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// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/zucchini/zucchini_gen.h"
#include <stddef.h>
#include <stdint.h>
#include <algorithm>
#include <map>
#include <memory>
#include <string>
#include <utility>
#include "base/logging.h"
#include "base/numerics/safe_conversions.h"
#include "components/zucchini/disassembler.h"
#include "components/zucchini/element_detection.h"
#include "components/zucchini/encoded_view.h"
#include "components/zucchini/ensemble_matcher.h"
#include "components/zucchini/equivalence_map.h"
#include "components/zucchini/heuristic_ensemble_matcher.h"
#include "components/zucchini/image_index.h"
#include "components/zucchini/imposed_ensemble_matcher.h"
#include "components/zucchini/patch_writer.h"
#include "components/zucchini/suffix_array.h"
#include "components/zucchini/targets_affinity.h"
namespace zucchini {
namespace {
// Parameters for patch generation.
constexpr double kMinEquivalenceSimilarity = 12.0;
constexpr double kMinLabelAffinity = 64.0;
} // namespace
std::vector<offset_t> FindExtraTargets(const TargetPool& projected_old_targets,
const TargetPool& new_targets) {
std::vector<offset_t> extra_targets;
std::set_difference(
new_targets.begin(), new_targets.end(), projected_old_targets.begin(),
projected_old_targets.end(), std::back_inserter(extra_targets));
return extra_targets;
}
// Label matching (between "old" and "new") can guide EquivalenceMap
// construction; but EquivalenceMap induces Label matching. This apparent "chick
// and egg" problem is solved by alternating 2 steps |num_iterations| times:
// - Associate targets based on previous EquivalenceMap. Note on the first
// iteration, EquivalenceMap is empty, resulting in a no-op.
// - Construct refined EquivalenceMap based on new targets associations.
EquivalenceMap CreateEquivalenceMap(const ImageIndex& old_image_index,
const ImageIndex& new_image_index,
int num_iterations) {
size_t pool_count = old_image_index.PoolCount();
// |target_affinities| is outside the loop to reduce allocation.
std::vector<TargetsAffinity> target_affinities(pool_count);
EquivalenceMap equivalence_map;
for (int i = 0; i < num_iterations; ++i) {
EncodedView old_view(old_image_index);
EncodedView new_view(new_image_index);
// Associate targets from "old" to "new" image based on |equivalence_map|
// for each reference pool.
for (const auto& old_pool_tag_and_targets :
old_image_index.target_pools()) {
PoolTag pool_tag = old_pool_tag_and_targets.first;
target_affinities[pool_tag.value()].InferFromSimilarities(
equivalence_map, old_pool_tag_and_targets.second.targets(),
new_image_index.pool(pool_tag).targets());
// Creates labels for strongly associated targets.
std::vector<uint32_t> old_labels;
std::vector<uint32_t> new_labels;
size_t label_bound = target_affinities[pool_tag.value()].AssignLabels(
kMinLabelAffinity, &old_labels, &new_labels);
old_view.SetLabels(pool_tag, std::move(old_labels), label_bound);
new_view.SetLabels(pool_tag, std::move(new_labels), label_bound);
}
// Build equivalence map, where references in "old" and "new" that share
// common semantics (i.e., their respective targets were associated earlier
// on) are considered equivalent.
equivalence_map.Build(
MakeSuffixArray<InducedSuffixSort>(old_view, old_view.Cardinality()),
old_view, new_view, target_affinities, kMinEquivalenceSimilarity);
}
return equivalence_map;
}
bool GenerateEquivalencesAndExtraData(ConstBufferView new_image,
const EquivalenceMap& equivalence_map,
PatchElementWriter* patch_writer) {
// Make 2 passes through |equivalence_map| to reduce write churn.
// Pass 1: Write all equivalences.
EquivalenceSink equivalences_sink;
for (const EquivalenceCandidate& candidate : equivalence_map)
equivalences_sink.PutNext(candidate.eq);
patch_writer->SetEquivalenceSink(std::move(equivalences_sink));
// Pass 2: Write data in gaps in |new_image| before / between after
// |equivalence_map| as "extra data".
