f15da231c5
we just loaded from the disk. The code to call it was commented out, and it easily fit into the extra sector, but remove it anyway as it is unneeded.
488 lines
14 KiB
ArmAsm
488 lines
14 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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# A 1024-byte boot manager.
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.set NHRDRV,0x475 # Number of hard drives
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.set ORIGIN,0x600 # Execution address
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.set SECTOR_SIZE,0x200 # Length of a sector
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.set NUM_SECTORS,2 # Total length in sectors
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.set FAKE,ORIGIN+(SECTOR_SIZE*NUM_SECTORS) # Partition entry
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.set LOAD,0x7c00 # Load address
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.set PRT_OFF,0x1be # Partition table
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.set TBL0SZ,table0_end-table0 # Table 0 size
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.set TBL1SZ,table1_end-table1 # Table 1 size
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.set MAGIC,0xaa55 # Magic: bootable
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.set KEY_ENTER,0x1c # Enter key scan code
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.set KEY_F1,0x3b # F1 key scan code
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#
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# Flag bits
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#
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.set FL_PACKET,0x80 # Packet mode
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.set FL_NOUPDATE,0x40 # Don't save selection
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.set FL_SETDRV,0x20 # Override drive number
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#
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# Addresses in the sector of embedded data values.
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# Accessed with negative offsets from the end of the relocated sectors (%bp).
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#
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.set _PRT_END,(FAKE-(ORIGIN+SECTOR_SIZE))
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.set _NXTDRV,-(_PRT_END+0x48) # Next drive
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.set _OPT,-(_PRT_END+0x47) # Default option
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.set _SETDRV,-(_PRT_END+0x46) # Drive to force
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.set _FLAGS,-(_PRT_END+0x45) # Flags
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.set _TICKS,-(_PRT_END+0x44) # Timeout ticks
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.set _FAKE,0x0 # Fake partition entry
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.set _MNUOPT,0xc # Menu options
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.globl start # Entry point
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.code16 # This runs in real mode
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#
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# Initialise segments and registers to known values.
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# segments start at 0.
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# The stack is immediatly below the address we were loaded to.
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#
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# Note that this section of code is used as the first signature check in
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# boot0cfg(8).
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#
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start: cld # String ops inc
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xorw %ax,%ax # Zero
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movw %ax,%es # Address
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movw %ax,%ds # data
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movw %ax,%ss # Set up
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movw $LOAD,%sp # stack
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#
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# End signature code
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#
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#
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# Set address for variable space beyond code, and clear it.
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# Notice that this is also used to point to the values embedded in in the block,
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# by using negative offsets.
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#
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movw $fake,%bp # Address variables
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movw %bp,%di # %di used in stosw
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movb $0x8,%cl # Words to clear
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rep # Zero
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stosw # them
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incb -0xe(%di) # Sector number 1
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#
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# Reload all of boot0 (including the extra sectors) into memory at the
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# relocation address.
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#
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push %dx # Save drive number
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movw $start,%bx # Origin we were linked for
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movw %bp,%si # Fake PTE
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movw $0x200+NUM_SECTORS,%ax # Read in all
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callw intx13 # of boot0
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pop %dx # Restore
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#
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# Relocate to the new copy of the code.
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#
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jmp main+ORIGIN-LOAD # To relocated code
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#
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# Check what flags were loaded with us; specifically, use a predefined Drive.
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# If what the bios gives us is bad, use the '0' in the block instead, as well.
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#
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main: testb $FL_SETDRV,_FLAGS(%bp) # Set number drive?
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jnz main.1 # Yes
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testb %dl,%dl # Drive number valid?
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js main.2 # Possibly (0x80 set)
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main.1: movb _SETDRV(%bp),%dl # Drive number to use
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#
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# Whatever we decided to use, now store it into the fake
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# partition entry that lives in the data space above us.
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#
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main.2: movb %dl,_FAKE(%bp) # Save drive number
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callw putn # To new line
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pushw %dx # Save drive number
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#
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# Start out with a pointer to the 4th byte of the first table entry
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# so that after 4 iterations it's beyond the end of the sector.
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# and beyond a 256 byte boundary and thos overflowed 8 bits (see next comment).
