Handle code_cache dir creation in libnativebridge

Also:

- add kPreInitiliazed state to native bridge with check transition:
kOpened->kPreInitialized->kInitialized
- made sure we free the memory for the code_cache_path
- tidy up some error messages
- tidy up tests
- add a dummy native bridge to test with

Bug: 18027433
Bug: 18097480

Change-Id: I39f74c93580f2e224080dd3df2ffaa9cf9f8cd9c

10 files changed, 311 insertions, 45 deletions

diff --git a/libnativebridge/Android.mk b/libnativebridge/Android.mk
index 6c2e43e..83169eb 100644
--- a/libnativebridge/Android.mk
+++ b/libnativebridge/Android.mk
@@ -13,7 +13,7 @@ LOCAL_SRC_FILES:= $(NATIVE_BRIDGE_COMMON_SRC_FILES)
 LOCAL_SHARED_LIBRARIES := liblog
 LOCAL_CLANG := true
 LOCAL_CPP_EXTENSION := .cc
-LOCAL_CFLAGS := -Werror -Wall
+LOCAL_CFLAGS += -Werror -Wall
 LOCAL_CPPFLAGS := -std=gnu++11 -fvisibility=protected
 LOCAL_LDFLAGS := -ldl
 LOCAL_MULTILIB := both
@@ -30,11 +30,11 @@ LOCAL_SRC_FILES:= $(NATIVE_BRIDGE_COMMON_SRC_FILES)
 LOCAL_SHARED_LIBRARIES := liblog
 LOCAL_CLANG := true
 LOCAL_CPP_EXTENSION := .cc
-LOCAL_CFLAGS := -Werror -Wall
+LOCAL_CFLAGS += -Werror -Wall
 LOCAL_CPPFLAGS := -std=gnu++11 -fvisibility=protected
 LOCAL_LDFLAGS := -ldl
 LOCAL_MULTILIB := both
 
 include $(BUILD_HOST_SHARED_LIBRARY)
 
-include $(LOCAL_PATH)/tests/Android.mk
\ No newline at end of file
+include $(LOCAL_PATH)/tests/Android.mk
diff --git a/libnativebridge/native_bridge.cc b/libnativebridge/native_bridge.cc
index 1eb2d5b..f8e1b33 100644
--- a/libnativebridge/native_bridge.cc
+++ b/libnativebridge/native_bridge.cc
@@ -43,14 +43,16 @@ static constexpr const char* kNativeBridgeInterfaceSymbol = "NativeBridgeItf";
 enum class NativeBridgeState {
   kNotSetup,                        // Initial state.
   kOpened,                          // After successful dlopen.
+  kPreInitialized,                  // After successful pre-initialization.
   kInitialized,                     // After successful initialization.
   kClosed                           // Closed or errors.
 };
 
-static const char* kNotSetupString = "kNotSetup";
-static const char* kOpenedString = "kOpened";
-static const char* kInitializedString = "kInitialized";
-static const char* kClosedString = "kClosed";
+static constexpr const char* kNotSetupString = "kNotSetup";
+static constexpr const char* kOpenedString = "kOpened";
+static constexpr const char* kPreInitializedString = "kPreInitialized";
+static constexpr const char* kInitializedString = "kInitialized";
+static constexpr const char* kClosedString = "kClosed";
 
 static const char* GetNativeBridgeStateString(NativeBridgeState state) {
   switch (state) {
@@ -60,6 +62,9 @@ static const char* GetNativeBridgeStateString(NativeBridgeState state) {
     case NativeBridgeState::kOpened:
       return kOpenedString;
 
+    case NativeBridgeState::kPreInitialized:
+      return kPreInitializedString;
+
     case NativeBridgeState::kInitialized:
       return kInitializedString;
 
@@ -82,8 +87,14 @@ static NativeBridgeCallbacks* callbacks = nullptr;
 // Callbacks provided by the environment to the bridge. Passed to LoadNativeBridge.
 static const NativeBridgeRuntimeCallbacks* runtime_callbacks = nullptr;
 
-// The app's data directory.
-static char* app_data_dir = nullptr;
+// The app's code cache directory.
+static char* app_code_cache_dir = nullptr;
+
+// Code cache directory (relative to the application private directory)
+// Ideally we'd like to call into framework to retrieve this name. However that's considered an
+// implementation detail and will require either hacks or consistent refactorings. We compromise
+// and hard code the directory name again here.
+static constexpr const char* kCodeCacheDir = "code_cache";
 
 static constexpr uint32_t kNativeBridgeCallbackVersion = 1;
 