ExtraDataSink extra_data_sink;
offset_t dst_offset = 0;
for (const EquivalenceCandidate& candidate : equivalence_map) {
extra_data_sink.PutNext(
new_image[{dst_offset, candidate.eq.dst_offset - dst_offset}]);
dst_offset = candidate.eq.dst_end();
DCHECK_LE(dst_offset, new_image.size());
}
extra_data_sink.PutNext(
new_image[{dst_offset, new_image.size() - dst_offset}]);
patch_writer->SetExtraDataSink(std::move(extra_data_sink));
return true;
}
bool GenerateRawDelta(
ConstBufferView old_image,
ConstBufferView new_image,
const EquivalenceMap& equivalence_map,
const ImageIndex& new_image_index,
const std::map<TypeTag, std::unique_ptr<ReferenceMixer>>& reference_mixers,
PatchElementWriter* patch_writer) {
RawDeltaSink raw_delta_sink;
// Visit |equivalence_map| blocks in |new_image| order. Find and emit all
// bytewise differences.
offset_t base_copy_offset = 0;
for (const EquivalenceCandidate& candidate : equivalence_map) {
Equivalence equivalence = candidate.eq;
// For each bytewise delta from |old_image| to |new_image|, compute "copy
// offset" and pass it along with delta to the sink.
for (offset_t i = 0; i < equivalence.length;) {
if (new_image_index.IsReference(equivalence.dst_offset + i)) {
DCHECK(new_image_index.IsToken(equivalence.dst_offset + i));
TypeTag type_tag =
new_image_index.LookupType(equivalence.dst_offset + i);
ReferenceMixer* mixer = reference_mixers.at(type_tag).get();
offset_t width = new_image_index.refs(type_tag).width();
// Reference delta has its own flow. On some architectures (e.g., x86)
// this does not involve raw delta, so we skip. On other architectures
// (e.g., ARM) references are mixed with other bits that may change, so
// we need to "mix" data and store some changed bits into raw delta.
if (mixer) {
ConstBufferView mixed_reference = mixer->Mix(
equivalence.src_offset + i, equivalence.dst_offset + i);
for (offset_t j = 0; j < width; ++j) {
int8_t diff =
mixed_reference[j] - old_image[equivalence.src_offset + i + j];
if (diff != 0)
raw_delta_sink.PutNext({base_copy_offset + i + j, diff});
}
}
i += width;
DCHECK_LE(i, equivalence.length);
} else {
int8_t diff = new_image[equivalence.dst_offset + i] -
old_image[equivalence.src_offset + i];
if (diff)
raw_delta_sink.PutNext({base_copy_offset + i, diff});
++i;
}
}
base_copy_offset += equivalence.length;
}
patch_writer->SetRawDeltaSink(std::move(raw_delta_sink));
return true;
}
bool GenerateReferencesDelta(const ReferenceSet& src_refs,
const ReferenceSet& dst_refs,
const TargetPool& projected_target_pool,
const OffsetMapper& offset_mapper,
const EquivalenceMap& equivalence_map,
ReferenceDeltaSink* reference_delta_sink) {
size_t ref_width = src_refs.width();
auto dst_ref = dst_refs.begin();
// For each equivalence, for each covered |dst_ref| and the matching
// |src_ref|, emit the delta between the respective target labels. Note: By
// construction, each reference location (with |ref_width|) lies either
// completely inside an equivalence or completely outside. We perform
// "straddle checks" throughout to verify this assertion.
for (const auto& candidate : equivalence_map) {
const Equivalence equiv = candidate.eq;
// Increment |dst_ref| until it catches up to |equiv|.
while (dst_ref != dst_refs.end() && dst_ref->location < equiv.dst_offset)
++dst_ref;
if (dst_ref == dst_refs.end())
break;
if (dst_ref->location >= equiv.dst_end())
continue;
// Straddle check.
