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Fix CPUID subleaf iteration #17527

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Merged
merged 2 commits into from
Nov 24, 2019
Merged

Fix CPUID subleaf iteration #17527

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ba2c5fe
Fix CPUID subleaf iteration
sipa Nov 19, 2019
f93fc61
Put bounds on the number of CPUID leaves explored
sipa Nov 20, 2019
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25 changes: 18 additions & 7 deletions src/randomenv.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -197,19 +197,30 @@ void AddAllCPUID(CSHA512& hasher)
// Iterate over all standard leaves
AddCPUID(hasher, 0, 0, ax, bx, cx, dx); // Returns max leaf in ax
uint32_t max = ax;
for (uint32_t leaf = 1; leaf <= max; ++leaf) {
for (uint32_t subleaf = 0;; ++subleaf) {
for (uint32_t leaf = 1; leaf <= max && leaf <= 0xFF; ++leaf) {
uint32_t maxsub = 0;
for (uint32_t subleaf = 0; subleaf <= 0xFF; ++subleaf) {
AddCPUID(hasher, leaf, subleaf, ax, bx, cx, dx);
// Iterate over subleaves for leaf 4, 11, 13
if (leaf != 4 && leaf != 11 && leaf != 13) break;
if ((leaf == 4 || leaf == 13) && ax == 0) break;
if (leaf == 11 && (cx & 0xFF00) == 0) break;
// Iterate subleafs for leaf values 4, 7, 11, 13
if (leaf == 4) {
if ((ax & 0x1f) == 0) break;
} else if (leaf == 7) {
if (subleaf == 0) maxsub = ax;
if (subleaf == maxsub) break;
} else if (leaf == 11) {
if ((cx & 0xff00) == 0) break;
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@mzumsande mzumsande Nov 23, 2019 •
edited
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Got slightly confused here because the intel pdf linked above recommends eax=0 and ebx=0 as break condition for leaf 11 (p.40), but checking cx & 0xff00 should be equivalent according to this.

} else if (leaf == 13) {
if (ax == 0 && bx == 0 && cx == 0 && dx == 0) break;
} else {
// For any other leaf, stop after subleaf 0.
break;
}
}
}
// Iterate over all extended leaves
AddCPUID(hasher, 0x80000000, 0, ax, bx, cx, dx); // Returns max extended leaf in ax
uint32_t ext_max = ax;
for (uint32_t leaf = 0x80000001; leaf <= ext_max; ++leaf) {
for (uint32_t leaf = 0x80000001; leaf <= ext_max && leaf <= 0x800000FF; ++leaf) {
AddCPUID(hasher, leaf, 0, ax, bx, cx, dx);
}
}
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