mirror of
https://github.com/elliotnunn/NetBoot.git
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The outline of a solution
But it doesn't actually work yet.
This commit is contained in:
Elliot Nunn
parent
c898af28d3
commit
3cbc61b625
485
ChainLoader.a
485
ChainLoader.a
@ -1,19 +1,173 @@
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myUnitNum equ 52
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myDRefNum equ ~myUnitNum
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serverBufSize equ 32
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Code
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; This is the entry point, which the ROM jumps to with one of three
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; selectors. This whole block of code lives inside the system heap, in a
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; block that the ROM code forgets ever to free. So we simply drop our
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; driver here, and relegate the one-time init code to the end of the
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; block.
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; The ROM issued a _Read call that eventually reached here.
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; We need to handle this _Read trap directly, without the intervening .netBOOT and .ATBOOT drivers.
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; We do this by rewinding the Device Manager's return address by 2 bytes.
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bra OneTimeInitCode
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dc.l 'NtBt'
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; Why?
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; The ROM network boot mechanism is complicated and buggy.
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; The workarounds are difficult.
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; Therefore this big hack obviates many little hacks.
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; First problem: this is not a safe place to keep code. Jump away.
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; (Using the heap while all the netBOOT junk is there would cause fragmentation.)
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lea ResumeAfterCopy,A0
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move.l #CodeEnd-ResumeAfterCopy,D0
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lea 4096(A5),A1
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dc.w $A02E ; _BlockMove
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jmp 4096(A5)
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ResumeAfterCopy
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; Salvage some possibly useful information from ATBOOT, while it is still running:
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; Server address
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move.l 8(SP),A0 ; global pointer
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move.l 24(A0),D0 ; AddrBlock
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lea gSaveAddr,A0
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move.b #10,15(A0) ; hardcode DDP protocol ID
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move.b D0,13(A0) ; socket
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lsr.w #4,D0
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lsr.w #4,D0
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move.b D0,11(A0) ; node
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swap D0
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move.w D0,7(A0) ; network
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; User record
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lea gUserRec,A1
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move.l 8(SP),A0 ; global pointer
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move.l 40(A0),A0
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move.l #574,D0
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dc.w $A02E ; _BlockMove
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; Currently the call stack looks like this:
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; ROM _Read to get boot blocks
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; .netBOOT Read routine
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; .ATBOOT Control routine
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; direct call to this block of code
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; But we want to close and remove .netBOOT & .ATBOOT, so we need to return
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; from their Device Manager calls, and steal control from the ROM.
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; We do this by scanning the stack for the return address of the original _Read.
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move.l $2AE,A0 ; A0 = ROMBase (lower limit)
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lea $4000(A0),A1 ; A1 = ROMBase + a bit (upper limit)
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lea -2(SP),A2
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.loop subq.l #2,A2 ; A2 = where we search the stack
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move.l (A2),A3 ; A3 = potential return address
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cmp.l A0,A3 ; lower limit check
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bls.s .loop
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cmp.l A1,A3 ; upper limit check
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bhi.s .loop
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cmp.w #$A002,-2(A3) ; _Read trap check
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bne.s .loop
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pea GoHereFromReadTrap ; take over
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move.l (SP)+,(A2)
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lea ROMAfterReadTrap,A2 ; save original for later
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move.l A3,(A2)
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moveq.l #-1,D0 ; .netBOOT/.ATBOOT don't do any more damage if an error is returned
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rts
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ROMAfterReadTrap
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dc.l 0
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GoHereFromReadTrap
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; Now we are outside .netBOOT/.ATBOOT. We can shut them down, and set up our driver in a clean environment.
