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Document VERR/VERW and helper function

This commit is contained in:
Dan Luu 2013-03-19 14:53:58 -04:00
parent fc016ceee6
commit b52e4ead18
1 changed files with 10 additions and 8 deletions
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18
cpux86-ta.js
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@ -4787,7 +4787,7 @@ CPU_X86.prototype.exec_internal = function(N_cycles, interrupt) {
}
//utility function for op_VERR_VERW
function rf(selector, ud) {
function segment_isnt_accessible(selector, is_verw) {
var e, descriptor_low4bytes, descriptor_high4bytes, rpl, dpl, cpl_var;
if ((selector & 0xfffc) == 0)
return 0;
@ -4796,13 +4796,13 @@ CPU_X86.prototype.exec_internal = function(N_cycles, interrupt) {
return 0;
descriptor_low4bytes = e[0];
descriptor_high4bytes = e[1];
if (!(descriptor_high4bytes & (1 << 12)))
if (!(descriptor_high4bytes & (1 << 12))) // s bit (system == 0)
return 0;
rpl = selector & 3;
dpl = (descriptor_high4bytes >> 13) & 3;
cpl_var = cpu.cpl;
if (descriptor_high4bytes & (1 << 11)) {
if (ud) {
if (descriptor_high4bytes & (1 << 11)) { // code == 1, data == 0
if (is_verw) { // code segments are never writable
return 0;
} else {
if (!(descriptor_high4bytes & (1 << 9)))
@ -4813,17 +4813,19 @@ CPU_X86.prototype.exec_internal = function(N_cycles, interrupt) {
}
}
} else {
if (dpl < cpl_var || dpl < rpl)
if (dpl < cpl_var || dpl < rpl) // data segments are always readable, if privilege is sufficient
return 0;
if (ud && !(descriptor_high4bytes & (1 << 9)))
if (is_verw && !(descriptor_high4bytes & (1 << 9))) //writable data segment
return 0;
}
return 1;
}
function op_VERR_VERW(selector, ud) {
function op_VERR_VERW(selector, is_verw) {
var z;
z = rf(selector, ud);
z = segment_isnt_accessible(selector, is_verw);
_src = get_conditional_flags();
// clear eflags.zf if selector is accessible and (readable (for VERR) or writable (for VERW))
if (z)
_src |= 0x0040;
else