From ea0011d57295b3b5daca49a0683dbc2ec203b667 Mon Sep 17 00:00:00 2001 From: Michael Scire Date: Thu, 13 Feb 2020 22:37:30 -0800 Subject: [PATCH] kern: use TinyMT instead of mt19937_t --- .../nintendo/switch/kern_k_system_control.cpp | 39 ++- .../include/stratosphere/util/util_tinymt.hpp | 149 ++++++++++- .../source/util/util_tinymt.cpp | 187 ------------- libraries/libvapours/include/vapours/util.hpp | 1 + .../include/vapours/util/util_tinymt.hpp | 248 ++++++++++++++++++ .../kernel}/source/libc/kern_env.cpp | 0 6 files changed, 418 insertions(+), 206 deletions(-) delete mode 100644 libraries/libstratosphere/source/util/util_tinymt.cpp create mode 100644 libraries/libvapours/include/vapours/util/util_tinymt.hpp rename {libraries/libmesosphere => mesosphere/kernel}/source/libc/kern_env.cpp (100%) diff --git a/libraries/libmesosphere/source/board/nintendo/switch/kern_k_system_control.cpp b/libraries/libmesosphere/source/board/nintendo/switch/kern_k_system_control.cpp index 358645e7d..4e653159d 100644 --- a/libraries/libmesosphere/source/board/nintendo/switch/kern_k_system_control.cpp +++ b/libraries/libmesosphere/source/board/nintendo/switch/kern_k_system_control.cpp @@ -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 + 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::max() && min == std::numeric_limits::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::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::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(&seed), sizeof(seed) / sizeof(u32)); g_initialized_random_generator = true; } - return (std::uniform_int_distribution(min, max))(g_random_generator); + return GenerateUniformRange(min, max, GenerateRandomU64FromGenerator); } void KSystemControl::StopSystem() { diff --git a/libraries/libstratosphere/include/stratosphere/util/util_tinymt.hpp b/libraries/libstratosphere/include/stratosphere/util/util_tinymt.hpp index a5fea59d4..6c1a86233 100644 --- a/libraries/libstratosphere/include/stratosphere/util/util_tinymt.hpp +++ b/libraries/libstratosphere/include/stratosphere/util/util_tinymt.hpp @@ -41,6 +41,14 @@ namespace ams::util { static constexpr int MinimumInitIterations = 8; static constexpr int NumDiscardedInitOutputs = 8; + + constexpr inline u32 XorByShifted27(u32 value) { + return value ^ (value >> 27); + } + + constexpr inline u32 XorByShifted30(u32 value) { + return value ^ (value >> 30); + } private: State state; private: @@ -49,22 +57,147 @@ namespace ams::util { u32 GenerateRandomU24() { return (this->GenerateRandomU32() >> 8); } - static void GenerateInitialValuePlus(TinyMT::State *state, int index, u32 value); - static void GenerateInitialValueXor(TinyMT::State *state, int index); + static void GenerateInitialValuePlus(TinyMT::State *state, int index, u32 value) { + u32 &state0 = state->data[(index + 0) % NumStateWords]; + u32 &state1 = state->data[(index + 1) % NumStateWords]; + u32 &state2 = state->data[(index + 2) % NumStateWords]; + u32 &state3 = state->data[(index + 3) % NumStateWords]; + + const u32 x = XorByShifted27(state0 ^ state1 ^ state3) * ParamPlus; + const u32 y = x + index + value; + + state0 = y; + state1 += x; + state2 += y; + } + + static void GenerateInitialValueXor(TinyMT::State *state, int index) { + u32 &state0 = state->data[(index + 0) % NumStateWords]; + u32 &state1 = state->data[(index + 1) % NumStateWords]; + u32 &state2 = state->data[(index + 2) % NumStateWords]; + u32 &state3 = state->data[(index + 3) % NumStateWords]; + + const u32 x = XorByShifted27(state0 + state1 + state3) * ParamXor; + const u32 y = x - index; + + state0 = y; + state1 ^= x; + state2 ^= y; + } public: + constexpr TinyMT() : state() { /* ... */ } + /* Public API. */ /* Initialization. */ - void Initialize(u32 seed); - void Initialize(const u32 *seed, int seed_count); + void Initialize(u32 seed) { + this->state.data[0] = seed; + this->state.data[1] = ParamMat1; + this->state.data[2] = ParamMat2; + this->state.data[3] = ParamTmat; + + for (int i = 1; i < MinimumInitIterations; i++) { + const u32 mixed = XorByShifted30(this->state.data[(i - 1) % NumStateWords]); + this->state.data[i % NumStateWords] ^= mixed * ParamMult + i; + } + + this->FinalizeInitialization(); + } + + void Initialize(const u32 *seed, int seed_count) { + this->state.data[0] = 0; + this->state.data[1] = ParamMat1; + this->state.data[2] = ParamMat2; + this->state.data[3] = ParamTmat; + + { + const int num_init_iterations = std::max(seed_count + 1, MinimumInitIterations) - 1; + + GenerateInitialValuePlus(&this->state, 0, seed_count); + + for (int i = 0; i < num_init_iterations; i++) { + GenerateInitialValuePlus(&this->state, (i + 1) % NumStateWords, (i < seed_count) ? seed[i] : 0); + } + + for (int i = 0; i < static_cast(NumStateWords); i++) { + GenerateInitialValueXor(&this->state, (i + 1 + num_init_iterations) % NumStateWords); + } + } + + this->FinalizeInitialization(); + } /* State management. */ - void GetState(TinyMT::State *out) const; - void SetState(const TinyMT::State *state); + void GetState(TinyMT::State *out) const { + std::memcpy(out->data, this->state.data, sizeof(this->state)); + } + + void SetState(const TinyMT::State *state) { + std::memcpy(this->state.data, state->data, sizeof(this->state)); + } /* Random generation. */ - void GenerateRandomBytes(void *dst, size_t size); - u32 GenerateRandomU32(); + NOINLINE void GenerateRandomBytes(void *dst, size_t size) { + const uintptr_t start = reinterpret_cast(dst); + const uintptr_t end = start + size; + const uintptr_t aligned_start = util::AlignUp(start, 4); + const uintptr_t aligned_end = util::AlignDown(end, 4); + + /* Make sure we're aligned. */ + if (start < aligned_start) { + const u32 rnd = this->GenerateRandomU32(); + std::memcpy(dst, &rnd, aligned_start - start); + } + + /* Write as many aligned u32s as we can. */ + { + u32 * cur_dst = reinterpret_cast(aligned_start); + u32 * const end_dst = reinterpret_cast(aligned_end); + + while (cur_dst < end_dst) { + *(cur_dst++) = this->GenerateRandomU32(); + } + } + + /* Handle any leftover unaligned data. */ + if (aligned_end < end) { + const u32 rnd = this->GenerateRandomU32(); + std::memcpy(reinterpret_cast(aligned_end), &rnd, end - aligned_end); + } + } + + NOINLINE u32 GenerateRandomU32() { + /* Advance state. */ + const u32 x0 = (this->state.data[0] & TopBitmask) ^ this->state.data[1] ^ this->state.data[2]; + const u32 y0 = this->state.data[3]; + const u32 x1 = x0 ^ (x0 << 1); + const u32 y1 = y0 ^ (y0 >> 1) ^ x1; + + const u32 state0 = this->state.data[1]; + u32 state1 = this->state.data[2]; + u32 state2 = x1 ^ (y1 << 10); + const u32 state3 = y1; + + if ((y1 & 1) != 0) { + state1 ^= ParamMat1; + state2 ^= ParamMat2; + } + + this->state.data[0] = state0; + this->state.data[1] = state1; + this->state.data[2] = state2; + this->state.data[3] = state3; + + /* Temper. */ + const u32 t1 = state0 + (state2 >> 8); + u32 t0 = state3 ^ t1; + + if ((t1 & 1) != 0) { + t0 ^= ParamTmat; + } + + return t0; + } inline u64 GenerateRandomU64() { const u32 lo = this->GenerateRandomU32(); diff --git a/libraries/libstratosphere/source/util/util_tinymt.cpp b/libraries/libstratosphere/source/util/util_tinymt.cpp deleted file mode 100644 index 9506dc69e..000000000 --- a/libraries/libstratosphere/source/util/util_tinymt.cpp +++ /dev/null @@ -1,187 +0,0 @@ -/* - * Copyright (c) 2018-2020 Atmosphère-NX - * - * This program is free software; you can redistribute it and/or modify it - * under the terms and conditions of the GNU General Public License, - * version 2, as published by the Free Software Foundation. - * - * This program is distributed in the hope it will be useful, but WITHOUT - * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or - * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for - * more details. - * - * You should have received a copy of the GNU General Public License - * along with this program. If not, see . - */ - -#include - -namespace ams::util { - - namespace { - - constexpr inline u32 XorByShifted27(u32 value) { - return value ^ (value >> 27); - } - - constexpr inline u32 XorByShifted30(u32 value) { - return value ^ (value >> 30); - } - - } - - void TinyMT::GenerateInitialValuePlus(TinyMT::State *state, int index, u32 value) { - u32 &state0 = state->data[(index + 0) % NumStateWords]; - u32 &state1 = state->data[(index + 1) % NumStateWords]; - u32 &state2 = state->data[(index + 2) % NumStateWords]; - u32 &state3 = state->data[(index + 3) % NumStateWords]; - - const u32 x = XorByShifted27(state0 ^ state1 ^ state3) * ParamPlus; - const u32 y = x + index + value; - - state0 = y; - state1 += x; - state2 += y; - } - - void TinyMT::GenerateInitialValueXor(TinyMT::State *state, int index) { - u32 &state0 = state->data[(index + 0) % NumStateWords]; - u32 &state1 = state->data[(index + 1) % NumStateWords]; - u32 &state2 = state->data[(index + 2) % NumStateWords]; - u32 &state3 = state->data[(index + 3) % NumStateWords]; - - const u32 x = XorByShifted27(state0 + state1 + state3) * ParamXor; - const u32 y = x - index; - - state0 = y; - state1 ^= x; - state2 ^= y; - } - - void TinyMT::Initialize(u32 seed) { - this->state.data[0] = seed; - this->state.data[1] = ParamMat1; - this->state.data[2] = ParamMat2; - this->state.data[3] = ParamTmat; - - for (int i = 1; i < MinimumInitIterations; i++) { - const u32 mixed = XorByShifted30(this->state.data[(i - 1) % NumStateWords]); - this->state.data[i % NumStateWords] ^= mixed * ParamMult + i; - } - - this->FinalizeInitialization(); - } - - void TinyMT::Initialize(const u32 *seed, int seed_count) { - this->state.data[0] = 0; - this->state.data[1] = ParamMat1; - this->state.data[2] = ParamMat2; - this->state.data[3] = ParamTmat; - - { - const int num_init_iterations = std::max(seed_count + 1, MinimumInitIterations) - 1; - - GenerateInitialValuePlus(&this->state, 0, seed_count); - - for (int i = 0; i < num_init_iterations; i++) { - GenerateInitialValuePlus(&this->state, (i + 1) % NumStateWords, (i < seed_count) ? seed[i] : 0); - } - - for (int i = 0; i < static_cast(NumStateWords); i++) { - GenerateInitialValueXor(&this->state, (i + 1 + num_init_iterations) % NumStateWords); - } - } - - this->FinalizeInitialization(); - } - - void TinyMT::FinalizeInitialization() { - const u32 state0 = this->state.data[0] & TopBitmask; - const u32 state1 = this->state.data[1]; - const u32 state2 = this->state.data[2]; - const