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move.l ROMAfterReadTrap,-(SP) ; our return address is to ROM
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sub.l #2,-(SP) ; repeating the _Read trap
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movem.l A0-A6/D0-D7,-(SP) ; save registers conservatively (especially A0)
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; A4 = param block to the .netBOOT _Read call, because we will use it a lot
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move.l A0,A4
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; Close and delete .netBOOT (which will close .ATBOOT)
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lea -$32(SP),SP
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move.l SP,A0
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move.w $18(A4),$18(A0) ; ioRefNum
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dc.w $A001 ; _Close
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lea $32(SP),SP
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move.w $18(A4),D0 ; ioRefNum
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dc.w $A03E ; _DrvrRemove
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move.w #-52,D0 ; ioRefNum ; also delete .ATBOOT for neatness
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dc.w $A03E ; _DrvrRemove
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; A3 = our driver in sysheap (plus 574 bytes for the user record)
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move.l #DrvrEnd-DrvrBase+574,D0
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dc.w $A51E ; NewPtrSys
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move.l A0,A1
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lea DrvrBase,A0
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move.l #DrvrEnd-DrvrBase+574,D0
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dc.w $A02E ; BlockMove
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move.l A1,A3
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; Install the driver in the unit table. Take over netBOOT's old unit number.
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move.w $18(A4),D0 ; ioRefNum
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dc.w $A43D ; _DrvrInstall ReserveMem
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; That call created a driver control entry (DCE). Find and lock.
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move.l $11C,A0 ; UTableBase
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move.w $18(A4),D0 ; ioRefNum
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not.w D0
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lsl.w #2,D0
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add.w D0,A0
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move.l (A0),A0
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dc.w $A029 ; _HLock
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move.l (A0),A0
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; Populate the empty DCE that DrvrInstall left us (forget fields related desk accessories)
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move.l A3,(A0) ; dCtlDriver = driver pointer (not handle)
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move.w (A3),4(A0) ; dCtlFlags = drvrFlags
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; Open our driver
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lea -$32(SP),SP
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move.l SP,A0
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bsr clearblock
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lea DrvrName,A1
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move.l A1,$12(A0) ; IOFileName
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dc.w $A000 ; _Open
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lea $32(SP),SP
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; Create & add a drive queue entry (DQE).
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move.l #$16,D0
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dc.w $A71E ; _NewPtrSysClear
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add.l #4,A0 ; has some cheeky flags at negative offset
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move.l #$00080000,-4(A0) ; secret flags, see http://mirror.informatimago.com/next/developer.apple.com/documentation/mac/Files/Files-112.html
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move.w #1,4(A0) ; qType
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;move.w #0,$A(A0) ; dQFSID should be for a native fs
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;move.l #0,$C(A0) ; dQDrvSz/dQDrvSz2 ; whoa, better fix this!
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move.l $16(A4),D0 ; scoop drivenum & driver refnum from _Read PB
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dc.w $A04E ; _AddDrive (A0=DQE, D0=drvnum/drefnum)
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; Open .MPP (still open?) & our DDP socket
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lea -$32(SP),SP
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move.l SP,A0
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bsr clearblock
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pea MPPName
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move.l (SP)+,$12(A0) ; ioNamePtr
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dc.w $A000 ; _Open
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move.w #248,$1A(A0) ; csCode = openSkt
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move.b #10,$1C(A0) ; socket = 10, same as ATBOOT uses
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pea DrvrSockListener-DrvrBase(A3)
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move.l (SP)+,$1E(A0) ; listener
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dc.w $A004 ; _Control
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lea $32(SP),SP
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; Re-execute the _Read trap in ROM
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movem.l (SP)+,A0-A6/D0-D7
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rts
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MPPName dc.b 4, '.MPP', 0
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clearblock move.w #$32/2-1,D0
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.loop clr.w (A0)+
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dbra D0,.loop
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lea -$32(A0),A0
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rts
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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@ -28,7 +182,7 @@ DrvrBase
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dc.w DrvrControl-DrvrBase
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dc.w DrvrStatus-DrvrBase
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dc.w DrvrClose-DrvrBase
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DrvrName dc.b 8, ".LANDisk", 0
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DrvrName dc.b 8, ".netBOOT", 0
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g
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gNumBlks dc.l 0 ; the source of all truth
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@ -562,303 +716,8 @@ DrvrIcon
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dc.l %11111111111111111111111111111111
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dc.l %11111111111111111111111111111111
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dc.b 22, "AppleTalk NetBoot Disk", 0
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gUserRec ; append some 574 zeroes here later on
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DrvrEnd
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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OneTimeInitCode
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cmp.l #1,4(SP)
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beq getBootBlocks
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cmp.l #2,4(SP)
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beq getSysVol
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cmp.l #3,4(SP)
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beq mountSysVol
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move.l #-1,d0
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rts
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getBootBlocks
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; Now is the time to install our DRVR because we are guaranteed an opportunity to boot if we don't fuck up.
