| // Copyright (c) 2019 Google LLC |
| // |
| // 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 "source/fuzz/shrinker.h" |
| |
| #include <sstream> |
| |
| #include "source/fuzz/pseudo_random_generator.h" |
| #include "source/fuzz/replayer.h" |
| #include "source/opt/build_module.h" |
| #include "source/opt/ir_context.h" |
| #include "source/spirv_fuzzer_options.h" |
| #include "source/util/make_unique.h" |
| |
| namespace spvtools { |
| namespace fuzz { |
| |
| namespace { |
| |
| // A helper to get the size of a protobuf transformation sequence in a less |
| // verbose manner. |
| uint32_t NumRemainingTransformations( |
| const protobufs::TransformationSequence& transformation_sequence) { |
| return static_cast<uint32_t>(transformation_sequence.transformation_size()); |
| } |
| |
| // A helper to return a transformation sequence identical to |transformations|, |
| // except that a chunk of size |chunk_size| starting from |chunk_index| x |
| // |chunk_size| is removed (or as many transformations as available if the whole |
| // chunk is not). |
| protobufs::TransformationSequence RemoveChunk( |
| const protobufs::TransformationSequence& transformations, |
| uint32_t chunk_index, uint32_t chunk_size) { |
| uint32_t lower = chunk_index * chunk_size; |
| uint32_t upper = std::min((chunk_index + 1) * chunk_size, |
| NumRemainingTransformations(transformations)); |
| assert(lower < upper); |
| assert(upper <= NumRemainingTransformations(transformations)); |
| protobufs::TransformationSequence result; |
| for (uint32_t j = 0; j < NumRemainingTransformations(transformations); j++) { |
| if (j >= lower && j < upper) { |
| continue; |
| } |
| protobufs::Transformation transformation = |
| transformations.transformation()[j]; |
| *result.mutable_transformation()->Add() = transformation; |
| } |
| return result; |
| } |
| |
| } // namespace |
| |
| Shrinker::Shrinker( |
| spv_target_env target_env, MessageConsumer consumer, |
| const std::vector<uint32_t>& binary_in, |
| const protobufs::FactSequence& initial_facts, |
| const protobufs::TransformationSequence& transformation_sequence_in, |
| const InterestingnessFunction& interestingness_function, |
| uint32_t step_limit, bool validate_during_replay, |
| spv_validator_options validator_options) |
| : target_env_(target_env), |
| consumer_(consumer), |
| binary_in_(binary_in), |
| initial_facts_(initial_facts), |
| transformation_sequence_in_(transformation_sequence_in), |
| interestingness_function_(interestingness_function), |
| step_limit_(step_limit), |
| validate_during_replay_(validate_during_replay), |
| validator_options_(validator_options) {} |
| |
| Shrinker::~Shrinker() = default; |
| |
| Shrinker::ShrinkerResult Shrinker::Run() { |
| // Check compatibility between the library version being linked with and the |
| // header files being used. |
| GOOGLE_PROTOBUF_VERIFY_VERSION; |
| |
| SpirvTools tools(target_env_); |
| if (!tools.IsValid()) { |
| consumer_(SPV_MSG_ERROR, nullptr, {}, |
| "Failed to create SPIRV-Tools interface; stopping."); |
| return {Shrinker::ShrinkerResultStatus::kFailedToCreateSpirvToolsInterface, |
| std::vector<uint32_t>(), protobufs::TransformationSequence()}; |
| } |
| |
| // Initial binary should be valid. |
| if (!tools.Validate(&binary_in_[0], binary_in_.size(), validator_options_)) { |
| consumer_(SPV_MSG_INFO, nullptr, {}, |
| "Initial binary is invalid; stopping."); |
| return {Shrinker::ShrinkerResultStatus::kInitialBinaryInvalid, |
| std::vector<uint32_t>(), protobufs::TransformationSequence()}; |
| } |
| |
| // Run a replay of the initial transformation sequence to check that it |
| // succeeds. |
| auto initial_replay_result = |
| Replayer(target_env_, consumer_, binary_in_, initial_facts_, |
| transformation_sequence_in_, |
| static_cast<uint32_t>( |
| transformation_sequence_in_.transformation_size()), |
| /* No overflow ids */ 0, validate_during_replay_, |
| validator_options_) |
| .Run(); |
| if (initial_replay_result.status != |
| Replayer::ReplayerResultStatus::kComplete) { |
| return {ShrinkerResultStatus::kReplayFailed, std::vector<uint32_t>(), |
| protobufs::TransformationSequence()}; |
| } |
| // Get the binary that results from running these transformations, and the |
| // subsequence of the initial transformations that actually apply (in |
| // principle this could be a strict subsequence). |
| std::vector<uint32_t> current_best_binary = |
| std::move(initial_replay_result.transformed_binary); |
| protobufs::TransformationSequence current_best_transformations = |
| std::move(initial_replay_result.applied_transformations); |
| |
| // Check that the binary produced by applying the initial transformations is |
| // indeed interesting. |
| if (!interestingness_function_(current_best_binary, 0)) { |
| consumer_(SPV_MSG_INFO, nullptr, {}, |
| "Initial binary is not interesting; stopping."); |
| return {ShrinkerResultStatus::kInitialBinaryNotInteresting, |
| std::vector<uint32_t>(), protobufs::TransformationSequence()}; |
| } |
| |
| // The largest id used by the module before any shrinking has been applied |
| // serves as the first id that can be used for overflow purposes. |
| const uint32_t first_overflow_id = GetIdBound(current_best_binary); |
| assert(first_overflow_id >= GetIdBound(binary_in_) && |
| "Applying transformations should only increase a module's id bound."); |
| |
| uint32_t attempt = 0; // Keeps track of the number of shrink attempts that |
