ARM/Memory: Correct Exclusive Monitor and Implement Exclusive Memory Writes.

12 files changed, 325 insertions, 24 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index 3cc17d0e9..d120c8d3d 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -98,6 +98,8 @@ add_library(common STATIC
     algorithm.h
     alignment.h
     assert.h
+    atomic_ops.cpp
+    atomic_ops.h
     detached_tasks.cpp
     detached_tasks.h
     bit_field.h
diff --git a/src/common/atomic_ops.cpp b/src/common/atomic_ops.cpp
new file mode 100644
index 000000000..65cdfb4fd
--- /dev/null
+++ b/src/common/atomic_ops.cpp
@@ -0,0 +1,70 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <cstring>
+
+#include "common/atomic_ops.h"
+
+#if _MSC_VER
+#include <intrin.h>
+#endif
+
+namespace Common {
+
+#if _MSC_VER
+
+bool AtomicCompareAndSwap(u8 volatile* pointer, u8 value, u8 expected) {
+    u8 result = _InterlockedCompareExchange8((char*)pointer, value, expected);
+    return result == expected;
+}
+
+bool AtomicCompareAndSwap(u16 volatile* pointer, u16 value, u16 expected) {
+    u16 result = _InterlockedCompareExchange16((short*)pointer, value, expected);
+    return result == expected;
+}
+
+bool AtomicCompareAndSwap(u32 volatile* pointer, u32 value, u32 expected) {
+    u32 result = _InterlockedCompareExchange((long*)pointer, value, expected);
+    return result == expected;
+}
+
+bool AtomicCompareAndSwap(u64 volatile* pointer, u64 value, u64 expected) {
+    u64 result = _InterlockedCompareExchange64((__int64*)pointer, value, expected);
+    return result == expected;
+}
+
+bool AtomicCompareAndSwap(u64 volatile* pointer, u128 value, u128 expected) {
+    return _InterlockedCompareExchange128((__int64*)pointer, value[1], value[0], (__int64*)expected.data()) != 0;
+}
+
+
+#else
+
+bool AtomicCompareAndSwap(u8 volatile* pointer, u8 value, u8 expected) {
+    return __sync_bool_compare_and_swap (pointer, value, expected);
+}
+
+bool AtomicCompareAndSwap(u16 volatile* pointer, u16 value, u16 expected) {
+    return __sync_bool_compare_and_swap (pointer, value, expected);
+}
+
+bool AtomicCompareAndSwap(u32 volatile* pointer, u32 value, u32 expected) {
+    return __sync_bool_compare_and_swap (pointer, value, expected);
+}
+
+bool AtomicCompareAndSwap(u64 volatile* pointer, u64 value, u64 expected) {
+    return __sync_bool_compare_and_swap (pointer, value, expected);
+}
+
+bool AtomicCompareAndSwap(u64 volatile* pointer, u128 value, u128 expected) {
+    unsigned __int128 value_a;
+    unsigned __int128 expected_a;
+    std::memcpy(&value_a, value.data(), sizeof(u128));
+    std::memcpy(&expected_a, expected.data(), sizeof(u128));
+    return __sync_bool_compare_and_swap ((unsigned __int128*)pointer, value_a, expected_a);
+}
+
+#endif
+
+} // namespace Common
diff --git a/src/common/atomic_ops.h b/src/common/atomic_ops.h
new file mode 100644
index 000000000..22cb3a402
--- /dev/null
+++ b/src/common/atomic_ops.h
@@ -0,0 +1,17 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "common/common_types.h"
+
+namespace Common {
+
+bool AtomicCompareAndSwap(u8 volatile * pointer, u8 value, u8 expected);
+bool AtomicCompareAndSwap(u16 volatile* pointer, u16 value, u16 expected);
+bool AtomicCompareAndSwap(u32 volatile* pointer, u32 value, u32 expected);
+bool AtomicCompareAndSwap(u64 volatile* pointer, u64 value, u64 expected);
+bool AtomicCompareAndSwap(u64 volatile* pointer, u128 value, u128 expected);
+
+} // namespace Common
diff --git a/src/core/arm/dynarmic/arm_dynarmic_64.cpp b/src/core/arm/dynarmic/arm_dynarmic_64.cpp
index 5e316ffd4..a22c22bf0 100644
--- a/src/core/arm/dynarmic/arm_dynarmic_64.cpp
+++ b/src/core/arm/dynarmic/arm_dynarmic_64.cpp
@@ -66,6 +66,22 @@ public:
         memory.Write64(vaddr + 8, value[1]);
     }
 
