Add explicit OMAP support to dump_syms.

common/windows/omap.cc

+// Copyright 2013 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.
+
+// This contains a suite of tools for transforming symbol information when
+// when that information has been extracted from a PDB containing OMAP
+// information.
+
+// OMAP information is a lightweight description of a mapping between two
+// address spaces. It consists of two streams, each of them a vector 2-tuples.
+// The OMAPTO stream contains tuples of the form
+//
+//   (RVA in transformed image, RVA in original image)
+//
+// while the OMAPFROM stream contains tuples of the form
+//
+//   (RVA in original image, RVA in transformed image)
+//
+// The entries in each vector are sorted by the first value of the tuple, and
+// the lengths associated with a mapping are implicit as the distance between
+// two successive addresses in the vector.
+
+// Consider a trivial 10-byte function described by the following symbol:
+//
+//   Function: RVA 0x00001000, length 10, "foo"
+//
+// Now consider the same function, but with 5-bytes of instrumentation injected
+// at offset 5. The OMAP streams describing this would look like:
+//
+//   OMAPTO  :  [ [0x00001000, 0x00001000],
+//                [0x00001005, 0xFFFFFFFF],
+//                [0x0000100a, 0x00001005] ]
+//   OMAPFROM:  [ [0x00001000, 0x00001000],
+//                [0x00001005, 0x0000100a] ]
+//
+// In this case the injected code has been marked as not originating in the
+// source image, and thus it will have no symbol information at all. However,
+// the injected code may also be associated with an original address range;
+// for example, when prepending instrumentation to a basic block the
+// instrumentation can be labelled as originating from the same source BB such
+// that symbol resolution will still find the appropriate source code line
+// number. In this case the OMAP stream would look like:
+//
+//   OMAPTO  :  [ [0x00001000, 0x00001000],
+//                [0x00001005, 0x00001005],
+//                [0x0000100a, 0x00001005] ]
+//   OMAPFROM:  [ [0x00001000, 0x00001000],
+//                [0x00001005, 0x0000100a] ]
+//
+// Suppose we asked DIA to lookup the symbol at location 0x0000100a of the
+// instrumented image. It would first run this through the OMAPTO table and
+// translate that address to 0x00001005. It would then lookup the symbol
+// at that address and return the symbol for the function "foo". This is the
+// correct result.
+//
+// However, if we query DIA for the length and address of the symbol it will
+// tell us that it has length 10 and is at RVA 0x00001000. The location is
+// correct, but the length doesn't take into account the 5-bytes of injected
+// code. Symbol resolution works (starting from an instrumented address,
+// mapping to an original address, and looking up a symbol), but the symbol
+// metadata is incorrect.
+//
+// If we dump the symbols using DIA they will have their addresses
+// appropriately transformed and reflect positions in the instrumented image.
+// However, if we try to do a lookup using those symbols resolution can fail.
+// For example, the address 0x0000100a will not map to the symbol for "foo",
+// because DIA tells us it is at location 0x00001000 (correct) with length
+// 10 (incorrect). The problem is one of order of operations: in this case
+// we're attempting symbol resolution by looking up an instrumented address
+// in the table of translated symbols.
+//
+// One way to handle this is to dump the OMAP information as part of the
+// breakpad symbols. This requires the rest of the toolchain to be aware of
+// OMAP information and to use it when present prior to performing lookup. The
+// other option is to properly transform the symbols (updating length as well as
+// position) so that resolution will work as expected for translated addresses.
+// This is transparent to the rest of the toolchain.
+
+#include "common/windows/omap.h"
+
+#include <atlbase.h>
+
+#include <algorithm>
+#include <cassert>
+#include <set>
+
+#include "common/windows/dia_util.h"
+
+namespace google_breakpad {
+
+namespace {
+
+static const wchar_t kOmapToDebugStreamName[] = L"OMAPTO";
+static const wchar_t kOmapFromDebugStreamName[] = L"OMAPFROM";
+
+// Dependending on where this is used in breakpad we sometimes get min/max from
+// windef, and other times from algorithm. To get around this we simply
+// define our own min/max functions.
+template<typename T>
+const T& Min(const T& t1, const T& t2) { return t1 < t2 ? t1 : t2; }
+template<typename T>
+const T& Max(const T& t1, const T& t2) { return t1 > t2 ? t1 : t2; }
+
+// It makes things more readable to have two different OMAP types. We cast
+// normal OMAPs into these. They must be the same size as the OMAP structure
+// for this to work, hence the static asserts.
