Move shared object code into DlHelp.{h,c}

Bug: 151443957
Test: m & boot
Change-Id: I85039aee69907c2375bd4e1d6f229ae566062149

Author: ohodson

Android.bp

@@ -71,6 +71,7 @@ cc_library {
     name: "libnativehelper",
     host_supported: true,
     srcs: [
+        "DlHelp.c",
         "JNIHelp.cpp",
         "JniConstants.cpp",
         "JniInvocation.cpp",
@@ -128,6 +129,7 @@ cc_library_shared {
         "platform_include",
     ],
     srcs: [
+        "DlHelp.c",
         "JNIHelp.cpp",
         "JniConstants.cpp",
     ],

DlHelp.c

@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2020 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 "DlHelp.h"
+
+#include <stdbool.h>
+
+#ifdef WIN32_LEAN_AND_MEAN
+#include <stdio.h>
+#include <windows.h>
+#else
+#include <dlfcn.h>
+#endif
+
+DlLibrary DlOpenLibrary(const char* filename) {
+#ifdef _WIN32
+  return LoadLibrary(filename);
+#else
+  // Load with RTLD_NODELETE in order to ensure that libart.so is not unmapped when it is closed.
+  // This is due to the fact that it is possible that some threads might have yet to finish
+  // exiting even after JNI_DeleteJavaVM returns, which can lead to segfaults if the library is
+  // unloaded.
+  return dlopen(filename, RTLD_NOW | RTLD_NODELETE);
+#endif
+}
+
+bool DlCloseLibrary(DlLibrary library) {
+#ifdef _WIN32
+  return (FreeLibrary(library) == TRUE);
+#else
+  return (dlclose(library) == 0);
+#endif
+}
+
+DlSymbol DlGetSymbol(DlLibrary handle, const char* symbol) {
+#ifdef _WIN32
+  return (DlSymbol) GetProcAddress(handle, symbol);
+#else
+  return dlsym(handle, symbol);
+#endif
+}
+
+const char* DlGetError() {
+#ifdef _WIN32
+  static char buffer[256];
+
+  DWORD cause = GetLastError();
+  DWORD flags = FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS;
+  DWORD length = FormatMessageA(flags, NULL, cause, 0, buffer, sizeof(buffer), NULL);
+  if (length == 0) {
+    snprintf(buffer, sizeof(buffer),
+             "Error %lu while retrieving message for error %lu",
+             GetLastError(), cause);
+    length = strlen(buffer);
+  }
+
+  // Trim trailing whitespace.
+  for (DWORD i = length - 1; i > 0; --i) {
+    if (!isspace(buffer[i])) {
+      break;
+    }
+    buffer[i] = '\0';
+  }
+
+  return buffer;
+#else
+  return dlerror();
+#endif
+}

DlHelp.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#pragma once
+
+#include <sys/cdefs.h>
+#include <stdbool.h>
+
+__BEGIN_DECLS
+
+typedef void* DlLibrary;
+typedef void* DlSymbol;
+
+DlLibrary DlOpenLibrary(const char* filename);
+bool DlCloseLibrary(DlLibrary library);
+DlSymbol DlGetSymbol(DlLibrary library, const char* symbol);
+const char* DlGetError();
+
+__END_DECLS

JniInvocation.cpp

@@ -33,6 +33,7 @@
 #include <android-base/errors.h>
 #endif
 
+#include "DlHelp.h"
 #include "JniConstants.h"
 
 namespace {
@@ -65,43 +66,6 @@ int GetLibrarySystemProperty(char* buffer) {
 #define FUNC_POINTER void*
 #endif
 
-void* OpenLibrary(const char* filename) {
-#ifdef _WIN32
-  return LoadLibrary(filename);
-#else
-  // Load with RTLD_NODELETE in order to ensure that libart.so is not unmapped when it is closed.
-  // This is due to the fact that it is possible that some threads might have yet to finish
-  // exiting even after JNI_DeleteJavaVM returns, which can lead to segfaults if the library is
-  // unloaded.
-  const int kDlopenFlags = RTLD_NOW | RTLD_NODELETE;
-  return dlopen(filename, kDlopenFlags);
-#endif
-}
-
-int CloseLibrary(void* handle) {
-#ifdef _WIN32
-  return FreeLibrary(static_cast<HMODULE>(handle));
-#else
-  return dlclose(handle);
-#endif
-}
-
-FUNC_POINTER GetSymbol(void* handle, const char* symbol) {
-#ifdef _WIN32
-  return GetProcAddress(static_cast<HMODULE>(handle), symbol);
-#else
-  return dlsym(handle, symbol);
-#endif
-}
-
-std::string GetError() {
-#ifdef _WIN32
-  return android::base::SystemErrorCodeToString(GetLastError());
-#else
-  return std::string(dlerror());
-#endif
-}
-
 }  // namespace
 
 struct JniInvocationImpl final {
@@ -158,7 +122,7 @@ JniInvocationImpl::JniInvocationImpl() :
 JniInvocationImpl::~JniInvocationImpl() {
   jni_invocation_ = NULL;
   if (handle_ != NULL) {
-    CloseLibrary(handle_);
+    DlCloseLibrary(handle_);
   }
 }
 
@@ -213,11 +177,11 @@ bool JniInvocationImpl::Init(const char* library) {
   char* buffer = NULL;
 #endif
   library = GetLibrary(library, buffer);
-  handle_ = OpenLibrary(library);
+  handle_ = DlOpenLibrary(library);
   if (handle_ == NULL) {
     if (strcmp(library, kLibraryFallback) == 0) {
       // Nothing else to try.
-      ALOGE("Failed to dlopen %s: %s", library, GetError().c_str());
+      ALOGE("Failed to dlopen %s: %s", library, DlGetError());
       return false;
     }
     // Note that this is enough to get something like the zygote
@@ -226,11 +190,11 @@ bool JniInvocationImpl::Init(const char* library) {
     // RuntimeInit.commonInit for where we fix up the property to
     // avoid future fallbacks. http://b/11463182
     ALOGW("Falling back from %s to %s after dlopen error: %s",
-          library, kLibraryFallback, GetError().c_str());
+          library, kLibraryFallback, DlGetError());
     library = kLibraryFallback;
-    handle_ = OpenLibrary(library);
+    handle_ = DlOpenLibrary(library);
     if (handle_ == NULL) {
-      ALOGE("Failed to dlopen %s: %s", library, GetError().c_str());
+      ALOGE("Failed to dlopen %s: %s", library, DlGetError());
       return false;
     }
   }
@@ -262,10 +226,10 @@ jint JniInvocationImpl::JNI_GetCreatedJavaVMs(JavaVM** vms, jsize size, jsize* v
 }
 
 bool JniInvocationImpl::FindSymbol(FUNC_POINTER* pointer, const char* symbol) {
-  *pointer = GetSymbol(handle_, symbol);
+  *pointer = reinterpret_cast<FUNC_POINTER>(DlGetSymbol(handle_, symbol));
   if (*pointer == NULL) {
-    ALOGE("Failed to find symbol %s: %s\n", symbol, GetError().c_str());
-    CloseLibrary(handle_);
+    ALOGE("Failed to find symbol %s: %s\n", symbol, DlGetError());
+    DlCloseLibrary(handle_);
     handle_ = NULL;
     return false;
   }