a3b5a4369c
it possible to make UFS1_ONLY and UFS2_ONLY versions which fit inside the traditional 16 sectors. Remove assorted now unneeded hackery. UFS1_AND_UFS2 still needs another 150 bytes to work, and that is probably not within our reach, ever.
362 lines
11 KiB
ArmAsm
362 lines
11 KiB
ArmAsm
//
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// Copyright (c) 1998 Robert Nordier
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms are freely
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// permitted provided that the above copyright notice and this
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// paragraph and the following disclaimer are duplicated in all
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// such forms.
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//
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// This software is provided "AS IS" and without any express or
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// implied warranties, including, without limitation, the implied
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// warranties of merchantability and fitness for a particular
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// purpose.
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//
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// $FreeBSD$
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// Memory Locations
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.set MEM_REL,0x700 // Relocation address
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.set MEM_ARG,0x900 // Arguments
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.set MEM_ORG,0x7c00 // Origin
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.set MEM_BUF,0x8cec // Load area
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.set MEM_BTX,0x9000 // BTX start
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.set MEM_JMP,0x9010 // BTX entry point
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.set MEM_USR,0xa000 // Client start
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.set BDA_BOOT,0x472 // Boot howto flag
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// Partition Constants
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.set PRT_OFF,0x1be // Partition offset
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.set PRT_NUM,0x4 // Partitions
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.set PRT_BSD,0xa5 // Partition type
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// Flag Bits
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.set FL_PACKET,0x80 // Packet mode
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// Misc. Constants
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.set SIZ_PAG,0x1000 // Page size
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.set SIZ_SEC,0x200 // Sector size
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.set NSECT,0x10
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.globl start
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.globl xread
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.code16
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start: jmp main // Start recognizably
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// This is the start of a standard BIOS Parameter Block (BPB). Most bootable
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// FAT disks have this at the start of their MBR. While normal BIOS's will
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// work fine without this section, IBM's El Torito emulation "fixes" up the
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// BPB by writing into the memory copy of the MBR. Rather than have data
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// written into our xread routine, we'll define a BPB to work around it.
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// The data marked with (T) indicates a field required for a ThinkPad to
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// recognize the disk and (W) indicates fields written from IBM BIOS code.
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// The use of the BPB is based on what OpenBSD and NetBSD implemented in
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// their boot code but the required fields were determined by trial and error.
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//
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// Note: If additional space is needed in boot1, one solution would be to
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// move the "prompt" message data (below) to replace the OEM ID.
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.org 0x03, 0x00
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oemid: .space 0x08, 0x00 // OEM ID
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.org 0x0b, 0x00
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bpb: .word 512 // sector size (T)
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.byte 0 // sectors/clustor
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.word 0 // reserved sectors
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.byte 0 // number of FATs
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.word 0 // root entries
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.word 0 // small sectors
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.byte 0 // media type (W)
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.word 0 // sectors/fat
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.word 18 // sectors per track (T)
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.word 2 // number of heads (T)
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.long 0 // hidden sectors (W)
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.long 0 // large sectors
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.org 0x24, 0x00
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ebpb: .byte 0 // BIOS physical drive number (W)
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.org 0x25,0x90
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//
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// Trampoline used by boot2 to call read to read data from the disk via
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// the BIOS. Call with:
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//
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// %cx:%ax - long - LBA to read in
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// %es:(%bx) - caddr_t - buffer to read data into
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// %dl - byte - drive to read from
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// %dh - byte - num sectors to read
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//
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xread: push %ss // Address
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pop %ds // data
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//
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// Setup an EDD disk packet and pass it to read
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//
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xread.1: // Starting
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pushl $0x0 // absolute
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push %cx // block
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push %ax // number
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push %es // Address of
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push %bx // transfer buffer
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xor %ax,%ax // Number of
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movb %dh,%al // blocks to
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push %ax // transfer
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push $0x10 // Size of packet
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mov %sp,%bp // Packet pointer
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callw read // Read from disk
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lea 0x10(%bp),%sp // Clear stack
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lret // To far caller
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//
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// Load the rest of boot2 and BTX up, copy the parts to the right locations,
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// and start it all up.
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//
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//
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// Setup the segment registers to flat addressing (segment 0) and setup the
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// stack to end just below the start of our code.
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//
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main: cld // String ops inc
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xor %cx,%cx // Zero
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mov %cx,%es // Address
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mov %cx,%ds // data
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mov %cx,%ss // Set up
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mov $start,%sp // stack
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//
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// Relocate ourself to MEM_REL. Since %cx == 0, the inc %ch sets
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// %cx == 0x100.
