From 1b7d619914c8d132dbffb8b6a5bb3a1aab686f9d Mon Sep 17 00:00:00 2001
From: Zach Hilman <zachhilman@gmail.com>
Date: Thu, 30 May 2019 08:52:20 -0400
Subject: [PATCH 1/4] memory: Add class to manage and enforce memory freezing

---
 src/core/CMakeLists.txt     |   2 +
 src/core/core.cpp           |   2 +
 src/core/memory/freezer.cpp | 186 ++++++++++++++++++++++++++++++++++++
 src/core/memory/freezer.h   |  58 +++++++++++
 4 files changed, 248 insertions(+)
 create mode 100644 src/core/memory/freezer.cpp
 create mode 100644 src/core/memory/freezer.h

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 4204ace2b..c17528134 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -454,6 +454,8 @@ add_library(core STATIC
     loader/nsp.h
     loader/xci.cpp
     loader/xci.h
+    memory/freezer.cpp
+    memory/freezer.h
     memory.cpp
     memory.h
     memory_setup.h
diff --git a/src/core/core.cpp b/src/core/core.cpp
index ff0721079..94ebe0995 100644
--- a/src/core/core.cpp
+++ b/src/core/core.cpp
@@ -28,6 +28,7 @@
 #include "core/hle/service/service.h"
 #include "core/hle/service/sm/sm.h"
 #include "core/loader/loader.h"
+#include "core/memory/freezer.h"
 #include "core/perf_stats.h"
 #include "core/settings.h"
 #include "core/telemetry_session.h"
@@ -243,6 +244,7 @@ struct System::Impl {
     bool is_powered_on = false;
 
     std::unique_ptr<FileSys::CheatEngine> cheat_engine;
+    std::unique_ptr<Memory::Freezer> memory_freezer;
 
