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test for uninitialized dpb on INT25,26 and always allow rw block zero

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The problem is that ISFAT32 macro only tests for dpb->fatsize = 0, and
not also for xfatsize != 0. So the ISFAT32 macro returns a
"false positive" on uninitialized dpbs, where both fatsize and xfatsize
are zero.

This fixes https://github.com/FDOS/kernel/issues/200. However, the dpb
is not properly initialized via a media check by an INT25,26 yet.

This commit makes sure that written sectors are removed from the
block cache.
This commit is contained in:
Bernd Boeckmann 2025-06-02 11:21:36 +02:00
parent 654e7b7a6c
commit 8d29d66148
1 changed files with 11 additions and 6 deletions
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17
kernel/inthndlr.c
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@ -1812,6 +1812,7 @@ VOID ASMCFUNC int2526_handler(WORD mode, struct int25regs FAR * r)
UWORD nblks;
BYTE FAR *buf;
UBYTE drv;
struct dpb FAR *dpbp;
if (mode == 0x26)
mode = DSKWRITEINT26;
@ -1822,17 +1823,23 @@ VOID ASMCFUNC int2526_handler(WORD mode, struct int25regs FAR * r)
/* high bit of AL set, so mask it together with AH */
/* otherwise we might access a non-existing unit */
if (drv >= lastdrive)
dpbp = get_dpb(drv);
if (drv >= lastdrive || dpbp == NULL)
{
r->ax = 0x201;
SET_CARRY_FLAG();
return;
}
nblks = r->cx;
blkno = r->dx;
#ifdef WITHFAT32
{
struct dpb FAR *dpbp = get_dpb(drv);
if (dpbp != NULL && ISFAT32(dpbp))
/* if reading / writing block other than bootsecter,
prevent using INT25,26 on initialized FAT32 */
if ((blkno != 0) && ISFAT32(dpbp) && (dpbp->dpb_xfatsize != 0))
{
r->ax = 0x207;
SET_CARRY_FLAG();
@ -1841,9 +1848,6 @@ VOID ASMCFUNC int2526_handler(WORD mode, struct int25regs FAR * r)
}
#endif
nblks = r->cx;
blkno = r->dx;
buf = MK_FP(r->ds, r->bx);
if (nblks == 0xFFFF)
@ -1856,6 +1860,7 @@ VOID ASMCFUNC int2526_handler(WORD mode, struct int25regs FAR * r)
InDOS++;
DeleteBlockInBufferCache(blkno, blkno, drv, XFR_WRITE);
r->ax = dskxfer(drv, blkno, buf, nblks, mode);
CLEAR_CARRY_FLAG();