* * Switch.a - Copyright 1990 D.W.Reisig * * # date by Comment * -- --------- ----- --------------------- * 0 29-Oct-89 DWR Created for Tracksalve * 1 10-Apr-90 DWR TrackSalve 1.3, second pc catch * * nolist INCLUDE "Call.i" INCLUDE "ts.i" INCLUDE "exec/tasks.i" INCLUDE "exec/resident.i" * list CSECT text,code,0,1,2 Any xref's after this are 16-bit reloc ********************************************************* * * PCtoTS * * We need to catch Trackdisk in its highest task-loop. Otherwise we could lose control * after an rts. This loop is rather small: 7 instuctions. One of the instructions is a * jsr _LVOWait(a6). Trackdisk is waiting here for a timer or an IORequest and will be here * most of the time. If we change the return address to our code, Trackdisk smoothly enters * our code. We change this address only if TD is at this point. * * Input: a0 UnitData structure * a4 Globals * * Output: d0 0 if caught else E_CATCHTD * * Usage: d2 PC of TD-task at the point where we want to change it * d6 Timeout counter * d7 Error * * a2 TSControl structure * a3 UnitData structure * a5 Task stucture of Trackdisk unit task * * NB! We are accessing the TSControl structure in a way that needs protection. * XREF _PCSubOffset,_PCWaitOffset WaitRtnPC equ -20 Offset PC to TC_SPUPPER during a Wait() SubRtnPC equ -16 Offset PC to TC_SPUPPER during a subcall Func PCtoTS,@PCtoTS movem.l d2-d4/d6-d7/a2-a3/a5,-(a7) moveq.l #0,d7 No error for now move.l a0,a3 UnitData structure move.l UD_TDReq+IO_UNIT(a3),a5 Lea Unit structure of the Trackdisk IORequest move.b TDU_UnitNr(a5),d4 Get unit number (to set InUse flag later) move.l MP_SIGTASK(a5),a5 Lea Task control block associated with this port move.l UD_TSControl(a3),a2 Control structure move.l TSC_TDTag(a2),d2 Begin of TD code move.l d2,d3 add.l #$1582,d2 Add offset for PC in subroutine add.l #$1592,d3 Add offset for PC when waiting moveq.l #25,d6 We put a limit here, so we will not hang forever if TD is dead SearchPC ExCall Forbid Prevent TD to become active move.l TC_SPUPPER(a5),a0 Initial stackpointer of TD cmp.l SubRtnPC(a0),d2 Is TD in its single taskloop subroutine? beq.s ChangePCSub Yes, change the return address.. cmp.l WaitRtnPC(a0),d3 Is TD Waiting()? beq.s ChangePCWait Yes, change the return address.. LibCall Permit No, give TD a chance to change its situation moveq.l #10,d1 We will wait for a fifth of a second DOSCall Delay Sleeping dbra d6,SearchPC And try again.. moveq.l #E_CATCHTD,d7 But not forever, so set error bra.s PCtoTSRtn Quit.. ChangePCSub move.l _PCSubOffset(a4),d0 PC found in the subroutine, get matching offset in TrackSalve add.l TSC_TSCode(a2),d0 Add begin of TrackSalve code move.l d0,SubRtnPC(a0) Change return addres to adress in our code bra.s PCChanged ChangePCWait move.l _PCWaitOffset(a4),d0 PC found waiting, get matching offset in TrackSalve add.l TSC_TSCode(a2),d0 Add begin of TrackSalve code move.l d0,WaitRtnPC(a0) Change return addres to adress in our code PCChanged move.l d3,UD_ReturnTD(a3) Save TD return address (we use the Wait() call to leave TS) move.l TC_Userdata(a5),UD_Userdata(a3) Keep original value (although TD does not use it) move.l a3,TC_Userdata(a5) Make UnitData structure known to TD-task bset.b d4,TSC_InUse(a2) Set flag to prevent freeing the TSControl structure LibCall Permit Multitasking on again PCtoTSRtn move.l d7,d0 Error movem.l (a7)+,d2-d4/d6/d7/a2-a3/a5 rts ********************************************************* * * RelocateTS * * Modify position dependend values in copied TSCode * * Input: a0 TSControl structure * Func RelocateTS,@RelocateTS move.l TSC_TSCode(a0),a0 lea.l TSCodeRelocTable(pc),a1 10$ move.w (a1)+,d0 beq.s 20$ move.l a0,d1 add.l 0(a0,d0.w),d1 move.l d1,0(a0,d0.w) bra.s 10$ 20$ rts xref TSCodeRelocTable ********************************************************* * * RelocateTD * * Modify position dependend values in relocated Trackdisk code versions 33.127 and 34.1 * * Input: a0 TSControl structure * ifd __stdargs Func _RelocateTD move.l 4(a7),a0 endc Func RelocateTD,@RelocateTD move.l TSC_TSTag(a0),a1 Begin of copy of Trackdisk code move.l TSC_TDTag(a0),d0 Begin of Trackdisk code (in ROM) * cmp.l a1,RT_MATCHTAG(a1) Does our copy has its self-pointer right? * beq.s RelocateRtn Yes, already relocated.. sub.l a1,d0 TD org minus TD copy = relocation value lea.l RelocTable(pc),a0 Table of relative addresses to relocate bra.s Relocate20 Enter loop.. Relocate10 sub.l d0,0(a1,d1.w) Only Amiga makes it possible! Relocate20 move.w (a0)+,d1 Get offset in TD-code bne.s Relocate10 RelocateRtn rts *-- You can obtain this table by comparing version 1.2 and 1.3 and do some editing on the result RelocTable dc.w $0002 dc.w $0006 dc.w $000E dc.w $0012 dc.w $0016 dc.w $0324 dc.w $032A dc.w $03C0 dc.w $091C dc.w $0940 dc.w $0966 dc.w $0980 dc.w $0994 dc.w $09B6 dc.w $09C4 dc.w $09CC dc.w $0A00 dc.w $0A04 dc.w $0A08 dc.w $0A0C dc.w $0A10 dc.w $0A14 dc.w $0A1C dc.w $0A20 dc.w $0A24 dc.w $0A28 dc.w $0A2C dc.w $0A30 dc.w $0A34 dc.w $0A38 dc.w $0A3C dc.w $0A40 dc.w $0A44 dc.w $0A48 dc.w $0A4C dc.w $0A50 dc.w $0A54 dc.w $0A58 dc.w $0A5C dc.w $0A60 dc.w $0A64 dc.w $0A68 dc.w $0A6C dc.w $0A70 dc.w $127E dc.w $12EA dc.w $1316 dc.w $1352 dc.w $1386 dc.w $13E4 dc.w $1446 dc.w $1690 dc.w $16B8 dc.w $195A dc.w $19A2 dc.w $19B2 dc.w 0 ********************************************************* * * PatchMem * * Change memory according to a table * * Input: a0 Memory to change * a1 Patchtable (Offset.w, Size.w, Patch.w[Size]) * Func PatchMem,@PatchMem movem.l a2,-(a7) move.l a0,a2 Lea begin of memory GetNextPatch move.l a2,a0 Begin of memory move.w (a1)+,d0 Get offset in code to put patch add.w d0,a0 Lea destination of patch move.w (a1)+,d1 Get size of patch in words beq.s PatchMemRtn No patch, done.. bra.s CopyPatch10 Enter copyloop CopyPatch move.w (a1)+,(a0)+ Copy word of code CopyPatch10 dbra d1,CopyPatch Loop .. bra.s GetNextPatch Examine next entry in Patchtable PatchMemRtn movem.l (a7)+,a2 rts ********************************************************* END