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https://github.com/KhronosGroup/SPIRV-Tools
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9c4481419e
spirv-fuzz features transformations that should be applicable by construction. Assertions are used to detect when such transformations turn out to be inapplicable. Failures of such assertions indicate bugs in the fuzzer. However, when using the fuzzer at scale (e.g. in ClusterFuzz) reports of these assertion failures create noise, and cause the fuzzer to exit early. This change adds an option whereby inapplicable transformations can be ignored. This reduces noise and allows fuzzing to continue even when a transformation that should be applicable but is not has been erroneously created.
132 lines
5.2 KiB
C++
132 lines
5.2 KiB
C++
// Copyright (c) 2020 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "source/fuzz/fuzzer_pass_add_stores.h"
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#include "source/fuzz/fuzzer_util.h"
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#include "source/fuzz/transformation_store.h"
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namespace spvtools {
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namespace fuzz {
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FuzzerPassAddStores::FuzzerPassAddStores(
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opt::IRContext* ir_context, TransformationContext* transformation_context,
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FuzzerContext* fuzzer_context,
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protobufs::TransformationSequence* transformations,
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bool ignore_inapplicable_transformations)
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: FuzzerPass(ir_context, transformation_context, fuzzer_context,
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transformations, ignore_inapplicable_transformations) {}
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void FuzzerPassAddStores::Apply() {
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ForEachInstructionWithInstructionDescriptor(
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[this](opt::Function* function, opt::BasicBlock* block,
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opt::BasicBlock::iterator inst_it,
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const protobufs::InstructionDescriptor& instruction_descriptor)
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-> void {
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assert(inst_it->opcode() ==
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instruction_descriptor.target_instruction_opcode() &&
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"The opcode of the instruction we might insert before must be "
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"the same as the opcode in the descriptor for the instruction");
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// Check whether it is legitimate to insert a store before this
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// instruction.
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if (!fuzzerutil::CanInsertOpcodeBeforeInstruction(SpvOpStore,
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inst_it)) {
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return;
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}
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// Randomly decide whether to try inserting a store here.
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if (!GetFuzzerContext()->ChoosePercentage(
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GetFuzzerContext()->GetChanceOfAddingStore())) {
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return;
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}
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// Look for pointers we might consider storing to.
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std::vector<opt::Instruction*> relevant_pointers =
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FindAvailableInstructions(
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function, block, inst_it,
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[this, block](opt::IRContext* context,
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opt::Instruction* instruction) -> bool {
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if (!instruction->result_id() || !instruction->type_id()) {
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return false;
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}
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auto type_inst = context->get_def_use_mgr()->GetDef(
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instruction->type_id());
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if (type_inst->opcode() != SpvOpTypePointer) {
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// Not a pointer.
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return false;
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}
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if (instruction->IsReadOnlyPointer()) {
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// Read only: cannot store to it.
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return false;
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}
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switch (instruction->opcode()) {
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case SpvOpConstantNull:
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case SpvOpUndef:
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// Do not allow storing to a null or undefined pointer;
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// this might be OK if the block is dead, but for now we
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// conservatively avoid it.
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return false;
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default:
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break;
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}
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return GetTransformationContext()
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->GetFactManager()
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->BlockIsDead(block->id()) ||
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GetTransformationContext()
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->GetFactManager()
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->PointeeValueIsIrrelevant(
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instruction->result_id());
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});
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// At this point, |relevant_pointers| contains all the pointers we might
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// think of storing to.
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if (relevant_pointers.empty()) {
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return;
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}
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auto pointer = relevant_pointers[GetFuzzerContext()->RandomIndex(
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relevant_pointers)];
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std::vector<opt::Instruction*> relevant_values =
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FindAvailableInstructions(
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function, block, inst_it,
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[pointer](opt::IRContext* context,
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opt::Instruction* instruction) -> bool {
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if (!instruction->result_id() || !instruction->type_id()) {
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return false;
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}
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return instruction->type_id() ==
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context->get_def_use_mgr()
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->GetDef(pointer->type_id())
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->GetSingleWordInOperand(1);
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});
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if (relevant_values.empty()) {
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return;
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}
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// Choose a value at random, and create and apply a storing
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// transformation based on it and the pointer.
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ApplyTransformation(TransformationStore(
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pointer->result_id(),
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relevant_values[GetFuzzerContext()->RandomIndex(relevant_values)]
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->result_id(),
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instruction_descriptor));
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});
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}
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} // namespace fuzz
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} // namespace spvtools
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