core_timing: Allow configuring a fixed or random initial system tick value. (#7309)

* core_timing: Apply random base ticks value on startup.

* core: Maintain consistent base system ticks in TAS movies.

* frontend: Add setting to configure a fixed base system ticks value.

src/android/app/src/main/jni/config.cpp

@@ -215,6 +215,8 @@ void Config::ReadValues() {
         } catch (...) {
         }
     }
+    ReadSetting("System", Settings::values.init_ticks_type);
+    ReadSetting("System", Settings::values.init_ticks_override);
     ReadSetting("System", Settings::values.plugin_loader_enabled);
     ReadSetting("System", Settings::values.allow_plugin_loader);
 

src/android/app/src/main/jni/default_ini.h

@@ -288,6 +288,14 @@ init_clock =
 # Note: 3DS can only handle times later then Jan 1 2000
 init_time =
 
+# The system ticks count to use when citra starts
+# 0: Random (default), 1: Fixed
+init_ticks_type =
+
+# Tick count to use when init_ticks_type is set to Fixed.
+# Defaults to 0.
+init_ticks_override =
+
 # Plugin loader state, if enabled plugins will be loaded from the SD card.
 # You can also set if homebrew apps are allowed to enable the plugin loader
 plugin_loader =

src/citra/config.cpp

@@ -225,6 +225,8 @@ void Config::ReadValues() {
                 std::chrono::system_clock::from_time_t(std::mktime(&t)).time_since_epoch())
                 .count();
     }
+    ReadSetting("System", Settings::values.init_ticks_type);
+    ReadSetting("System", Settings::values.init_ticks_override);
     ReadSetting("System", Settings::values.plugin_loader_enabled);
     ReadSetting("System", Settings::values.allow_plugin_loader);
 

src/citra/default_ini.h

@@ -307,6 +307,14 @@ init_clock =
 # Note: 3DS can only handle times later then Jan 1 2000
 init_time =
 
+# The system ticks count to use when citra starts
+# 0: Random (default), 1: Fixed
+init_ticks_type =
+
+# Tick count to use when init_ticks_type is set to Fixed.
+# Defaults to 0.
+init_ticks_override =
+
 [Camera]
 # Which camera engine to use for the right outer camera
 # blank (default): a dummy camera that always returns black image

src/citra_qt/configuration/config.cpp

@@ -687,6 +687,8 @@ void Config::ReadSystemValues() {
         ReadBasicSetting(Settings::values.init_clock);
         ReadBasicSetting(Settings::values.init_time);
         ReadBasicSetting(Settings::values.init_time_offset);
+        ReadBasicSetting(Settings::values.init_ticks_type);
+        ReadBasicSetting(Settings::values.init_ticks_override);
         ReadBasicSetting(Settings::values.plugin_loader_enabled);
         ReadBasicSetting(Settings::values.allow_plugin_loader);
     }
@@ -1173,6 +1175,8 @@ void Config::SaveSystemValues() {
         WriteBasicSetting(Settings::values.init_clock);
         WriteBasicSetting(Settings::values.init_time);
         WriteBasicSetting(Settings::values.init_time_offset);
+        WriteBasicSetting(Settings::values.init_ticks_type);
+        WriteBasicSetting(Settings::values.init_ticks_override);
         WriteBasicSetting(Settings::values.plugin_loader_enabled);
         WriteBasicSetting(Settings::values.allow_plugin_loader);
     }

src/citra_qt/configuration/configure_system.cpp

@@ -230,6 +230,8 @@ ConfigureSystem::ConfigureSystem(Core::System& system_, QWidget* parent)
             &ConfigureSystem::UpdateBirthdayComboBox);
     connect(ui->combo_init_clock, qOverload<int>(&QComboBox::currentIndexChanged), this,
             &ConfigureSystem::UpdateInitTime);
+    connect(ui->combo_init_ticks_type, qOverload<int>(&QComboBox::currentIndexChanged), this,
+            &ConfigureSystem::UpdateInitTicks);
     connect(ui->button_regenerate_console_id, &QPushButton::clicked, this,
             &ConfigureSystem::RefreshConsoleID);
     connect(ui->button_start_download, &QPushButton::clicked, this,
@@ -293,6 +295,11 @@ void ConfigureSystem::SetConfiguration() {
     QTime time = QTime::fromMSecsSinceStartOfDay(static_cast<int>(time_offset * 1000));
     ui->edit_init_time_offset_time->setTime(time);
 
