Refactor linker allocator

Makes it reusable for different fixed sized and not very
big structures (<PAGE_SIZE).

Change-Id: Id5ec13fc6541b1935ef7fe3671c22b98685abbae

linker/tests/linker_allocator_test.cpp

@@ -0,0 +1,161 @@
+/*
+ * Copyright (C) 2013 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 <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+
+#include <gtest/gtest.h>
+
+#include "../linker_allocator.h"
+
+#include <unistd.h>
+
+namespace {
+
+struct test_struct_nominal {
+  void* pointer;
+  ssize_t value;
+};
+
+/*
+ * this one has size below allocator cap which is 2*sizeof(void*)
+ */
+struct test_struct_small {
+  char dummy_str[5];
+};
+
+/*
+ * 1009 byte struct (1009 is prime)
+ */
+struct test_struct_larger {
+  char dummy_str[1009];
+};
+
+static size_t kPageSize = sysconf(_SC_PAGE_SIZE);
+};
+
+TEST(linker_allocator, test_nominal) {
+  LinkerAllocator<test_struct_nominal> allocator;
+  allocator.init();
+
+  test_struct_nominal* ptr1 = allocator.alloc();
+  ASSERT_TRUE(ptr1 != nullptr);
+  test_struct_nominal* ptr2 = allocator.alloc();
+  ASSERT_TRUE(ptr2 != nullptr);
+  // they should be next to each other.
+  ASSERT_EQ(ptr1+1, ptr2);
+
+  ptr1->value = 42;
+
+  allocator.protect_page(ptr1, PROT_READ);
+
+  allocator.free(ptr1);
+  allocator.free(ptr2);
+}
+
+TEST(linker_allocator, test_small) {
+  LinkerAllocator<test_struct_small> allocator;
+  allocator.init();
+
+  char* ptr1 = reinterpret_cast<char*>(allocator.alloc());
+  char* ptr2 = reinterpret_cast<char*>(allocator.alloc());
+
+  ASSERT_TRUE(ptr1 != nullptr);
+  ASSERT_TRUE(ptr2 != nullptr);
+  ASSERT_EQ(ptr1+2*sizeof(void*), ptr2);
+}
+
+TEST(linker_allocator, test_larger) {
+  LinkerAllocator<test_struct_larger> allocator;
+  allocator.init();
+
+  test_struct_larger* ptr1 = allocator.alloc();
+  test_struct_larger* ptr2 = allocator.alloc();
+
+  ASSERT_TRUE(ptr1 != nullptr);
+  ASSERT_TRUE(ptr2 != nullptr);
+
+  ASSERT_EQ(ptr1+1, ptr2);
+
+  allocator.protect_page(ptr2, PROT_READ);
+
+  // lets allocate until we reach next page.
+  size_t n = kPageSize/sizeof(test_struct_larger) + 1 - 2;
+
+  for (size_t i=0; i<n; ++i) {
+    ASSERT_TRUE(allocator.alloc() != nullptr);
+  }
+
+}
+
+static void protect_one_page() {
+  LinkerAllocator<test_struct_larger> allocator;
+  allocator.init();
+
+  // number of allocs to reach the end of first page
+  size_t n = kPageSize/sizeof(test_struct_larger) - 1;
+  test_struct_larger* page1_ptr = allocator.alloc();
+
+  for (size_t i=0; i<n; ++i) {
+    allocator.alloc();
+  }
+
+  test_struct_larger* page2_ptr = allocator.alloc();
+
+  allocator.protect_page(page2_ptr, PROT_READ);
+
+  // check that we still have access to page1
+  page1_ptr->dummy_str[17] = 52;
+
+  fprintf(stderr, "trying to access protected page");
+
+  // this should result in segmentation fault
+  page2_ptr->dummy_str[12] = 3;
+}
+
+static void protect_all() {
+  LinkerAllocator<test_struct_larger> allocator;
+  allocator.init();
+
+  // number of allocs to reach the end of first page
+  size_t n = kPageSize/sizeof(test_struct_larger) - 1;
+  test_struct_larger* page1_ptr = allocator.alloc();
+
+  for (size_t i=0; i<n; ++i) {
+    allocator.alloc();
+  }
+
+  test_struct_larger* page2_ptr = allocator.alloc();
+  allocator.protect_all(PROT_READ);
+  allocator.protect_all(PROT_READ | PROT_WRITE);
+  // check access
+  page2_ptr->dummy_str[23] = 27;
+  page1_ptr->dummy_str[13] = 11;
+
+  allocator.protect_all(PROT_READ);
+  fprintf(stderr, "trying to access protected page");
+
+  // this should result in segmentation fault
+  page1_ptr->dummy_str[11] = 7;
+}
+
+TEST(linker_allocator, test_protect) {
+  testing::FLAGS_gtest_death_test_style = "threadsafe";
+  ASSERT_EXIT(protect_one_page(), testing::KilledBySignal(SIGSEGV), "trying to access protected page");
+  ASSERT_EXIT(protect_all(), testing::KilledBySignal(SIGSEGV), "trying to access protected page");
+}
+