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
Apply()30 void FuzzerPassAddLoads::Apply() {
31 ForEachInstructionWithInstructionDescriptor(
32 [this](opt::Function* function, opt::BasicBlock* block,
33 opt::BasicBlock::iterator inst_it,
34 const protobufs::InstructionDescriptor& instruction_descriptor)
35 -> void {
36 assert(inst_it->opcode() ==
37 instruction_descriptor.target_instruction_opcode() &&
38 "The opcode of the instruction we might insert before must be "
39 "the same as the opcode in the descriptor for the instruction");
40
41 // Check whether it is legitimate to insert a load before this
42 // instruction.
43 if (!fuzzerutil::CanInsertOpcodeBeforeInstruction(SpvOpLoad, inst_it)) {
44 return;
45 }
46
47 // Randomly decide whether to try inserting a load here.
48 if (!GetFuzzerContext()->ChoosePercentage(
49 GetFuzzerContext()->GetChanceOfAddingLoad())) {
50 return;
51 }
52
53 std::vector<opt::Instruction*> relevant_instructions =
54 FindAvailableInstructions(
55 function, block, inst_it,
56 [](opt::IRContext* context,
57 opt::Instruction* instruction) -> bool {
58 if (!instruction->result_id() || !instruction->type_id()) {
59 return false;
60 }
61 switch (instruction->opcode()) {
62 case SpvOpConstantNull:
63 case SpvOpUndef:
64 // Do not allow loading from a null or undefined pointer;
65 // this might be OK if the block is dead, but for now we
66 // conservatively avoid it.
67 return false;
68 default:
69 break;
70 }
71 return context->get_def_use_mgr()
72 ->GetDef(instruction->type_id())
73 ->opcode() == SpvOpTypePointer;
74 });
75
76 // At this point, |relevant_instructions| contains all the pointers
77 // we might think of loading from.
78 if (relevant_instructions.empty()) {
79 return;
80 }
81
82 // Choose a pointer at random, and create and apply a loading
83 // transformation based on it.
84 ApplyTransformation(TransformationLoad(
85 GetFuzzerContext()->GetFreshId(),
86 relevant_instructions[GetFuzzerContext()->RandomIndex(
87 relevant_instructions)]
88 ->result_id(),
89 instruction_descriptor));
90 });
91 }
92
93 } // namespace fuzz
94 } // namespace spvtools
95