@@ -132,6 +143,13 @@ static bool VersionCheck(NativeBridgeCallbacks* cb) {
   return cb != nullptr && cb->version == kNativeBridgeCallbackVersion;
 }
 
+static void CloseNativeBridge(bool with_error) {
+  state = NativeBridgeState::kClosed;
+  had_error |= with_error;
+  delete[] app_code_cache_dir;
+  app_code_cache_dir = nullptr;
+}
+
 bool LoadNativeBridge(const char* nb_library_filename,
                       const NativeBridgeRuntimeCallbacks* runtime_cbs) {
   // We expect only one place that calls LoadNativeBridge: Runtime::Init. At that point we are not
@@ -149,12 +167,11 @@ bool LoadNativeBridge(const char* nb_library_filename,
   }
 
   if (nb_library_filename == nullptr || *nb_library_filename == 0) {
-    state = NativeBridgeState::kClosed;
-    return true;
+    CloseNativeBridge(false);
+    return false;
   } else {
     if (!NativeBridgeNameAcceptable(nb_library_filename)) {
-      state = NativeBridgeState::kClosed;
-      had_error = true;
+      CloseNativeBridge(true);
     } else {
       // Try to open the library.
       void* handle = dlopen(nb_library_filename, RTLD_LAZY);
@@ -178,8 +195,7 @@ bool LoadNativeBridge(const char* nb_library_filename,
       // Two failure conditions: could not find library (dlopen failed), or could not find native
       // bridge interface (dlsym failed). Both are an error and close the native bridge.
       if (callbacks == nullptr) {
-        had_error = true;
-        state = NativeBridgeState::kClosed;
+        CloseNativeBridge(true);
       } else {
         runtime_callbacks = runtime_cbs;
         state = NativeBridgeState::kOpened;
@@ -216,19 +232,32 @@ bool NeedsNativeBridge(const char* instruction_set) {
 template<typename T> void UNUSED(const T&) {}
 #endif
 
-void PreInitializeNativeBridge(const char* app_data_dir_in, const char* instruction_set) {
+bool PreInitializeNativeBridge(const char* app_data_dir_in, const char* instruction_set) {
+  if (state != NativeBridgeState::kOpened) {
+    ALOGE("Invalid state: native bridge is expected to be opened.");
+    CloseNativeBridge(true);
+    return false;
+  }
+
   if (app_data_dir_in == nullptr) {
-    return;
+    ALOGE("Application private directory cannot be null.");
+    CloseNativeBridge(true);
+    return false;
   }
 
-  const size_t len = strlen(app_data_dir_in);
-  // Make a copy for us.
-  app_data_dir = new char[len];
-  strncpy(app_data_dir, app_data_dir_in, len);
+  // Create the path to the application code cache directory.
+  // The memory will be release after Initialization or when the native bridge is closed.
+  const size_t len = strlen(app_data_dir_in) + strlen(kCodeCacheDir) + 2; // '\0' + '/'
+  app_code_cache_dir = new char[len];
+  snprintf(app_code_cache_dir, len, "%s/%s", app_data_dir_in, kCodeCacheDir);
+
+  // Bind-mount /system/lib{,64}/<isa>/cpuinfo to /proc/cpuinfo.
+  // Failure is not fatal and will keep the native bridge in kPreInitialized.
+  state = NativeBridgeState::kPreInitialized;
 
 #ifndef __APPLE__
   if (instruction_set == nullptr) {
-    return;
+    return true;
   }
   size_t isa_len = strlen(instruction_set);
   if (isa_len > 10) {
@@ -237,11 +266,11 @@ void PreInitializeNativeBridge(const char* app_data_dir_in, const char* instruct
     // be another instruction set in the future.
     ALOGW("Instruction set %s is malformed, must be less than or equal to 10 characters.",
           instruction_set);
-    return;
+    return true;
   }
 
-  // Bind-mount /system/lib{,64}/<isa>/cpuinfo to /proc/cpuinfo. If the file does not exist, the
-  // mount command will fail, so we safe the extra file existence check...
+  // If the file does not exist, the mount command will fail,
+  // so we save the extra file existence check.
   char cpuinfo_path[1024];
 
 #ifdef HAVE_ANDROID_OS
@@ -263,10 +292,12 @@ void PreInitializeNativeBridge(const char* app_data_dir_in, const char* instruct
                                nullptr)) == -1) {   // "Data."
     ALOGW("Failed to bind-mount %s as /proc/cpuinfo: %s", cpuinfo_path, strerror(errno));
   }
-#else
+#else  // __APPLE__
   UNUSED(instruction_set);
   ALOGW("Mac OS does not support bind-mounting. Host simulation of native bridge impossible.");
 #endif
+
+  return true;
 }
 
 static void SetCpuAbi(JNIEnv* env, jclass build_class, const char* field, const char* value) {
@@ -396,20 +427,40 @@ bool InitializeNativeBridge(JNIEnv* env, const char* instruction_set) {
   // We expect only one place that calls InitializeNativeBridge: Runtime::DidForkFromZygote. At that
   // point we are not multi-threaded, so we do not need locking here.
 
