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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/transformation_access_chain.h"
#include <vector>
#include "source/fuzz/fuzzer_util.h"
#include "source/fuzz/instruction_descriptor.h"
namespace spvtools {
namespace fuzz {
TransformationAccessChain::TransformationAccessChain(
const spvtools::fuzz::protobufs::TransformationAccessChain& message)
: message_(message) {}
TransformationAccessChain::TransformationAccessChain(
uint32_t fresh_id, uint32_t pointer_id,
const std::vector<uint32_t>& index_id,
const protobufs::InstructionDescriptor& instruction_to_insert_before) {
message_.set_fresh_id(fresh_id);
message_.set_pointer_id(pointer_id);
for (auto id : index_id) {
message_.add_index_id(id);
}
*message_.mutable_instruction_to_insert_before() =
instruction_to_insert_before;
}
bool TransformationAccessChain::IsApplicable(
opt::IRContext* context,
const spvtools::fuzz::FactManager& /*unused*/) const {
// The result id must be fresh
if (!fuzzerutil::IsFreshId(context, message_.fresh_id())) {
return false;
}
// The pointer id must exist and have a type.
auto pointer = context->get_def_use_mgr()->GetDef(message_.pointer_id());
if (!pointer || !pointer->type_id()) {
return false;
}
// The type must indeed be a pointer
auto pointer_type = context->get_def_use_mgr()->GetDef(pointer->type_id());
if (pointer_type->opcode() != SpvOpTypePointer) {
return false;
}
// The described instruction to insert before must exist and be a suitable
// point where an OpAccessChain instruction could be inserted.
auto instruction_to_insert_before =
FindInstruction(message_.instruction_to_insert_before(), context);
if (!instruction_to_insert_before) {
return false;
}
if (!fuzzerutil::CanInsertOpcodeBeforeInstruction(
SpvOpAccessChain, instruction_to_insert_before)) {
return false;
}
// Do not allow making an access chain from a null or undefined pointer, as
// we do not want to allow accessing such pointers. This might be acceptable
// in dead blocks, but we conservatively avoid it.
switch (pointer->opcode()) {
case SpvOpConstantNull:
case SpvOpUndef:
// TODO(https://github.com/KhronosGroup/SPIRV-Tools/issues/3185): When
// fuzzing for real we would like an 'assert(false)' here. But we also
// want to be able to write negative unit tests.
return false;
default:
break;
}
// The pointer on which the access chain is to be based needs to be available
// (according to dominance rules) at the insertion point.
if (!fuzzerutil::IdIsAvailableBeforeInstruction(
context, instruction_to_insert_before, message_.pointer_id())) {
return false;
}
// We now need to use the given indices to walk the type structure of the
// base type of the pointer, making sure that (a) the indices correspond to
// integers, and (b) these integer values are in-bounds.
// Start from the base type of the pointer.
uint32_t subobject_type_id = pointer_type->GetSingleWordInOperand(1);
// Consider the given index ids in turn.
for (auto index_id : message_.index_id()) {
// Try to get the integer value associated with this index is. The first
// component of the result will be false if the id did not correspond to an
// integer. Otherwise, the integer with which the id is associated is the
// second component.
std::pair<bool, uint32_t> maybe_index_value =
GetIndexValue(context, index_id);
if (!maybe_index_value.first) {
// There was no integer: this index is no good.
return false;
}
// Try to walk down the type using this index. This will yield 0 if the
// type is not a composite or the index is out of bounds, and the id of
// the next type otherwise.
subobject_type_id = fuzzerutil::WalkOneCompositeTypeIndex(
context, subobject_type_id, maybe_index_value.second);
if (!subobject_type_id) {
// Either the type was not a composite (so that too many indices were
// provided), or the index was out of bounds.
return false;
}
}
// At this point, |subobject_type_id| is the type of the value targeted by
// the new access chain. The result type of the access chain should be a
// pointer to this type, with the same storage class as for the original
// pointer. Such a pointer type needs to exist in the module.