     /// Frontend applets
     Service::AM::Applets::AppletManager applet_manager;
diff --git a/src/core/memory/freezer.cpp b/src/core/memory/freezer.cpp
new file mode 100644
index 000000000..1d0ccf328
--- /dev/null
+++ b/src/core/memory/freezer.cpp
@@ -0,0 +1,186 @@
+// Copyright 2019 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "common/assert.h"
+#include "core/core.h"
+#include "core/core_timing_util.h"
+#include "core/memory.h"
+#include "core/memory/freezer.h"
+
+namespace Memory {
+
+constexpr s64 MEMORY_FREEZER_TICKS = static_cast<s64>(Core::Timing::BASE_CLOCK_RATE / 60);
+
+namespace {
+
+u64 MemoryReadWidth(u8 width, VAddr addr) {
+    switch (width) {
+    case 1:
+        return Read8(addr);
+    case 2:
+        return Read16(addr);
+    case 4:
+        return Read32(addr);
+    case 8:
+        return Read64(addr);
+    default:
+        UNREACHABLE();
+        return 0;
+    }
+}
+
+void MemoryWriteWidth(u8 width, VAddr addr, u64 value) {
+    switch (width) {
+    case 1:
+        Write8(addr, static_cast<u8>(value));
+        break;
+    case 2:
+        Write16(addr, static_cast<u16>(value));
+        break;
+    case 4:
+        Write32(addr, static_cast<u32>(value));
+        break;
+    case 8:
+        Write64(addr, value);
+        break;
+    default:
+        UNREACHABLE();
+    }
+}
+
+} // Anonymous namespace
+
+Freezer::Freezer(Core::Timing::CoreTiming& core_timing) : core_timing(core_timing) {
+    event = core_timing.RegisterEvent(
+        "MemoryFreezer::FrameCallback",
+        [this](u64 userdata, s64 cycles_late) { FrameCallback(userdata, cycles_late); });
+    core_timing.ScheduleEvent(MEMORY_FREEZER_TICKS, event);
+}
+
+Freezer::~Freezer() {
+    core_timing.UnscheduleEvent(event, 0);
+}
+
+void Freezer::SetActive(bool active) {
+    if (!this->active.exchange(active)) {
+        FillEntryReads();
+        core_timing.ScheduleEvent(MEMORY_FREEZER_TICKS, event);
+        LOG_DEBUG(Common_Memory, "Memory freezer activated!");
+    } else {
+        LOG_DEBUG(Common_Memory, "Memory freezer deactivated!");
+    }
+}
+
+bool Freezer::IsActive() const {
+    return active.load();
+}
+
+void Freezer::Clear() {
+    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+
+    LOG_DEBUG(Common_Memory, "Clearing all frozen memory values.");
+
+    entries.clear();
+}
+
+u64 Freezer::Freeze(VAddr address, u8 width) {
+    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+
+    const auto current_value = MemoryReadWidth(width, address);
+    entries.push_back({address, width, current_value});
+
+    LOG_DEBUG(Common_Memory,
+              "Freezing memory for address={:016X}, width={:02X}, current_value={:016X}", address,
+              width, current_value);
+
+    return current_value;
+}
+
+void Freezer::Unfreeze(VAddr address) {
+    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+
+    LOG_DEBUG(Common_Memory, "Unfreezing memory for address={:016X}", address);
+
+    entries.erase(
+        std::remove_if(entries.begin(), entries.end(),
+                       [&address](const Entry& entry) { return entry.address == address; }),
+        entries.end());
+}
+
+bool Freezer::IsFrozen(VAddr address) {
+    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+
+    return std::find_if(entries.begin(), entries.end(), [&address](const Entry& entry) {
+               return entry.address == address;
+           }) != entries.end();
+}
+
+void Freezer::SetFrozenValue(VAddr address, u64 value) {
+    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+
+    const auto iter = std::find_if(entries.begin(), entries.end(), [&address](const Entry& entry) {
+        return entry.address == address;
+    });
+
+    if (iter == entries.end()) {
+        LOG_ERROR(Common_Memory,
+                  "Tried to set freeze value for address={:016X} that is not frozen!", address);
+        return;
+    }
+
+    LOG_DEBUG(Common_Memory,
+              "Manually overridden freeze value for address={:016X}, width={:02X} to value={:016X}",
+              iter->address, iter->width, value);
+    iter->value = value;
+}
+
+std::optional<Freezer::Entry> Freezer::GetEntry(VAddr address) {
+    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+
+    const auto iter = std::find_if(entries.begin(), entries.end(), [&address](const Entry& entry) {
+        return entry.address == address;
+    });
+
+    if (iter == entries.end()) {
+        return std::nullopt;
+    }
+
+    return *iter;
+}
+
+std::vector<Freezer::Entry> Freezer::GetEntries() {
+    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+
+    return entries;
+}
+
+void Freezer::FrameCallback(u64 userdata, s64 cycles_late) {
+    if (!active.load()) {
+        LOG_DEBUG(Common_Memory, "Memory freezer has been deactivated, ending callback events.");
+        return;
+    }
+
+    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+
+    for (const auto& entry : entries) {
+        LOG_DEBUG(Common_Memory,
+                  "Enforcing memory freeze at address={:016X}, value={:016X}, width={:02X}",
+                  entry.address, entry.value, entry.width);
+        MemoryWriteWidth(entry.width, entry.address, entry.value);
+    }
+
+    core_timing.ScheduleEvent(MEMORY_FREEZER_TICKS - cycles_late, event);
+}
+
+void Freezer::FillEntryReads() {
+    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+
+    LOG_DEBUG(Common_Memory, "Updating memory freeze entries to current values.");
+
+    for (auto& entry : entries) {
+        entry.value = MemoryReadWidth(entry.width, entry.address);
+    }
+}
+
+} // namespace Memory
diff --git a/src/core/memory/freezer.h b/src/core/memory/freezer.h
new file mode 100644
index 000000000..3e271793e
--- /dev/null
+++ b/src/core/memory/freezer.h
@@ -0,0 +1,58 @@
+// Copyright 2019 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <optional>
+#include <vector>
+#include "common/common_types.h"
+#include "core/core_timing.h"
+
+namespace Core {
+class System;
+} // namespace Core
+
+namespace Memory {
+
+// A class that will effectively freeze memory values.
+class Freezer {
+public:
+    struct Entry {
+        VAddr address;
+        u8 width;
+        u64 value;
+    };
+
+    Freezer(Core::Timing::CoreTiming& core_timing);
+    ~Freezer();
+
+    void SetActive(bool active);
+    bool IsActive() const;
+
+    void Clear();
+
+    u64 Freeze(VAddr address, u8 width);
+    void Unfreeze(VAddr address);
+
+    bool IsFrozen(VAddr address);
+    void SetFrozenValue(VAddr address, u64 value);
+
+    std::optional<Entry> GetEntry(VAddr address);
+
+    std::vector<Entry> GetEntries();
+
+private:
+    void FrameCallback(u64 userdata, s64 cycles_late);
+    void FillEntryReads();
+
+    std::atomic_bool active{false};
+
+    std::recursive_mutex entries_mutex;
+    std::vector<Entry> entries;
+
+    Core::Timing::EventType* event;
+    Core::Timing::CoreTiming& core_timing;
+};
+
+} // namespace Memory