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//
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mov %sp,%si // Source
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mov $MEM_REL,%di // Destination
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incb %ch // Word count
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rep // Copy
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movsw // code
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//
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// If we are on a hard drive, then load the MBR and look for the first
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// FreeBSD slice. We use the fake partition entry below that points to
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// the MBR when we call nread. The first pass looks for the first active
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// FreeBSD slice. The second pass looks for the first non-active FreeBSD
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// slice if the first one fails.
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//
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mov $part4,%si // Partition
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cmpb $0x80,%dl // Hard drive?
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jb main.4 // No
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movb $0x1,%dh // Block count
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callw nread // Read MBR
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mov $0x1,%cx // Two passes
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main.1: mov $MEM_BUF+PRT_OFF,%si // Partition table
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movb $0x1,%dh // Partition
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main.2: cmpb $PRT_BSD,0x4(%si) // Our partition type?
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jne main.3 // No
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jcxz main.5 // If second pass
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testb $0x80,(%si) // Active?
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jnz main.5 // Yes
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main.3: add $0x10,%si // Next entry
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incb %dh // Partition
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cmpb $0x1+PRT_NUM,%dh // In table?
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jb main.2 // Yes
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dec %cx // Do two
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jcxz main.1 // passes
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//
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// If we get here, we didn't find any FreeBSD slices at all, so print an
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// error message and die.
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//
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mov $msg_part,%si // Message
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jmp error // Error
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//
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// Floppies use partition 0 of drive 0.
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//
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main.4: xor %dx,%dx // Partition:drive
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//
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// Ok, we have a slice and drive in %dx now, so use that to locate and load
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// boot2. %si references the start of the slice we are looking for, so go
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// ahead and load up the first 16 sectors (boot1 + boot2) from that. When
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// we read it in, we conveniently use 0x8cec as our transfer buffer. Thus,
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// boot1 ends up at 0x8cec, and boot2 starts at 0x8cec + 0x200 = 0x8eec.
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// The first part of boot2 is the disklabel, which is 0x114 bytes long.
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// The second part is BTX, which is thus loaded into 0x9000, which is where
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// it also runs from. The boot2.bin binary starts right after the end of
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// BTX, so we have to figure out where the start of it is and then move the
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// binary to 0xc000. Normally, BTX clients start at MEM_USR, or 0xa000, but
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// when we use btxld to create boot2, we use an entry point of 0x2000. That
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// entry point is relative to MEM_USR; thus boot2.bin starts at 0xc000.
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//
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main.5: mov %dx,MEM_ARG // Save args
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movb $NSECT,%dh // Sector count
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callw nread // Read disk
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mov $MEM_BTX,%bx // BTX
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mov 0xa(%bx),%si // Get BTX length and set
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add %bx,%si // %si to start of boot2.bin
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mov $MEM_USR+SIZ_PAG*2,%di // Client page 2
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mov $MEM_BTX+(NSECT-1)*SIZ_SEC,%cx // Byte
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sub %si,%cx // count
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rep // Relocate
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movsb // client
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sub %di,%cx // Byte count
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xorb %al,%al // Zero assumed bss from
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rep // the end of boot2.bin
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stosb // up to 0x10000
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callw seta20 // Enable A20
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jmp start+MEM_JMP-MEM_ORG // Start BTX
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//
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// Enable A20 so we can access memory above 1 meg.
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//
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seta20: cli // Disable interrupts
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seta20.1: inb $0x64,%al // Get status
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testb $0x2,%al // Busy?
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jnz seta20.1 // Yes
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movb $0xd1,%al // Command: Write
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outb %al,$0x64 // output port
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seta20.2: inb $0x64,%al // Get status
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testb $0x2,%al // Busy?
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jnz seta20.2 // Yes
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movb $0xdf,%al // Enable
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outb %al,$0x60 // A20
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sti // Enable interrupts
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retw // To caller
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//
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// Trampoline used to call read from within boot1.
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//
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nread: mov $MEM_BUF,%bx // Transfer buffer
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mov 0x8(%si),%ax // Get
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mov 0xa(%si),%cx // LBA
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push %cs // Read from
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callw xread.1 // disk
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jnc return // If success, return
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mov $msg_read,%si // Otherwise, set the error
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// message and fall through to
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// the error routine
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//
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// Print out the error message pointed to by %ds:(%si) followed
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// by a prompt, wait for a keypress, and then reboot the machine.