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# (remember that the table starts 2 bytes earlier than you would expect
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# as the bootable flag is after it in the block)
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#
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movw $(partbl+0x4),%bx # Partition table (+4)
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xorw %dx,%dx # Item number
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#
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# Loop around on the partition table, printing values until we
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# pass a 256 byte boundary. The end of loop test is at main.5.
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#
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main.3: movb %ch,-0x4(%bx) # Zero active flag (ch == 0)
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btw %dx,_FLAGS(%bp) # Entry enabled?
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jnc main.5 # No
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#
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# If any of the entries in the table are
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# the same as the 'type' in the slice table entry,
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# then this is an empty or non bootable partition. Skip it.
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#
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movb (%bx),%al # Load type
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movw $tables,%di # Lookup tables
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movb $TBL0SZ,%cl # Number of entries
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repne # Exclude
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scasb # partition?
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je main.5 # Yes
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#
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# Now scan the table of known types
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#
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movb $TBL1SZ,%cl # Number of entries
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repne # Known
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scasb # type?
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jne main.4 # No
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#
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# If it matches get the matching element in the
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# next array. If it doesn't, we are already
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# pointing at its first element which points to a "?".
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#
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addw $TBL1SZ,%di # Adjust
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main.4: movb (%di),%cl # Partition
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addw %cx,%di # description
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callw putx # Display it
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main.5: incw %dx # Next item
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addb $0x10,%bl # Next entry
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jnc main.3 # Till done
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#
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# Passed a 256 byte boundary..
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# table is finished.
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# Add one to the drive number and check it is valid,
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#
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popw %ax # Drive number
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subb $0x80-0x1,%al # Does next
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cmpb NHRDRV,%al # drive exist? (from BIOS?)
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jb main.6 # Yes
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# If not then if there is only one drive,
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# Don't display drive as an option.
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#
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decw %ax # Already drive 0?
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jz main.7 # Yes
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# If it was illegal or we cycled through them,
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# then go back to drive 0.
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#
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xorb %al,%al # Drive 0
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#
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# Whatever drive we selected, make it an ascii digit and save it back
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# to the "next drive" location in the loaded block in case we
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# want to save it for next time.
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# This also is part of the printed drive string so add 0x80 to indicate
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# end of string.
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#
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main.6: addb $'0'|0x80,%al # Save next
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movb %al,_NXTDRV(%bp) # drive number
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movw $drive,%di # Display
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callw putx # item
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#
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# Now that we've printed the drive (if we needed to), display a prompt.
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# Get ready for the input by noting the time.
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#
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main.7: movw $prompt,%si # Display
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callw putstr # prompt
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movb _OPT(%bp),%dl # Display
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decw %si # default
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callw putkey # key
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xorb %ah,%ah # BIOS: Get
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int $0x1a # system time
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movw %dx,%di # Ticks when
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addw _TICKS(%bp),%di # timeout
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#
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# Busy loop, looking for keystrokes but
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# keeping one eye on the time.
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#
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main.8: movb $0x1,%ah # BIOS: Check
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int $0x16 # for keypress
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jnz main.11 # Have one
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xorb %ah,%ah # BIOS: Get
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int $0x1a # system time
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cmpw %di,%dx # Timeout?
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jb main.8 # No
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#
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# If timed out or defaulting, come here.
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#
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main.9: movb _OPT(%bp),%al # Load default
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jmp main.12 # Join common code
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#
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# User's last try was bad, beep in displeasure.
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# Since nothing was printed, just continue on as if the user
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# hadn't done anything. This gives the effect of the user getting a beep
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# for all bad keystrokes but no action until either the timeout
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# occurs or the user hits a good key.
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#
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main.10: movb $0x7,%al # Signal
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callw putchr # error
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#
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# Get the keystroke.
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#
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main.11: xorb %ah,%ah # BIOS: Get
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int $0x16 # keypress
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movb %ah,%al # Scan code
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#
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# If it's CR act as if timed out.
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#
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cmpb $KEY_ENTER,%al # Enter pressed?
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je main.9 # Yes
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#
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# Otherwise check if legal
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# If not ask again.
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#
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subb $KEY_F1,%al # Less F1 scan code
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cmpb $0x4,%al # F1..F5?
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ja main.10 # No
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#
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# We have a selection.
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# but if it's a bad selection go back to complain.
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# The bits in MNUOPT were set when the options were printed.
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# Anything not printed is not an option.