+    ui->combo_init_ticks_type->setCurrentIndex(
+        static_cast<u8>(Settings::values.init_ticks_type.GetValue()));
+    ui->edit_init_ticks_value->setText(
+        QString::number(Settings::values.init_ticks_override.GetValue()));
+
     cfg = Service::CFG::GetModule(system);
     ReadSystemSettings();
 
@@ -413,6 +420,11 @@ void ConfigureSystem::ApplyConfiguration() {
             static_cast<Settings::InitClock>(ui->combo_init_clock->currentIndex());
         Settings::values.init_time = ui->edit_init_time->dateTime().toSecsSinceEpoch();
 
+        Settings::values.init_ticks_type =
+            static_cast<Settings::InitTicks>(ui->combo_init_ticks_type->currentIndex());
+        Settings::values.init_ticks_override =
+            static_cast<s64>(ui->edit_init_ticks_value->text().toLongLong());
+
         s64 time_offset_time = ui->edit_init_time_offset_time->time().msecsSinceStartOfDay() / 1000;
         s64 time_offset_days = ui->edit_init_time_offset_days->value() * 86400;
 
@@ -462,6 +474,7 @@ void ConfigureSystem::ConfigureTime() {
     SetConfiguration();
 
     UpdateInitTime(ui->combo_init_clock->currentIndex());
+    UpdateInitTicks(ui->combo_init_ticks_type->currentIndex());
 }
 
 void ConfigureSystem::UpdateInitTime(int init_clock) {
@@ -477,6 +490,15 @@ void ConfigureSystem::UpdateInitTime(int init_clock) {
     ui->edit_init_time_offset_time->setVisible(!is_fixed_time && is_global);
 }
 
+void ConfigureSystem::UpdateInitTicks(int init_ticks_type) {
+    const bool is_global = Settings::IsConfiguringGlobal();
+    const bool is_fixed =
+        static_cast<Settings::InitTicks>(init_ticks_type) == Settings::InitTicks::Fixed;
+
+    ui->label_init_ticks_value->setVisible(is_fixed && is_global);
+    ui->edit_init_ticks_value->setVisible(is_fixed && is_global);
+}
+
 void ConfigureSystem::RefreshConsoleID() {
     QMessageBox::StandardButton reply;
     QString warning_text = tr("This will replace your current virtual 3DS with a new one. "
@@ -512,6 +534,8 @@ void ConfigureSystem::SetupPerGameUI() {
     ui->label_birthday->setVisible(false);
     ui->label_init_clock->setVisible(false);
     ui->label_init_time->setVisible(false);
+    ui->label_init_ticks_type->setVisible(false);
+    ui->label_init_ticks_value->setVisible(false);
     ui->label_console_id->setVisible(false);
     ui->label_sound->setVisible(false);
     ui->label_language->setVisible(false);
@@ -522,12 +546,14 @@ void ConfigureSystem::SetupPerGameUI() {
     ui->combo_birthday->setVisible(false);
     ui->combo_birthmonth->setVisible(false);
     ui->combo_init_clock->setVisible(false);
+    ui->combo_init_ticks_type->setVisible(false);
     ui->combo_sound->setVisible(false);
     ui->combo_language->setVisible(false);
     ui->combo_country->setVisible(false);
     ui->label_init_time_offset->setVisible(false);
     ui->edit_init_time_offset_days->setVisible(false);
     ui->edit_init_time_offset_time->setVisible(false);
+    ui->edit_init_ticks_value->setVisible(false);
     ui->toggle_system_setup->setVisible(false);
     ui->button_regenerate_console_id->setVisible(false);
     // Apps can change the state of the plugin loader, so plugins load

