Add a MappedMemory interface to TaskMemory and use it in MachOImageSymbolTableReader

util/mach/task_memory.cc

 // 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"
+#include "util/stdlib/strnlen.h"
 
 namespace crashpad {
 
+TaskMemory::MappedMemory::~MappedMemory() {
+}
+
+bool TaskMemory::MappedMemory::ReadCString(
+    size_t offset, std::string* string) const {
+  if (offset >= user_size_) {
+    LOG(WARNING) << "offset out of range";
+    return false;
+  }
+
+  const char* string_base = reinterpret_cast<const char*>(data_) + offset;
+  size_t max_length = user_size_ - offset;
+  size_t string_length = strnlen(string_base, max_length);
+  if (string_length == max_length) {
+    LOG(WARNING) << "unterminated string";
+    return false;
+  }
+
+  string->assign(string_base, string_length);
+  return true;
+}
+
+TaskMemory::MappedMemory::MappedMemory(vm_address_t vm_address,
+                                       size_t vm_size,
+                                       size_t user_offset,
+                                       size_t user_size)
+    : vm_(vm_address, vm_size),
+      data_(reinterpret_cast<const void*>(vm_address + user_offset)),
+      user_size_(user_size) {
+  vm_address_t vm_end = vm_address + vm_size;
+  vm_address_t user_address = reinterpret_cast<vm_address_t>(data_);
+  vm_address_t user_end = user_address + user_size;
+  DCHECK_GE(user_address, vm_address);
+  DCHECK_LE(user_address, vm_end);
+  DCHECK_GE(user_end, vm_address);
+  DCHECK_LE(user_end, vm_end);
+}
+
 TaskMemory::TaskMemory(mach_port_t task) : task_(task) {
 }
 
 bool TaskMemory::Read(mach_vm_address_t address, size_t size, void* buffer) {
+  scoped_ptr<MappedMemory> memory = ReadMapped(address, size);
+  if (!memory) {
+    return false;
+  }
+
+  memcpy(buffer, memory->data(), size);
+  return true;
+}
+
+scoped_ptr<TaskMemory::MappedMemory> TaskMemory::ReadMapped(
+    mach_vm_address_t address, size_t size) {
   if (size == 0) {
-    return true;
+    return scoped_ptr<MappedMemory>(new MappedMemory(0, 0, 0, 0));
   }
 
   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;
+    return scoped_ptr<MappedMemory>();
   }
 
   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;
+  return scoped_ptr<MappedMemory>(
+      new MappedMemory(region, region_size, address - region_address, size));
 }
 
 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);
@@ skipping 10 matching lines @@
     }
   } 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])) {
+    scoped_ptr<MappedMemory> read_region =
+        ReadMapped(read_address, read_length);
+    if (!read_region) {
       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);
+    const char* read_region_data =
+        reinterpret_cast<const char*>(read_region->data());
+    size_t read_region_data_length = strnlen(read_region_data, read_length);
+    local_string.append(read_region_data, read_region_data_length);
+    if (read_region_data_length < read_length) {
       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