From 81cb4d3c7f5f959ad6ed3710171517334af23e22 Mon Sep 17 00:00:00 2001
From: bunnei <bunneidev@gmail.com>
Date: Sun, 5 Apr 2020 14:48:50 -0400
Subject: [PATCH] kernel: memory: Add system_control code, which will be used
 for ASLR support.

---
 src/core/CMakeLists.txt                       |  2 +
 src/core/hle/kernel/memory/system_control.cpp | 41 +++++++++++++++++++
 src/core/hle/kernel/memory/system_control.h   | 18 ++++++++
 3 files changed, 61 insertions(+)
 create mode 100644 src/core/hle/kernel/memory/system_control.cpp
 create mode 100644 src/core/hle/kernel/memory/system_control.h

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 504ee2777..92ed3bdcf 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -159,6 +159,8 @@ add_library(core STATIC
     hle/kernel/memory/memory_block.h
     hle/kernel/memory/memory_types.h
     hle/kernel/memory/slab_heap.h
+    hle/kernel/memory/system_control.cpp
+    hle/kernel/memory/system_control.h
     hle/kernel/mutex.cpp
     hle/kernel/mutex.h
     hle/kernel/object.cpp
diff --git a/src/core/hle/kernel/memory/system_control.cpp b/src/core/hle/kernel/memory/system_control.cpp
new file mode 100644
index 000000000..e61522dc0
--- /dev/null
+++ b/src/core/hle/kernel/memory/system_control.cpp
@@ -0,0 +1,41 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <random>
+
+#include "core/hle/kernel/memory/system_control.h"
+
+namespace Kernel::Memory::SystemControl {
+
+u64 GenerateRandomU64ForInit() {
+    std::random_device device;
+    std::mt19937 gen(device());
+    std::uniform_int_distribution<u64> distribution(1, std::numeric_limits<u64>::max());
+    return distribution(gen);
+}
+
+template <typename F>
+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);
+        }
+    }
+}
+
+u64 GenerateRandomRange(u64 min, u64 max) {
+    return GenerateUniformRange(min, max, GenerateRandomU64ForInit);
+}
+
+} // namespace Kernel::Memory::SystemControl
diff --git a/src/core/hle/kernel/memory/system_control.h b/src/core/hle/kernel/memory/system_control.h
new file mode 100644
index 000000000..3fa93111d
--- /dev/null
+++ b/src/core/hle/kernel/memory/system_control.h
@@ -0,0 +1,18 @@
+// 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 Kernel::Memory::SystemControl {
+
+u64 GenerateRandomU64ForInit();
+
+template <typename F>
+u64 GenerateUniformRange(u64 min, u64 max, F f);
+
+u64 GenerateRandomRange(u64 min, u64 max);
+
+} // namespace Kernel::Memory::SystemControl