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#
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main.12: cbtw # Option
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btw %ax,_MNUOPT(%bp) # enabled?
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jnc main.10 # No
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#
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# Save the info in the original tables
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# for rewriting to the disk.
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#
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movb %al,_OPT(%bp) # Save option
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movw $fake,%si # Partition for write
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movb (%si),%dl # Drive number
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movw %si,%bx # Partition for read
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cmpb $0x4,%al # F5 pressed?
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pushf # Save
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je main.13 # Yes
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shlb $0x4,%al # Point to
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addw $partbl,%ax # selected
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xchgw %bx,%ax # partition
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movb $0x80,(%bx) # Flag active
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#
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# If not asked to do a write-back (flags 0x40) don't do one.
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#
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main.13: pushw %bx # Save
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testb $FL_NOUPDATE,_FLAGS(%bp) # Skip update?
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jnz main.14 # Yes
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movw $start,%bx # Data to write
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movw $0x301,%ax # Write 1 sector
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callw intx13 # to disk
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main.14: popw %si # Restore
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popf # Restore
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#
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# If going to next drive, replace drive with selected one.
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# Remember to un-ascii it. Hey 0x80 is already set, cool!
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#
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jne main.15 # If not F5
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movb _NXTDRV(%bp),%dl # Next drive
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subb $'0',%dl # number
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#
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# load selected bootsector to the LOAD location in RAM.
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# If it fails to read or isn't marked bootable, treat it
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# as a bad selection.
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#
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main.15: movw $LOAD,%bx # Address for read
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movw $0x201,%ax # Read 1 sector
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callw intx13 # from disk
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jc main.10 # If error
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cmpw $MAGIC,0x1fe(%bx) # Bootable?
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jne main.10 # No
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callw putn # Leave some space
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jmp *%bx # Invoke bootstrap
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#
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# Display routines
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#
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putkey: movb $'F',%al # Display
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callw putchr # 'F'
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movb $'1',%al # Prepare
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addb %dl,%al # digit
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jmp putstr.1 # Display the rest
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#
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# Display the option and note that it is a valid option.
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# That last point is a bit tricky..
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#
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putx: btsw %dx,_MNUOPT(%bp) # Enable menu option
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movw $item,%si # Display
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callw putkey # key
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movw %di,%si # Display the rest
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puts: callw putstr # Display string
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putn: movw $crlf,%si # To next line
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putstr: lodsb # Get byte
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testb $0x80,%al # End of string?
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jnz putstr.2 # Yes
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putstr.1: callw putchr # Display char
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jmp putstr # Continue
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putstr.2: andb $~0x80,%al # Clear MSB
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putchr: pushw %bx # Save
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movw $0x7,%bx # Page:attribute
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movb $0xe,%ah # BIOS: Display
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int $0x10 # character
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popw %bx # Restore
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retw # To caller
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# One-sector disk I/O routine
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#
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# Calling conventions: (assumes %si -> partition table entry)
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#
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# 0x1(%si) - byte - head
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# 0x2(%si) - word - cylinder/sector
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# 0x8(%si) - long - LBA to use if needed
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# %ah - byte - operation, 2 = read, 3 = write
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# %al - byte - sector count
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# %dl - byte - drive number
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# %es:(%bx) - void - buffer to use for transfer
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#
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# If the head == 0xff, and cylinder/sector == 0xffff, then try
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# to use the EDD stuff with the LBA offset instead of CHS. However,
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# use CHS if at all possible.
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intx13: movb 0x1(%si),%dh # Load head
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movw 0x2(%si),%cx # Load cylinder:sector
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pushw %si # Save
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movw %sp,%di # Save
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cmpb $0xff,%dh # Might we need LBA?
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jne intx13.2 # No, just use CHS
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cmpw $0xffff,%cx # Do we need LBA?
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jne intx13.2 # No
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testb $FL_PACKET,_FLAGS(%bp) # Try the packet interface?
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jz intx13.2 # No
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pushw %cx # Save
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pushw %bx # Save
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movw $0x55aa,%bx # Magic
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pushw %ax # Save
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movb $0x41,%ah # BIOS: EDD extensions
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int $0x13 # present?
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popw %ax # Restore
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jc intx13.1 # Not present, use CHS
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cmpw $0xaa55,%bx # Magic?