src/citra_qt/configuration/configure_system.h

@@ -43,6 +43,7 @@ private:
 
     void UpdateBirthdayComboBox(int birthmonth_index);
     void UpdateInitTime(int init_clock);
+    void UpdateInitTicks(int init_ticks_type);
     void RefreshConsoleID();
 
     void SetupPerGameUI();

src/citra_qt/configuration/configure_system.ui

@@ -304,34 +304,75 @@
          </layout>
         </item>
         <item row="9" column="0">
+         <widget class="QLabel" name="label_init_ticks_type">
+          <property name="text">
+           <string>Initial System Ticks</string>
+          </property>
+         </widget>
+        </item>
+        <item row="9" column="1">
+         <widget class="QComboBox" name="combo_init_ticks_type">
+          <item>
+           <property name="text">
+            <string>Random</string>
+           </property>
+          </item>
+          <item>
+           <property name="text">
+            <string>Fixed</string>
+           </property>
+          </item>
+         </widget>
+        </item>
+        <item row="10" column="0">
+         <widget class="QLabel" name="label_init_ticks_value">
+          <property name="text">
+           <string>Initial System Ticks Override</string>
+          </property>
+         </widget>
+        </item>
+        <item row="10" column="1">
+         <widget class="QLineEdit" name="edit_init_ticks_value">
+          <property name="sizePolicy">
+           <sizepolicy hsizetype="Preferred" vsizetype="Fixed">
+            <horstretch>0</horstretch>
+            <verstretch>0</verstretch>
+           </sizepolicy>
+          </property>
+          <property name="maxLength">
+           <number>20</number>
+          </property>
+         </widget>
+        </item>
+        <item row="11" column="0">
          <widget class="QLabel" name="label_play_coins">
           <property name="text">
            <string>Play Coins:</string>
           </property>
          </widget>
         </item>
-        <item row="9" column="1">
+        <item row="11" column="1">
          <widget class="QSpinBox" name="spinBox_play_coins">
           <property name="maximum">
            <number>300</number>
           </property>
          </widget>
         </item>
-        <item row="10" column="1">
+        <item row="12" column="1">
          <widget class="QCheckBox" name="toggle_system_setup">
           <property name="text">
            <string>Run System Setup when Home Menu is launched</string>
           </property>
          </widget>
         </item>
-        <item row="11" column="0">
+        <item row="13" column="0">
          <widget class="QLabel" name="label_console_id">
           <property name="text">
            <string>Console ID:</string>
           </property>
          </widget>
         </item>
-        <item row="11" column="1">
+        <item row="13" column="1">
          <widget class="QPushButton" name="button_regenerate_console_id">
           <property name="sizePolicy">
            <sizepolicy hsizetype="Fixed" vsizetype="Fixed">
@@ -347,35 +388,35 @@
           </property>
          </widget>
         </item>
-        <item row="12" column="0">
+        <item row="14" column="0">
          <widget class="QLabel" name="label_plugin_loader">
           <property name="text">
            <string>3GX Plugin Loader:</string>
           </property>
          </widget>
         </item>
-        <item row="12" column="1">
+        <item row="14" column="1">
          <widget class="QCheckBox" name="plugin_loader">
           <property name="text">
            <string>Enable 3GX plugin loader</string>
           </property>
          </widget>
         </item>
-        <item row="13" column="1">
+        <item row="15" column="1">
          <widget class="QCheckBox" name="allow_plugin_loader">
           <property name="text">
            <string>Allow games to change plugin loader state</string>
           </property>
          </widget>
         </item>
-        <item row="14" column="0">
+        <item row="16" column="0">
          <widget class="QLabel" name="label_nus_download">
           <property name="text">
            <string>Download System Files from Nitendo servers</string>
           </property>
          </widget>
         </item>
-        <item row="14" column="1">
+        <item row="16" column="1">
          <widget class="QWidget" name="body_nus_download">
           <layout class="QHBoxLayout" name="horizontalLayout_nus_download">
            <item>

src/common/settings.h

@@ -28,6 +28,11 @@ enum class InitClock : u32 {
     FixedTime = 1,
 };
 