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link A6,#-$32
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movem.l A2-A4/D3-D7,-(SP)
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; Patch the server address into the DRVR code (TODO: concentrate all global patches here)
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move.l 12(A6),A0 ; global pointer
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move.l 24(A0),D0 ; AddrBlock
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lea gSaveAddr,A0
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move.b #10,15(A0) ; hardcode DDP protocol ID
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move.b D0,13(A0) ; socket
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lsr.w #4,D0
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lsr.w #4,D0
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move.b D0,11(A0) ; node
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swap D0
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move.w D0,7(A0) ; network
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; Patch the disk image name and size into the DRVR code
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; bsr BootPicker ; A0 = pstring ptr
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; lea gNumBlks,A1
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; move.l -4(A0),(A1) ; the size is underneath the pstring ptr
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; move.l -4(A0),D6 ; D6 = block count, needed for DQE
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; lea gQFilename,A1 ; A1 = dest
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; moveq.l #1,D0
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; add.b (A0),D0
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; dc.w $A22E ; _BlockMoveData
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; Install the driver in the unit table
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lea DrvrBase,A0
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move.l #myDRefNum,D0
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dc.w $A43D ; _DrvrInstall ReserveMem
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; That call created a DCE. Find and lock.
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move.l $11C,A0 ; UTableBase
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move.l myUnitNum*4(A0),A0
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dc.w $A029 ; _HLock
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move.l (A0),A0
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; Populate the empty DCE that DrvrInstall left us (forget fields related desk accessories)
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lea DrvrBase,A2
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move.l A2,0(A0) ; dCtlDriver = driver pointer (not handle)
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move.w 0(A2),4(A0) ; dCtlFlags = drvrFlags
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; Open the driver
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lea -$32(SP),SP
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move.l SP,A0
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bsr clearblock
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lea DrvrName,A1
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move.l A1,$12(A0) ; IOFileName
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dc.w $A000 ; _Open
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lea $32(SP),SP
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; Create a DQE. The fate of this exact DQE is to be copied and deleted by ROM code.