+    bool MemoryWriteExclusive8(u64 vaddr, std::uint8_t value, std::uint8_t expected) override {
+        return parent.system.Memory().WriteExclusive8(vaddr, value, expected);
+    }
+    bool MemoryWriteExclusive16(u64 vaddr, std::uint16_t value, std::uint16_t expected) override {
+        return parent.system.Memory().WriteExclusive16(vaddr, value, expected);
+    }
+    bool MemoryWriteExclusive32(u64 vaddr, std::uint32_t value, std::uint32_t expected) override {
+        return parent.system.Memory().WriteExclusive32(vaddr, value, expected);
+    }
+    bool MemoryWriteExclusive64(u64 vaddr, std::uint64_t value, std::uint64_t expected) override {
+        return parent.system.Memory().WriteExclusive64(vaddr, value, expected);
+    }
+    bool MemoryWriteExclusive128(u64 vaddr, Vector value, Vector expected) override {
+        return parent.system.Memory().WriteExclusive128(vaddr, value, expected);
+    }
+
     void InterpreterFallback(u64 pc, std::size_t num_instructions) override {
         LOG_INFO(Core_ARM, "Unicorn fallback @ 0x{:X} for {} instructions (instr = {:08X})", pc,
                  num_instructions, MemoryReadCode(pc));
@@ -284,9 +300,29 @@ DynarmicExclusiveMonitor::DynarmicExclusiveMonitor(Memory::Memory& memory, std::
 
 DynarmicExclusiveMonitor::~DynarmicExclusiveMonitor() = default;
 
-void DynarmicExclusiveMonitor::SetExclusive(std::size_t core_index, VAddr addr) {
-    // Size doesn't actually matter.
-    monitor.Mark(core_index, addr, 16);
+void DynarmicExclusiveMonitor::SetExclusive8(std::size_t core_index, VAddr addr) {
+    monitor.Mark<u8>(core_index, addr, 1, [&]() -> u8 { return memory.Read8(addr); });
+}
+
+void DynarmicExclusiveMonitor::SetExclusive16(std::size_t core_index, VAddr addr) {
+    monitor.Mark<u16>(core_index, addr, 2, [&]() -> u16 { return memory.Read16(addr); });
+}
+
+void DynarmicExclusiveMonitor::SetExclusive32(std::size_t core_index, VAddr addr) {
+    monitor.Mark<u32>(core_index, addr, 4, [&]() -> u32 { return memory.Read32(addr); });
+}
+
+void DynarmicExclusiveMonitor::SetExclusive64(std::size_t core_index, VAddr addr) {
+    monitor.Mark<u64>(core_index, addr, 8, [&]() -> u64 { return memory.Read64(addr); });
+}
+
+void DynarmicExclusiveMonitor::SetExclusive128(std::size_t core_index, VAddr addr) {
+    monitor.Mark<u128>(core_index, addr, 16, [&]() -> u128 {
+        u128 result;
+        result[0] = memory.Read64(addr);
+        result[1] = memory.Read64(addr + 8);
+        return result;
+    });
 }
 
 void DynarmicExclusiveMonitor::ClearExclusive() {
@@ -294,28 +330,32 @@ void DynarmicExclusiveMonitor::ClearExclusive() {
 }
 