DCHECK_LE(dst_ref->location + ref_width, equiv.dst_end());
offset_t src_loc =
equiv.src_offset + (dst_ref->location - equiv.dst_offset);
auto src_ref = std::lower_bound(
src_refs.begin(), src_refs.end(), src_loc,
[](const Reference& a, offset_t b) { return a.location < b; });
for (; dst_ref != dst_refs.end() &&
dst_ref->location + ref_width <= equiv.dst_end();
++dst_ref, ++src_ref) {
// Local offset of |src_ref| should match that of |dst_ref|.
DCHECK_EQ(src_ref->location - equiv.src_offset,
dst_ref->location - equiv.dst_offset);
offset_t old_offset = src_ref->target;
offset_t new_estimated_offset =
offset_mapper.ExtendedForwardProject(old_offset);
offset_t new_estimated_key =
projected_target_pool.KeyForNearestOffset(new_estimated_offset);
offset_t new_offset = dst_ref->target;
offset_t new_key = projected_target_pool.KeyForOffset(new_offset);
reference_delta_sink->PutNext(
static_cast<int32_t>(new_key - new_estimated_key));
}
if (dst_ref == dst_refs.end())
break; // Done.
// Straddle check.
DCHECK_GE(dst_ref->location, equiv.dst_end());
}
return true;
}
bool GenerateExtraTargets(const std::vector<offset_t>& extra_targets,
PoolTag pool_tag,
PatchElementWriter* patch_writer) {
TargetSink target_sink;
for (offset_t target : extra_targets)
target_sink.PutNext(target);
patch_writer->SetTargetSink(pool_tag, std::move(target_sink));
return true;
}
bool GenerateRawElement(const std::vector<offset_t>& old_sa,
ConstBufferView old_image,
ConstBufferView new_image,
PatchElementWriter* patch_writer) {
ImageIndex old_image_index(old_image);
ImageIndex new_image_index(new_image);
EquivalenceMap equivalences;
equivalences.Build(old_sa, EncodedView(old_image_index),
EncodedView(new_image_index), {},
kMinEquivalenceSimilarity);
patch_writer->SetReferenceDeltaSink({});
std::map<TypeTag, std::unique_ptr<ReferenceMixer>> reference_mixers;
return GenerateEquivalencesAndExtraData(new_image, equivalences,
patch_writer) &&
GenerateRawDelta(old_image, new_image, equivalences, new_image_index,
reference_mixers, patch_writer);
}
bool GenerateExecutableElement(ExecutableType exe_type,
ConstBufferView old_image,
ConstBufferView new_image,
PatchElementWriter* patch_writer) {
// Initialize Disassemblers.
std::unique_ptr<Disassembler> old_disasm =
MakeDisassemblerOfType(old_image, exe_type);
std::unique_ptr<Disassembler> new_disasm =
MakeDisassemblerOfType(new_image, exe_type);
if (!old_disasm || !new_disasm) {
LOG(ERROR) << "Failed to create Disassembler.";
return false;
}
DCHECK_EQ(old_disasm->GetExeType(), new_disasm->GetExeType());
// Initialize ImageIndexes.
