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_stores.h"
16
17 #include "source/fuzz/fuzzer_util.h"
18 #include "source/fuzz/transformation_store.h"
19
20 namespace spvtools {
21 namespace fuzz {
22
FuzzerPassAddStores(opt::IRContext * ir_context,TransformationContext * transformation_context,FuzzerContext * fuzzer_context,protobufs::TransformationSequence * transformations)23 FuzzerPassAddStores::FuzzerPassAddStores(
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 FuzzerPassAddStores::~FuzzerPassAddStores() = default;
31
Apply()32 void FuzzerPassAddStores::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 store before this
44 // instruction.
45 if (!fuzzerutil::CanInsertOpcodeBeforeInstruction(SpvOpStore,
46 inst_it)) {
47 return;
48 }
49
50 // Randomly decide whether to try inserting a store here.
51 if (!GetFuzzerContext()->ChoosePercentage(
52 GetFuzzerContext()->GetChanceOfAddingStore())) {
53 return;
54 }
55
56 // Look for pointers we might consider storing to.
57 std::vector<opt::Instruction*> relevant_pointers =
58 FindAvailableInstructions(
59 function, block, inst_it,
60 [this, block](opt::IRContext* context,
61 opt::Instruction* instruction) -> bool {
62 if (!instruction->result_id() || !instruction->type_id()) {
63 return false;
64 }
65 auto type_inst = context->get_def_use_mgr()->GetDef(
66 instruction->type_id());
67 if (type_inst->opcode() != SpvOpTypePointer) {
68 // Not a pointer.
69 return false;
70 }
71 if (type_inst->GetSingleWordInOperand(0) ==
72 SpvStorageClassInput) {
73 // Read-only: cannot store to it.
74 return false;
75 }
76 switch (instruction->result_id()) {
77 case SpvOpConstantNull:
78 case SpvOpUndef:
79 // Do not allow storing to a null or undefined pointer;
80 // this might be OK if the block is dead, but for now we
81 // conservatively avoid it.
82 return false;
83 default:
84 break;
85 }
86 return GetTransformationContext()
87 ->GetFactManager()
88 ->BlockIsDead(block->id()) ||
89 GetTransformationContext()
90 ->GetFactManager()
91 ->PointeeValueIsIrrelevant(
92 instruction->result_id());
93 });
94
95 // At this point, |relevant_pointers| contains all the pointers we might
96 // think of storing to.
97 if (relevant_pointers.empty()) {
98 return;
99 }
100
101 auto pointer = relevant_pointers[GetFuzzerContext()->RandomIndex(
102 relevant_pointers)];
103
104 std::vector<opt::Instruction*> relevant_values =
105 FindAvailableInstructions(
106 function, block, inst_it,
107 [pointer](opt::IRContext* context,
108 opt::Instruction* instruction) -> bool {
109 if (!instruction->result_id() || !instruction->type_id()) {
110 return false;
111 }
112 return instruction->type_id() ==
113 context->get_def_use_mgr()
114 ->GetDef(pointer->type_id())
115 ->GetSingleWordInOperand(1);
116 });
117
118 if (relevant_values.empty()) {
119 return;
120 }
121
122 // Choose a value at random, and create and apply a storing
123 // transformation based on it and the pointer.
124 ApplyTransformation(TransformationStore(
125 pointer->result_id(),
126 relevant_values[GetFuzzerContext()->RandomIndex(relevant_values)]
127 ->result_id(),
128 instruction_descriptor));
129 });
130 }
131
132 } // namespace fuzz
133 } // namespace spvtools
134