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: head/sys/boot/i386/zfsboot/zfsldr.S 221177 2011-04-28 17:44:24Z jhb $ |
16 */ 17 18/* Memory Locations */ 19 .set MEM_REL,0x700 # Relocation address 20 .set MEM_ARG,0x900 # Arguments 21 .set MEM_ORG,0x7c00 # Origin 22 .set MEM_BUF,0x8000 # Load area 23 .set MEM_BTX,0x9000 # BTX start 24 .set MEM_JMP,0x9010 # BTX entry point 25 .set MEM_USR,0xa000 # Client start 26 .set BDA_BOOT,0x472 # Boot howto flag 27 28/* Partition Constants */ 29 .set PRT_OFF,0x1be # Partition offset 30 .set PRT_NUM,0x4 # Partitions 31 .set PRT_BSD,0xa5 # Partition type 32 |
33/* Misc. Constants */ 34 .set SIZ_PAG,0x1000 # Page size 35 .set SIZ_SEC,0x200 # Sector size 36 37 .set NSECT,0x80 38 .globl start |
39 .code16 40 41start: jmp main # Start recognizably 42 43/* 44 * This is the start of a standard BIOS Parameter Block (BPB). Most bootable 45 * FAT disks have this at the start of their MBR. While normal BIOS's will 46 * work fine without this section, IBM's El Torito emulation "fixes" up the 47 * BPB by writing into the memory copy of the MBR. Rather than have data |
48 * written into our code, we'll define a BPB to work around it. |
49 * The data marked with (T) indicates a field required for a ThinkPad to 50 * recognize the disk and (W) indicates fields written from IBM BIOS code. 51 * The use of the BPB is based on what OpenBSD and NetBSD implemented in 52 * their boot code but the required fields were determined by trial and error. 53 * 54 * Note: If additional space is needed in boot1, one solution would be to 55 * move the "prompt" message data (below) to replace the OEM ID. 56 */ --- 14 unchanged lines hidden (view full) --- 71 .long 0 # hidden sectors (W) 72 .long 0 # large sectors 73 74 .org 0x24, 0x00 75ebpb: .byte 0 # BIOS physical drive number (W) 76 77 .org 0x25,0x90 78/* |
79 * Load the rest of zfsboot2 and BTX up, copy the parts to the right locations, |
80 * and start it all up. 81 */ 82 83/* 84 * Setup the segment registers to flat addressing (segment 0) and setup the 85 * stack to end just below the start of our code. 86 */ 87main: cld # String ops inc --- 57 unchanged lines hidden (view full) --- 145 * (compare to this section of the UFS bootstrap) so we just load it 146 * all at 0x8000. The first part of boot2 is BTX, which wants to run 147 * at 0x9000. The boot2.bin binary starts right after the end of BTX, 148 * so we have to figure out where the start of it is and then move the 149 * binary to 0xc000. After we have moved the client, we relocate BTX 150 * itself to 0x9000 - doing it in this order means that none of the 151 * memcpy regions overlap which would corrupt the copy. Normally, BTX 152 * clients start at MEM_USR, or 0xa000, but when we use btxld to |
153 * create zfsboot2, we use an entry point of 0x2000. That entry point is |
154 * relative to MEM_USR; thus boot2.bin starts at 0xc000. 155 * 156 * The load area and the target area for the client overlap so we have 157 * to use a decrementing string move. We also play segment register 158 * games with the destination address for the move so that the client 159 * can be larger than 16k (which would overflow the zero segment since 160 * the client starts at 0xc000). Relocating BTX is easy since the load 161 * area and target area do not overlap. --- 43 unchanged lines hidden (view full) --- 205 movb $0xdf,%al # Enable 206 outb %al,$0x60 # A20 207seta20.3: sti # Enable interrupts 208 209 jmp start+MEM_JMP-MEM_ORG # Start BTX 210 211 212/* |
213 * Trampoline used to call read from within zfsldr. Sets up an EDD 214 * packet on the stack and passes it to read. 215 * 216 * %eax - int - LBA to read in relative to partition start 217 * %dl - byte - drive to read from 218 * %dh - byte - num sectors to read 219 * %si - ptr - MBR partition entry |
220 */ 221nread: xor %eax,%eax # Sector offset in partition |
222nread.1: xor %ecx,%ecx # Get |
223 addl 0x8(%si),%eax # LBA 224 adc $0,%ecx |
225 pushl %ecx # Starting absolute block 226 pushl %eax # block number 227 push %es # Address of 228 push $MEM_BUF # transfer buffer 229 xor %ax,%ax # Number of 230 movb %dh,%al # blocks to 231 push %ax # transfer 232 push $0x10 # Size of packet 233 mov %sp,%bp # Packet pointer 234 callw read # Read from disk 235 lea 0x10(%bp),%sp # Clear stack |
236 jnc return # If success, return 237 mov $msg_read,%si # Otherwise, set the error 238 # message and fall through to 239 # the error routine 240/* 241 * Print out the error message pointed to by %ds:(%si) followed 242 * by a prompt, wait for a keypress, and then reboot the machine. 243 */ --- 27 unchanged lines hidden (view full) --- 271 * installed and use it if it is. If it is not installed or not enabled, then 272 * fall back to using CHS. Since we use a LBA, if we are using CHS, we have to 273 * fetch the drive parameters from the BIOS and divide it out ourselves. 274 * Call with: 275 * 276 * %dl - byte - drive number 277 * stack - 10 bytes - EDD Packet 278 */ |
279read: cmpb $0x80,%dl # Hard drive? |
280 jb read.1 # No, use CHS 281 mov $0x55aa,%bx # Magic 282 push %dx # Save 283 movb $0x41,%ah # BIOS: Check 284 int $0x13 # extensions present 285 pop %dx # Restore 286 jc read.1 # If error, use CHS 287 cmp $0xaa55,%bx # Magic? 288 jne read.1 # No, so use CHS 289 testb $0x1,%cl # Packet interface? 290 jz read.1 # No, so use CHS 291 mov %bp,%si # Disk packet 292 movb $0x42,%ah # BIOS: Extended 293 int $0x13 # read 294 retw # To caller |
295read.1: mov $msg_chs,%si 296 jmp error 297msg_chs: .asciz "CHS not supported" |
298 299/* Messages */ 300 301msg_read: .asciz "Read" 302msg_part: .asciz "Boot" 303 304prompt: .asciz " error\r\n" 305 |
306 .org PRT_OFF,0x90 307 308/* Partition table */ 309 310 .fill 0x30,0x1,0x0 311part4: .byte 0x80, 0x00, 0x01, 0x00 312 .byte 0xa5, 0xfe, 0xff, 0xff 313 .byte 0x00, 0x00, 0x00, 0x00 314 .byte 0x50, 0xc3, 0x00, 0x00 # 50000 sectors long, bleh 315 316 .word 0xaa55 # Magic number |