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// Copyright (c) 2020 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/fuzzer_pass_add_access_chains.h"
#include "source/fuzz/fuzzer_util.h"
#include "source/fuzz/transformation_access_chain.h"
namespace spvtools {
namespace fuzz {
FuzzerPassAddAccessChains::FuzzerPassAddAccessChains(
opt::IRContext* ir_context, TransformationContext* transformation_context,
FuzzerContext* fuzzer_context,
protobufs::TransformationSequence* transformations,
bool ignore_inapplicable_transformations)
: FuzzerPass(ir_context, transformation_context, fuzzer_context,
transformations, ignore_inapplicable_transformations) {}
void FuzzerPassAddAccessChains::Apply() {
ForEachInstructionWithInstructionDescriptor(
[this](opt::Function* function, opt::BasicBlock* block,
opt::BasicBlock::iterator inst_it,
const protobufs::InstructionDescriptor& instruction_descriptor)
-> void {
assert(inst_it->opcode() ==
instruction_descriptor.target_instruction_opcode() &&
"The opcode of the instruction we might insert before must be "
"the same as the opcode in the descriptor for the instruction");
// Check whether it is legitimate to insert an access chain
// instruction before this instruction.
if (!fuzzerutil::CanInsertOpcodeBeforeInstruction(SpvOpAccessChain,
inst_it)) {
return;
}
// Randomly decide whether to try inserting a load here.
if (!GetFuzzerContext()->ChoosePercentage(
GetFuzzerContext()->GetChanceOfAddingAccessChain())) {
return;
}
// Get all of the pointers that are currently in scope, excluding
// explicitly null and undefined pointers.
std::vector<opt::Instruction*> relevant_pointer_instructions =
FindAvailableInstructions(
function, block, inst_it,
[](opt::IRContext* context,
opt::Instruction* instruction) -> bool {
if (!instruction->result_id() || !instruction->type_id()) {
// A pointer needs both a result and type id.
return false;
}
switch (instruction->opcode()) {
case SpvOpConstantNull:
case SpvOpUndef:
// Do not allow making an access chain from a null or
// undefined pointer. (We can eliminate these cases
// before actually checking that the instruction is a
// pointer.)
return false;
default:
break;
}
// If the instruction has pointer type, we can legitimately
// make an access chain from it.
return context->get_def_use_mgr()
->GetDef(instruction->type_id())
->opcode() == SpvOpTypePointer;
});
// At this point, |relevant_instructions| contains all the pointers
// we might think of making an access chain from.
if (relevant_pointer_instructions.empty()) {
return;
}
auto chosen_pointer =
relevant_pointer_instructions[GetFuzzerContext()->RandomIndex(
relevant_pointer_instructions)];
std::vector<uint32_t> index_ids;
// Each index accessing a non-struct composite will be clamped, thus
// needing a pair of fresh ids
std::vector<std::pair<uint32_t, uint32_t>> fresh_ids_for_clamping;
auto pointer_type = GetIRContext()->get_def_use_mgr()->GetDef(
chosen_pointer->type_id());
uint32_t subobject_type_id = pointer_type->GetSingleWordInOperand(1);
while (true) {
auto subobject_type =
GetIRContext()->get_def_use_mgr()->GetDef(subobject_type_id);
if (!spvOpcodeIsComposite(subobject_type->opcode())) {
break;
}
if (!GetFuzzerContext()->ChoosePercentage(
GetFuzzerContext()
->GetChanceOfGoingDeeperWhenMakingAccessChain())) {
break;
}
uint32_t bound;
switch (subobject_type->opcode()) {
case SpvOpTypeArray:
bound = fuzzerutil::GetArraySize(*subobject_type, GetIRContext());
break;
case SpvOpTypeMatrix:
case SpvOpTypeVector:
bound = subobject_type->GetSingleWordInOperand(1);
break;
case SpvOpTypeStruct:
bound = fuzzerutil::GetNumberOfStructMembers(*subobject_type);
break;
default:
assert(false && "Not a composite type opcode.");
// Set the bound to a value in order to keep release compilers
// happy.
bound = 0;
break;
}
if (bound == 0) {
// It is possible for a composite type to legitimately have zero
// sub-components, at least in the case of a struct, which
// can have no fields.
break;
}
uint32_t index_value =
GetFuzzerContext()->GetRandomIndexForAccessChain(bound);
switch (subobject_type->opcode()) {
case SpvOpTypeArray:
case SpvOpTypeMatrix:
case SpvOpTypeVector: {
// The index will be clamped
bool is_signed = GetFuzzerContext()->ChooseEven();
// Make the constant ready for clamping. We need:
// - an OpTypeBool to be present in the module
// - an OpConstant with the same type as the index and value
// the maximum value for an index
// - a new pair of fresh ids for the clamping instructions
FindOrCreateBoolType();
FindOrCreateIntegerConstant({bound - 1}, 32, is_signed, false);
std::pair<uint32_t, uint32_t> fresh_pair_of_ids = {
GetFuzzerContext()->GetFreshId(),
GetFuzzerContext()->GetFreshId()};
fresh_ids_for_clamping.emplace_back(fresh_pair_of_ids);
index_ids.push_back(FindOrCreateIntegerConstant(
{index_value}, 32, is_signed, false));
subobject_type_id = subobject_type->GetSingleWordInOperand(0);
} break;
case SpvOpTypeStruct:
index_ids.push_back(FindOrCreateIntegerConstant(
{index_value}, 32, GetFuzzerContext()->ChooseEven(), false));
subobject_type_id =
subobject_type->GetSingleWordInOperand(index_value);
break;
default:
assert(false && "Not a composite type opcode.");
}
}
// The transformation we are about to create will only apply if a
// pointer suitable for the access chain's result type exists, so we
// create one if it does not.
FindOrCreatePointerType(subobject_type_id,
static_cast<SpvStorageClass>(
pointer_type->GetSingleWordInOperand(0)));
// Apply the transformation to add an access chain.
ApplyTransformation(TransformationAccessChain(
GetFuzzerContext()->GetFreshId(), chosen_pointer->result_id(),
index_ids, instruction_descriptor, fresh_ids_for_clamping));
});
}
} // namespace fuzz
} // namespace spvtools
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