87 lines
3.4 KiB
Python
Executable File
87 lines
3.4 KiB
Python
Executable File
#!/usr/bin/env python3
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import sys
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import struct
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# Awful hack to run code through vasm
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def assemble(the_code):
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with open('/tmp/vasm.elliot', 'w') as f:
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f.write(the_code)
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import os
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from os import path
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assembler = path.join(path.dirname(path.abspath(__file__)), 'vasm-1/vasmm68k_std')
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os.system(f'{assembler} -quiet -Fbin -pic -o /tmp/vasm.elliot.bin /tmp/vasm.elliot')
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with open('/tmp/vasm.elliot.bin', 'rb') as f:
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return f.read()
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def write_asm(f, asm):
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f.write(assemble(f' .org {hex(f.tell())} \n rom: \n {asm}'))
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with open(sys.argv[1], 'r+b') as f:
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# Skip the initial PRAM check in forXO.a:InstallNetBoot
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f.seek(0x1d928)
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while f.tell() < 0x1D982:
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f.write(b'Nq') # nop
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# Find a safe place to store our overridden NetBoot config struct
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# (Which would otherwise be cobbled from various parts of PRAM)
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garbage_location = 0x67046 # The MacsBug copyright string in the ROM Disk
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# Make out own structure, as adapted from NetBoot.h
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the_netboot_structure = struct.pack('>BBBB BB 16s 32s 8s H', # Note that "int"s are 4 bytes, somehow!
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# First 4 bytes at PRAM+4
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1, # char osType; /* preferred os to boot from */
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1, # char protocol; /* preferred protocol to boot from */
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0, # char errors; /* last error in network booting */
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0xC0, # char flags; /* flags for: never net boot, boot first, etc. */
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# Now, the AppleTalk-protocol-specific part
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0, # unsigned char nbpVars; /* address of last server that we booted off of */
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0, # unsigned char timeout; /* seconds to wait for bootserver response */
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b'', # unsigned int signature[4]; /* image signature */ Elliot notes: zeroes match anything!
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b'Elliot', # char userName[31]; /* an array of char, no length byte */
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b'volapuk', # char password[8]; /* '' */
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0xBABE, # short serverNum; /* the server number */
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).ljust(72, b'\0')
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# the_netboot_structure = bytearray(the_netboot_structure)
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# for i, j in enumerate(range(54, len(the_netboot_structure))):
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# the_netboot_structure[j] = i
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# This is the guts of the NetBoot ReadPRAM procedure
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f.seek(0x1DF08)
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write_asm(f, f'''
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move.l a0,a1
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move.l 0x2ae,a0 ; RomBase
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add.l #{hex(garbage_location)},a0
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move.l #{hex(len(the_netboot_structure))},d0
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.2byte 0xA02E ; BlockMove
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rts
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''')
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f.seek(garbage_location)
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f.write(the_netboot_structure)
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# Do the dodgy... cancel signature validation!
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f.seek(0x21A84)
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while f.tell() < 0x21A98:
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f.write(b'Nq') # nop
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# Work around Mini vMac's cutesy many-drives hack (it steals out preferred drivenum of 4 from us)
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f.seek(0x1DF51) # AddMyDrive: moveq #4,d9
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f.write(b'\x10')
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f.seek(0x1DFDF) # myExtFSFilter: cmp.w #4,d0
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f.write(b'\x10')
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# Enable this to make a SysError, for rudimentaly debug output
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# for x in '9380'.split():
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# x = eval('0x' + x)
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# f.seek(x)
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# f.write(assemble(f' move.l #{x},D0 \n .2byte 0xA9C9'))
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