have do anything fancy here to allow for an extra copy of boot1 and 97 * a partition table (compare to this section of the UFS bootstrap) so we 98 * just load it all at 0x9000. The first part of boot2 is BTX, which wants 99 * to run at 0x9000. The boot2.bin binary starts right after the end of BTX, 100 * so we have to figure out where the start of it is and then move the 101 * binary to 0xc000. Normally, BTX clients start at MEM_USR, or 0xa000, 102 * but when we use btxld to create zfsboot2, we use an entry point of 103 * 0x2000. That entry point is relative to MEM_USR; thus boot2.bin 104 * starts at 0xc000. 105 * 106 * The load area and the target area for the client overlap so we have 107 * to use a decrementing string move. We also play segment register 108 * games with the destination address for the move so that the client 109 * can be larger than 16k (which would overflow the zero segment since 110 * the client starts at 0xc000). 111 */ 112main.5: mov %dx,MEM_ARG # Save args 113 mov $NSECT,%cx # Sector count 114 movl $1024,%eax # Offset to boot2 115 mov $MEM_BTX,%ebx # Destination buffer 116main.6: pushal # Save params 117 call read # Read disk 118 popal # Restore 119 incl %eax # Advance to 120 add $SIZ_SEC,%ebx # next sector 121 loop main.6 # If not last, read another 122 123 mov $MEM_BTX,%bx # BTX 124 mov 0xa(%bx),%si # Get BTX length and set 125 add %bx,%si # %si to start of boot2 126 dec %si # Set %ds:%si to point at the 127 mov %si,%ax # last byte we want to copy 128 shr $4,%ax # from boot2, with %si made as 129 add $(COPY_BLKS*COPY_BLK_SZ/16),%ax # small as possible. 130 and $0xf,%si # 131 mov %ax,%ds # 132 mov $(MEM_USR+2*SIZ_PAG)/16,%ax # Set %es:(-1) to point at 133 add $(COPY_BLKS*COPY_BLK_SZ/16),%ax # the last byte we 134 mov %ax,%es # want to copy boot2 into. 135 mov $COPY_BLKS,%bx # Copy COPY_BLKS 32k blocks 136copyloop: 137 add $COPY_BLK_SZ,%si # Adjust %ds:%si to point at 138 mov %ds,%ax # the end of the next 32k to 139 sub $COPY_BLK_SZ/16,%ax # copy from boot2 140 mov %ax,%ds 141 mov $COPY_BLK_SZ-1,%di # Adjust %es:%di to point at 142 mov %es,%ax # the end of the next 32k into 143 sub $COPY_BLK_SZ/16,%ax # which we want boot2 copied 144 mov %ax,%es 145 mov $COPY_BLK_SZ,%cx # Copy 32k 146 std 147 rep movsb 148 dec %bx 149 jnz copyloop 150 mov %cx,%ds # Reset %ds and %es 151 mov %cx,%es 152 cld # Back to increment 153 154/* 155 * Enable A20 so we can access memory above 1 meg. 156 * Use the zero-valued %cx as a timeout for embedded hardware which do not 157 * have a keyboard controller. 158 */ 159seta20: cli # Disable interrupts 160seta20.1: dec %cx # Timeout? 161 jz seta20.3 # Yes 162 inb $0x64,%al # Get status 163 testb $0x2,%al # Busy? 164 jnz seta20.1 # Yes 165 movb $0xd1,%al # Command: Write 166 outb %al,$0x64 # output port 167seta20.2: inb $0x64,%al # Get status 168 testb $0x2,%al # Busy? 169 jnz seta20.2 # Yes 170 movb $0xdf,%al # Enable 171 outb %al,$0x60 # A20 172seta20.3: sti # Enable interrupts 173 174 jmp start+MEM_JMP-MEM_ORG # Start BTX 175 176 177/* 178 * Read a sector from the disk. Sets up an EDD packet on the stack 179 * and passes it to read. We assume that the destination address is 180 * always segment-aligned. 