| // have been tried, whether successful or not. |
| |
| uint32_t chunk_size = |
| std::max(1u, NumRemainingTransformations(current_best_transformations) / |
| 2); // The number of contiguous transformations that the |
| // shrinker will try to remove in one go; starts |
| // high and decreases during the shrinking process. |
| |
| // Keep shrinking until we: |
| // - reach the step limit, |
| // - run out of transformations to remove, or |
| // - cannot make the chunk size any smaller. |
| while (attempt < step_limit_ && |
| !current_best_transformations.transformation().empty() && |
| chunk_size > 0) { |
| bool progress_this_round = |
| false; // Used to decide whether to make the chunk size with which we |
| // remove transformations smaller. If we managed to remove at |
| // least one chunk of transformations at a particular chunk |
| // size, we set this flag so that we do not yet decrease the |
| // chunk size. |
| |
| assert(chunk_size <= |
| NumRemainingTransformations(current_best_transformations) && |
| "Chunk size should never exceed the number of transformations that " |
| "remain."); |
| |
| // The number of chunks is the ceiling of (#remaining_transformations / |
| // chunk_size). |
| const uint32_t num_chunks = |
| (NumRemainingTransformations(current_best_transformations) + |
| chunk_size - 1) / |
| chunk_size; |
| assert(num_chunks >= 1 && "There should be at least one chunk."); |
| assert(num_chunks * chunk_size >= |
| NumRemainingTransformations(current_best_transformations) && |
| "All transformations should be in some chunk."); |
| |
| // We go through the transformations in reverse, in chunks of size |
| // |chunk_size|, using |chunk_index| to track which chunk to try removing |
| // next. The loop exits early if we reach the shrinking step limit. |
| for (int chunk_index = num_chunks - 1; |
| attempt < step_limit_ && chunk_index >= 0; chunk_index--) { |
| // Remove a chunk of transformations according to the current index and |
| // chunk size. |
| auto transformations_with_chunk_removed = |
| RemoveChunk(current_best_transformations, |
| static_cast<uint32_t>(chunk_index), chunk_size); |
| |
| // Replay the smaller sequence of transformations to get a next binary and |
| // transformation sequence. Note that the transformations arising from |
| // replay might be even smaller than the transformations with the chunk |
| // removed, because removing those transformations might make further |
| // transformations inapplicable. |
| auto replay_result = |
| Replayer( |
| target_env_, consumer_, binary_in_, initial_facts_, |
| transformations_with_chunk_removed, |
| static_cast<uint32_t>( |
| transformations_with_chunk_removed.transformation_size()), |
| first_overflow_id, validate_during_replay_, validator_options_) |
| .Run(); |
| if (replay_result.status != Replayer::ReplayerResultStatus::kComplete) { |
| // Replay should not fail; if it does, we need to abort shrinking. |
| return {ShrinkerResultStatus::kReplayFailed, std::vector<uint32_t>(), |
| protobufs::TransformationSequence()}; |
| } |
| |
| assert( |
| NumRemainingTransformations(replay_result.applied_transformations) >= |
| chunk_index * chunk_size && |
| "Removing this chunk of transformations should not have an effect " |
| "on earlier chunks."); |
| |
| if (interestingness_function_(replay_result.transformed_binary, |
| attempt)) { |
| // If the binary arising from the smaller transformation sequence is |
| // interesting, this becomes our current best binary and transformation |
| // sequence. |
| current_best_binary = std::move(replay_result.transformed_binary); |
| current_best_transformations = |
| std::move(replay_result.applied_transformations); |
| progress_this_round = true; |
| } |
| // Either way, this was a shrink attempt, so increment our count of shrink |
| // attempts. |
| attempt++; |
| } |
| if (!progress_this_round) { |
| // If we didn't manage to remove any chunks at this chunk size, try a |
| // smaller chunk size. |
| chunk_size /= 2; |
| } |
| // Decrease the chunk size until it becomes no larger than the number of |
| // remaining transformations. |
| while (chunk_size > |
| NumRemainingTransformations(current_best_transformations)) { |
| chunk_size /= 2; |
| } |
| } |
| |
| // Indicate whether shrinking completed or was truncated due to reaching the |
| // step limit. |
| // |
| // Either way, the output from the shrinker is the best binary we saw, and the |
| // transformations that led to it. |
| assert(attempt <= step_limit_); |
| if (attempt == step_limit_) { |
| std::stringstream strstream; |
| strstream << "Shrinking did not complete; step limit " << step_limit_ |
| << " was reached."; |
| consumer_(SPV_MSG_WARNING, nullptr, {}, strstream.str().c_str()); |
| return {Shrinker::ShrinkerResultStatus::kStepLimitReached, |
| std::move(current_best_binary), |
| std::move(current_best_transformations)}; |
| } |
| return {Shrinker::ShrinkerResultStatus::kComplete, |
| std::move(current_best_binary), |
| std::move(current_best_transformations)}; |
| } |
| |
| uint32_t Shrinker::GetIdBound(const std::vector<uint32_t>& binary) const { |
| // Build the module from the input binary. |
| std::unique_ptr<opt::IRContext> ir_context = |
| BuildModule(target_env_, consumer_, binary.data(), binary.size()); |
| assert(ir_context && "Error building module."); |
| return ir_context->module()->id_bound(); |
| } |
| |
| } // namespace fuzz |
| } // namespace spvtools |