 bool DynarmicExclusiveMonitor::ExclusiveWrite8(std::size_t core_index, VAddr vaddr, u8 value) {
-    return monitor.DoExclusiveOperation(core_index, vaddr, 1, [&] { memory.Write8(vaddr, value); });
+    return monitor.DoExclusiveOperation<u8>(core_index, vaddr, 1, [&](u8 expected) -> bool {
+        return memory.WriteExclusive8(vaddr, value, expected);
+    });
 }
 
 bool DynarmicExclusiveMonitor::ExclusiveWrite16(std::size_t core_index, VAddr vaddr, u16 value) {
-    return monitor.DoExclusiveOperation(core_index, vaddr, 2,
-                                        [&] { memory.Write16(vaddr, value); });
+    return monitor.DoExclusiveOperation<u16>(core_index, vaddr, 2, [&](u16 expected) -> bool {
+        return memory.WriteExclusive16(vaddr, value, expected);
+    });
 }
 
 bool DynarmicExclusiveMonitor::ExclusiveWrite32(std::size_t core_index, VAddr vaddr, u32 value) {
-    return monitor.DoExclusiveOperation(core_index, vaddr, 4,
-                                        [&] { memory.Write32(vaddr, value); });
+    return monitor.DoExclusiveOperation<u32>(core_index, vaddr, 4, [&](u32 expected) -> bool {
+        return memory.WriteExclusive32(vaddr, value, expected);
+    });
 }
 
 bool DynarmicExclusiveMonitor::ExclusiveWrite64(std::size_t core_index, VAddr vaddr, u64 value) {
-    return monitor.DoExclusiveOperation(core_index, vaddr, 8,
-                                        [&] { memory.Write64(vaddr, value); });
+    return monitor.DoExclusiveOperation<u64>(core_index, vaddr, 8, [&](u64 expected) -> bool {
+        return memory.WriteExclusive64(vaddr, value, expected);
+    });
 }
 
 bool DynarmicExclusiveMonitor::ExclusiveWrite128(std::size_t core_index, VAddr vaddr, u128 value) {
-    return monitor.DoExclusiveOperation(core_index, vaddr, 16, [&] {
-        memory.Write64(vaddr + 0, value[0]);
-        memory.Write64(vaddr + 8, value[1]);
+    return monitor.DoExclusiveOperation<u128>(core_index, vaddr, 16, [&](u128 expected) -> bool {
+        return memory.WriteExclusive128(vaddr, value, expected);
     });
 }
 
diff --git a/src/core/arm/dynarmic/arm_dynarmic_64.h b/src/core/arm/dynarmic/arm_dynarmic_64.h
index 9e94b58c2..3ead59f16 100644
--- a/src/core/arm/dynarmic/arm_dynarmic_64.h
+++ b/src/core/arm/dynarmic/arm_dynarmic_64.h
@@ -82,7 +82,11 @@ public:
     explicit DynarmicExclusiveMonitor(Memory::Memory& memory, std::size_t core_count);
     ~DynarmicExclusiveMonitor() override;
 
-    void SetExclusive(std::size_t core_index, VAddr addr) override;
+    void SetExclusive8(std::size_t core_index, VAddr addr) override;
+    void SetExclusive16(std::size_t core_index, VAddr addr) override;
+    void SetExclusive32(std::size_t core_index, VAddr addr) override;
+    void SetExclusive64(std::size_t core_index, VAddr addr) override;
+    void SetExclusive128(std::size_t core_index, VAddr addr) override;
     void ClearExclusive() override;
 
     bool ExclusiveWrite8(std::size_t core_index, VAddr vaddr, u8 value) override;
diff --git a/src/core/arm/exclusive_monitor.h b/src/core/arm/exclusive_monitor.h
index ccd73b80f..2ee312eee 100644
--- a/src/core/arm/exclusive_monitor.h
+++ b/src/core/arm/exclusive_monitor.h
@@ -18,7 +18,11 @@ class ExclusiveMonitor {
 public:
     virtual ~ExclusiveMonitor();
 