From c9983ad9a71c9462319d27c3791e13fae9d73e46 Mon Sep 17 00:00:00 2001
From: Zach Hilman <zachhilman@gmail.com>
Date: Thu, 30 May 2019 16:57:23 -0400
Subject: [PATCH 2/4] freezer: Add documentation for methods

---
 src/core/memory/freezer.cpp | 40 +++++++++++++++++++------------------
 src/core/memory/freezer.h   | 39 ++++++++++++++++++++++++++----------
 2 files changed, 49 insertions(+), 30 deletions(-)

diff --git a/src/core/memory/freezer.cpp b/src/core/memory/freezer.cpp
index 1d0ccf328..6b20e8388 100644
--- a/src/core/memory/freezer.cpp
+++ b/src/core/memory/freezer.cpp
@@ -3,18 +3,20 @@
 // Refer to the license.txt file included.
 
 #include "common/assert.h"
+#include "common/logging/log.h"
 #include "core/core.h"
+#include "core/core_timing.h"
 #include "core/core_timing_util.h"
 #include "core/memory.h"
 #include "core/memory/freezer.h"
 
 namespace Memory {
 
-constexpr s64 MEMORY_FREEZER_TICKS = static_cast<s64>(Core::Timing::BASE_CLOCK_RATE / 60);
-
 namespace {
 
-u64 MemoryReadWidth(u8 width, VAddr addr) {
+constexpr s64 MEMORY_FREEZER_TICKS = static_cast<s64>(Core::Timing::BASE_CLOCK_RATE / 60);
+
+u64 MemoryReadWidth(u32 width, VAddr addr) {
     switch (width) {
     case 1:
         return Read8(addr);
@@ -30,7 +32,7 @@ u64 MemoryReadWidth(u8 width, VAddr addr) {
     }
 }
 
-void MemoryWriteWidth(u8 width, VAddr addr, u64 value) {
+void MemoryWriteWidth(u32 width, VAddr addr, u64 value) {
     switch (width) {
     case 1:
         Write8(addr, static_cast<u8>(value));
@@ -73,19 +75,19 @@ void Freezer::SetActive(bool active) {
 }
 
 bool Freezer::IsActive() const {
-    return active.load();
+    return active.load(std::memory_order_relaxed);
 }
 
 void Freezer::Clear() {
-    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+    std::lock_guard lock{entries_mutex};
 
     LOG_DEBUG(Common_Memory, "Clearing all frozen memory values.");
 
     entries.clear();
 }
 
-u64 Freezer::Freeze(VAddr address, u8 width) {
-    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+u64 Freezer::Freeze(VAddr address, u32 width) {
+    std::lock_guard lock{entries_mutex};
 
     const auto current_value = MemoryReadWidth(width, address);
     entries.push_back({address, width, current_value});
@@ -98,7 +100,7 @@ u64 Freezer::Freeze(VAddr address, u8 width) {
 }
 
 void Freezer::Unfreeze(VAddr address) {
-    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+    std::lock_guard lock{entries_mutex};
 
