path: root/src/client/mac/handler/dynamic_images.cc

// Copyright (c) 2007, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

extern "C" { // needed to compile on Leopard
  #include <mach-o/nlist.h>
  #include <stdlib.h>
  #include <stdio.h>
}

#include <dlfcn.h>
#include <mach/mach_vm.h>
#include <algorithm>
#include "client/mac/handler/dynamic_images.h"

namespace google_breakpad {

//==============================================================================
// Returns the size of the memory region containing |address| and the
// number of bytes from |address| to the end of the region.
// We potentially, will extend the size of the original
// region by the size of the following region if it's contiguous with the
// first in order to handle cases when we're reading strings and they
// straddle two vm regions.
//
static mach_vm_size_t GetMemoryRegionSize(task_port_t target_task,
                                          const void* address,
                                          mach_vm_size_t *size_to_end) {
  mach_vm_address_t region_base = (mach_vm_address_t)address;
  mach_vm_size_t region_size;
  natural_t nesting_level = 0;
  vm_region_submap_info submap_info;
  mach_msg_type_number_t info_count = VM_REGION_SUBMAP_INFO_COUNT;

  // Get information about the vm region containing |address|
  vm_region_recurse_info_t region_info;
  region_info = reinterpret_cast<vm_region_recurse_info_t>(&submap_info);

  kern_return_t result =
    mach_vm_region_recurse(target_task,
                           &region_base,
                           &region_size,
                           &nesting_level,
                           region_info,
                           &info_count);

  if (result == KERN_SUCCESS) {
    // Get distance from |address| to the end of this region
    *size_to_end = region_base + region_size -(mach_vm_address_t)address;

    // If we want to handle strings as long as 4096 characters we may need
    // to check if there's a vm region immediately following the first one.
    // If so, we need to extend |*size_to_end| to go all the way to the end
    // of the second region.
    if (*size_to_end < 4096) {
      // Second region starts where the first one ends
      mach_vm_address_t region_base2 =
        (mach_vm_address_t)(region_base + region_size);
      mach_vm_size_t region_size2;

      // Get information about the following vm region
      result =
        mach_vm_region_recurse(target_task,
                               &region_base2,
                               &region_size2,
                               &nesting_level,
                               region_info,
                               &info_count);

      // Extend region_size to go all the way to the end of the 2nd region
      if (result == KERN_SUCCESS
          && region_base2 == region_base + region_size) {
        region_size += region_size2;
      }
    }

    *size_to_end = region_base + region_size -(mach_vm_address_t)address;
  } else {
    region_size = 0;
    *size_to_end = 0;
  }

  return region_size;
}

#define kMaxStringLength 8192
//==============================================================================
// Reads a NULL-terminated string from another task.
//
// Warning!  This will not read any strings longer than kMaxStringLength-1
//
static void* ReadTaskString(task_port_t target_task,
                            const void* address) {
  // The problem is we don't know how much to read until we know how long
  // the string is. And we don't know how long the string is, until we've read
  // the memory!  So, we'll try to read kMaxStringLength bytes
  // (or as many bytes as we can until we reach the end of the vm region).
  mach_vm_size_t size_to_end;
  GetMemoryRegionSize(target_task, address, &size_to_end);

  if (size_to_end > 0) {
    mach_vm_size_t size_to_read =
      size_to_end > kMaxStringLength ? kMaxStringLength : size_to_end;

    return ReadTaskMemory(target_task, address, size_to_read);
  }

  return NULL;
}

//==============================================================================
// Reads an address range from another task.  A block of memory is malloced
// and should be freed by the caller.
void* ReadTaskMemory(task_port_t target_task,
                     const void* address,
                     size_t length) {
  void* result = NULL;
  int systemPageSize = getpagesize();

  // use the negative of the page size for the mask to find the page address
  mach_vm_address_t page_address =
      reinterpret_cast<mach_vm_address_t>(address) && (-systemPageSize);

  mach_vm_address_t last_page_address =
      (reinterpret_cast<mach_vm_address_t>(address) + length +
       (systemPageSize - 1)) & (-systemPageSize);

  mach_vm_size_t page_size = last_page_address - page_address;
  uint8_t* local_start;
  uint32_t local_length;

  kern_return_t r = mach_vm_read(target_task,
                                 page_address,
                                 page_size,
                                 reinterpret_cast<vm_offset_t*>(&local_start),
                                 &local_length);

  if (r == KERN_SUCCESS) {
    result = malloc(length);
    if (result != NULL) {
      memcpy(result,
             &local_start[(mach_vm_address_t)address - page_address],
             length);
    }
    mach_vm_deallocate(mach_task_self(), (uintptr_t)local_start, local_length);
  }

  return result;
}

#pragma mark -

//==============================================================================
// Initializes vmaddr_, vmsize_, and slide_
void DynamicImage::CalculateMemoryInfo() {
  breakpad_mach_header *header = GetMachHeader();

  // unless we can process the header, ensure that calls to
  // IsValid() will return false
  vmaddr_ = 0;
  vmsize_ = 0;
  slide_ = 0;