-    virtual void SetExclusive(std::size_t core_index, VAddr addr) = 0;
+    virtual void SetExclusive8(std::size_t core_index, VAddr addr) = 0;
+    virtual void SetExclusive16(std::size_t core_index, VAddr addr) = 0;
+    virtual void SetExclusive32(std::size_t core_index, VAddr addr) = 0;
+    virtual void SetExclusive64(std::size_t core_index, VAddr addr) = 0;
+    virtual void SetExclusive128(std::size_t core_index, VAddr addr) = 0;
     virtual void ClearExclusive() = 0;
 
     virtual bool ExclusiveWrite8(std::size_t core_index, VAddr vaddr, u8 value) = 0;
diff --git a/src/core/hle/kernel/address_arbiter.cpp b/src/core/hle/kernel/address_arbiter.cpp
index ebabde921..07acabc1d 100644
--- a/src/core/hle/kernel/address_arbiter.cpp
+++ b/src/core/hle/kernel/address_arbiter.cpp
@@ -90,7 +90,7 @@ ResultCode AddressArbiter::IncrementAndSignalToAddressIfEqual(VAddr address, s32
     auto& monitor = system.Monitor();
     u32 current_value;
     do {
-        monitor.SetExclusive(current_core, address);
+        monitor.SetExclusive32(current_core, address);
         current_value = memory.Read32(address);
 
         if (current_value != value) {
@@ -120,7 +120,7 @@ ResultCode AddressArbiter::ModifyByWaitingCountAndSignalToAddressIfEqual(VAddr a
     auto& monitor = system.Monitor();
     s32 updated_value;
     do {
-        monitor.SetExclusive(current_core, address);
+        monitor.SetExclusive32(current_core, address);
         updated_value = memory.Read32(address);
 
         if (updated_value != value) {
@@ -191,7 +191,7 @@ ResultCode AddressArbiter::WaitForAddressIfLessThan(VAddr address, s32 value, s6
         const std::size_t current_core = system.CurrentCoreIndex();
         auto& monitor = system.Monitor();
         do {
-            monitor.SetExclusive(current_core, address);
+            monitor.SetExclusive32(current_core, address);
             current_value = static_cast<s32>(memory.Read32(address));
             if (should_decrement) {
                 decrement_value = current_value - 1;
diff --git a/src/core/hle/kernel/mutex.cpp b/src/core/hle/kernel/mutex.cpp
index ebe3f6050..16c95782a 100644
--- a/src/core/hle/kernel/mutex.cpp
+++ b/src/core/hle/kernel/mutex.cpp
@@ -10,6 +10,7 @@
 #include "common/logging/log.h"
 #include "core/core.h"
 #include "core/arm/exclusive_monitor.h"
+#include "core/core.h"
 #include "core/hle/kernel/errors.h"
 #include "core/hle/kernel/handle_table.h"
 #include "core/hle/kernel/kernel.h"
@@ -138,7 +139,7 @@ std::pair<ResultCode, std::shared_ptr<Thread>> Mutex::Unlock(std::shared_ptr<Thr
     const std::size_t current_core = system.CurrentCoreIndex();
     if (new_owner == nullptr) {
         do {
-            monitor.SetExclusive(current_core, address);
+            monitor.SetExclusive32(current_core, address);
         } while (!monitor.ExclusiveWrite32(current_core, address, 0));
         return {RESULT_SUCCESS, nullptr};
     }
@@ -154,7 +155,7 @@ std::pair<ResultCode, std::shared_ptr<Thread>> Mutex::Unlock(std::shared_ptr<Thr
     new_owner->ResumeFromWait();
 