u32 state3 = this->state.data[3]; - - if (state0 == 0 && state1 == 0 && state2 == 0 && state3 == 0) { - this->state.data[0] = 'T'; - this->state.data[1] = 'I'; - this->state.data[2] = 'N'; - this->state.data[3] = 'Y'; - } - - for (int i = 0; i < NumDiscardedInitOutputs; i++) { - this->GenerateRandomU32(); - } - } - - - void TinyMT::GetState(TinyMT::State *out) const { - std::memcpy(out->data, this->state.data, sizeof(this->state)); - } - - void TinyMT::SetState(const TinyMT::State *state) { - std::memcpy(this->state.data, state->data, sizeof(this->state)); - } - - void TinyMT::GenerateRandomBytes(void *dst, size_t size) { - const uintptr_t start = reinterpret_cast(dst); - const uintptr_t end = start + size; - const uintptr_t aligned_start = util::AlignUp(start, 4); - const uintptr_t aligned_end = util::AlignDown(end, 4); - - /* Make sure we're aligned. */ - if (start < aligned_start) { - const u32 rnd = this->GenerateRandomU32(); - std::memcpy(dst, &rnd, aligned_start - start); - } - - /* Write as many aligned u32s as we can. */ - { - u32 * cur_dst = reinterpret_cast(aligned_start); - u32 * const end_dst = reinterpret_cast(aligned_end); - - while (cur_dst < end_dst) { - *(cur_dst++) = this->GenerateRandomU32(); - } - } - - /* Handle any leftover unaligned data. */ - if (aligned_end < end) { - const u32 rnd = this->GenerateRandomU32(); - std::memcpy(reinterpret_cast(aligned_end), &rnd, end - aligned_end); - } - } - - u32 TinyMT::GenerateRandomU32() { - /* Advance state. */ - const u32 x0 = (this->state.data[0] & TopBitmask) ^ this->state.data[1] ^ this->state.data[2]; - const u32 y0 = this->state.data[3]; - const u32 x1 = x0 ^ (x0 << 1); - const u32 y1 = y0 ^ (y0 >> 1) ^ x1; - - const u32 state0 = this->state.data[1]; - u32 state1 = this->state.data[2]; - u32 state2 = x1 ^ (y1 << 10); - const u32 state3 = y1; - - if ((y1 & 1) != 0) { - state1 ^= ParamMat1; - state2 ^= ParamMat2; - } - - this->state.data[0] = state0; - this->state.data[1] = state1; - this->state.data[2] = state2; - this->state.data[3] = state3; - - /* Temper. */ - const u32 t1 = state0 + (state2 >> 8); - u32 t0 = state3 ^ t1; - - if ((t1 & 1) != 0) { - t0 ^= ParamTmat; - } - - return t0; - } - -} \ No newline at end of file diff --git a/libraries/libvapours/include/vapours/util.hpp b/libraries/libvapours/include/vapours/util.hpp index 97d6c0cba..94013a1a9 100644 --- a/libraries/libvapours/include/vapours/util.hpp +++ b/libraries/libvapours/include/vapours/util.hpp @@ -27,3 +27,4 @@ #include "util/util_typed_storage.hpp" #include "util/util_intrusive_list.hpp" #include "util/util_intrusive_red_black_tree.hpp" +#include "util/util_tinymt.hpp" diff --git a/libraries/libvapours/include/vapours/util/util_tinymt.hpp b/libraries/libvapours/include/vapours/util/util_tinymt.hpp new file mode 100644 index 000000000..6a2c97e99 --- /dev/null +++ b/libraries/libvapours/include/vapours/util/util_tinymt.hpp @@ -0,0 +1,248 @@ +/* + * Copyright (c) 2018-2020 Atmosphère-NX + * + * This program is free software; you can redistribute it and/or modify it + * under the terms and conditions of the GNU General Public License, + * version 2, as published by the Free Software Foundation. + * + * This program is distributed in the hope it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for + * more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see . + */ + +#pragma once +#include + +namespace ams::util { + + /* Implementation of TinyMT (mersenne twister