#if __LP64__
  if(header->magic != MH_MAGIC_64) {
    return;
  }
#else
  if(header->magic != MH_MAGIC) {
    return;
  }
#endif

  const struct load_command *cmd =
    reinterpret_cast<const struct load_command *>(header + 1);

  for (unsigned int i = 0; cmd && (i < header->ncmds); ++i) {
    if (cmd->cmd == LC_SEGMENT) {
      const breakpad_mach_segment_command *seg =
        reinterpret_cast<const breakpad_mach_segment_command *>(cmd);

      if (!strcmp(seg->segname, "__TEXT")) {
        vmaddr_ = seg->vmaddr;
        vmsize_ = seg->vmsize;
        slide_ = 0;

        if (seg->fileoff == 0  &&  seg->filesize != 0) {
          slide_ = (uintptr_t)GetLoadAddress() - (uintptr_t)seg->vmaddr;
        }
        return;
      }
    }

    cmd = reinterpret_cast<const struct load_command *>
      (reinterpret_cast<const char *>(cmd) + cmd->cmdsize);
  }

}

void DynamicImage::Print() {
  const char *path = GetFilePath();
  if (!path) {
    path = "(unknown)";
  }
  printf("%p: %s\n", GetLoadAddress(), path);
  breakpad_mach_header *header = GetMachHeader();
  MachHeader(*header).Print();
  printf("vmaddr\t\t: %p\n", reinterpret_cast<void*>(GetVMAddr()));
  printf("vmsize\t\t: %llu\n", GetVMSize());
  printf("slide\t\t: %td\n", GetVMAddrSlide());
}

#pragma mark -

//==============================================================================
// Loads information about dynamically loaded code in the given task.
DynamicImages::DynamicImages(mach_port_t task)
  : task_(task) {
  ReadImageInfoForTask();
}

//==============================================================================
// This code was written using dyld_debug.c (from Darwin) as a guide.
void DynamicImages::ReadImageInfoForTask() {
  struct nlist l[8];
  memset(l, 0, sizeof(l) );

  // First we lookup the address of the "_dyld_all_image_infos" struct
  // which lives in "dyld".  This structure contains information about all
  // of the loaded dynamic images.
  struct nlist &list = l[0];
  list.n_un.n_name = const_cast<char *>("_dyld_all_image_infos");
  nlist("/usr/lib/dyld", &list);

  if (list.n_value) {
    // Read the structure inside of dyld that contains information about
    // loaded images.  We're reading from the desired task's address space.

    // Here we make the assumption that dyld loaded at the same address in
    // the crashed process vs. this one.  This is an assumption made in
    // "dyld_debug.c" and is said to be nearly always valid.
    dyld_all_image_infos *dyldInfo = reinterpret_cast<dyld_all_image_infos*>
      (ReadTaskMemory(task_,
                      reinterpret_cast<void*>(list.n_value),
                      sizeof(dyld_all_image_infos)));

    if (dyldInfo) {
      // number of loaded images
      int count = dyldInfo->infoArrayCount;

      // Read an array of dyld_image_info structures each containing
      // information about a loaded image.
      dyld_image_info *infoArray = reinterpret_cast<dyld_image_info*>
        (ReadTaskMemory(task_,
                        dyldInfo->infoArray,
                        count*sizeof(dyld_image_info)));

      image_list_.reserve(count);

      for (int i = 0; i < count; ++i) {
        dyld_image_info &info = infoArray[i];

        // First read just the mach_header from the image in the task.
        breakpad_mach_header *header = reinterpret_cast<breakpad_mach_header*>
          (ReadTaskMemory(task_,
                          info.load_address_,
                          sizeof(breakpad_mach_header)));

        if (!header)
          break;   // bail on this dynamic image

        // Now determine the total amount we really want to read based on the
        // size of the load commands.  We need the header plus all of the
        // load commands.
        unsigned int header_size =
            sizeof(breakpad_mach_header) + header->sizeofcmds;

        free(header);

        header = reinterpret_cast<breakpad_mach_header*>
          (ReadTaskMemory(task_, info.load_address_, header_size));

        // Read the file name from the task's memory space.
        char *file_path = NULL;
        if (info.file_path_) {
          // Although we're reading kMaxStringLength bytes, it's copied in the
          // the DynamicImage constructor below with the correct string length,
          // so it's not really wasting memory.
          file_path = reinterpret_cast<char*>
            (ReadTaskString(task_, info.file_path_));
        }

        // Create an object representing this image and add it to our list.
        DynamicImage *new_image;
        new_image = new DynamicImage(header,
                                     header_size,
                                     (breakpad_mach_header*)info.load_address_,
                                     file_path,
                                     info.file_mod_date_,
                                     task_);

        if (new_image->IsValid()) {
          image_list_.push_back(DynamicImageRef(new_image));
        } else {
          delete new_image;
        }

        if (file_path) {
          free(file_path);
        }
      }

      free(dyldInfo);
      free(infoArray);

      // sorts based on loading address
      sort(image_list_.begin(), image_list_.end() );
    }
  }
}

//==============================================================================
DynamicImage  *DynamicImages::GetExecutableImage() {
  int executable_index = GetExecutableImageIndex();

  if (executable_index >= 0) {
    return GetImage(executable_index);
  }

  return NULL;
}

//==============================================================================
// returns -1 if failure to find executable
int DynamicImages::GetExecutableImageIndex() {
  int image_count = GetImageCount();

  for (int i = 0; i < image_count; ++i) {
    DynamicImage  *image = GetImage(i);
    if (image->GetMachHeader()->filetype == MH_EXECUTE) {
      return i;
    }
  }

  return -1;
}

}  // namespace google_breakpad