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//
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error: callw putstr // Display message
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mov $prompt,%si // Display
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callw putstr // prompt
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xorb %ah,%ah // BIOS: Get
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int $0x16 // keypress
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movw $0x1234, BDA_BOOT // Do a warm boot
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ljmp $0xffff,$0x0 // reboot the machine
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//
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// Display a null-terminated string using the BIOS output.
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//
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putstr.0: mov $0x7,%bx // Page:attribute
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movb $0xe,%ah // BIOS: Display
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int $0x10 // character
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putstr: lodsb // Get char
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testb %al,%al // End of string?
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jne putstr.0 // No
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//
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// Overused return code. ereturn is used to return an error from the
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// read function. Since we assume putstr succeeds, we (ab)use the
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// same code when we return from putstr.
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//
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ereturn: movb $0x1,%ah // Invalid
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stc // argument
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return: retw // To caller
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//
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// Reads sectors from the disk. If EDD is enabled, then check if it is
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// installed and use it if it is. If it is not installed or not enabled, then
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// fall back to using CHS. Since we use a LBA, if we are using CHS, we have to
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// fetch the drive parameters from the BIOS and divide it out ourselves.
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// Call with:
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//
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// %dl - byte - drive number
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// stack - 10 bytes - EDD Packet
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//
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read: push %dx // Save
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movb $0x8,%ah // BIOS: Get drive
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int $0x13 // parameters
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movb %dh,%ch // Max head number
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pop %dx // Restore
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jc return // If error
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andb $0x3f,%cl // Sectors per track
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jz ereturn // If zero
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cli // Disable interrupts
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mov 0x8(%bp),%eax // Get LBA
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push %dx // Save
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movzbl %cl,%ebx // Divide by
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xor %edx,%edx // sectors
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div %ebx // per track
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movb %ch,%bl // Max head number
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movb %dl,%ch // Sector number
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inc %bx // Divide by
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xorb %dl,%dl // number
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div %ebx // of heads
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movb %dl,%bh // Head number
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pop %dx // Restore
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cmpl $0x3ff,%eax // Cylinder number supportable?
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sti // Enable interrupts
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ja read.7 // No, try EDD
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xchgb %al,%ah // Set up cylinder
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rorb $0x2,%al // number
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orb %ch,%al // Merge
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inc %ax // sector
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xchg %ax,%cx // number
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movb %bh,%dh // Head number
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subb %ah,%al // Sectors this track
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mov 0x2(%bp),%ah // Blocks to read
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cmpb %ah,%al // To read
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jb read.2 // this
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movb %ah,%al // track
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read.2: mov $0x5,%di // Try count
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read.3: les 0x4(%bp),%bx // Transfer buffer
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push %ax // Save
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movb $0x2,%ah // BIOS: Read
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int $0x13 // from disk
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pop %bx // Restore
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jnc read.4 // If success
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dec %di // Retry?
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jz read.6 // No
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xorb %ah,%ah // BIOS: Reset
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int $0x13 // disk system
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xchg %bx,%ax // Block count
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jmp read.3 // Continue
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read.4: movzbw %bl,%ax // Sectors read
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add %ax,0x8(%bp) // Adjust
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jnc read.5 // LBA,
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incw 0xa(%bp) // transfer
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read.5: shlb %bl // buffer
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add %bl,0x5(%bp) // pointer,
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sub %al,0x2(%bp) // block count
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ja read // If not done
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read.6: retw // To caller
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read.7: testb $FL_PACKET,%cs:MEM_REL+flags-start // LBA support enabled?
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jz ereturn // No, so return an error
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mov $0x55aa,%bx // Magic
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push %dx // Save
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movb $0x41,%ah // BIOS: Check
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int $0x13 // extensions present
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pop %dx // Restore
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jc return // If error, return an error
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cmp $0xaa55,%bx // Magic?
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jne ereturn // No, so return an error
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testb $0x1,%cl // Packet interface?
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jz ereturn // No, so return an error
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mov %bp,%si // Disk packet
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movb $0x42,%ah // BIOS: Extended
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int $0x13 // read
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retw // To caller
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// Messages
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msg_read: .asciz "Read"
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msg_part: .asciz "Boot"
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prompt: .asciz " error\r\n"
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flags: .byte FLAGS // Flags
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.org PRT_OFF,0x90
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// Partition table
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.fill 0x30,0x1,0x0
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part4: .byte 0x80, 0x00, 0x01, 0x00
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.byte 0xa5, 0xfe, 0xff, 0xff
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.byte 0x00, 0x00, 0x00, 0x00
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.byte 0x50, 0xc3, 0x00, 0x00 // 50000 sectors long, bleh
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.word 0xaa55 // Magic number
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