ImageIndex old_image_index(old_image);
ImageIndex new_image_index(new_image);
if (!old_image_index.Initialize(old_disasm.get()) ||
!new_image_index.Initialize(new_disasm.get())) {
LOG(ERROR) << "Failed to create ImageIndex: Overlapping references found?";
return false;
}
DCHECK_EQ(old_image_index.PoolCount(), new_image_index.PoolCount());
EquivalenceMap equivalences =
CreateEquivalenceMap(old_image_index, new_image_index,
new_disasm->num_equivalence_iterations());
OffsetMapper offset_mapper(equivalences,
base::checked_cast<offset_t>(old_image.size()),
base::checked_cast<offset_t>(new_image.size()));
ReferenceDeltaSink reference_delta_sink;
for (const auto& old_targets : old_image_index.target_pools()) {
PoolTag pool_tag = old_targets.first;
TargetPool projected_old_targets = old_targets.second;
projected_old_targets.FilterAndProject(offset_mapper);
std::vector<offset_t> extra_target =
FindExtraTargets(projected_old_targets, new_image_index.pool(pool_tag));
projected_old_targets.InsertTargets(extra_target);
if (!GenerateExtraTargets(extra_target, pool_tag, patch_writer))
return false;
for (TypeTag type_tag : old_targets.second.types()) {
if (!GenerateReferencesDelta(old_image_index.refs(type_tag),
new_image_index.refs(type_tag),
projected_old_targets, offset_mapper,
equivalences, &reference_delta_sink)) {
return false;
}
}
}
std::map<TypeTag, std::unique_ptr<ReferenceMixer>> reference_mixers;
std::vector<ReferenceGroup> ref_groups = old_disasm->MakeReferenceGroups();
for (const auto& group : ref_groups) {
auto result = reference_mixers.emplace(
group.type_tag(),
group.GetMixer(old_image, new_image, old_disasm.get()));
DCHECK(result.second);
}
patch_writer->SetReferenceDeltaSink(std::move(reference_delta_sink));
return GenerateEquivalencesAndExtraData(new_image, equivalences,
patch_writer) &&
GenerateRawDelta(old_image, new_image, equivalences, new_image_index,
reference_mixers, patch_writer);
}
status::Code GenerateBufferCommon(ConstBufferView old_image,
ConstBufferView new_image,
std::unique_ptr<EnsembleMatcher> matcher,
EnsemblePatchWriter* patch_writer) {
if (!matcher->RunMatch(old_image, new_image)) {
LOG(INFO) << "RunMatch() failed, generating raw patch.";
return GenerateBufferRaw(old_image, new_image, patch_writer);
}
const std::vector<ElementMatch>& matches = matcher->matches();
LOG(INFO) << "Matching: Found " << matches.size()
<< " nontrivial matches and " << matcher->num_identical()
<< " identical matches.";
size_t num_elements = matches.size();
if (num_elements == 0) {
LOG(INFO) << "No nontrival matches, generating raw patch.";
return GenerateBufferRaw(old_image, new_image, patch_writer);
}
// "Gaps" are |new_image| bytes not covered by new_elements in |matches|.
// These are treated as raw data, and patched against the entire |old_image|.
// |patch_element_map| (keyed by "new" offsets) stores PatchElementWriter
// results so elements and "gap" results can be computed separately (to reduce
// peak memory usage), and later, properly serialized to |patch_writer|
// ordered by "new" offset.
std::map<offset_t, PatchElementWriter> patch_element_map;
// Variables to track element patching successes.
std::vector<BufferRegion> covered_new_regions;
size_t covered_new_bytes = 0;
// Process elements first, since non-fatal failures may turn some into gaps.
for (const ElementMatch& match : matches) {
BufferRegion new_region = match.new_element.region();
LOG(INFO) << "--- Match [" << new_region.lo() << "," << new_region.hi()
<< ")";
auto it_and_success = patch_element_map.emplace(
base::checked_cast<offset_t>(new_region.lo()), match);
DCHECK(it_and_success.second);
PatchElementWriter& patch_element = it_and_success.first->second;
ConstBufferView old_sub_image = old_image[match.old_element.region()];
ConstBufferView new_sub_image = new_image[new_region];
if (GenerateExecutableElement(match.exe_type(), old_sub_image,
new_sub_image, &patch_element)) {
covered_new_regions.push_back(new_region);
covered_new_bytes += new_region.size;
} else {
LOG(INFO) << "Fall back to raw patching.";
patch_element_map.erase(it_and_success.first);
}
}
if (covered_new_bytes < new_image.size()) {
// Process all "gaps", which are patched against the entire "old" image. To
// compute equivalence maps, "gaps" share a common suffix array
// |old_sa_raw|, whose lifetime is kept separated from elements' suffix
// arrays to reduce peak memory.