     LOG_DEBUG(Common_Memory, "Unfreezing memory for address={:016X}", address);
 
@@ -108,8 +110,8 @@ void Freezer::Unfreeze(VAddr address) {
         entries.end());
 }
 
-bool Freezer::IsFrozen(VAddr address) {
-    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+bool Freezer::IsFrozen(VAddr address) const {
+    std::lock_guard lock{entries_mutex};
 
     return std::find_if(entries.begin(), entries.end(), [&address](const Entry& entry) {
                return entry.address == address;
@@ -117,7 +119,7 @@ bool Freezer::IsFrozen(VAddr address) {
 }
 
 void Freezer::SetFrozenValue(VAddr address, u64 value) {
-    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+    std::lock_guard lock{entries_mutex};
 
     const auto iter = std::find_if(entries.begin(), entries.end(), [&address](const Entry& entry) {
         return entry.address == address;
@@ -135,8 +137,8 @@ void Freezer::SetFrozenValue(VAddr address, u64 value) {
     iter->value = value;
 }
 
-std::optional<Freezer::Entry> Freezer::GetEntry(VAddr address) {
-    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+std::optional<Freezer::Entry> Freezer::GetEntry(VAddr address) const {
+    std::lock_guard lock{entries_mutex};
 
     const auto iter = std::find_if(entries.begin(), entries.end(), [&address](const Entry& entry) {
         return entry.address == address;
@@ -149,19 +151,19 @@ std::optional<Freezer::Entry> Freezer::GetEntry(VAddr address) {
     return *iter;
 }
 
-std::vector<Freezer::Entry> Freezer::GetEntries() {
-    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+std::vector<Freezer::Entry> Freezer::GetEntries() const {
+    std::lock_guard lock{entries_mutex};
 
     return entries;
 }
 
 void Freezer::FrameCallback(u64 userdata, s64 cycles_late) {
-    if (!active.load()) {
+    if (!IsActive()) {
         LOG_DEBUG(Common_Memory, "Memory freezer has been deactivated, ending callback events.");
         return;
     }
 
-    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+    std::lock_guard lock{entries_mutex};
 
     for (const auto& entry : entries) {
         LOG_DEBUG(Common_Memory,
@@ -174,7 +176,7 @@ void Freezer::FrameCallback(u64 userdata, s64 cycles_late) {
 }
 
 void Freezer::FillEntryReads() {
-    std::lock_guard<std::recursive_mutex> lock(entries_mutex);
+    std::lock_guard lock{entries_mutex};
 
     LOG_DEBUG(Common_Memory, "Updating memory freeze entries to current values.");
 
diff --git a/src/core/memory/freezer.h b/src/core/memory/freezer.h
index 3e271793e..b0c610039 100644
--- a/src/core/memory/freezer.h
+++ b/src/core/memory/freezer.h
@@ -4,14 +4,16 @@
 
 #pragma once
 
+#include <atomic>
+#include <mutex>
 #include <optional>
 #include <vector>
 #include "common/common_types.h"
-#include "core/core_timing.h"
 
-namespace Core {
-class System;
-} // namespace Core
+namespace Core::Timing {
+class CoreTiming;
+struct EventType;
+} // namespace Core::Timing
 
 namespace Memory {
 
@@ -20,27 +22,42 @@ class Freezer {
 public:
     struct Entry {
         VAddr address;
-        u8 width;
+        u32 width;
         u64 value;
     };
 
-    Freezer(Core::Timing::CoreTiming& core_timing);
+    explicit Freezer(Core::Timing::CoreTiming& core_timing);
     ~Freezer();
 
+    // Enables or disables the entire memory freezer.
     void SetActive(bool active);
+
+    // Returns whether or not the freezer is active.
     bool IsActive() const;
 
