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Fixed problems booting the Oct 86 CP-DOS boot disk (the showstopper was allowing the mode of the LDT register to be changed by LOADALL)

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This commit is contained in:
Jeff Parsons 2016-01-25 15:07:44 -08:00
commit b9a2968f03
26 changed files with 7184 additions and 160 deletions
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26
modules/pcjs/lib/x86seg.js
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@ -141,8 +141,7 @@ X86Seg.ID = {
TSS: 4, // "TSS"
LDT: 5, // "LDT"
VER: 6, // "VER"
FPU: 7, // "FPU"
DBG: 8 // "DBG"
DBG: 7 // "DBG"
};
X86Seg.CALLBREAK_SEL = 0x0001;
@ -581,7 +580,14 @@ X86Seg.prototype.loadDesc6 = function(addrDesc, sel)
this.type = (acc & X86.DESC.ACC.TYPE.MASK);
this.ext = 0;
this.addrDesc = addrDesc;
this.updateMode(true);
/*
* NOTE: This code must take care to leave the mode of the TSS, LDT, and VER segment registers alone;
* in particular, we must not allow a real-mode LOADALL to modify their mode, because the rest of PCjs
* assumes that their mode will never change (they were allocated with fProt set to true), so there's
* no code to force them back into protected-mode.
*/
if (this.id < X86Seg.ID.TSS) this.updateMode(true);
if (DEBUG) this.messageSeg(sel, base, limit, this.type);
@ -876,6 +882,10 @@ X86Seg.prototype.loadDesc8 = function(addrDesc, sel, fProbe)
cpu.setProtMode(true, false);
}
/*
* TODO: Consider whether we can skip this loadProt() call if this.sel already contains selCode
* (and the previous mode matches, which might require we cache the mode in the X86Seg object, too).
*/
if (this.loadProt(selCode) === X86.ADDR_INVALID) {
return X86.ADDR_INVALID;
}
@ -1466,7 +1476,15 @@ X86Seg.prototype.updateMode = function(fLoad, fProt, fV86)
*/
if ((this.sel & ~X86.SEL.RPL) && this.addrDesc !== X86.ADDR_INVALID) {
var addrType = this.addrDesc + X86.DESC.ACC.TYPE.OFFSET;
this.cpu.setByte(addrType, this.cpu.getByte(addrType) | (X86.DESC.ACC.TYPE.ACCESSED >> 8));
var bType = this.cpu.getByte(addrType);
/*
* This code used to ALWAYS call setByte(), but that's a waste of time if ACCESSED is already
* set. TODO: It would also be nice if we could simply use the cached type value, and eliminate
* the getByte() call; that seems a bit risky, but I think we should still try it someday.
*/
if (!(bType & (X86.DESC.ACC.TYPE.ACCESSED >> 8))) {
this.cpu.setByte(addrType, bType | (X86.DESC.ACC.TYPE.ACCESSED >> 8));
}
}
}
}