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Factored common RETF logic into opHelpRETF

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This commit is contained in:
Jeff Parsons 2014-12-01 14:50:38 -08:00 • committed by jeffpar
commit d628eacfc6
5 changed files with 72 additions and 37 deletions
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42
modules/pcjs/lib/x86seg.js
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@ -45,7 +45,7 @@ if (typeof module !== 'undefined') {
* @param {X86CPU} cpu
* @param {number} id
* @param {string} [sName] segment name
* @param {boolean} [fProt] true if segment register used exclusively in protected-mode
* @param {boolean} [fProt] true if segment register used exclusively in protected-mode (eg, segLDT)
*/
function X86Seg(cpu, id, sName, fProt)
{
@ -64,26 +64,25 @@ function X86Seg(cpu, id, sName, fProt)
* The following properties are used for CODE segments only (ie, segCS); if the process of loading
* CS also requires a stack switch, then fStackSwitch will be set to true; additionally, if the stack
* switch was the result of a CALL (ie, fCall is true) and one or more (up to 32) parameters are on
* the old stack, they will be copied to awScratch, and then once the stack is switched, the parameters
* will be pushed from awScratch onto the new stack.
* the old stack, they will be copied to awParms, and then once the stack is switched, the parameters
* will be pushed from awParms onto the new stack.
*
* The typical ways of loading a new segment into CS are JMPF, CALLF (or INT), and RETF (or IRET);
* prior to calling segCS.load(), each of those operations must first set segCS.fCall to one of null,
* true, or false, respectively.
*
* It's critical that fCall be properly set prior to calling segCS.load(); fCall == null means NO
* privilege level transition may occur, fCall == true allows a stack switch and a privilege transition
* to a numerically lower privilege, and fCall == false allows a stack switch (restore) and a privilege
* transition to a numerically greater privilege.
* It's critical that fCall be properly set prior to calling segCS.load(); fCall === null means NO
* privilege level transition may occur, fCall === true allows a stack switch and a privilege transition
* to a numerically lower privilege, and fCall === false allows a stack restore and a privilege transition
* to a numerically greater privilege.
*
* As long as setCSIP() or opHelpINT() are used for all CS changes, the foregoing is automatically
* taken care of.
* As long as setCSIP() or opHelpINT() are used for all CS changes, fCall is set automatically.
*
* TODO: Consider making fCall a parameter to load(), instead of a property that must be set prior to
* calling load(); the downside (and why I didn't do that in the first place) is that such a parameter
* is meaningless for segments other than segCS.
*/
this.awScratch = (this.id == X86Seg.ID.CODE? new Array(32) : []);
this.awParms = (this.id == X86Seg.ID.CODE? new Array(32) : []);
this.fCall = null;
this.fStackSwitch = false;
this.updateMode(fProt);
@ -136,7 +135,7 @@ X86Seg.loadReal = function loadReal(sel, fSuppress)
*
* See X86.DESC for offset and bit definitions.
*
* IDT descriptor entries are handled separately by loadIDT().
* IDT descriptor entries are handled separately by loadIDT(), which is mapped to loadRealIDT() or loadProtIDT().
*
* @this {X86Seg}
* @param {number} sel
@ -379,7 +378,7 @@ X86Seg.checkWriteProtDisallowed = function checkWriteProtDisallowed(off, cb, fSu
* 0090:067C EBFD JMP 067B
*
* but it may not have yet reprogrammed the master PIC to re-vector hardware interrupts to IDT entries 0x50-0x57,
* so when the next timer interrupt (IRQ 0) occurs, it vectors through IDT entry 0x08, which is the double-fault
* so when the next timer interrupt (IRQ 0) occurs, it vectors through IDT entry 0x08, which is the DF_FAULT
* vector. A spurious double-fault is generated, and a clean shutdown turns into a messy crash.
*
* Of course, that all could have been avoided if IBM had heeded Intel's advice and not used Intel-reserved IDT
@ -560,6 +559,10 @@ X86Seg.prototype.loadDesc8 = function(addrDesc, sel, fSuppress)
var accCode, selCode, cplPrev, addrTSS, offSP, offSS, regSPPrev, regSSPrev;
/*
* TODO: Consider moving the following chunks of code into worker functions for each X86Seg.ID;
* however, it's not clear that these tests are more costly than making additional function calls.
*/
if (this.id == X86Seg.ID.CODE) {
this.fStackSwitch = false;
var fCall = this.fCall;
@ -582,6 +585,10 @@ X86Seg.prototype.loadDesc8 = function(addrDesc, sel, fSuppress)
else if (type == X86.DESC.ACC.TYPE.GATE_CALL) {
/*
* Since we are X86Seg.ID.CODE, we can use this.cpl instead of the more generic cpu.segCS.cpl
*
* TODO: Consider factoring the GATE_CALL code, and the GATE_INT/GATE_TRAP code below it, into
* something that can be shared; the main differences are privilege level checks, parameter copying,
* and fault generation on error.
*/
selCode = base & 0xffff;
if (rpl < this.cpl) rpl = this.cpl;
@ -608,7 +615,7 @@ X86Seg.prototype.loadDesc8 = function(addrDesc, sel, fSuppress)
regSP = cpu.regSP;
var i = 0, nWords = (acc & 0x1f);
while (nWords--) {
this.awScratch[i++] = cpu.getSOWord(cpu.segSS, regSP);
this.awParms[i++] = cpu.getSOWord(cpu.segSS, regSP);
regSP += 2;
}
addrTSS = cpu.segTSS.base;
@ -620,7 +627,7 @@ X86Seg.prototype.loadDesc8 = function(addrDesc, sel, fSuppress)
cpu.segSS.load(cpu.getWord(addrTSS + offSS));
cpu.pushWord(regSSPrev);
cpu.pushWord(regSPPrev);
while (i) cpu.pushWord(this.awScratch[--i]);
while (i) cpu.pushWord(this.awParms[--i]);
this.fStackSwitch = true;
}
return this.base;
@ -663,11 +670,8 @@ X86Seg.prototype.loadDesc8 = function(addrDesc, sel, fSuppress)
cpu.pushWord(regSPPrev);
this.fStackSwitch = true;
}
if (type == X86.DESC.ACC.TYPE.GATE_INT) {
cpu.regPS &= ~(X86.PS.NT | X86.PS.TF | X86.PS.IF);
} else {
cpu.regPS &= ~(X86.PS.NT | X86.PS.TF);
}
cpu.regPS &= ~(X86.PS.NT | X86.PS.TF);
if (type == X86.DESC.ACC.TYPE.GATE_INT) cpu.regPS &= ~X86.PS.IF;
return this.base;
}
cpu.assert(false);