-  if (state == NativeBridgeState::kOpened) {
-    // Try to initialize.
-    if (callbacks->initialize(runtime_callbacks, app_data_dir, instruction_set)) {
-      SetupEnvironment(callbacks, env, instruction_set);
-      state = NativeBridgeState::kInitialized;
-    } else {
-      // Unload the library.
-      dlclose(native_bridge_handle);
-      had_error = true;
-      state = NativeBridgeState::kClosed;
+  if (state == NativeBridgeState::kPreInitialized) {
+    // Check for code cache: if it doesn't exist try to create it.
+    struct stat st;
+    if (stat(app_code_cache_dir, &st) == -1) {
+      if (errno == ENOENT) {
+        if (mkdir(app_code_cache_dir, S_IRWXU | S_IRWXG | S_IXOTH) == -1) {
+          ALOGE("Cannot create code cache directory %s: %s.", app_code_cache_dir, strerror(errno));
+          CloseNativeBridge(true);
+        }
+      } else {
+        ALOGE("Cannot stat code cache directory %s: %s.", app_code_cache_dir, strerror(errno));
+        CloseNativeBridge(true);
+      }
+    } else if (!S_ISDIR(st.st_mode)) {
+      ALOGE("Code cache is not a directory %s.", app_code_cache_dir);
+      CloseNativeBridge(true);
+    }
+
+    // If we're still PreInitialized (dind't fail the code cache checks) try to initialize.
+    if (state == NativeBridgeState::kPreInitialized) {
+      if (callbacks->initialize(runtime_callbacks, app_code_cache_dir, instruction_set)) {
+        SetupEnvironment(callbacks, env, instruction_set);
+        state = NativeBridgeState::kInitialized;
+        // We no longer need the code cache path, release the memory.
+        delete[] app_code_cache_dir;
+        app_code_cache_dir = nullptr;
+      } else {
+        // Unload the library.
+        dlclose(native_bridge_handle);
+        CloseNativeBridge(true);
+      }
     }
   } else {
-    had_error = true;
-    state = NativeBridgeState::kClosed;
+    CloseNativeBridge(true);
   }
 
   return state == NativeBridgeState::kInitialized;
@@ -421,22 +472,22 @@ void UnloadNativeBridge() {
 
   switch(state) {
     case NativeBridgeState::kOpened:
+    case NativeBridgeState::kPreInitialized:
     case NativeBridgeState::kInitialized:
       // Unload.
       dlclose(native_bridge_handle);
+      CloseNativeBridge(false);
       break;
 
     case NativeBridgeState::kNotSetup:
       // Not even set up. Error.
-      had_error = true;
+      CloseNativeBridge(true);
       break;
 
     case NativeBridgeState::kClosed:
       // Ignore.
       break;
   }
-
-  state = NativeBridgeState::kClosed;
 }
 
 bool NativeBridgeError() {
@@ -444,7 +495,9 @@ bool NativeBridgeError() {
 }
 
 bool NativeBridgeAvailable() {
-  return state == NativeBridgeState::kOpened || state == NativeBridgeState::kInitialized;
+  return state == NativeBridgeState::kOpened
+      || state == NativeBridgeState::kPreInitialized
+      || state == NativeBridgeState::kInitialized;
 }
 
 bool NativeBridgeInitialized() {
diff --git a/libnativebridge/tests/Android.mk b/libnativebridge/tests/Android.mk
index a94d2f7..295696e 100644
--- a/libnativebridge/tests/Android.mk
+++ b/libnativebridge/tests/Android.mk
@@ -1,18 +1,26 @@
 # Build the unit tests.
 LOCAL_PATH := $(call my-dir)
+
+include $(LOCAL_PATH)/Android.nativebridge-dummy.mk
+
 include $(CLEAR_VARS)
 
