152 lines
6.9 KiB
Text
152 lines
6.9 KiB
Text
$!
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$! This procedure patches the VMB.EXE provided with VAX/VMS V7.3 to
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$! support the Boot Block boot functionality provided on all VAX
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$! systems which run a ROM based VMB.
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$!
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$ PATCH /ABSOLUTE /NEW_VERSION /OUTPUT=cp$exe:VMB.EXE cp$src:VMB_orig.EXE
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! The native VMB.EXE program historically supported a Boot Block oriented
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! boot if Bit 3 of the parameter register (R5) was set when VMB was invoked.
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! This Boot Block boot operation reads sector 0 into memory and starts
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! execution at offset 2 of the data block in memory.
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! When portitions of VMB were migrated into ROM to support the earliest
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! MicroVAX system (MicroVAX I) and all subsequent ROM based VMB versions
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! the concept of Boot Block booting was extended in these ROM VMB
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! implementations. The change in boot block booting functionality included
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! several features:
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! 1) If a normal boot attempt to a device failed (due to VMB not being
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! able to locate a secondary bootstrap program), a boot block boot is
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! automatically attempted. If the Bit 3 of R5 was set, then the
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! initial search for a secondary boot block was avoided and a boot
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! block boot was immediately attempted.
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! 2) When performing a boot block boot, the sector 0 contents are examined
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! and if these contents conform to the pattern defined for ROM based
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! (PRA0) booting, the ROM format Offset, Size, and Starting address
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! information is used directly by VMB to load a program into memory
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! and control is transferred to that program. If the contents of
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! sector 0 do not fit the pattern required for ROM based booting, then
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! the code in sector 0 is executed directly starting at offset 2,
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! the same as was originally done with the non ROM based VMB versions.
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! Note that this extended behavior allows sector 0 to contain very little
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! information and quite possibly no actual boot code.
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! Developers of alternate operating systems for VAX computers noticed the ROM
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! based boot block behavior and changed their installation media AND the disk
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! structures to only provide the minimal boot information required on the
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! systems with VMB installed in ROM.
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!
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! Since, when this active development of these alternate operating systems for
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! VAX computers was happening, the vast majority of development and new system
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! deployments were to hardware which had ROM base VMB, no one noticed that
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! older systems which booted with the non ROM based VMB could no longer boot
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! from new install media or disks formatted with these operating systems.
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!
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! This patch addeds the ROM based VMB boot block boot functionality to the
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! original dynamically loaded VMB.EXE used by the older systems to boot.
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!
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! The patch overwrites some VMB code which exists to support NVAX(1302) and
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! Neon-V(1701) systems. If simh simulators for these systems are ever built
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! an alternate location must be found to accomodate this extended logic
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!
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define PAA = 08190 ! INIT_ADP_1302 (I think!)
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define NEWFIL_OPNERR = PAA+1F ! Replacement to generate File Not Found Error Message
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define TRY_BBLOCK = PAA+2B
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define OLDFIL_OPNERR = 69A8 ! Original File Not Found Error
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define ORIG_BBLOCK_BOOT = 68B6 ! Original code that did Boot Block Boot
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define RPB$V_BBLOCK = 3
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define RPB$L_BOOTR5 = 30
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define READFILE = 0120
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define READIN_BOOT = 6A37
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define START_SECOND_HALT = 00BB
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define SS$_FILESTRUCT = 08C0
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define SS$_BADCHKSUM = 0808
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define SS$_BADFILEHDR = 0810
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define SS$_BADDIRECTORY = 0828
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dep /long PAA = 0
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dep /long PAA+04 = 0
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dep /long PAA+08 = 0
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dep /long PAA+0C = 0
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dep /long PAA+10 = 0