+struct OmapOrigToTran {
+  DWORD rva_original;
+  DWORD rva_transformed;
+};
+struct OmapTranToOrig {
+  DWORD rva_transformed;
+  DWORD rva_original;
+};
+static_assert(sizeof(OmapOrigToTran) == sizeof(OMAP),
+              "OmapOrigToTran must have same size as OMAP.");
+static_assert(sizeof(OmapTranToOrig) == sizeof(OMAP),
+              "OmapTranToOrig must have same size as OMAP.");
+typedef std::vector<OmapOrigToTran> OmapFromTable;
+typedef std::vector<OmapTranToOrig> OmapToTable;
+
+// Used for sorting and searching through a Mapping.
+bool MappedRangeOriginalLess(const MappedRange& lhs, const MappedRange& rhs) {
+  if (lhs.rva_original < rhs.rva_original)
+    return true;
+  if (lhs.rva_original > rhs.rva_original)
+    return false;
+  return lhs.length < rhs.length;
+}
+bool MappedRangeMappedLess(const MappedRange& lhs, const MappedRange& rhs) {
+  if (lhs.rva_transformed < rhs.rva_transformed)
+    return true;
+  if (lhs.rva_transformed > rhs.rva_transformed)
+    return false;
+  return lhs.length < rhs.length;
+}
+
+// Used for searching through the EndpointIndexMap.
+bool EndpointIndexLess(const EndpointIndex& ei1, const EndpointIndex& ei2) {
+  return ei1.endpoint < ei2.endpoint;
+}
+
+// Finds the debug stream with the given |name| in the given |session|, and
+// populates |table| with its contents. Casts the data directly into OMAP
+// structs.
+bool FindAndLoadOmapTable(const wchar_t* name,
+                          IDiaSession* session,
+                          OmapTable* table) {
+  assert(name != NULL);
+  assert(session != NULL);
+  assert(table != NULL);
+
+  CComPtr<IDiaEnumDebugStreamData> stream;
+  if (!FindDebugStream(name, session, &stream))
+    return false;
+  assert(stream.p != NULL);
+
+  LONG count = 0;
+  if (FAILED(stream->get_Count(&count))) {
+    fprintf(stderr, "IDiaEnumDebugStreamData::get_Count failed for stream "
+                    "\"%ws\"\n", name);
+    return false;
+  }
+
+  // Get the length of the stream in bytes.
+  DWORD bytes_read = 0;
+  ULONG count_read = 0;
+  if (FAILED(stream->Next(count, 0, &bytes_read, NULL, &count_read))) {
+    fprintf(stderr, "IDiaEnumDebugStreamData::Next failed while reading "
+                    "length of stream \"%ws\"\n", name);
+    return false;
+  }
+
+  // Ensure it's consistent with the OMAP data type.
+  DWORD bytes_expected = count * sizeof(OmapTable::value_type);
+  if (count * sizeof(OmapTable::value_type) != bytes_read) {
+    fprintf(stderr, "DIA debug stream \"%ws\" has an unexpected length", name);
+    return false;
+  }
+
+  // Read the table.
+  table->resize(count);
+  bytes_read = 0;
+  count_read = 0;
+  if (FAILED(stream->Next(count, bytes_expected, &bytes_read,
+                          reinterpret_cast<BYTE*>(&table->at(0)),
+                          &count_read))) {
+    fprintf(stderr, "IDiaEnumDebugStreamData::Next failed while reading "
+                    "data from stream \"%ws\"\n");
+    return false;
+  }
+
+  return true;
+}
+
+// This determines the original image length by looking through the segment
+// table.