+    // Removes all entries from the freezer.
     void Clear();
 
-    u64 Freeze(VAddr address, u8 width);
+    // Freezes a value to its current memory address. The value the memory is kept at will be the
+    // value that is read during this function. Width can be 1, 2, 4, or 8 (in bytes).
+    u64 Freeze(VAddr address, u32 width);
+
+    // Unfreezes the memory value at address. If the address isn't frozen, this is a no-op.
     void Unfreeze(VAddr address);
 
-    bool IsFrozen(VAddr address);
+    // Returns whether or not the address is frozen.
+    bool IsFrozen(VAddr address) const;
+
+    // Sets the value that address should be frozen to. This doesn't change the width set by using
+    // Freeze(). If the value isn't frozen, this will not freeze it and is thus a no-op.
     void SetFrozenValue(VAddr address, u64 value);
 
-    std::optional<Entry> GetEntry(VAddr address);
+    // Returns the entry corresponding to the address if the address is frozen, otherwise
+    // std::nullopt.
+    std::optional<Entry> GetEntry(VAddr address) const;
 
-    std::vector<Entry> GetEntries();
+    // Returns all the entries in the freezer, an empty vector means nothing is frozen.
+    std::vector<Entry> GetEntries() const;
 
 private:
     void FrameCallback(u64 userdata, s64 cycles_late);
@@ -48,7 +65,7 @@ private:
 
     std::atomic_bool active{false};
 
-    std::recursive_mutex entries_mutex;
+    mutable std::mutex entries_mutex;
     std::vector<Entry> entries;
 
     Core::Timing::EventType* event;

From ed82fa3a91fc84f7f906b898d8f71e15fb42c16e Mon Sep 17 00:00:00 2001
From: Zach Hilman <zachhilman@gmail.com>
Date: Fri, 7 Jun 2019 11:11:11 -0400
Subject: [PATCH 3/4] core: Move Freezer class to tools namespace

---
 src/core/CMakeLists.txt                |  4 ++--
 src/core/core.cpp                      |  4 ++--
 src/core/{memory => tools}/freezer.cpp | 22 +++++++++++-----------
 src/core/{memory => tools}/freezer.h   |  4 ++--
 4 files changed, 17 insertions(+), 17 deletions(-)
 rename src/core/{memory => tools}/freezer.cpp (91%)
 rename src/core/{memory => tools}/freezer.h (98%)

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index c17528134..59b64407a 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -454,8 +454,6 @@ add_library(core STATIC
     loader/nsp.h
     loader/xci.cpp
     loader/xci.h
-    memory/freezer.cpp
-    memory/freezer.h
     memory.cpp
     memory.h
     memory_setup.h
@@ -465,6 +463,8 @@ add_library(core STATIC
     settings.h
     telemetry_session.cpp
     telemetry_session.h
+    tools/freezer.cpp
+    tools/freezer.h
 )
 
 create_target_directory_groups(core)
diff --git a/src/core/core.cpp b/src/core/core.cpp
index 94ebe0995..48d953442 100644
--- a/src/core/core.cpp
+++ b/src/core/core.cpp
@@ -28,10 +28,10 @@
 #include "core/hle/service/service.h"
 #include "core/hle/service/sm/sm.h"
 #include "core/loader/loader.h"
-#include "core/memory/freezer.h"
 #include "core/perf_stats.h"
 #include "core/settings.h"
 #include "core/telemetry_session.h"
+#include "core/tools/freezer.h"
 #include "file_sys/cheat_engine.h"
 #include "video_core/debug_utils/debug_utils.h"
 #include "video_core/renderer_base.h"
@@ -244,7 +244,7 @@ struct System::Impl {
     bool is_powered_on = false;
 
     std::unique_ptr<FileSys::CheatEngine> cheat_engine;
-    std::unique_ptr<Memory::Freezer> memory_freezer;
+    std::unique_ptr<Tools::Freezer> memory_freezer;
 