RNG). */ + /* Like Nintendo, we will use the sample parameters. */ + class TinyMT { + public: + static constexpr size_t NumStateWords = 4; + + struct State { + u32 data[NumStateWords]; + }; + private: + static constexpr u32 ParamMat1 = 0x8F7011EE; + static constexpr u32 ParamMat2 = 0xFC78FF1F; + static constexpr u32 ParamTmat = 0x3793FDFF; + + static constexpr u32 ParamMult = 0x6C078965; + static constexpr u32 ParamPlus = 0x0019660D; + static constexpr u32 ParamXor = 0x5D588B65; + + static constexpr u32 TopBitmask = 0x7FFFFFFF; + + static constexpr int MinimumInitIterations = 8; + static constexpr int NumDiscardedInitOutputs = 8; + + static constexpr inline u32 XorByShifted27(u32 value) { + return value ^ (value >> 27); + } + + static constexpr inline u32 XorByShifted30(u32 value) { + return value ^ (value >> 30); + } + private: + State state; + private: + /* Internal API. */ + void FinalizeInitialization() { + const u32 state0 = this->state.data[0] & TopBitmask; + const u32 state1 = this->state.data[1]; + const u32 state2 = this->state.data[2]; + const u32 state3 = this->state.data[3]; + + if (state0 == 0 && state1 == 0 && state2 == 0 && state3 == 0) { + this->state.data[0] = 'T'; + this->state.data[1] = 'I'; + this->state.data[2] = 'N'; + this->state.data[3] = 'Y'; + } + + for (int i = 0; i < NumDiscardedInitOutputs; i++) { + this->GenerateRandomU32(); + } + } + + u32 GenerateRandomU24() { return (this->GenerateRandomU32() >> 8); } + + static void GenerateInitialValuePlus(TinyMT::State *state, int index, u32 value) { + u32 &state0 = state->data[(index + 0) % NumStateWords]; + u32 &state1 = state->data[(index + 1) % NumStateWords]; + u32 &state2 = state->data[(index + 2) % NumStateWords]; + u32 &state3 = state->data[(index + 3) % NumStateWords]; + + const u32 x = XorByShifted27(state0 ^ state1 ^ state3) * ParamPlus; + const u32 y = x + index + value; + + state0 = y; + state1 += x; + state2 += y; + } + + static void GenerateInitialValueXor(TinyMT::State *state, int index) { + u32 &state0 = state->data[(index + 0) % NumStateWords]; + u32 &state1 = state->data[(index + 1) % NumStateWords]; + u32 &state2 = state->data[(index + 2) % NumStateWords]; + u32 &state3 = state->data[(index + 3) % NumStateWords]; + + const u32 x = XorByShifted27(state0 + state1 + state3) * ParamXor; + const u32 y = x - index; + + state0 = y; + state1 ^= x; + state2 ^= y; + } + public: + constexpr TinyMT() : state() { /* ... */ } + + /* Public API. */ + + /* Initialization. */ + void Initialize(u32 seed) { + this->state.data[0] = seed; + this->state.data[1] = ParamMat1; + this->state.data[2] = ParamMat2; + this->state.data[3] = ParamTmat; + + for (int i = 1; i < MinimumInitIterations; i++) { + const u32 mixed = XorByShifted30(this->state.data[(i - 1) % NumStateWords]); + this->state.data[i % NumStateWords] ^= mixed * ParamMult + i; + } + + this->FinalizeInitialization(); + } + + void Initialize(const u32 *seed, int seed_count) { + this->state.data[0] = 0; + this->state.data[1] = ParamMat1; + this->state.data[2] = ParamMat2; + this->state.data[3] = ParamTmat; + + { + const int num_init_iterations = std::max(seed_count + 1, MinimumInitIterations) - 1; + + GenerateInitialValuePlus(&this->state, 0, seed_count); + + for (int i = 0; i < num_init_iterations; i++) { + GenerateInitialValuePlus(&this->state, (i + 1) % NumStateWords, (i < seed_count) ? seed[i] : 0); + } + + for (int i = 0; i < static_cast(NumStateWords); i++) { + GenerateInitialValueXor(&this->state, (i + 1 + num_init_iterations) % NumStateWords); + } + } + + this->FinalizeInitialization(); + } + + /* State management. */ + void GetState(TinyMT::State *out) const { + std::memcpy(out->data, this->state.data, sizeof(this->state)); + } + + void SetState(const TinyMT::State *state) { + std::memcpy(this->state.data, state->data, sizeof(this->state)); + } + + /* Random generation. */ + NOINLINE void GenerateRandomBytes(void *dst, size_t size) { + const uintptr_t start = reinterpret_cast(dst); + const uintptr_t end = start + size; + const uintptr_t aligned_start = util::AlignUp(start, 4); + const uintptr_t aligned_end = util::AlignDown(end, 4); + + /* Make sure we're aligned. */ + if (start < aligned_start) { + const u32 rnd = this->GenerateRandomU32(); + std::memcpy(dst, &rnd, aligned_start - start); + } + + /* Write as many aligned u32s as we can. */ + { + u32 * cur_dst = reinterpret_cast(aligned_start); + u32 * const end_dst = reinterpret_cast(aligned_end); + + while (cur_dst < end_dst) { + *(cur_dst++) = this->GenerateRandomU32(); + } + } + + /* Handle any leftover unaligned data. */ + if (aligned_end < end) { + const u32 rnd = this->GenerateRandomU32(); + std::memcpy(reinterpret_cast(aligned_end), &rnd, end - aligned_end); + } + } + + NOINLINE u32 GenerateRandomU32() { + /* Advance state. */ + const u32 x0 = (this->state.data[0] & TopBitmask) ^ this->state.data[1] ^ this->state.data[2]; + const u32 y0 = this->state.data[3]; + const u32 x1 = x0 ^ (x0 << 1); + const u32 y1 = y0 ^ (y0 >> 1) ^ x1; + + const u32 state0 = this->state.data[1]; + u32 state1 = this->state.data[2]; + u32 state2 = x1 ^ (y1 << 10); + const u32 state3 = y1; + + if ((y1 & 1) != 0) { + state1 ^= ParamMat1; + state2 ^= ParamMat2; + } + + this->state.data[0] = state0; + this->state.data[1] = state1; + this->state.data[2] = state2; + this->state.data[3] = state3; + + /* Temper. */ + const u32 t1 = state0 + (state2 >> 8); + u32 t0 = state3 ^ t1; + + if ((t1 & 1) != 0) { + t0 ^= ParamTmat; + } + + return t0; + } + + inline u64 GenerateRandomU64() { + const u32 lo = this->GenerateRandomU32(); + const u32 hi = this->GenerateRandomU32(); + return (static_cast(hi) << 32) | static_cast(lo); + } + + inline float GenerateRandomF32() { + /* Floats have 24 bits of mantissa. */ + constexpr int MantissaBits = 24; + return GenerateRandomU24() * (1.0f / (1ul << MantissaBits)); + } + + inline double GenerateRandomF64() { + /* Doubles have 53 bits of mantissa. */ + /* The smart way to generate 53 bits of random would be to use 32 bits */ + /* from the first rnd32() call, and then 21 from the second. */ + /* Nintendo does not. They use (32 - 5) = 27 bits from the first rnd32() */ + /* call, and (32 - 6) bits from the second. We'll do what they do, but */ + /* There's not a clear reason why. */ + constexpr int MantissaBits = 53; + constexpr int Shift1st = (64 - MantissaBits) / 2; + constexpr int Shift2nd = (64 - MantissaBits) - Shift1st; + + const u32 first = (this->GenerateRandomU32() >> Shift1st); + const u32 second = (this->GenerateRandomU32() >> Shift2nd); + + return (1.0 * first * (1ul << (32 - Shift2nd)) + second) * (1.0 / (1ul << MantissaBits)); + } + }; + +} \ No newline at end of file diff --git a/libraries/libmesosphere/source/libc/kern_env.cpp b/mesosphere/kernel/source/libc/kern_env.cpp similarity index 100% rename from libraries/libmesosphere/source/libc/kern_env.cpp rename to mesosphere/kernel/source/libc/kern_env.cpp