+bool GetOriginalImageLength(IDiaSession* session, DWORD* image_length) {
+  assert(session != NULL);
+  assert(image_length != NULL);
+
+  CComPtr<IDiaEnumSegments> enum_segments;
+  if (!FindTable(session, &enum_segments))
+    return false;
+  assert(enum_segments.p != NULL);
+
+  DWORD temp_image_length = 0;
+  CComPtr<IDiaSegment> segment;
+  ULONG fetched = 0;
+  while (SUCCEEDED(enum_segments->Next(1, &segment, &fetched)) &&
+         fetched == 1) {
+    assert(segment.p != NULL);
+
+    DWORD rva = 0;
+    DWORD length = 0;
+    DWORD frame = 0;
+    if (FAILED(segment->get_relativeVirtualAddress(&rva)) ||
+        FAILED(segment->get_length(&length)) ||
+        FAILED(segment->get_frame(&frame))) {
+      fprintf(stderr, "Failed to get basic properties for IDiaSegment\n");
+      return false;
+    }
+
+    if (frame > 0) {
+      DWORD segment_end = rva + length;
+      if (segment_end > temp_image_length)
+        temp_image_length = segment_end;
+    }
+    segment.Release();
+  }
+
+  *image_length = temp_image_length;
+  return true;
+}
+
+// Detects regions of the original image that have been removed in the
+// transformed image, and sets the 'removed' property on all mapped ranges
+// immediately preceding a gap. The mapped ranges must be sorted by
+// 'rva_original'.
+void FillInRemovedLengths(Mapping* mapping) {
+  assert(mapping != NULL);
+
+  // Find and fill gaps. We do this with two sweeps. We first sweep forward
+  // looking for gaps. When we identify a gap we then sweep forward with a
+  // second scan and set the 'removed' property for any intervals that
+  // immediately precede the gap.
+  //
+  // Gaps are typically between two successive intervals, but not always:
+  //
+  //   Range 1: ---------------
+  //   Range 2:     -------

[chrisha, 2013/05/01 14:38:37]

Siggi: This should give some more insight into how 'repeated source ranges' are
handled. This is the pertinent function.

+  //   Range 3:                      -------------
+  //   Gap    :                ******
+  //
+  // In the above example the gap is between range 1 and range 3. A forward
+  // sweep finds the gap, and a second forward sweep identifies that range 1
+  // immediately precedes the gap and sets its 'removed' property.
+
+  size_t fill = 0;
+  DWORD rva_front = 0;
+  for (size_t find = 0; find < mapping->size(); ++find) {
+#ifndef NDEBUG
+    // We expect the mapped ranges to be sorted by 'rva_original'.
+    if (find > 0) {
+      assert(mapping->at(find - 1).rva_original <=
+                 mapping->at(find).rva_original);
+    }
+#endif
+
+    if (rva_front < mapping->at(find).rva_original) {
+      // We've found a gap. Fill it in by setting the 'removed' property for
+      // any affected intervals.
+      DWORD removed = mapping->at(find).rva_original - rva_front;
+      for (; fill < find; ++fill) {
+        if (mapping->at(fill).rva_original + mapping->at(fill).length !=
+                rva_front) {
+          continue;
+        }
+
+        // This interval ends right where the gap starts. It needs to have its
+        // 'removed' information filled in.
+        mapping->at(fill).removed = removed;
+      }
+    }
+
+    // Advance the front that indicates the covered portion of the image.
+    rva_front = mapping->at(find).rva_original + mapping->at(find).length;
+  }
+}
+
+// Builds a unified view of the mapping between the original and transformed
+// image space by merging OMAPTO and OMAPFROM data.
+void BuildMapping(const OmapData& omap_data, Mapping* mapping) {
+  assert(mapping != NULL);
+
+  mapping->clear();
+
+  if (omap_data.omap_from.empty() || omap_data.omap_to.empty())
+    return;
+
+  // The names 'omap_to' and 'omap_from' are awfully confusing, so we make
+  // ourselves more explicit here. This cast is only safe because the underlying
+  // types have the exact same size.
+  const OmapToTable& tran2orig =
+      reinterpret_cast<const OmapToTable&>(omap_data.omap_to);
+  const OmapFromTable& orig2tran = reinterpret_cast<const OmapFromTable&>(
+      omap_data.omap_from);
+
+  // Handle the range of data at the beginning of the image. This is not usually
+  // specified by the OMAP data.
+  if (tran2orig[0].rva_transformed > 0 && orig2tran[0].rva_original > 0) {
+    DWORD header_transformed = tran2orig[0].rva_transformed;
+    DWORD header_original = orig2tran[0].rva_original;
+    DWORD header = Min(header_transformed, header_original);
+
+    MappedRange mr = {};
+    mr.length = header;
+    mr.injected = header_transformed - header;
+    mr.removed = header_original - header;
+    mapping->push_back(mr);
+  }
+
+  // Convert the implied lengths to explicit lengths, and infer which content
+  // has been injected into the transformed image. Injected content is inferred
+  // as regions of the transformed address space that does not map back to
+  // known valid content in the original image.