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jne intx13.1 # Not present, use CHS
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testb $0x1,%cl # Packet mode available?
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jz intx13.1 # No, use CHS
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orb $0x40,%ah # Use disk packet
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intx13.1: popw %bx # Restore
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popw %cx # Restore
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testb $0x40,%ah # Using packet mode?
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jz intx13.2 # No, so skip the rest
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pushl $0x0 # Set the
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pushl 0x8(%si) # LBA address
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pushw %es # Set the transfer
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pushw %bx # buffer address
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push $0x0 # Punch a hole in the stack
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push $0x10 # Packet size
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movw %sp,%si # Packet pointer
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xchgb %al,0x2(%si) # Set the block count in the
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# packet and zero %al,
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# turning verify off for writes
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intx13.2: int $0x13 # BIOS: Disk I/O
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movw %di,%sp # Restore
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popw %si # Restore
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retw # To caller
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.org PRT_OFF-0xe,0x90
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#
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# These values are sometimes changed before writing back to the drive
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# Be especially careful that nxtdrv: must come after drive:, as it
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# is part of the same string.
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#
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# Note that the 'drive' string variable is used as the second signature
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# check in boot0cfg(8).
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#
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version_minor: .byte 0x1 # minor version
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version_major: .byte 0x1 # major version
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drive: .ascii "Drive "
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nxtdrv: .byte 0x0 # Next drive number
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opt: .byte 0x0 # Option
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setdrv: .byte 0x80 # Drive to force
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flags: .byte FLAGS # Flags
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ticks: .word TICKS # Delay
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#
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# here is the 64 byte partition table that fdisk would fiddle with.
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#
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partbl: .fill 0x40,0x1,0x0 # Partition table
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.word MAGIC # Magic number
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#
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# start of sector two.. ugh
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#
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.org SECTOR_SIZE,0x90
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# Menu strings
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item: .ascii " "; .byte ' '|0x80
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prompt: .ascii "\nDefault:"; .byte ' '|0x80
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crlf: .ascii "\r"; .byte '\n'|0x80
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# Partition type tables
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tables:
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#
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# These entries identify invalid or NON BOOT types and partitions.
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#
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table0: .byte 0x0, 0x5, 0xf
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table0_end:
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#
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# These valuse indicate botable types we know the names of
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#
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table1: .byte 0x1, 0x4, 0x6, 0x7, 0xb, 0xc, 0xe, 0x63, 0x83
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.byte 0xa5, 0xa6, 0xa9, 0xb7
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table1_end:
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#
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# These are offsets that match the known names above and point to the strings
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# that will be printed.
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#
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.byte os_misc-. # Unknown
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.byte os_dos-. # DOS
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.byte os_dos-. # DOS
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.byte os_dos-. # DOS
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.byte os_nt-. # NT or OS/2
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.byte os_windows-. # Windows
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.byte os_windows-. # Windows
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.byte os_windows-. # Windows
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.byte os_unix-. # UNIX
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.byte os_linux-. # Linux
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.byte os_freebsd-. # FreeBSD
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.byte os_openbsd-. # OpenBSD
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.byte os_netbsd-. # NetBSD
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.byte os_bsdos-. # BSD/OS
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#
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# And here are the strings themselves. 0x80 or'd into a byte indicates
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# the end of the string. (not so great for Russians but...)
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#
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os_misc: .ascii "Unknow"; .byte 'n'|0x80
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os_dos: .ascii "DO"; .byte 'S'|0x80
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os_nt: .ascii "Windows N"; .byte 'T'|0x80
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os_windows: .ascii "Window"; .byte 's'|0x80
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os_unix: .ascii "UNI"; .byte 'X'|0x80
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os_linux: .ascii "Linu"; .byte 'x'|0x80
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os_freebsd: .ascii "FreeBS"; .byte 'D'|0x80
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os_openbsd: .ascii "OpenBS"; .byte 'D'|0x80
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os_netbsd: .ascii "NetBS"; .byte 'D'|0x80
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os_bsdos: .ascii "BSD/O"; .byte 'S'|0x80
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#
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# Fake partition entry created at the end of the table used when loading
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# boot0 at the very beginning and when loading an MBR from another disk when
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# F5 is pressed.
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#
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.org SECTOR_SIZE*NUM_SECTORS, 0x0
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fake:
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