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move.l #$16,D0
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dc.w $A71E ; _NewPtr ,Sys,Clear
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add.l #4,A0 ; has some cheeky flags at negative offset
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move.l A0,A3
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lea gDQEAddr,A0
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move.l A3,(A0)
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; Populate the DQE
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move.l D6,D0 ; needs fixing for Ruby Slipper
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lsl.l #5,D0 ; convert to bytes
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lsl.l #4,D0
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swap D0
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move.l D0,$C(A3) ; dQDrvSz/dQDrvSz2
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move.l #$00080000,-4(A3) ; secret flags, see http://mirror.informatimago.com/next/developer.apple.com/documentation/mac/Files/Files-112.html
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move.w #1,4(A3) ; qType
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move.w #0,$A(A3) ; dQFSID should be for a native fs
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; Into the drive queue (which will further populate the DQE)
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bsr findFreeDriveNum ; get drvnum in D0
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lea gDriveNum,A0
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move.w D0,(A0)
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swap D0
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move.w #myDRefNum,D0 ; D0.H = drvnum, D0.L = drefnum
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move.l D0,D3 ; we need this in a sec
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move.l A3,A0
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dc.w $A04E ; _AddDrive
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; Open our socket
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lea -$32(SP),SP
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move.l SP,A0
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bsr clearblock
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move.w #-10,$18(A0) ; ioRefNum = .MPP
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move.w #248,$1A(A0) ; csCode = openSkt
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move.b #10,$1C(A0) ; socket = 10, same as ATBOOT uses
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lea DrvrSockListener,A2
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move.l A2,$1E(A0) ; listener
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dc.w $A004 ; _Control
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lea $32(SP),SP
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; Get the real 1024k of boot blocks to a temp location
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; (it will eventually get trashed, but we have time)
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lea 4096(A5),A4 ; above BootGlobals
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lea -$32(SP),SP
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move.l SP,A0
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bsr clearblock
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move.l D3,22(A0) ; IOVRefNum=drvnum, IORefNum=drefnum
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move.l A4,32(A0) ; IOBuffer
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move.l #1024,36(A0) ; IOReqCount = 2 blocks
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move.l #0,46(A0) ; IOPosOffset = 0
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move.w #1,44(A0) ; IOPosMode = from start
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dc.w $A002 ; _Read
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lea $32(SP),SP
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; Put the boot blocks in netBOOT's global data structure as requested
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move.l A4,A0
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move.l 12(A6),A1
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lea $BA(A1),A1
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move.l #$138,D0
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dc.w $A22E ; _BlockMoveData
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move.l A1,A0 ; A0 = truncated BBs
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move.l A4,A1 ; A1 = full-length BBs
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bsr HealInjuredBootBlocks
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; Clean up our stack frame
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movem.l (SP)+,A2-A4/D3-D7
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unlk A6
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move.l #0,D0
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rts
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getSysVol ; pointless call :(
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move.l #0,D0
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rts
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mountSysVol
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link A6,#-$32
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movem.l A2-A4/D3,-(SP)
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lea gDriveNum,A0
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move.w (A0),D3
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; System 7 needs MountVol to return the right vRefNum
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move.l $366,A0 ; Steal existing PB from FSQHead
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; Set aside the FS queue to stop MountVol deadlocking
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move.w $360,-(SP) ; FSBusy
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move.l $362,-(SP) ; FSQHead
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move.l $366,-(SP) ; FSQTail
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clr.w $360
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clr.l $362
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clr.l $366
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; MountVol
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bsr clearblock
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move.w D3,$16(A0) ; ioVRefNum = ioDrvNum = the drive number
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dc.w $A00F ; _MountVol
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bne error
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; Restore the FS queue
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move.l (SP)+,$366
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move.l (SP)+,$362
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move.w (SP)+,$360
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; Tattle about the DQE and VCB
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move.l 4+12(A6),A1
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move.l $356+2,A0 ; VCBQHdr.QHead (maybe I should be clever-er)
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move.l A0,(A1)
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move.l 4+16(A6),A1
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lea gDQEAddr,A0
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move.l (A0),(A1)
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lea Code,A0
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move.l #OneTimeInitCode-Code,D0
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dc.w $A020 ; Cut the unnecessary code off me
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movem.l (SP)+,A2-A4/D3
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unlk A6
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move.l #0,d0
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rts
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error
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move.w #$7777,D0
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dc.w $A9C9
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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gDriveNum dc.w 0
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gDQEAddr dc.l 0
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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clearblock
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move.w #$32/2-1,D0
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.loop clr.w (A0)+
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dbra D0,.loop
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lea -$32(A0),A0
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rts
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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findFreeDriveNum ; and return it in D0. Free to trash the usual registers
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; Find a free drive number (nicked this code from BootUtils.a:AddMyDrive)
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LEA $308,A0 ; [DrvQHdr]
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MOVEQ #4,D0 ; start with drive number 4
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.CheckDrvNum
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MOVE.L 2(A0),A1 ; [qHead] start with first drive
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.CheckDrv
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CMP.W 6(A1),D0 ; [dqDrive] does this drive already have our number?
