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kern: use TinyMT instead of mt19937_t

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This commit is contained in:
Michael Scire 2020-02-13 22:37:30 -08:00
parent 364b04b68a
commit ea0011d572
6 changed files with 418 additions and 206 deletions
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39
libraries/libmesosphere/source/board/nintendo/switch/kern_k_system_control.cpp
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@ -24,9 +24,11 @@ namespace ams::kern {
bool g_call_smc_on_panic;
/* Global variables for randomness. */
/* Incredibly, N really does use std:: randomness... */
/* Nintendo uses std::mt19937_t for randomness. */
/* To save space (and because mt19337_t isn't secure anyway), */
/* We will use TinyMT. */
bool g_initialized_random_generator;
std::mt19937 g_random_generator;
util::TinyMT g_random_generator;
KSpinLock g_random_lock;
ALWAYS_INLINE size_t GetRealMemorySizeForInit() {
@ -73,6 +75,27 @@ namespace ams::kern {
return value;
}
ALWAYS_INLINE u64 GenerateRandomU64FromGenerator() {
return g_random_generator.GenerateRandomU64();
}
template<typename F>
ALWAYS_INLINE u64 GenerateUniformRange(u64 min, u64 max, F f) {
/* Handle the case where the difference is too large to represent. */
if (max == std::numeric_limits<u64>::max() && min == std::numeric_limits<u64>::min()) {
return f();
}
/* Iterate until we get a value in range. */
const u64 range_size = ((max + 1) - min);
const u64 effective_max = (std::numeric_limits<u64>::max() / range_size) * range_size;
while (true) {
if (const u64 rnd = f(); rnd < effective_max) {
return min + (rnd % range_size);
}
}
}
ALWAYS_INLINE u64 GetConfigU64(smc::ConfigItem which) {
u64 value;
smc::GetConfig(&value, 1, which);
@ -168,13 +191,7 @@ namespace ams::kern {
}
u64 KSystemControl::Init::GenerateRandomRange(u64 min, u64 max) {
const u64 range_size = ((max + 1) - min);
const u64 effective_max = (std::numeric_limits<u64>::max() / range_size) * range_size;
while (true) {
if (const u64 rnd = GenerateRandomU64ForInit(); rnd < effective_max) {
return min + (rnd % range_size);
}
}
return GenerateUniformRange(min, max, GenerateRandomU64ForInit);
}
/* System Initialization. */
@ -250,11 +267,11 @@ namespace ams::kern {
if (AMS_UNLIKELY(!g_initialized_random_generator)) {
u64 seed;
GenerateRandomBytes(&seed, sizeof(seed));
g_random_generator.seed(seed);
g_random_generator.Initialize(reinterpret_cast<u32*>(&seed), sizeof(seed) / sizeof(u32));
g_initialized_random_generator = true;
}
return (std::uniform_int_distribution<u64>(min, max))(g_random_generator);
return GenerateUniformRange(min, max, GenerateRandomU64FromGenerator);
}
void KSystemControl::StopSystem() {