181 * 182 * %eax - int - LBA to read in relative to partition start 183 * %ebx - ptr - destination address 184 * %dl - byte - drive to read from 185 * %si - ptr - MBR partition entry 186 */ 187read: xor %ecx,%ecx # Get 188 addl 0x8(%si),%eax # LBA 189 adc $0,%ecx 190 pushl %ecx # Starting absolute block 191 pushl %eax # block number 192 shr $4,%ebx # Convert to segment 193 push %bx # Address of 194 push $0 # transfer buffer 195 push $0x1 # Read 1 sector 196 push $0x10 # Size of packet 197 mov %sp,%si # Packet pointer 198 mov $0x42,%ah # BIOS: Extended 199 int $0x13 # read 200 jc read.1 # If error, fail 201 lea 0x10(%si),%sp # Clear stack 202 ret # If success, return 203read.1: mov %ah,%al # Format 204 mov $read_err,%di # error 205 call hex8 # code 206 mov $msg_read,%si # Set the error message and 207 # fall through to the error 208 # routine 209/* 210 * Print out the error message pointed to by %ds:(%si) followed 211 * by a prompt, wait for a keypress, and then reboot the machine. 212 */ 213error: callw putstr # Display message 214 mov $prompt,%si # Display 215 callw putstr # prompt 216 xorb %ah,%ah # BIOS: Get 217 int $0x16 # keypress 218 movw $0x1234, BDA_BOOT # Do a warm boot 219 ljmp $0xffff,$0x0 # reboot the machine 220/* 221 * Display a null-terminated string using the BIOS output. 222 */ 223putstr.0: mov $0x7,%bx # Page:attribute 224 movb $0xe,%ah # BIOS: Display 225 int $0x10 # character 226putstr: lodsb # Get char 227 testb %al,%al # End of string? 228 jne putstr.0 # No 229 ret # To caller 230/* 231 * Check to see if the disk supports EDD. zfsboot requires EDD and does not 232 * support older C/H/S disk I/O. 233 */ 234check_edd: cmpb $0x80,%dl # Hard drive? 235 jb check_edd.1 # No, fail to boot 236 mov $0x55aa,%bx # Magic 237 push %dx # Save 238 movb $0x41,%ah # BIOS: Check 239 int $0x13 # extensions present 240 pop %dx # Restore 241 jc check_edd.1 # If error, fail 242 cmp $0xaa55,%bx # Magic? 243 jne check_edd.1 # No, so fail 244 testb $0x1,%cl # Packet interface? 245 jz check_edd.1 # No, so fail 246 ret # EDD ok, keep booting 247check_edd.1: mov $msg_chs,%si # Warn that CHS is 248 jmp error # unsupported and fail 249/* 250 * AL to hex, saving the result to [EDI]. 251 */ 252hex8: push %ax # Save 253 shrb $0x4,%al # Do upper 254 call hex8.1 # 4 255 pop %ax # Restore 256hex8.1: andb $0xf,%al # Get lower 4 257 cmpb $0xa,%al # Convert 258 sbbb $0x69,%al # to hex 259 das # digit 260 orb $0x20,%al # To lower case 261 stosb # Save char 262 ret # (Recursive) 263 264/* Messages */ 265 266msg_chs: .asciz "CHS not supported" 267msg_read: .ascii "Read error: " 268read_err: .asciz "XX" 269msg_part: .asciz "Boot error" 270 271prompt: .asciz "\r\n" 272 273 .org PRT_OFF,0x90 274 275/* Partition table */ 276 277 .fill 0x30,0x1,0x0 278part4: .byte 0x80, 0x00, 0x01, 0x00 279 .byte 0xa5, 0xfe, 0xff, 0xff 280 .byte 0x00, 0x00, 0x00, 0x00 281 .byte 0x50, 0xc3, 0x00, 0x00 # 50000 sectors long, bleh 282 283 .word 0xaa55 # Magic number 284