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Some task-switching fixes

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This commit is contained in:
Jeff Parsons 2015-05-17 11:58:36 -07:00 • committed by jeffpar
commit d97c773613
2 changed files with 48 additions and 5 deletions
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36
disks/pc/unix/microport/system-v/2.3/README.md Normal file
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@ -0,0 +1,36 @@
Debugging Notes
---
The boot sector contains the following code:
0000:7C3E B003 MOV AL,03
0000:7C40 B200 MOV DL,00
0000:7C42 B417 MOV AH,17
0000:7C44 CD13 INT 13
0000:7C46 72B8 JC 7C00
For BIOSes that don't support INT 0x13, AH function 0x17, patch the JC with two NOPs; eg:
e 0:7c46 90 90
After booting, the following code is executed:
12E8:01D3 52 PUSH DX ;history=5
12E8:01D4 51 PUSH CX ;history=4
12E8:01D5 2BC9 SUB CX,CX ;history=3
12E8:01D7 BA6400 MOV DX,0064 ;history=2
12E8:01DA ED IN AX,DX ;history=1
For virtual machines that don't support word I/O to port 0x64, patch IN AX,DX with IN AL,DX; eg:
e 12e8:1da ec
Here's where the first task switch (far jump using a TSS selector) occurs:
AX=02F0 BX=0008 CX=0000 DX=0000 SP=037E BP=037E SI=1852 DI=0000
SS=0044[001800,07FF] DS=0228[009E00,851B] ES=0220[001000,8DFB] A20=ON
CS=0200[012320,FFFD] LD=02E0[002000,01FF] GD=[001006,072F] ID=[0053E2,07FF]
TR=02D0 MS=FFF5 PS=0016 V0 D0 I0 T0 S0 Z0 A1 P1 C0
0200:016D FF6E06 JMP FAR [BP+06]
The far address at [BP+6] is 02F0:0000.

17
modules/pcjs/lib/x86seg.js
View file

@ -555,11 +555,10 @@ X86Seg.prototype.loadDesc8 = function(addrDesc, sel, fSuppress)
fGate = false;
}
else if (type == X86.DESC.ACC.TYPE.TSS) {
if (!this.switchTSS(sel, true)) {
if (!this.switchTSS(sel, fCall)) {
base = addrDesc = X86.ADDR_INVALID;
break;
}
if (DEBUG) cpu.stopCPU();
return this.base;
}
else if (type == X86.DESC.ACC.TYPE.GATE_CALL) {
@ -581,7 +580,7 @@ X86Seg.prototype.loadDesc8 = function(addrDesc, sel, fSuppress)
cpu.assert(!(acc & 0x1f));
}
else if (type == X86.DESC.ACC.TYPE.GATE_TASK) {
if (!this.switchTSS(base & 0xffff, true)) {
if (!this.switchTSS(base & 0xffff, fCall)) {
base = addrDesc = X86.ADDR_INVALID;
break;
}
@ -746,7 +745,7 @@ X86Seg.prototype.loadDesc8 = function(addrDesc, sel, fSuppress)
*
* @this {X86Seg}
* @param {number} selNew
* @param {boolean} fNest is true if nesting, false if un-nesting
* @param {boolean|null} [fNest] is true if nesting, false if un-nesting, null if neither
* @return {boolean} true if successful, false if error
*/
X86Seg.prototype.switchTSS = function switchTSS(selNew, fNest)
@ -758,6 +757,9 @@ X86Seg.prototype.switchTSS = function switchTSS(selNew, fNest)
var cplOld = this.cpl;
var selOld = cpu.segTSS.sel;
if (!fNest) {
/*
* TODO: Verify that it is (always) correct to require that the BUSY bit be currently set.
*/
if (cpu.segTSS.type != X86.DESC.ACC.TYPE.TSS_BUSY) {
X86.fnFault.call(cpu, X86.EXCEPTION.TS_FAULT, selNew, true);
return false;
@ -771,7 +773,12 @@ X86Seg.prototype.switchTSS = function switchTSS(selNew, fNest)
if (DEBUG && DEBUGGER && this.dbg && this.dbg.messageEnabled(Messages.TSS)) {
this.dbg.message((fNest? "Task switch" : "Task return") + ": TR " + str.toHexWord(selOld) + " (%" + str.toHex(addrOld, 6) + "), new TR " + str.toHexWord(selNew) + " (%" + str.toHex(addrNew, 6) + ")");
}
if (fNest) {
if (fNest === false) {
if (cpu.segTSS.type != X86.DESC.ACC.TYPE.TSS_BUSY) {
X86.fnFault.call(cpu, X86.EXCEPTION.GP_FAULT, selNew, true);
return false;
}
} else {
if (cpu.segTSS.type == X86.DESC.ACC.TYPE.TSS_BUSY) {
X86.fnFault.call(cpu, X86.EXCEPTION.GP_FAULT, selNew, true);
return false;