     /// Frontend applets
     Service::AM::Applets::AppletManager applet_manager;
diff --git a/src/core/memory/freezer.cpp b/src/core/tools/freezer.cpp
similarity index 91%
rename from src/core/memory/freezer.cpp
rename to src/core/tools/freezer.cpp
index 6b20e8388..17f050068 100644
--- a/src/core/memory/freezer.cpp
+++ b/src/core/tools/freezer.cpp
@@ -8,9 +8,9 @@
 #include "core/core_timing.h"
 #include "core/core_timing_util.h"
 #include "core/memory.h"
-#include "core/memory/freezer.h"
+#include "core/tools/freezer.h"
 
-namespace Memory {
+namespace Tools {
 
 namespace {
 
@@ -19,13 +19,13 @@ constexpr s64 MEMORY_FREEZER_TICKS = static_cast<s64>(Core::Timing::BASE_CLOCK_R
 u64 MemoryReadWidth(u32 width, VAddr addr) {
     switch (width) {
     case 1:
-        return Read8(addr);
+        return Memory::Read8(addr);
     case 2:
-        return Read16(addr);
+        return Memory::Read16(addr);
     case 4:
-        return Read32(addr);
+        return Memory::Read32(addr);
     case 8:
-        return Read64(addr);
+        return Memory::Read64(addr);
     default:
         UNREACHABLE();
         return 0;
@@ -35,16 +35,16 @@ u64 MemoryReadWidth(u32 width, VAddr addr) {
 void MemoryWriteWidth(u32 width, VAddr addr, u64 value) {
     switch (width) {
     case 1:
-        Write8(addr, static_cast<u8>(value));
+        Memory::Write8(addr, static_cast<u8>(value));
         break;
     case 2:
-        Write16(addr, static_cast<u16>(value));
+        Memory::Write16(addr, static_cast<u16>(value));
         break;
     case 4:
-        Write32(addr, static_cast<u32>(value));
+        Memory::Write32(addr, static_cast<u32>(value));
         break;
     case 8:
-        Write64(addr, value);
+        Memory::Write64(addr, value);
         break;
     default:
         UNREACHABLE();
@@ -185,4 +185,4 @@ void Freezer::FillEntryReads() {
     }
 }
 
-} // namespace Memory
+} // namespace Tools
diff --git a/src/core/memory/freezer.h b/src/core/tools/freezer.h
similarity index 98%
rename from src/core/memory/freezer.h
rename to src/core/tools/freezer.h
index b0c610039..5edd049c1 100644
--- a/src/core/memory/freezer.h
+++ b/src/core/tools/freezer.h
@@ -15,7 +15,7 @@ class CoreTiming;
 struct EventType;
 } // namespace Core::Timing
 
-namespace Memory {
+namespace Tools {
 
 // A class that will effectively freeze memory values.
 class Freezer {
@@ -72,4 +72,4 @@ private:
     Core::Timing::CoreTiming& core_timing;
 };
 
-} // namespace Memory
+} // namespace Tools

From 4111971cbdae3a4700156a802f8e0c9309a9cf1e Mon Sep 17 00:00:00 2001
From: Zach Hilman <zachhilman@gmail.com>
Date: Mon, 10 Jun 2019 14:11:06 -0400
Subject: [PATCH 4/4] freezer: Update documentation

---
 src/core/tools/freezer.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/core/tools/freezer.h b/src/core/tools/freezer.h
index 5edd049c1..b58de5472 100644
--- a/src/core/tools/freezer.h
+++ b/src/core/tools/freezer.h
@@ -17,7 +17,14 @@ struct EventType;
 
 namespace Tools {
 
-// A class that will effectively freeze memory values.
+/**
+ * This class allows the user to prevent an application from writing new values to certain memory
+ * locations. This has a variety of uses when attempting to reverse a game.
+ *
+ * One example could be a cheat to prevent Mario from taking damage in SMO. One could freeze the
+ * memory address that the game uses to store Mario's health so when he takes damage (and the game
+ * tries to write the new health value to memory), the value won't change.
+ */
 class Freezer {
 public:
     struct Entry {