+enum class InitTicks : u32 {
+    Random = 0,
+    Fixed = 1,
+};
+
 enum class LayoutOption : u32 {
     Default,
     SingleScreen,
@@ -437,6 +442,8 @@ struct Values {
     Setting<InitClock> init_clock{InitClock::SystemTime, "init_clock"};
     Setting<u64> init_time{946681277ULL, "init_time"};
     Setting<s64> init_time_offset{0, "init_time_offset"};
+    Setting<InitTicks> init_ticks_type{InitTicks::Random, "init_ticks_type"};
+    Setting<s64> init_ticks_override{0, "init_ticks_override"};
     Setting<bool> plugin_loader_enabled{false, "plugin_loader"};
     Setting<bool> allow_plugin_loader{true, "allow_plugin_loader"};
 

src/core/core.cpp

@@ -379,7 +379,8 @@ System::ResultStatus System::Init(Frontend::EmuWindow& emu_window,
 
     memory = std::make_unique<Memory::MemorySystem>(*this);
 
-    timing = std::make_unique<Timing>(num_cores, Settings::values.cpu_clock_percentage.GetValue());
+    timing = std::make_unique<Timing>(num_cores, Settings::values.cpu_clock_percentage.GetValue(),
+                                      movie.GetOverrideBaseTicks());
 
     kernel = std::make_unique<Kernel::KernelSystem>(
         *memory, *timing, [this] { PrepareReschedule(); }, memory_mode, num_cores, n3ds_hw_caps,

src/core/core_timing.cpp

@@ -3,9 +3,11 @@
 // Refer to the license.txt file included.
 
 #include <algorithm>
+#include <random>
 #include <tuple>
 #include "common/assert.h"
 #include "common/logging/log.h"
+#include "common/settings.h"
 #include "core/core_timing.h"
 
 namespace Core {
@@ -19,15 +21,28 @@ bool Timing::Event::operator<(const Timing::Event& right) const {
     return std::tie(time, fifo_order) < std::tie(right.time, right.fifo_order);
 }
 
-Timing::Timing(std::size_t num_cores, u32 cpu_clock_percentage) {
+Timing::Timing(std::size_t num_cores, u32 cpu_clock_percentage, s64 override_base_ticks) {
+    // Generate non-zero base tick count to simulate time the system ran before launching the game.
+    // This accounts for games that rely on the system tick to seed randomness.
+    const auto base_ticks = override_base_ticks >= 0 ? override_base_ticks : GenerateBaseTicks();
+
     timers.resize(num_cores);
     for (std::size_t i = 0; i < num_cores; ++i) {
-        timers[i] = std::make_shared<Timer>();
+        timers[i] = std::make_shared<Timer>(base_ticks);
     }
     UpdateClockSpeed(cpu_clock_percentage);
     current_timer = timers[0].get();
 }
 
+s64 Timing::GenerateBaseTicks() {
+    if (Settings::values.init_ticks_type.GetValue() == Settings::InitTicks::Fixed) {
+        return Settings::values.init_ticks_override.GetValue();
+    }
+    // Bounded to 32 bits to make sure we don't generate too high of a counter and risk overflowing.
+    std::mt19937 random_gen(std::random_device{}());
+    return random_gen();
+}
+
 void Timing::UpdateClockSpeed(u32 cpu_clock_percentage) {
     for (auto& timer : timers) {
         timer->cpu_clock_scale = 100.0 / cpu_clock_percentage;
@@ -146,7 +161,7 @@ std::shared_ptr<Timing::Timer> Timing::GetTimer(std::size_t cpu_id) {
     return timers[cpu_id];
 }
 
-Timing::Timer::Timer() = default;
+Timing::Timer::Timer(s64 base_ticks) : executed_ticks(base_ticks) {}
 