 # Build the unit tests.
 test_src_files := \
+    CompleteFlow_test.cpp \
     InvalidCharsNativeBridge_test.cpp \
     NeedsNativeBridge_test.cpp \
     PreInitializeNativeBridge_test.cpp \
+    PreInitializeNativeBridgeFail1_test.cpp \
+    PreInitializeNativeBridgeFail2_test.cpp \
     ReSetupNativeBridge_test.cpp \
     UnavailableNativeBridge_test.cpp \
     ValidNameNativeBridge_test.cpp
 
+
 shared_libraries := \
-    libnativebridge
+    libnativebridge \
+    libnativebridge-dummy
 
 $(foreach file,$(test_src_files), \
     $(eval include $(CLEAR_VARS)) \
diff --git a/libnativebridge/tests/Android.nativebridge-dummy.mk b/libnativebridge/tests/Android.nativebridge-dummy.mk
new file mode 100644
index 0000000..1caf50a
--- /dev/null
+++ b/libnativebridge/tests/Android.nativebridge-dummy.mk
@@ -0,0 +1,34 @@
+LOCAL_PATH:= $(call my-dir)
+
+NATIVE_BRIDGE_COMMON_SRC_FILES := \
+  DummyNativeBridge.cpp
+
+# Shared library for target
+# ========================================================
+include $(CLEAR_VARS)
+
+LOCAL_MODULE:= libnativebridge-dummy
+
+LOCAL_SRC_FILES:= $(NATIVE_BRIDGE_COMMON_SRC_FILES)
+LOCAL_CLANG := true
+LOCAL_CFLAGS += -Werror -Wall
+LOCAL_CPPFLAGS := -std=gnu++11 -fvisibility=protected
+LOCAL_LDFLAGS := -ldl
+LOCAL_MULTILIB := both
+
+include $(BUILD_SHARED_LIBRARY)
+
+# Shared library for host
+# ========================================================
+include $(CLEAR_VARS)
+
+LOCAL_MODULE:= libnativebridge-dummy
+
+LOCAL_SRC_FILES:= $(NATIVE_BRIDGE_COMMON_SRC_FILES)
+LOCAL_CLANG := true
+LOCAL_CFLAGS += -Werror -Wall
+LOCAL_CPPFLAGS := -std=gnu++11 -fvisibility=protected
+LOCAL_LDFLAGS := -ldl
+LOCAL_MULTILIB := both
+
+include $(BUILD_HOST_SHARED_LIBRARY)
diff --git a/libnativebridge/tests/CompleteFlow_test.cpp b/libnativebridge/tests/CompleteFlow_test.cpp
new file mode 100644
index 0000000..4f0fe8b
--- /dev/null
+++ b/libnativebridge/tests/CompleteFlow_test.cpp
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "NativeBridgeTest.h"
+
+namespace android {
+
+TEST_F(NativeBridgeTest, CompleteFlow) {
+    // Init
+    ASSERT_TRUE(LoadNativeBridge(kNativeBridgeLibrary, nullptr));
+    ASSERT_TRUE(NativeBridgeAvailable());
+    ASSERT_TRUE(PreInitializeNativeBridge(".", "isa"));
+    ASSERT_TRUE(NativeBridgeAvailable());
+    ASSERT_TRUE(InitializeNativeBridge(nullptr, nullptr));
+    ASSERT_TRUE(NativeBridgeAvailable());
+
+    // Basic calls to check that nothing crashes
+    ASSERT_FALSE(NativeBridgeIsSupported(nullptr));
+    ASSERT_EQ(nullptr, NativeBridgeLoadLibrary(nullptr, 0));
+    ASSERT_EQ(nullptr, NativeBridgeGetTrampoline(nullptr, nullptr, nullptr, 0));
+
+    // Unload
+    UnloadNativeBridge();
+
+    ASSERT_FALSE(NativeBridgeError());
+}
+
+}  // namespace android
diff --git a/libnativebridge/tests/DummyNativeBridge.cpp b/libnativebridge/tests/DummyNativeBridge.cpp
new file mode 100644
index 0000000..b9894f6
--- /dev/null
+++ b/libnativebridge/tests/DummyNativeBridge.cpp
@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// A dummy implementation of the native-bridge interface.
+
+#include "nativebridge/native_bridge.h"
+
+// NativeBridgeCallbacks implementations
+extern "C" bool native_bridge_initialize(const android::NativeBridgeRuntimeCallbacks* /* art_cbs */,
+                                         const char* /* app_code_cache_dir */,
+                                         const char* /* isa */) {
+  return true;
+}
+
+extern "C" void* native_bridge_loadLibrary(const char* /* libpath */, int /* flag */) {
+  return nullptr;
+}
+
+extern "C" void* native_bridge_getTrampoline(void* /* handle */, const char* /* name */,
+                                             const char* /* shorty */, uint32_t /* len */) {
+  return nullptr;
+}
+
+extern "C" bool native_bridge_isSupported(const char* /* libpath */) {
+  return false;
+}
+
+extern "C" const struct android::NativeBridgeRuntimeValues* native_bridge_getAppEnv(
+    const char* /* abi */) {
+  return nullptr;
+}
+
+android::NativeBridgeCallbacks NativeBridgeItf {
+  .version = 1,
+  .initialize = &native_bridge_initialize,
+  .loadLibrary = &native_bridge_loadLibrary,
+  .getTrampoline = &native_bridge_getTrampoline,
+  .isSupported = &native_bridge_isSupported,
+  .getAppEnv = &native_bridge_getAppEnv
+};
diff --git a/libnativebridge/tests/NativeBridgeTest.h b/libnativebridge/tests/NativeBridgeTest.h
index 0d731cb..73c92f1 100644
--- a/libnativebridge/tests/NativeBridgeTest.h
+++ b/libnativebridge/tests/NativeBridgeTest.h
@@ -22,6 +22,8 @@
 #include <nativebridge/native_bridge.h>
 #include <gtest/gtest.h>
 