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dep /long PAA+14 = 0
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dep /long PAA+18 = 0
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dep /long PAA+1C = 0
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dep /long PAA+20 = 0
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dep /long PAA+24 = 0
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dep /long PAA+28 = 0
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dep /long PAA+2C = 0
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dep /long PAA+30 = 0
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dep /long PAA+34 = 0
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dep /long PAA+38 = 0
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dep /long PAA+3C = 0
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dep /long PAA+40 = 0
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dep /long PAA+44 = 0
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dep /long PAA+48 = 0
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dep /long PAA+4C = 0
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dep /long PAA+50 = 0
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dep /long PAA+54 = 0
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dep /long PAA+58 = 0
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dep /long PAA+5C = 0
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dep /long PAA+60 = 0
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dep /long PAA+64 = 0
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dep /long PAA+68 = 0
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dep /long PAA+6C = 0
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dep /long PAA+70 = 0
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dep /long PAA+74 = 0
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dep /long PAA+78 = 0
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dep /long PAA+8C = 0
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dep /long PAA+80 = 0
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dep /long PAA+84 = 0
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dep /long PAA+88 = 0
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dep /long PAA+8C = 0
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dep /long PAA+90 = 0
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dep /long PAA+94 = 0
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dep /long PAA+98 = 0
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dep /long PAA+9C = 0
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dep /ins OLDFIL_OPNERR = ' BRW PAA '
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dep /ins PAA = ' CMPW R0, #SS$_BADCHKSUM '
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dep /ins PAA+05 = ' BEQL TRY_BBLOCK '
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dep /ins PAA+07 = ' CMPW R0, #SS$_FILESTRUCT '
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dep /ins PAA+0C = ' BEQL TRY_BBLOCK '
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dep /ins PAA+0E = ' CMPW R0, #SS$_BADFILEHDR '
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dep /ins PAA+13 = ' BEQL TRY_BBLOCK '
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dep /ins PAA+15 = ' CMPW R0, #SS$_BADDIRECTORY '
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dep /ins PAA+1A = ' BEQL TRY_BBLOCK '
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dep /ins PAA+1C = ' BRW NEWFIL_OPNERR '
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dep /ins NEWFIL_OPNERR = ' PUSHAB L^000069AE '
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dep /ins NEWFIL_OPNERR+6 = ' JMP L^00000294 '
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dep /ins TRY_BBLOCK
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' CLRL R8 ' ! Block to read
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' MOVL #1,R9 ' ! Size to read
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' MOVL R10,R6 ' ! Start of free memory
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' JSB L^READFILE ' ! Read the block to R10
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' BLBC R0,TRY_OLD_BBLOCK ' ! Br if error
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!
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! validate the boot block
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!
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' MOVZBL B^2(R10),R2 ' ! Get offset to secondary id field
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' CMPB B^3(R10),#1 ' ! Next field a BR instruction
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' BNEQ TRY_OLD_BBLOCK ' ! Br if no
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' MOVAW (R10)[R2],R1 ' ! Address next field
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' CMPW (R1),#^x18 ' ! VAX instruction set id?
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' BNEQ TRY_OLD_BBLOCK ' ! Br if no, error
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' ADDB3 #^x18,B^2(R1),R2 ' ! Get optional value
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' MCOMB R2,R2 ' ! Ones's complement it
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' CMPB R2,B^3(R1) ' ! Check the check sum byte
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' BNEQ TRY_OLD_BBLOCK ' ! Continue if no match
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' ADDL3 B^8(R1),B^0C(R1),R2 ' ! Check other words
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' ADDL B^10(R1),R2 ' ! Get augment to load address
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' CMPL R2,B^14(R1) ' ! Match?
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' BNEQ TRY_OLD_BBLOCK ' ! Br if no
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' ROTL #10,B^4(R10),R8 ' ! Get secondary image LBN
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' MOVL B^8(R1),R9 ' ! Get image size
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' ADDL B^0C(R1),R10 ' ! Compute load address
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' MOVL B^10(R1),R5 ' ! Compute transfer offset
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' BRW READIN_BOOT ' ! Boot block is valid, read file
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'TRY_OLD_BBLOCK:BBS #RPB$V_BBLOCK,B^RPB$L_BOOTR5(R11),OLD_BBLOCK_BOOT'
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' BRW NEWFIL_OPNERR ' ! Report error
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'OLD_BBLOCK_BOOT:MOVL #2,R5 ' ! Transfer address from start of block
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' JMP L^START_SECOND_HALT ' ! Do it.
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exit
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dep /ins ORIG_BBLOCK_BOOT = ' BRW TRY_BBLOCK ' ! make BOOT /R5:8 work the same way
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update
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exit
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