1 // Copyright (c) 2020 Google LLC
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #include "source/fuzz/fuzzer_pass_add_loads.h"
16
17 #include "source/fuzz/fuzzer_util.h"
18 #include "source/fuzz/transformation_load.h"
19
20 namespace spvtools {
21 namespace fuzz {
22
FuzzerPassAddLoads(opt::IRContext * ir_context,TransformationContext * transformation_context,FuzzerContext * fuzzer_context,protobufs::TransformationSequence * transformations)23 FuzzerPassAddLoads::FuzzerPassAddLoads(
24 opt::IRContext* ir_context, TransformationContext* transformation_context,
25 FuzzerContext* fuzzer_context,
26 protobufs::TransformationSequence* transformations)
27 : FuzzerPass(ir_context, transformation_context, fuzzer_context,
28 transformations) {}
29
30 FuzzerPassAddLoads::~FuzzerPassAddLoads() = default;
31
Apply()32 void FuzzerPassAddLoads::Apply() {
33 ForEachInstructionWithInstructionDescriptor(
34 [this](opt::Function* function, opt::BasicBlock* block,
35 opt::BasicBlock::iterator inst_it,
36 const protobufs::InstructionDescriptor& instruction_descriptor)
37 -> void {
38 assert(inst_it->opcode() ==
39 instruction_descriptor.target_instruction_opcode() &&
40 "The opcode of the instruction we might insert before must be "
41 "the same as the opcode in the descriptor for the instruction");
42
43 // Check whether it is legitimate to insert a load before this
44 // instruction.
45 if (!fuzzerutil::CanInsertOpcodeBeforeInstruction(SpvOpLoad, inst_it)) {
46 return;
47 }
48
49 // Randomly decide whether to try inserting a load here.
50 if (!GetFuzzerContext()->ChoosePercentage(
51 GetFuzzerContext()->GetChanceOfAddingLoad())) {
52 return;
53 }
54
55 std::vector<opt::Instruction*> relevant_instructions =
56 FindAvailableInstructions(
57 function, block, inst_it,
58 [](opt::IRContext* context,
59 opt::Instruction* instruction) -> bool {
60 if (!instruction->result_id() || !instruction->type_id()) {
61 return false;
62 }
63 switch (instruction->result_id()) {
64 case SpvOpConstantNull:
65 case SpvOpUndef:
66 // Do not allow loading from a null or undefined pointer;
67 // this might be OK if the block is dead, but for now we
68 // conservatively avoid it.
69 return false;
70 default:
71 break;
72 }
73 return context->get_def_use_mgr()
74 ->GetDef(instruction->type_id())
75 ->opcode() == SpvOpTypePointer;
76 });
77
78 // At this point, |relevant_instructions| contains all the pointers
79 // we might think of loading from.
80 if (relevant_instructions.empty()) {
81 return;
82 }
83
84 // Choose a pointer at random, and create and apply a loading
85 // transformation based on it.
86 ApplyTransformation(TransformationLoad(
87 GetFuzzerContext()->GetFreshId(),
88 relevant_instructions[GetFuzzerContext()->RandomIndex(
89 relevant_instructions)]
90 ->result_id(),
91 instruction_descriptor));
92 });
93 }
94
95 } // namespace fuzz
96 } // namespace spvtools
97