diff options
Diffstat (limited to 'stand/i386/zfsboot/zfsldr.S')
| -rw-r--r-- | stand/i386/zfsboot/zfsldr.S | 283 |
1 files changed, 283 insertions, 0 deletions
diff --git a/stand/i386/zfsboot/zfsldr.S b/stand/i386/zfsboot/zfsldr.S new file mode 100644 index 0000000..3e85e27 --- /dev/null +++ b/stand/i386/zfsboot/zfsldr.S @@ -0,0 +1,283 @@ +/* + * 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. + * + * $FreeBSD$ + */ + +/* Memory Locations */ + .set MEM_ARG,0x900 # Arguments + .set MEM_ORG,0x7c00 # Origin + .set MEM_BUF,0x8000 # 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 + +/* Misc. Constants */ + .set SIZ_PAG,0x1000 # Page size + .set SIZ_SEC,0x200 # Sector size + .set COPY_BLKS,0x8 # Number of blocks + # to copy for boot2 + .set COPY_BLK_SZ,0x8000 # Copy in 32k blocks; must be + # a multiple of 16 bytes + .set NSECT,(COPY_BLK_SZ / SIZ_SEC * COPY_BLKS) + .globl start + .code16 + +/* + * Load the rest of zfsboot2 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. + */ +start: 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 +/* + * 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 read. + * 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. + */ + call check_edd # Make sure EDD works + mov $part4,%si # Dummy partition + xor %eax,%eax # Read MBR + movl $MEM_BUF,%ebx # from first + call read # sector + 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 + +/* + * 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 COPY_BLKS*COPY_BLK_SZ/SIZ_SEC sectors + * starting at sector 1024 (i.e. after the two vdev labels). We don't + * have do anything fancy here to allow for an extra copy of boot1 and + * a partition table (compare to this section of the UFS bootstrap) so we + * just load it all at 0x9000. The first part of boot2 is BTX, which wants + * to run at 0x9000. 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 zfsboot2, we use an entry point of + * 0x2000. That entry point is relative to MEM_USR; thus boot2.bin + * starts at 0xc000. + * + * The load area and the target area for the client overlap so we have + * to use a decrementing string move. We also play segment register + * games with the destination address for the move so that the client + * can be larger than 16k (which would overflow the zero segment since + * the client starts at 0xc000). + */ +main.5: mov %dx,MEM_ARG # Save args + mov $NSECT,%cx # Sector count + movl $1024,%eax # Offset to boot2 + mov $MEM_BTX,%ebx # Destination buffer +main.6: pushal # Save params + call read # Read disk + popal # Restore + incl %eax # Advance to + add $SIZ_SEC,%ebx # next sector + loop main.6 # If not last, read another + + mov $MEM_BTX,%bx # BTX + mov 0xa(%bx),%si # Get BTX length and set + add %bx,%si # %si to start of boot2 + dec %si # Set %ds:%si to point at the + mov %si,%ax # last byte we want to copy + shr $4,%ax # from boot2, with %si made as + add $(COPY_BLKS*COPY_BLK_SZ/16),%ax # small as possible. + and $0xf,%si # + mov %ax,%ds # + mov $(MEM_USR+2*SIZ_PAG)/16,%ax # Set %es:(-1) to point at + add $(COPY_BLKS*COPY_BLK_SZ/16),%ax # the last byte we + mov %ax,%es # want to copy boot2 into. + mov $COPY_BLKS,%bx # Copy COPY_BLKS 32k blocks +copyloop: + add $COPY_BLK_SZ,%si # Adjust %ds:%si to point at + mov %ds,%ax # the end of the next 32k to + sub $COPY_BLK_SZ/16,%ax # copy from boot2 + mov %ax,%ds + mov $COPY_BLK_SZ-1,%di # Adjust %es:%di to point at + mov %es,%ax # the end of the next 32k into + sub $COPY_BLK_SZ/16,%ax # which we want boot2 copied + mov %ax,%es + mov $COPY_BLK_SZ,%cx # Copy 32k + std + rep movsb + dec %bx + jnz copyloop + mov %cx,%ds # Reset %ds and %es + mov %cx,%es + cld # Back to increment + +/* + * 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 + + +/* + * Read a sector from the disk. Sets up an EDD packet on the stack + * and passes it to read. We assume that the destination address is + * always segment-aligned. + * + * %eax - int - LBA to read in relative to partition start + * %ebx - ptr - destination address + * %dl - byte - drive to read from + * %si - ptr - MBR partition entry + */ +read: xor %ecx,%ecx # Get + addl 0x8(%si),%eax # LBA + adc $0,%ecx + pushl %ecx # Starting absolute block + pushl %eax # block number + shr $4,%ebx # Convert to segment + push %bx # Address of + push $0 # transfer buffer + push $0x1 # Read 1 sector + push $0x10 # Size of packet + mov %sp,%si # Packet pointer + mov $0x42,%ah # BIOS: Extended + int $0x13 # read + jc read.1 # If error, fail + lea 0x10(%si),%sp # Clear stack + ret # If success, return +read.1: mov %ah,%al # Format + mov $read_err,%di # error + call hex8 # code + mov $msg_read,%si # 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 $0xffff,$0x0 # 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 + ret # To caller +/* + * Check to see if the disk supports EDD. zfsboot requires EDD and does not + * support older C/H/S disk I/O. + */ +check_edd: cmpb $0x80,%dl # Hard drive? + jb check_edd.1 # No, fail to boot + mov $0x55aa,%bx # Magic + push %dx # Save + movb $0x41,%ah # BIOS: Check + int $0x13 # extensions present + pop %dx # Restore + jc check_edd.1 # If error, fail + cmp $0xaa55,%bx # Magic? + jne check_edd.1 # No, so fail + testb $0x1,%cl # Packet interface? + jz check_edd.1 # No, so fail + ret # EDD ok, keep booting +check_edd.1: mov $msg_chs,%si # Warn that CHS is + jmp error # unsupported and fail +/* + * AL to hex, saving the result to [EDI]. + */ +hex8: push %ax # Save + shrb $0x4,%al # Do upper + call hex8.1 # 4 + pop %ax # Restore +hex8.1: andb $0xf,%al # Get lower 4 + cmpb $0xa,%al # Convert + sbbb $0x69,%al # to hex + das # digit + orb $0x20,%al # To lower case + stosb # Save char + ret # (Recursive) + +/* Messages */ + +msg_chs: .asciz "CHS not supported" +msg_read: .ascii "Read error: " +read_err: .asciz "XX" +msg_part: .asciz "Boot error" + +prompt: .asciz "\r\n" + + .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 |
