Add TaskMemory, which can read another Mach task’s memory, and its test

util/mach/task_memory.cc

Index: util/mach/task_memory.cc
diff --git a/util/mach/task_memory.cc b/util/mach/task_memory.cc
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+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// 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 "util/mach/task_memory.h"
+
+#include <mach/mach_vm.h>
+#include <string.h>
+
+#include <algorithm>
+
+#include "base/logging.h"
+#include "base/mac/mach_logging.h"
+#include "base/mac/scoped_mach_vm.h"
+#include "base/strings/stringprintf.h"
+
+namespace crashpad {
+
+TaskMemory::TaskMemory(mach_port_t task) : task_(task) {
+}
+
+bool TaskMemory::Read(mach_vm_address_t address, size_t size, void* buffer) {
+  if (size == 0) {
+    return true;
+  }
+
+  mach_vm_address_t region_address = mach_vm_trunc_page(address);
+  mach_vm_size_t region_size =
+      mach_vm_round_page(address - region_address + size);
+
+  vm_offset_t region;
+  mach_msg_type_number_t region_count;
+  kern_return_t kr =
+      mach_vm_read(task_, region_address, region_size, &region, &region_count);
+  if (kr != KERN_SUCCESS) {
+    MACH_LOG(WARNING, kr) << base::StringPrintf(
+        "mach_vm_read(0x%llx, 0x%llx)", region_address, region_size);
+    return false;
+  }
+
+  DCHECK_EQ(region_count, region_size);
+  base::mac::ScopedMachVM region_owner(region, region_count);
+
+  const char* region_base = reinterpret_cast<const char*>(region);
+  memcpy(buffer, &region_base[address - region_address], size);
+
+  return true;
+}
+
+bool TaskMemory::ReadCString(mach_vm_address_t address, std::string* string) {
+  return ReadCStringInternal(address, false, 0, string);
+}
+
+bool TaskMemory::ReadCStringSizeLimited(mach_vm_address_t address,
+                                        mach_vm_size_t size,
+                                        std::string* string) {
+  return ReadCStringInternal(address, true, size, string);
+}
+
+bool TaskMemory::ReadCStringInternal(mach_vm_address_t address,
+                                     bool has_size,
+                                     mach_vm_size_t size,
+                                     std::string* string) {
+  if (has_size) {
+    if (size == 0)  {
+      string->clear();
+      return true;
+    }
+  } else {
+    size = PAGE_SIZE;
+  }
+
+  std::string local_string;
+  mach_vm_address_t read_address = address;
+  do {
+    mach_vm_size_t read_length =
+        std::min(size, PAGE_SIZE - (read_address % PAGE_SIZE));
+    std::string read_string(read_length, '\0');
+    if (!Read(read_address, read_length, &read_string[0])) {
+      return false;
+    }
+
+    size_t terminator = read_string.find_first_of('\0');
+    if (terminator == std::string::npos) {
+      local_string.append(read_string);
+    } else {
+      local_string.append(read_string, 0, terminator);
+      string->swap(local_string);
+      return true;
+    }
+
+    if (has_size) {
+      size -= read_length;
+    }
+    read_address = mach_vm_trunc_page(read_address + read_length);
+  } while ((!has_size || size > 0) && read_address > address);
+
+  LOG(WARNING) << base::StringPrintf("unterminated string at 0x%llx", address);
+  return false;
+}
+
+}  // namespace crashpad