+  for (size_t i = 0; i < tran2orig.size(); ++i) {
+    const OmapTranToOrig& o1 = tran2orig[i];
+
+    // This maps to content that is outside the original image, thus it
+    // describes injected content. We can skip this entry.
+    if (o1.rva_original >= omap_data.length_original)
+      continue;
+
+    // Calculate the length of the current OMAP entry. This is implicit as the
+    // distance between successive |rva| values, capped at the end of the
+    // original image.
+    DWORD length = 0;
+    if (i + 1 < tran2orig.size()) {
+      const OmapTranToOrig& o2 = tran2orig[i + 1];
+
+      // We expect the table to be sorted by rva_transformed.
+      assert(o1.rva_transformed <= o2.rva_transformed);
+
+      length = o2.rva_transformed - o1.rva_transformed;
+      if (o1.rva_original + length > omap_data.length_original) {
+        length = omap_data.length_original - o1.rva_original;
+      }
+    } else {
+      length = omap_data.length_original - o1.rva_original;
+    }
+
+    // Zero-length entries don't describe anything and can be ignored.
+    if (length == 0)
+      continue;
+
+    // Any gaps in the transformed address-space are due to injected content.
+    if (!mapping->empty()) {
+      MappedRange& prev_mr = mapping->back();
+      prev_mr.injected += o1.rva_transformed -
+          (prev_mr.rva_transformed + prev_mr.length);
+    }
+
+    MappedRange mr = {};
+    mr.rva_original = o1.rva_original;
+    mr.rva_transformed = o1.rva_transformed;
+    mr.length = length;
+    mapping->push_back(mr);
+  }
+
+  // Sort based on the original image addresses.
+  std::sort(mapping->begin(), mapping->end(), MappedRangeOriginalLess);
+
+  // Fill in the 'removed' lengths by looking for gaps in the coverage of the
+  // original address space.
+  FillInRemovedLengths(mapping);
+
+  return;
+}
+
+void BuildEndpointIndexMap(ImageMap* image_map) {
+  assert(image_map != NULL);
+
+  if (image_map->mapping.size() == 0)
+    return;
+
+  const Mapping& mapping = image_map->mapping;
+  EndpointIndexMap& eim = image_map->endpoint_index_map;
+
+  // Get the unique set of interval endpoints.
+  std::set<DWORD> endpoints;
+  for (size_t i = 0; i < mapping.size(); ++i) {
+    endpoints.insert(mapping[i].rva_original);
+    endpoints.insert(mapping[i].rva_original +
+                         mapping[i].length +
+                         mapping[i].removed);
+  }
+
+  // Use the endpoints to initialize the secondary search structure for the
+  // mapping.
+  eim.resize(endpoints.size());
+  std::set<DWORD>::const_iterator it = endpoints.begin();
+  for (size_t i = 0; it != endpoints.end(); ++it, ++i) {
+    eim[i].endpoint = *it;
+    eim[i].index = mapping.size();
+  }
+
+  // For each endpoint we want the smallest index of any interval containing
+  // it. We iterate over the intervals and update the indices associated with
+  // each interval endpoint contained in the current interval. In the general
+  // case of an arbitrary set of intervals this is O(n^2), but the structure of
+  // OMAP data makes this O(n).
+  for (size_t i = 0; i < mapping.size(); ++i) {
+    EndpointIndex ei1 = { mapping[i].rva_original, 0 };
+    EndpointIndexMap::iterator it1 = std::lower_bound(
+        eim.begin(), eim.end(), ei1, EndpointIndexLess);
+
+    EndpointIndex ei2 = { mapping[i].rva_original + mapping[i].length +
+                              mapping[i].removed, 0 };
+    EndpointIndexMap::iterator it2 = std::lower_bound(
+        eim.begin(), eim.end(), ei2, EndpointIndexLess);
+
+    for (; it1 != it2; ++it1)
+      it1->index = Min(i, it1->index);
+  }
+}
+
+// Clips the given mapped range.
+void ClipMappedRangeOriginal(const AddressRange& clip_range,
+                             MappedRange* mapped_range) {
+  assert(mapped_range != NULL);
+
+  // The clipping range is entirely outside of the mapped range.
+  if (clip_range.end() <= mapped_range->rva_original ||
+      mapped_range->rva_original + mapped_range->length +
+          mapped_range->removed <= clip_range.rva) {
+    mapped_range->length = 0;
+    mapped_range->injected = 0;
+    mapped_range->removed = 0;
+    return;
+  }
+
+  // Clip the left side.