Element entire_old_element(old_image.local_region(), kExeTypeNoOp);
ImageIndex old_image_index(old_image);
EncodedView old_view_raw(old_image_index);
std::vector<offset_t> old_sa_raw =
MakeSuffixArray<InducedSuffixSort>(old_view_raw, size_t(256));
offset_t gap_lo = 0;
// Add sentinel that points to end of "new" file, to simplify gap iteration.
covered_new_regions.emplace_back(BufferRegion{new_image.size(), 0});
for (const BufferRegion& covered : covered_new_regions) {
offset_t gap_hi = base::checked_cast<offset_t>(covered.lo());
DCHECK_GE(gap_hi, gap_lo);
offset_t gap_size = gap_hi - gap_lo;
if (gap_size > 0) {
LOG(INFO) << "--- Gap [" << gap_lo << "," << gap_hi << ")";
ElementMatch gap_match{{entire_old_element, kExeTypeNoOp},
{{gap_lo, gap_size}, kExeTypeNoOp}};
auto it_and_success = patch_element_map.emplace(gap_lo, gap_match);
DCHECK(it_and_success.second);
PatchElementWriter& patch_element = it_and_success.first->second;
ConstBufferView new_sub_image = new_image[{gap_lo, gap_size}];
if (!GenerateRawElement(old_sa_raw, old_image, new_sub_image,
&patch_element)) {
return status::kStatusFatal;
}
}
gap_lo = base::checked_cast<offset_t>(covered.hi());
}
}
// Write all PatchElementWriter sorted by "new" offset.
for (auto& new_lo_and_patch_element : patch_element_map)
patch_writer->AddElement(std::move(new_lo_and_patch_element.second));
return status::kStatusSuccess;
}
/******** Exported Functions ********/
status::Code GenerateBuffer(ConstBufferView old_image,
ConstBufferView new_image,
const GenerateOptions& options,
EnsemblePatchWriter* patch_writer) {
if (!options.imposed_matches.empty()) {
if (options.start_scan_at) {
LOG(WARNING) << "-start-scan-at option is meaningless under -imposed.";
}
return GenerateBufferCommon(
old_image, new_image,
std::make_unique<ImposedEnsembleMatcher>(options.imposed_matches),
patch_writer);
} else if (options.is_raw) {
if (options.start_scan_at) {
LOG(WARNING) << "-start-scan-at option is meaningless under -raw.";
}
ImageIndex old_image_index(old_image);
EncodedView old_view(old_image_index);
std::vector<offset_t> old_sa =
MakeSuffixArray<InducedSuffixSort>(old_view, old_view.Cardinality());
PatchElementWriter patch_element(
{Element(old_image.local_region()), Element(new_image.local_region())});
if (!GenerateRawElement(old_sa, old_image, new_image, &patch_element)) {
return status::kStatusFatal;
}
patch_writer->AddElement(std::move(patch_element));
return status::kStatusSuccess;
}
return GenerateBufferCommon(old_image, new_image,
std::make_unique<HeuristicEnsembleMatcher>(
options.start_scan_at, nullptr),
patch_writer);
}
status::Code GenerateBuffer(ConstBufferView old_image,
ConstBufferView new_image,
EnsemblePatchWriter* patch_writer) {
GenerateOptions options;
return GenerateBuffer(old_image, new_image, options, patch_writer);
}
status::Code GenerateBufferImposed(ConstBufferView old_image,
ConstBufferView new_image,
std::string imposed_matches,
EnsemblePatchWriter* patch_writer) {
GenerateOptions options{.imposed_matches = imposed_matches};
return GenerateBuffer(old_image, new_image, options, patch_writer);
}
status::Code GenerateBufferRaw(ConstBufferView old_image,
ConstBufferView new_image,
EnsemblePatchWriter* patch_writer) {
GenerateOptions options{.is_raw = true};
return GenerateBuffer(old_image, new_image, options, patch_writer);
}
} // namespace zucchini
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