+constexpr const char* kNativeBridgeLibrary = "libnativebridge-dummy.so";
+
 namespace android {
 
 class NativeBridgeTest : public testing::Test {
diff --git a/libnativebridge/tests/PreInitializeNativeBridgeFail1_test.cpp b/libnativebridge/tests/PreInitializeNativeBridgeFail1_test.cpp
new file mode 100644
index 0000000..69c30a1
--- /dev/null
+++ b/libnativebridge/tests/PreInitializeNativeBridgeFail1_test.cpp
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "NativeBridgeTest.h"
+
+#include <cstdio>
+#include <cstring>
+#include <cutils/log.h>
+#include <dlfcn.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+
+namespace android {
+
+TEST_F(NativeBridgeTest, PreInitializeNativeBridgeFail1) {
+  // Needs a valid application directory.
+  ASSERT_TRUE(LoadNativeBridge(kNativeBridgeLibrary, nullptr));
+  ASSERT_FALSE(PreInitializeNativeBridge(nullptr, "isa"));
+  ASSERT_TRUE(NativeBridgeError());
+}
+
+}  // namespace android
diff --git a/libnativebridge/tests/PreInitializeNativeBridgeFail2_test.cpp b/libnativebridge/tests/PreInitializeNativeBridgeFail2_test.cpp
new file mode 100644
index 0000000..74e96e0
--- /dev/null
+++ b/libnativebridge/tests/PreInitializeNativeBridgeFail2_test.cpp
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "NativeBridgeTest.h"
+
+#include <cstdio>
+#include <cstring>
+#include <cutils/log.h>
+#include <dlfcn.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+
+namespace android {
+
+TEST_F(NativeBridgeTest, PreInitializeNativeBridgeFail2) {
+  // Needs LoadNativeBridge() first
+  ASSERT_FALSE(PreInitializeNativeBridge(nullptr, "isa"));
+  ASSERT_TRUE(NativeBridgeError());
+}
+
+}  // namespace android
diff --git a/libnativebridge/tests/PreInitializeNativeBridge_test.cpp b/libnativebridge/tests/PreInitializeNativeBridge_test.cpp
index 84078f7..cec26ce 100644
--- a/libnativebridge/tests/PreInitializeNativeBridge_test.cpp
+++ b/libnativebridge/tests/PreInitializeNativeBridge_test.cpp
@@ -31,6 +31,7 @@ namespace android {
 static constexpr const char* kTestData = "PreInitializeNativeBridge test.";
 
 TEST_F(NativeBridgeTest, PreInitializeNativeBridge) {
+    ASSERT_TRUE(LoadNativeBridge(kNativeBridgeLibrary, nullptr));
 #ifndef __APPLE__         // Mac OS does not support bind-mount.
 #ifndef HAVE_ANDROID_OS   // Cannot write into the hard-wired location.
     // Try to create our mount namespace.
@@ -41,8 +42,7 @@ TEST_F(NativeBridgeTest, PreInitializeNativeBridge) {
         fprintf(cpuinfo, kTestData);
         fclose(cpuinfo);
 
-        // Call the setup.
-        PreInitializeNativeBridge("does not matter 1", "short 2");
+        ASSERT_TRUE(PreInitializeNativeBridge("does not matter 1", "short 2"));
 
         // Read /proc/cpuinfo
         FILE* proc_cpuinfo = fopen("/proc/cpuinfo", "r");