 Timing::Timer::~Timer() {
     MoveEvents();

src/core/core_timing.h

@@ -185,7 +185,7 @@ public:
 
     class Timer {
     public:
-        Timer();
+        Timer(s64 base_ticks = 0);
         ~Timer();
 
         s64 GetMaxSliceLength() const;
@@ -249,7 +249,7 @@ public:
         friend class boost::serialization::access;
     };
 
-    explicit Timing(std::size_t num_cores, u32 cpu_clock_percentage);
+    explicit Timing(std::size_t num_cores, u32 cpu_clock_percentage, s64 override_base_ticks = -1);
 
     ~Timing(){};
 
@@ -290,6 +290,9 @@ public:
         event_queue_locked = false;
     }
 
+    /// Generates a random tick count to seed the system tick timer with.
+    static s64 GenerateBaseTicks();
+
 private:
     // unordered_map stores each element separately as a linked list node so pointers to
     // elements remain stable regardless of rehashes/resizing.

src/core/movie.cpp

@@ -120,8 +120,9 @@ struct CTMHeader {
     std::array<char, 32> author; /// Author of the movie
     u32_le rerecord_count;       /// Number of rerecords when making the movie
     u64_le input_count;          /// Number of inputs (button and pad states) when making the movie
+    s64_le timing_base_ticks;    /// The base system tick count to initialize core timing with.
 
-    std::array<u8, 164> reserved; /// Make heading 256 bytes so it has consistent size
+    std::array<u8, 156> reserved; /// Make heading 256 bytes so it has consistent size
 };
 static_assert(sizeof(CTMHeader) == 256, "CTMHeader should be 256 bytes");
 #pragma pack(pop)
@@ -158,6 +159,7 @@ void Movie::serialize(Archive& ar, const unsigned int file_version) {
     ar& recorded_input_;
 
     ar& init_time;
+    ar& base_ticks;
 
     if (Archive::is_loading::value) {
         u64 savestate_movie_id;
@@ -453,6 +455,10 @@ u64 Movie::GetOverrideInitTime() const {
     return init_time;
 }
 
+s64 Movie::GetOverrideBaseTicks() const {
+    return base_ticks;
+}
+
 Movie::ValidationResult Movie::ValidateHeader(const CTMHeader& header) const {
     if (header_magic_bytes != header.filetype) {
         LOG_ERROR(Movie, "Playback file does not have valid header");
@@ -487,6 +493,7 @@ void Movie::SaveMovie() {
     header.filetype = header_magic_bytes;
     header.program_id = program_id;
     header.clock_init_time = init_time;
+    header.timing_base_ticks = base_ticks;
     header.id = id;
 
     std::memcpy(header.author.data(), record_movie_author.data(),
@@ -591,6 +598,7 @@ void Movie::PrepareForPlayback(const std::string& movie_file) {
         return;
 
     init_time = header.value().clock_init_time;
+    base_ticks = header.value().timing_base_ticks;
 }
 
 void Movie::PrepareForRecording() {
@@ -605,6 +613,8 @@ void Movie::PrepareForRecording() {
     } else {
         init_time = Settings::values.init_time.GetValue();
     }
+
+    base_ticks = Timing::GenerateBaseTicks();
 }
 
 Movie::ValidationResult Movie::ValidateMovie(const std::string& movie_file) const {
@@ -661,6 +671,7 @@ void Movie::Shutdown() {
     current_byte = 0;
     current_input = 0;
     init_time = 0;
+    base_ticks = -1;
     id = 0;
 }
 

src/core/movie.h

@@ -74,6 +74,9 @@ public:
     /// Get the init time that would override the one in the settings
     u64 GetOverrideInitTime() const;
 
+    /// Get the base system ticks value that would override the one generated by core timing
+    s64 GetOverrideBaseTicks() const;
+
     struct MovieMetadata {
         u64 program_id;
         std::string author;
@@ -169,6 +172,7 @@ private:
     std::string record_movie_author;
 
     u64 init_time;       // Clock init time override for RNG consistency
+    s64 base_ticks = -1; // Core timing base system ticks override for RNG consistency
 
     std::vector<u8> recorded_input;
     std::size_t current_byte = 0;