+  if (mapped_range->rva_original < clip_range.rva) {
+    DWORD clip_left = clip_range.rva - mapped_range->rva_original;
+    mapped_range->rva_original += clip_left;
+    mapped_range->rva_transformed += clip_left;
+
+    if (clip_left > mapped_range->length) {
+      // The left clipping boundary entirely erases the content section of the
+      // range.
+      DWORD trim = clip_left - mapped_range->length;
+      mapped_range->length = 0;
+      mapped_range->injected -= Min(trim, mapped_range->injected);
+      // We know that trim <= mapped_range->remove.
+      mapped_range->removed -= trim;
+    } else {
+      // The left clipping boundary removes some, but not all, of the content.
+      // As such it leaves the removed/injected component intact.
+      mapped_range->length -= clip_left;
+    }
+  }
+
+  // Clip the right side.
+  DWORD end_original = mapped_range->rva_original + mapped_range->length;
+  if (clip_range.end() < end_original) {
+    // The right clipping boundary lands in the 'content' section of the range,
+    // entirely clearing the injected/removed portion.
+    DWORD clip_right = end_original - clip_range.end();
+    mapped_range->length -= clip_right;
+    mapped_range->injected = 0;
+    mapped_range->removed = 0;
+    return;
+  } else {
+    // The right clipping boundary is outside of the content, but may affect
+    // the removed/injected portion of the range.
+    DWORD end_removed = end_original + mapped_range->removed;
+    if (clip_range.end() < end_removed)
+      mapped_range->removed = clip_range.end() - end_original;
+
+    DWORD end_injected = end_original + mapped_range->injected;
+    if (clip_range.end() < end_injected)
+      mapped_range->injected = clip_range.end() - end_original;
+  }
+
+  return;
+}
+
+}  // namespace
+
+int AddressRange::Compare(const AddressRange& rhs) const {
+  if (end() <= rhs.rva)
+    return -1;
+  if (rhs.end() <= rva)
+    return 1;
+  return 0;
+}
+
+bool GetOmapDataAndDisableTranslation(IDiaSession* session,
+                                      OmapData* omap_data) {
+  assert(session != NULL);
+  assert(omap_data != NULL);
+
+  CComPtr<IDiaAddressMap> address_map;
+  if (FAILED(session->QueryInterface(&address_map))) {
+    fprintf(stderr, "IDiaSession::QueryInterface(IDiaAddressMap) failed\n");
+    return false;
+  }
+  assert(address_map.p != NULL);
+
+  BOOL omap_enabled = FALSE;
+  if (FAILED(address_map->get_addressMapEnabled(&omap_enabled))) {
+    fprintf(stderr, "IDiaAddressMap::get_addressMapEnabled failed\n");
+    return false;
+  }
+
+  if (!omap_enabled) {
+    // We indicate the non-presence of OMAP data by returning empty tables.
+    omap_data->omap_from.clear();
+    omap_data->omap_to.clear();
+    omap_data->length_original = 0;
+    return true;
+  }
+
+  // OMAP data is present. Disable translation.
+  if (FAILED(address_map->put_addressMapEnabled(FALSE))) {
+    fprintf(stderr, "IDiaAddressMap::put_addressMapEnabled failed\n");
+    return false;
+  }
+
+  // Read the OMAP streams.
+  if (!FindAndLoadOmapTable(kOmapFromDebugStreamName,
+                            session,
+                            &omap_data->omap_from)) {
+    return false;
+  }
+  if (!FindAndLoadOmapTable(kOmapToDebugStreamName,
+                            session,
+                            &omap_data->omap_to)) {
+    return false;
+  }
+
+  // Get the lengths of the address spaces.
+  if (!GetOriginalImageLength(session, &omap_data->length_original))
+    return false;
+
+  return true;
+}
+
+void BuildImageMap(const OmapData& omap_data, ImageMap* image_map) {
+  assert(image_map != NULL);
+
+  BuildMapping(omap_data, &image_map->mapping);
+  BuildEndpointIndexMap(image_map);
+}
+
+void MapAddressRange(const ImageMap& image_map,
+                     const AddressRange& original_range,
+                     AddressRangeVector* mapped_ranges) {
+  assert(mapped_ranges != NULL);
+
+  const Mapping& map = image_map.mapping;
+
+  // Handle the trivial case of an empty image_map. This means that there is
+  // no transformation to be applied, and we can simply return the original
+  // range.