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BEQ.S .NextDrvNum ; yep, bump the number and try again.
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CMP.L 6(A0),A1 ; [qTail] no, are we at the end of the queue?
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BEQ.S .GotDrvNum ; if yes, our number's unique! Go use it.
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MOVE.L 0(A1),A1 ; [qLink] point to next queue element
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BRA.S .CheckDrv ; go check it.
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.NextDrvNum
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; this drive number is taken, pick another
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ADDQ.W #1,D0 ; bump to next possible drive number
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BRA.S .CheckDrvNum ; try the new number
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.GotDrvNum
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rts
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|
||||
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
||||
|
||||
HealInjuredBootBlocks ; patch the BBs to fix themselves if executed
|
||||
|
||||
; Args: A0 = truncated boot blocks (138b), A1 = correct boot blocks (1024b)
|
||||
|
||||
; If these boot blocks are executable (from offset 2), then the 138 bytes of
|
||||
; declarative data copied by the netBOOT driver are not enough. We edit the boot
|
||||
; blocks with a stub that copies the entire 1k into place. System 7 needs this.
|
||||
|
||||
; This unfortunately clobbers the declarative part of the boot blocks, so we need to
|
||||
; check for declarative boot blocks and leave them unchanged
|
||||
|
||||
move.l A0,-(SP) ; Save A1 to a global, but need to keep A0
|
||||
lea .gFullLoc,A0
|
||||
move.l A1,(A0)
|
||||
move.l (SP)+,A0
|
||||
|
||||
move.b 6(A0),D0 ; BBVersion
|
||||
cmp.b #$44,D0
|
||||
beq.s .executable
|
||||
and.b #$C0,D0
|
||||
cmp.b #$C0,D0
|
||||
beq.s .executable
|
||||
rts
|
||||
|
||||
; Relevant structure of the boot blocks:
|
||||
; 0-1 bbID always 'LK'
|
||||
; 2-5 bbEntry BRA.W base+128
|
||||
; 6-7 bbVersion interpreted as above
|
||||
; 8-137 data
|
||||
; 138-1023 code (MISSING from netBOOT's short version)
|
||||
|
||||
; Our self-repairing boot blocks:
|
||||
; 0-1 bbID always 'LK'
|
||||
; 2-5 bbEntry BRA.W base+8
|
||||
; 6-7 bbVersion interpreted as above
|
||||
; 8-13 JSR .inPlaceFixRoutine
|
||||
; 14-137 junk
|
||||
|
||||
|
||||
.executable ; Need to leave bytes 6,7 intact
|
||||
move.l #$60000004,2(A0) ; BB+2: BRA.W BB+8
|
||||
move.w #$4EB9,8(A0) ; BB+8: JSR .inPlaceFixRoutine (abs)
|
||||
lea .inPlaceFixRoutine,A1
|
||||
move.l A1,10(A0)
|
||||
|
||||
move.l A0,A1 ; Clear the icache with a BlockMove
|
||||
move.l #138,D0
|
||||
dc.w $A02E ; _BlockMove
|
||||
|
||||
rts
|
||||
|
||||
.inPlaceFixRoutine ; The BB stub JSRs to here
|
||||
move.l (SP)+,A1 ; so the return address will be at BB+14
|
||||
lea -14(A1),A1 ; "Rewind" to the start of the BB
|
||||
move.l .gFullLoc,A0 ; And here are our full boot blocks
|
||||
move.l #1024,D0
|
||||
dc.w $A02E ; _BlockMove (needs to clear cache)
|
||||
|
||||
jmp 2(A1) ; Jump to the fixed-up BB
|
||||
|
||||
.gFullLoc dc.l 0 ; Stuff addr of full-length BB in here
|
||||
CodeEnd
|
||||
|
||||
Loading…
Reference in New Issue
Block a user