     do {
-        monitor.SetExclusive(current_core, address);
+        monitor.SetExclusive32(current_core, address);
     } while (!monitor.ExclusiveWrite32(current_core, address, mutex_value));
     return {RESULT_SUCCESS, new_owner};
 }
diff --git a/src/core/hle/kernel/svc.cpp b/src/core/hle/kernel/svc.cpp
index da2f90a1d..371beed0d 100644
--- a/src/core/hle/kernel/svc.cpp
+++ b/src/core/hle/kernel/svc.cpp
@@ -1641,7 +1641,7 @@ static void SignalProcessWideKey(Core::System& system, VAddr condition_variable_
         u32 update_val = 0;
         const VAddr mutex_address = thread->GetMutexWaitAddress();
         do {
-            monitor.SetExclusive(current_core, mutex_address);
+            monitor.SetExclusive32(current_core, mutex_address);
 
             // If the mutex is not yet acquired, acquire it.
             mutex_val = memory.Read32(mutex_address);
diff --git a/src/core/hle/kernel/thread.cpp b/src/core/hle/kernel/thread.cpp
index b99e3b7a5..51cc5dcca 100644
--- a/src/core/hle/kernel/thread.cpp
+++ b/src/core/hle/kernel/thread.cpp
@@ -236,7 +236,7 @@ ResultVal<std::shared_ptr<Thread>> Thread::Create(Core::System& system, ThreadTy
         ResetThreadContext64(thread->context_64, stack_top, entry_point, arg);
     }
     thread->host_context =
-        std::make_shared<Common::Fiber>(std::move(thread_start_func), thread_start_parameter);

+        std::make_shared<Common::Fiber>(std::move(thread_start_func), thread_start_parameter);
 
     return MakeResult<std::shared_ptr<Thread>>(std::move(thread));
 }
@@ -412,12 +412,12 @@ ResultCode Thread::SetActivity(ThreadActivity value) {
     }
 
     if (value == ThreadActivity::Paused) {
-        if (pausing_state & static_cast<u32>(ThreadSchedFlags::ThreadPauseFlag) != 0) {
+        if ((pausing_state & static_cast<u32>(ThreadSchedFlags::ThreadPauseFlag)) != 0) {
             return ERR_INVALID_STATE;
         }
         AddSchedulingFlag(ThreadSchedFlags::ThreadPauseFlag);
     } else {
-        if (pausing_state & static_cast<u32>(ThreadSchedFlags::ThreadPauseFlag) == 0) {
+        if ((pausing_state & static_cast<u32>(ThreadSchedFlags::ThreadPauseFlag)) == 0) {
             return ERR_INVALID_STATE;
         }
         RemoveSchedulingFlag(ThreadSchedFlags::ThreadPauseFlag);
diff --git a/src/core/memory.cpp b/src/core/memory.cpp
index 66634596d..4cb5d05e5 100644
--- a/src/core/memory.cpp
+++ b/src/core/memory.cpp
@@ -8,6 +8,7 @@
 #include <utility>
 
 #include "common/assert.h"
+#include "common/atomic_ops.h"
 #include "common/common_types.h"
 #include "common/logging/log.h"
 #include "common/page_table.h"
@@ -176,6 +177,22 @@ struct Memory::Impl {
         }
     }
 
+    bool WriteExclusive8(const VAddr addr, const u8 data, const u8 expected) {
+        return WriteExclusive<u8>(addr, data, expected);
+    }
+
+    bool WriteExclusive16(const VAddr addr, const u16 data, const u16 expected) {
+        return WriteExclusive<u16_le>(addr, data, expected);
+    }
+
+    bool WriteExclusive32(const VAddr addr, const u32 data, const u32 expected) {
+        return WriteExclusive<u32_le>(addr, data, expected);
+    }
+
+    bool WriteExclusive64(const VAddr addr, const u64 data, const u64 expected) {
+        return WriteExclusive<u64_le>(addr, data, expected);
+    }
+
     std::string ReadCString(VAddr vaddr, std::size_t max_length) {
         std::string string;
         string.reserve(max_length);
@@ -679,6 +696,67 @@ struct Memory::Impl {
         }
     }
 