//
// We do not use the type manager to look up this type, due to problems
// associated with pointers to isomorphic structs being regarded as the same.
return fuzzerutil::MaybeGetPointerType(
context, subobject_type_id,
static_cast<SpvStorageClass>(
pointer_type->GetSingleWordInOperand(0))) != 0;
}
void TransformationAccessChain::Apply(
opt::IRContext* context, spvtools::fuzz::FactManager* fact_manager) const {
// The operands to the access chain are the pointer followed by the indices.
// The result type of the access chain is determined by where the indices
// lead. We thus push the pointer to a sequence of operands, and then follow
// the indices, pushing each to the operand list and tracking the type
// obtained by following it. Ultimately this yields the type of the
// component reached by following all the indices, and the result type is
// a pointer to this component type.
opt::Instruction::OperandList operands;
// Add the pointer id itself.
operands.push_back({SPV_OPERAND_TYPE_ID, {message_.pointer_id()}});
// Start walking the indices, starting with the pointer's base type.
auto pointer_type = context->get_def_use_mgr()->GetDef(
context->get_def_use_mgr()->GetDef(message_.pointer_id())->type_id());
uint32_t subobject_type_id = pointer_type->GetSingleWordInOperand(1);
// Go through the index ids in turn.
for (auto index_id : message_.index_id()) {
// Add the index id to the operands.
operands.push_back({SPV_OPERAND_TYPE_ID, {index_id}});
// Get the integer value associated with the index id.
uint32_t index_value = GetIndexValue(context, index_id).second;
// Walk to the next type in the composite object using this index.
subobject_type_id = fuzzerutil::WalkOneCompositeTypeIndex(
context, subobject_type_id, index_value);
}
// The access chain's result type is a pointer to the composite component that
// was reached after following all indices. The storage class is that of the
// original pointer.
uint32_t result_type = fuzzerutil::MaybeGetPointerType(
context, subobject_type_id,
static_cast<SpvStorageClass>(pointer_type->GetSingleWordInOperand(0)));
// Add the access chain instruction to the module, and update the module's id
// bound.
fuzzerutil::UpdateModuleIdBound(context, message_.fresh_id());
FindInstruction(message_.instruction_to_insert_before(), context)
->InsertBefore(
MakeUnique<opt::Instruction>(context, SpvOpAccessChain, result_type,
message_.fresh_id(), operands));
// Conservatively invalidate all analyses.
context->InvalidateAnalysesExceptFor(opt::IRContext::kAnalysisNone);
// If the base pointer's pointee value was irrelevant, the same is true of the
// pointee value of the result of this access chain.
if (fact_manager->PointeeValueIsIrrelevant(message_.pointer_id())) {
fact_manager->AddFactValueOfPointeeIsIrrelevant(message_.fresh_id());
}
}
protobufs::Transformation TransformationAccessChain::ToMessage() const {
protobufs::Transformation result;
*result.mutable_access_chain() = message_;
return result;
}
std::pair<bool, uint32_t> TransformationAccessChain::GetIndexValue(
opt::IRContext* context, uint32_t index_id) const {
auto index_instruction = context->get_def_use_mgr()->GetDef(index_id);
if (!index_instruction || !spvOpcodeIsConstant(index_instruction->opcode())) {
// TODO(https://github.com/KhronosGroup/SPIRV-Tools/issues/3179) We could
// allow non-constant indices when looking up non-structs, using clamping
// to ensure they are in-bounds.
return {false, 0};
}
auto index_type =
context->get_def_use_mgr()->GetDef(index_instruction->type_id());
if (index_type->opcode() != SpvOpTypeInt ||
index_type->GetSingleWordInOperand(0) != 32) {
return {false, 0};
}
return {true, index_instruction->GetSingleWordInOperand(0)};
}
} // namespace fuzz
} // namespace spvtools