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This commit is contained in:
Jeff Parsons 2015-08-25 12:33:54 -07:00
commit 0e9ce2d653
1 changed files with 18 additions and 9 deletions
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27
modules/pcjs/lib/x86seg.js
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@ -54,6 +54,8 @@ if (typeof module !== 'undefined') {
*/
/**
* X86Seg "public" properties
*
* @class X86Seg
* @property {number} sel
* @property {number} limit (in protected-mode, this comes from descriptor word 0x0)
@ -563,10 +565,17 @@ X86Seg.prototype.loadDesc6 = function(addrDesc, sel)
*
* See X86.DESC for offset and bit definitions.
*
* When fProbe is set, this function will not modify the X86Seg object; it will still generate a fault if any of
* the usual error conditions are detected (and return X86.ADDR_INVALID), but in the success case, it merely stashes
* all descriptor values it reads in the X86Seg's "probe" object. If the caller ultimately decides to propagate
* those "probed" values to the X86Seg object, it must then call loadProbe().
* When fProbe is set, we do NOT modify the public properties of the X86Seg object (see class X86Seg above).
* We will generate a fault if any of the usual error conditions are detected (and return X86.ADDR_INVALID), but
* otherwise, we merely stash all the descriptor values it reads in the X86Seg's private "probe" object.
*
* Probed loads allow us to deal with complex segment load operations (ie, those involving an implied stack-switch
* or task-switch), by allowing us to probe all the new selectors and generate the necessary faults before modifying
* any segment registers; if all the probes succeed, then all the loads can proceed.
*
* The next non-probed load of a probed selector will move those probed descriptor values into the X86Seg object,
* saving us from having to reload and reparse the descriptor. However, if a different selector is loaded between
* the probed and non-probed loads, the probed data is tossed.
*
* @this {X86Seg}
* @param {number} addrDesc is the descriptor address
@ -580,7 +589,7 @@ X86Seg.prototype.loadDesc8 = function(addrDesc, sel, fProbe)
/*
* If the previous load was a successful "probed" load of the same segment, then we simply load
* up all the cached descriptor values from that probe and return.
* up all the cached descriptor values from the probe and return.
*/
if (!fProbe && sel === this.probe.sel) {
this.sel = sel;
@ -859,9 +868,9 @@ X86Seg.prototype.loadDesc8 = function(addrDesc, sel, fProbe)
* base=0006C726 limit=0000 type=0x02 (ldt,not present) ext=0x0000 dpl=0x00
*
* In both cases, the segment type is not valid for the target segment register *and* the PRESENT bit
* is clear. OS/2 didn't seem to care whether I reported NP_FAULT or GP_FAULT, but Windows 95 definitely
* is clear. OS/2 doesn't seem to care whether I report an NP_FAULT or GP_FAULT, but Windows 95 definitely
* cares: it will resolve the fault only if a GP_FAULT is reported. And Intel's 80386 Programmers Reference
* suggests that, yes, NP_FAULT checks are supposed to come *after* GP_FAULT checks.
* implies that, yes, NP_FAULT checks are supposed to be performed *after* GP_FAULT checks.
*/
if (type < X86.DESC.ACC.TYPE.SEG || (type & (X86.DESC.ACC.TYPE.CODE | X86.DESC.ACC.TYPE.READABLE)) == X86.DESC.ACC.TYPE.CODE) {
if (this.id < X86Seg.ID.VER) X86.fnFault.call(cpu, X86.EXCEPTION.GP_FAULT, sel & X86.ERRCODE.SELMASK);
@ -1266,8 +1275,8 @@ X86Seg.prototype.updateMode = function(fLoad, fProt, fV86)
}
/*
* The following properties are used for STACK segments only (ie, segSS); we want to make it easier
* for setSS() to set stack lower and upper limits, which requires knowing whether or not the segment is
* The fExpDown property is used for STACK segments only (ie, segSS); we want to make it easier for
* setSS() to set stack lower and upper limits, which requires knowing whether or not the segment is
* marked as EXPDOWN.
*/
this.fExpDown = false;