Mercurial > hg > Members > kono > nitros9-code
changeset 3194:2ecebda8716b
mfree.asm: Fix zero-day Block Map entry bug
Previously, code assumed that the final entry in the block map would be
used. This was true for CoCo but is not necessarily true (and is not
true for mc09). Slight mod removes that implicit assumption; the code
now works correctly on both platforms.
| author | Neal Crook <foofoobedoo@gmail.com> |
|---|---|
| date | Tue, 30 May 2017 23:59:46 +0100 |
| parents | 489617e567c5 |
| children | 6eb2edad80d8 |
| files | level2/cmds/mfree.asm |
| diffstat | 1 files changed, 13 insertions(+), 13 deletions(-) [+] |
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--- a/level2/cmds/mfree.asm Tue May 30 23:45:40 2017 +0100 +++ b/level2/cmds/mfree.asm Tue May 30 23:59:46 2017 +0100 @@ -8,6 +8,11 @@ * ------------------------------------------------------------------ * 2 ????/??/?? * Original Tandy/Microware version. +* 3 2017/05/30 Neal Crook +* Original version misbehaved if final block in the map was free. +* That situation never occurs on coco, but it does occur on the mc09 +* target. Inferred behaviour and added comments as a side-effect of +* debugging effort. nam Mfree ttl Show free memory @@ -21,7 +26,7 @@ tylg set Prgrm+Objct atrv set ReEnt+rev rev set $00 -edition set 2 +edition set 3 mod eom,name,tylg,atrv,start,size @@ -78,7 +83,7 @@ beq L00BA yes - found a free block leay $01,y total number of blocks we have inspected cmpy <mapsiz at the end of the map? - bcs L00AD no, so carry on looking + bne L00AD no, so carry on looking bra alldone yes, and the last block was not free, so we're done. * Block number in Y is the first free block of a sequence (tho maybe a sequence of 1) @@ -100,8 +105,8 @@ L00D2 leau $01,u leay $01,y cmpy <mapsiz - beq alldone ??should never exit at this point, but -* on mc09 we do - terminate part-way through an entry. + beq last + tst ,x+ beq L00D2 haven't found it yet.. last lda <ppblk @@ -118,27 +123,22 @@ sta <u0008 1 LS byte of block end address is $FF bsr buf6hex append block end address in hex, to output buffer leax -$01,x - tfr u,d + tfr u,d number of blocks in this sequence u->d bsr buf4hex append number of blocks, in hex, to output buffer lbsr L0199 append size, in decimal, to output buffer addd <freeblks std <freeblks total number of blocks bsr wrbuf print this entry - bra loop loop for next entry + cmpy <mapsiz + bne loop loop for next entry * All of the entries have been printed. Print the trailer and totals. -* Bug: if the last block is unused, it and any unused blocks before it will -* not get reported, *and* the formatting of the last entry will be messed up. -* That never happens on the Coco, because the last block is always used. -* It does happen on mc09 though. alldone leay >Ftr,pcr bsr tobuf 1st line of footer to output buffer bsr wrbuf ..print it bsr tobuf 2nd line of footer to output buffer - tfr u,d ..add total #blocks, total memory size - addd <freeblks - std <freeblks + ldd <freeblks get total number of blocks bsr buf4hex append total number of blocks, in hex, to output buffer bsr L0199 append total size, in decimal, to output buffer bsr wrbuf ..print it