9213e54d95
boot time. Instead, read it a sector at a time. While this sounds like a significant slowdown, I've not been able to measure any signficant difference. Submitted by: luigi Reviewed by: jhb, sam (both a while ago) MFC After: 3 days
366 lines
11 KiB
ArmAsm
366 lines
11 KiB
ArmAsm
//
|
|
// 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_REL,0x700 // Relocation address
|
|
.set MEM_ARG,0x900 // Arguments
|
|
.set MEM_ORG,0x7c00 // Origin
|
|
.set MEM_BUF,0x8cec // 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 0x8cec as our transfer buffer. Thus,
|
|
// boot1 ends up at 0x8cec, and boot2 starts at 0x8cec + 0x200 = 0x8eec.
|
|
// The first part of boot2 is the disklabel, which is 0x114 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
|
|
sub %di,%cx // Byte count
|
|
xorb %al,%al // Zero assumed bss from
|
|
rep // the end of boot2.bin
|
|
stosb // up to 0x10000
|
|
callw seta20 // Enable A20
|
|
jmp start+MEM_JMP-MEM_ORG // Start BTX
|
|
//
|
|
// Enable A20 so we can access memory above 1 meg.
|
|
//
|
|
seta20: cli // Disable interrupts
|
|
seta20.1: 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
|
|
sti // Enable interrupts
|
|
retw // To caller
|
|
//
|
|
// 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 $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
|
|
|
|
//
|
|
// 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: 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 read.7 // No, try EDD
|
|
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 // If not done
|
|
read.6: retw // To caller
|
|
read.7: testb $FL_PACKET,%cs:MEM_REL+flags-start // LBA support enabled?
|
|
jz ereturn // No, so return an error
|
|
mov $0x55aa,%bx // Magic
|
|
push %dx // Save
|
|
movb $0x41,%ah // BIOS: Check
|
|
int $0x13 // extensions present
|
|
pop %dx // Restore
|
|
jc return // If error, return an error
|
|
cmp $0xaa55,%bx // Magic?
|
|
jne ereturn // No, so return an error
|
|
testb $0x1,%cl // Packet interface?
|
|
jz ereturn // No, so return an error
|
|
mov %bp,%si // Disk packet
|
|
movb $0x42,%ah // BIOS: Extended
|
|
int $0x13 // read
|
|
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
|