+    template <typename T>
+    bool WriteExclusive(const VAddr vaddr, const T data, const T expected) {
+        u8* page_pointer = current_page_table->pointers[vaddr >> PAGE_BITS];
+        if (page_pointer != nullptr) {
+            // NOTE: Avoid adding any extra logic to this fast-path block
+            T volatile* pointer = reinterpret_cast<T volatile*>(&page_pointer[vaddr]);
+            return Common::AtomicCompareAndSwap(pointer, data, expected);
+        }
+
+        const Common::PageType type = current_page_table->attributes[vaddr >> PAGE_BITS];
+        switch (type) {
+        case Common::PageType::Unmapped:
+            LOG_ERROR(HW_Memory, "Unmapped Write{} 0x{:08X} @ 0x{:016X}", sizeof(data) * 8,
+                      static_cast<u32>(data), vaddr);
+            return true;
+        case Common::PageType::Memory:
+            ASSERT_MSG(false, "Mapped memory page without a pointer @ {:016X}", vaddr);
+            break;
+        case Common::PageType::RasterizerCachedMemory: {
+            u8* host_ptr{GetPointerFromVMA(vaddr)};
+            system.GPU().InvalidateRegion(ToCacheAddr(host_ptr), sizeof(T));
+            T volatile* pointer = reinterpret_cast<T volatile*>(&host_ptr);
+            return Common::AtomicCompareAndSwap(pointer, data, expected);
+            break;
+        }
+        default:
+            UNREACHABLE();
+        }
+        return true;
+    }
+
+    bool WriteExclusive128(const VAddr vaddr, const u128 data, const u128 expected) {
+        u8* const page_pointer = current_page_table->pointers[vaddr >> PAGE_BITS];
+        if (page_pointer != nullptr) {
+            // NOTE: Avoid adding any extra logic to this fast-path block
+            u64 volatile* pointer = reinterpret_cast<u64 volatile*>(&page_pointer[vaddr]);
+            return Common::AtomicCompareAndSwap(pointer, data, expected);
+        }
+
+        const Common::PageType type = current_page_table->attributes[vaddr >> PAGE_BITS];
+        switch (type) {
+        case Common::PageType::Unmapped:
+            LOG_ERROR(HW_Memory, "Unmapped Write{} 0x{:08X} @ 0x{:016X}{:016X}", sizeof(data) * 8,
+                      static_cast<u64>(data[1]), static_cast<u64>(data[0]), vaddr);
+            return true;
+        case Common::PageType::Memory:
+            ASSERT_MSG(false, "Mapped memory page without a pointer @ {:016X}", vaddr);
+            break;
+        case Common::PageType::RasterizerCachedMemory: {
+            u8* host_ptr{GetPointerFromVMA(vaddr)};
+            system.GPU().InvalidateRegion(ToCacheAddr(host_ptr), sizeof(u128));
+            u64 volatile* pointer = reinterpret_cast<u64 volatile*>(&host_ptr);
+            return Common::AtomicCompareAndSwap(pointer, data, expected);
+            break;
+        }
+        default:
+            UNREACHABLE();
+        }
+        return true;
+    }
+
     Common::PageTable* current_page_table = nullptr;
     Core::System& system;
 };
@@ -761,6 +839,26 @@ void Memory::Write64(VAddr addr, u64 data) {
     impl->Write64(addr, data);
 }
 