+  if (map.empty()) {
+    mapped_ranges->push_back(original_range);
+    return;
+  }
+
+  // If we get a query of length 0 we need to handle it by using a non-zero
+  // query length.
+  AddressRange query_range(original_range);
+  if (query_range.length == 0)
+    query_range.length = 1;
+
+  // Find the range of intervals that can potentially intersect our query range.
+  size_t imin = 0;
+  size_t imax = 0;
+  {
+    // The index of the earliest possible range that can affect is us done by
+    // searching through the secondary indexing structure.
+    const EndpointIndexMap& eim = image_map.endpoint_index_map;
+    EndpointIndex q1 = { query_range.rva, 0 };
+    EndpointIndexMap::const_iterator it1 = std::lower_bound(
+        eim.begin(), eim.end(), q1, EndpointIndexLess);
+    if (it1 == eim.end()) {
+      imin  = map.size();
+    } else {
+      // Backup to find the interval that contains our query point.
+      if (it1 != eim.begin() && query_range.rva < it1->endpoint)
+        --it1;
+      imin = it1->index;
+    }
+
+    // The first range that can't possibly intersect us is found by searching
+    // through the image map directly as it is already sorted by interval start
+    // point.
+    MappedRange q2 = { query_range.end(), 0 };
+    Mapping::const_iterator it2 = std::lower_bound(
+        map.begin(), map.end(), q2, MappedRangeOriginalLess);
+    imax = it2 - map.begin();
+  }
+
+  // Find all intervals that intersect the query range.
+  Mapping temp_map;
+  for (size_t i = imin; i < imax; ++i) {
+    MappedRange mr = map[i];
+    ClipMappedRangeOriginal(query_range, &mr);
+    if (mr.length + mr.injected > 0)
+      temp_map.push_back(mr);
+  }
+
+  // If there are no intersecting ranges then the query range has been removed
+  // from the image in question.
+  if (temp_map.empty())
+    return;
+
+  // Sort based on transformed addresses.
+  std::sort(temp_map.begin(), temp_map.end(), MappedRangeMappedLess);
+
+  // Zero-length queries can't actually be merged. We simply output the set of
+  // unique RVAs that correspond to the query RVA.
+  if (original_range.length == 0) {
+    mapped_ranges->push_back(AddressRange(temp_map[0].rva_transformed, 0));
+    for (size_t i = 1; i < temp_map.size(); ++i) {
+      if (temp_map[i].rva_transformed > mapped_ranges->back().rva)
+        mapped_ranges->push_back(AddressRange(temp_map[i].rva_transformed, 0));
+    }
+    return;
+  }
+
+  // Merge any ranges that are consecutive in the mapped image. We merge over
+  // injected content if it makes ranges contiguous, but we ignore any injected
+  // content at the tail end of a range. This allows us to detect symbols that
+  // have been lengthened by injecting content in the middle. However, it
+  // misses the case where content has been injected at the head or the tail.
+  // The problem is that it doesn't know whether to attribute it to the
+  // preceding or following symbol. It is up to the author of the transform to
+  // output explicit OMAP info in these cases to ensure full coverage of the
+  // transformed address space.
+  DWORD rva_begin = temp_map[0].rva_transformed;
+  DWORD rva_cur_content = rva_begin + temp_map[0].length;
+  DWORD rva_cur_injected = rva_cur_content + temp_map[0].injected;
+  for (size_t i = 1; i < temp_map.size(); ++i) {
+    if (rva_cur_injected < temp_map[i].rva_transformed) {
+      // This marks the end of a continuous range in the image. Output the
+      // current range and start a new one.
+      if (rva_begin < rva_cur_content) {
+        mapped_ranges->push_back(
+            AddressRange(rva_begin, rva_cur_content - rva_begin));
+      }
+      rva_begin = temp_map[i].rva_transformed;
+    }
+
+    rva_cur_content = temp_map[i].rva_transformed + temp_map[i].length;
+    rva_cur_injected = rva_cur_content + temp_map[i].injected;
+  }
+
+  // Output the range in progress.
+  if (rva_begin < rva_cur_content) {
+    mapped_ranges->push_back(
+        AddressRange(rva_begin, rva_cur_content - rva_begin));
+  }
+
+  return;
+}
+
+}  // namespace google_breakpad