This patch adds a new third-party library that implements an ELF dynamic linker.

third_party/crazy_linker/crazy_linker/tests/bench_load_library.cpp

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// A crazy linker test to:
+// - Load a library (libfoo.so) with the linker.
+// - Find the address of the "Foo" function in it.
+// - Call the function.
+// - Close the library.
+
+#include <crazy_linker.h>
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+static void Panic(const char* fmt, ...) {
+  va_list args;
+  fprintf(stderr, "PANIC: ");
+  va_start(args, fmt);
+  vfprintf(stderr, fmt, args);
+  va_end(args);
+  exit(1);
+}
+
+static double now_ms() {
+  struct timespec ts;
+  clock_gettime(CLOCK_MONOTONIC, &ts);
+  return (ts.tv_sec * 1000.) + (ts.tv_nsec / 1000000.);
+}
+
+static void drop_caches() {
+  int fd = open("/proc/sys/vm/drop_caches", O_RDWR);
+  if (fd < 0) {
+    fprintf(stderr, "Could not drop caches! Please run this program as root!\n");
+    return;
+  }
+  write(fd, "3\n", 2);
+  close(fd);
+}
+
+class ScopedTimer {
+ public:
+  ScopedTimer(const char* name) {
+    name_ = name;
+    start_ms_ = now_ms();
+  }
+
+  ~ScopedTimer() {
+    double elapsed_ms = now_ms() - start_ms_;
+    printf("Timer %s: %.1f\n", name_, elapsed_ms);
+  }
+ private:
+  const char* name_;
+  double start_ms_;
+};
+
+int main(int argc, char** argv) {
+  const char* library_path = "libfoo.so";
+  if (argc >= 2)
+    library_path = argv[1];
+
+  {
+    ScopedTimer null_timer("empty");
+  }
+
+  // Load the library with dlopen().
+  void* lib;
+  drop_caches();
+  {
+    ScopedTimer timer("dlopen");
+    lib = dlopen(library_path, RTLD_NOW);
+  }
+  if (!lib)
+    Panic("Could not load library with dlopen(): %s\n", dlerror());
+
+  dlclose(lib);
+
+
+  crazy_library_t* library;
+  crazy_context_t* context = crazy_context_create();
+
+  // Ensure the program looks in its own directory too.
+  crazy_context_add_search_path_for_address(
+      context, reinterpret_cast<void*>(&main));
+
+  // Load the library with the crazy linker.
+  drop_caches();
+  {
+    ScopedTimer timer("crazy_linker");
+    // Load libfoo.so
+    if (!crazy_library_open(&library,
+                            library_path,
+                            context)) {
+      Panic("Could not open library: %s\n", crazy_context_get_error(context));
+    }
+  }
+  crazy_library_close(library);
+
+  // Load the library with the crazy linker. Preload libOpenSLES.so
+  drop_caches();
+  void* sles_lib = dlopen("libOpenSLES.so", RTLD_NOW);
+  {
+    ScopedTimer timer("crazy_linker (preload libOpenSLES.so)");
+    // Load libfoo.so
+    if (!crazy_library_open(&library,
+                            library_path,
+                            context)) {
+      Panic("Could not open library: %s\n", crazy_context_get_error(context));
+    }
+  }
+  crazy_library_close(library);
+  dlclose(sles_lib);
+
+
+  // Load the library with the crazy linker. Preload libOpenSLES.so
+  {
+    drop_caches();
+    void* sys1_lib = dlopen("libandroid.so", RTLD_NOW);
+    void* sys2_lib = dlopen("libjnigraphics.so", RTLD_NOW);
+    void* sys3_lib = dlopen("libOpenSLES.so", RTLD_NOW);
+    {
+      ScopedTimer timer("crazy_linker (preload 3 system libs)");
+      // Load libfoo.so
+      if (!crazy_library_open(&library,
+                              library_path,
+                              context)) {
+        Panic("Could not open library: %s\n", crazy_context_get_error(context));
+      }
+    }
+    crazy_library_close(library);
+    dlclose(sys3_lib);
+    dlclose(sys2_lib);
+    dlclose(sys1_lib);
+  }
+
+  // Load the library with the crazy linker. Create a shared RELRO as well.
+  drop_caches();
+  {
+    ScopedTimer timer("crazy_linker (with RELRO)");
+    // Load libfoo.so
+    if (!crazy_library_open(&library,
+                            library_path,
+                            context)) {
+      Panic("Could not open library: %s\n", crazy_context_get_error(context));
+    }
+
+    if (!crazy_library_enable_relro_sharing(library, context)) {
+      Panic("Could not create shared RELRO: %s\n",
+            crazy_context_get_error(context));
+    }
+  }
+  crazy_library_close(library);
+
+  printf("OK\n");
+  return 0;
+}