+bool Memory::WriteExclusive8(VAddr addr, u8 data, u8 expected) {
+    return impl->WriteExclusive8(addr, data, expected);
+}
+
+bool Memory::WriteExclusive16(VAddr addr, u16 data, u16 expected) {
+    return impl->WriteExclusive16(addr, data, expected);
+}
+
+bool Memory::WriteExclusive32(VAddr addr, u32 data, u32 expected) {
+    return impl->WriteExclusive32(addr, data, expected);
+}
+
+bool Memory::WriteExclusive64(VAddr addr, u64 data, u64 expected) {
+    return impl->WriteExclusive64(addr, data, expected);
+}
+
+bool Memory::WriteExclusive128(VAddr addr, u128 data, u128 expected) {
+    return impl->WriteExclusive128(addr, data, expected);
+}
+
 std::string Memory::ReadCString(VAddr vaddr, std::size_t max_length) {
     return impl->ReadCString(vaddr, max_length);
 }
diff --git a/src/core/memory.h b/src/core/memory.h
index 93f0c1d6c..4a1cc63f4 100644
--- a/src/core/memory.h
+++ b/src/core/memory.h
@@ -245,6 +245,71 @@ public:
     void Write64(VAddr addr, u64 data);
 
     /**
+     * Writes a 8-bit unsigned integer to the given virtual address in
+     * the current process' address space if and only if the address contains
+     * the expected value. This operation is atomic.
+     *
+     * @param addr The virtual address to write the 8-bit unsigned integer to.
+     * @param data The 8-bit unsigned integer to write to the given virtual address.
+     * @param expected The 8-bit unsigned integer to check against the given virtual address.
+     *
+     * @post The memory range [addr, sizeof(data)) contains the given data value.
+     */
+    bool WriteExclusive8(VAddr addr, u8 data, u8 expected);
+
+    /**
+     * Writes a 16-bit unsigned integer to the given virtual address in
+     * the current process' address space if and only if the address contains
+     * the expected value. This operation is atomic.
+     *
+     * @param addr The virtual address to write the 16-bit unsigned integer to.
+     * @param data The 16-bit unsigned integer to write to the given virtual address.
+     * @param expected The 16-bit unsigned integer to check against the given virtual address.
+     *
+     * @post The memory range [addr, sizeof(data)) contains the given data value.
+     */
+    bool WriteExclusive16(VAddr addr, u16 data, u16 expected);
+
+    /**
+     * Writes a 32-bit unsigned integer to the given virtual address in
+     * the current process' address space if and only if the address contains
+     * the expected value. This operation is atomic.
+     *
+     * @param addr The virtual address to write the 32-bit unsigned integer to.
+     * @param data The 32-bit unsigned integer to write to the given virtual address.
+     * @param expected The 32-bit unsigned integer to check against the given virtual address.
+     *
+     * @post The memory range [addr, sizeof(data)) contains the given data value.
+     */
+    bool WriteExclusive32(VAddr addr, u32 data, u32 expected);
+
+    /**
+     * Writes a 64-bit unsigned integer to the given virtual address in
+     * the current process' address space if and only if the address contains
+     * the expected value. This operation is atomic.
+     *
+     * @param addr The virtual address to write the 64-bit unsigned integer to.
+     * @param data The 64-bit unsigned integer to write to the given virtual address.
+     * @param expected The 64-bit unsigned integer to check against the given virtual address.
+     *
+     * @post The memory range [addr, sizeof(data)) contains the given data value.
+     */
+    bool WriteExclusive64(VAddr addr, u64 data, u64 expected);
+
+    /**
+     * Writes a 128-bit unsigned integer to the given virtual address in
+     * the current process' address space if and only if the address contains
+     * the expected value. This operation is atomic.
+     *
+     * @param addr The virtual address to write the 128-bit unsigned integer to.
+     * @param data The 128-bit unsigned integer to write to the given virtual address.
+     * @param expected The 128-bit unsigned integer to check against the given virtual address.
+     *
+     * @post The memory range [addr, sizeof(data)) contains the given data value.
+     */
+    bool WriteExclusive128(VAddr addr, u128 data, u128 expected);
+
+    /**
      * Reads a null-terminated string from the given virtual address.
      * This function will continually read characters until either:
      *