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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_function_calls.h"
#include "source/fuzz/call_graph.h"
#include "source/fuzz/fuzzer_util.h"
#include "source/fuzz/transformation_add_global_variable.h"
#include "source/fuzz/transformation_add_local_variable.h"
#include "source/fuzz/transformation_function_call.h"
namespace spvtools {
namespace fuzz {
FuzzerPassAddFunctionCalls::FuzzerPassAddFunctionCalls(
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 FuzzerPassAddFunctionCalls::Apply() {
ForEachInstructionWithInstructionDescriptor(
[this](opt::Function* function, opt::BasicBlock* block,
opt::BasicBlock::iterator inst_it,
const protobufs::InstructionDescriptor& instruction_descriptor)
-> void {
// Check whether it is legitimate to insert a function call before the
// instruction.
if (!fuzzerutil::CanInsertOpcodeBeforeInstruction(SpvOpFunctionCall,
inst_it)) {
return;
}
// Randomly decide whether to try inserting a function call here.
if (!GetFuzzerContext()->ChoosePercentage(
GetFuzzerContext()->GetChanceOfCallingFunction())) {
return;
}
// Compute the module's call graph - we don't cache it since it may
// change each time we apply a transformation. If this proves to be
// a bottleneck the call graph data structure could be made updatable.
CallGraph call_graph(GetIRContext());
// Gather all the non-entry point functions different from this
// function. It is important to ignore entry points as a function
// cannot be an entry point and the target of an OpFunctionCall
// instruction. We ignore this function to avoid direct recursion.
std::vector<opt::Function*> candidate_functions;
for (auto& other_function : *GetIRContext()->module()) {
if (&other_function != function &&
!fuzzerutil::FunctionIsEntryPoint(GetIRContext(),
other_function.result_id())) {
candidate_functions.push_back(&other_function);
}
}
// Choose a function to call, at random, by considering candidate
// functions until a suitable one is found.
opt::Function* chosen_function = nullptr;
while (!candidate_functions.empty()) {
opt::Function* candidate_function =
GetFuzzerContext()->RemoveAtRandomIndex(&candidate_functions);
if (!GetTransformationContext()->GetFactManager()->BlockIsDead(
block->id()) &&
!GetTransformationContext()->GetFactManager()->FunctionIsLivesafe(
candidate_function->result_id())) {
// Unless in a dead block, only livesafe functions can be invoked
continue;
}
if (call_graph.GetIndirectCallees(candidate_function->result_id())
.count(function->result_id())) {
// Calling this function could lead to indirect recursion
continue;
}
chosen_function = candidate_function;
break;
}
if (!chosen_function) {
// No suitable function was found to call. (This can happen, for
// instance, if the current function is the only function in the
// module.)
return;
}
ApplyTransformation(TransformationFunctionCall(
GetFuzzerContext()->GetFreshId(), chosen_function->result_id(),
ChooseFunctionCallArguments(*chosen_function, function, block,
inst_it),
instruction_descriptor));
});
}
std::vector<uint32_t> FuzzerPassAddFunctionCalls::ChooseFunctionCallArguments(
const opt::Function& callee, opt::Function* caller_function,
opt::BasicBlock* caller_block,
const opt::BasicBlock::iterator& caller_inst_it) {
auto available_pointers = FindAvailableInstructions(
caller_function, caller_block, caller_inst_it,
[this, caller_block](opt::IRContext* /*unused*/, opt::Instruction* inst) {
if (inst->opcode() != SpvOpVariable ||
inst->opcode() != SpvOpFunctionParameter) {
// Function parameters and variables are the only
// kinds of pointer that can be used as actual
// parameters.
return false;
}
return GetTransformationContext()->GetFactManager()->BlockIsDead(
caller_block->id()) ||
GetTransformationContext()
->GetFactManager()
->PointeeValueIsIrrelevant(inst->result_id());
});
std::unordered_map<uint32_t, std::vector<uint32_t>> type_id_to_result_id;
for (const auto* inst : available_pointers) {
type_id_to_result_id[inst->type_id()].push_back(inst->result_id());
}
std::vector<uint32_t> result;
for (const auto* param :
fuzzerutil::GetParameters(GetIRContext(), callee.result_id())) {
const auto* param_type =
GetIRContext()->get_type_mgr()->GetType(param->type_id());
assert(param_type && "Parameter has invalid type");
if (!param_type->AsPointer()) {
if (fuzzerutil::CanCreateConstant(GetIRContext(), param->type_id())) {
// We mark the constant as irrelevant so that we can replace it with a
// more interesting value later.
result.push_back(FindOrCreateZeroConstant(param->type_id(), true));
} else {
result.push_back(FindOrCreateGlobalUndef(param->type_id()));
}
continue;
}
if (type_id_to_result_id.count(param->type_id())) {
// Use an existing pointer if there are any.
const auto& candidates = type_id_to_result_id[param->type_id()];
result.push_back(candidates[GetFuzzerContext()->RandomIndex(candidates)]);
continue;
}
// Make a new variable, at function or global scope depending on the storage
// class of the pointer.
// Get a fresh id for the new variable.
uint32_t fresh_variable_id = GetFuzzerContext()->GetFreshId();
// The id of this variable is what we pass as the parameter to
// the call.
result.push_back(fresh_variable_id);
type_id_to_result_id[param->type_id()].push_back(fresh_variable_id);
// Now bring the variable into existence.
auto storage_class = param_type->AsPointer()->storage_class();
auto pointee_type_id = fuzzerutil::GetPointeeTypeIdFromPointerType(
GetIRContext(), param->type_id());
if (storage_class == SpvStorageClassFunction) {
// Add a new zero-initialized local variable to the current
// function, noting that its pointee value is irrelevant.
ApplyTransformation(TransformationAddLocalVariable(
fresh_variable_id, param->type_id(), caller_function->result_id(),
FindOrCreateZeroConstant(pointee_type_id, false), true));
} else {
assert((storage_class == SpvStorageClassPrivate ||
storage_class == SpvStorageClassWorkgroup) &&
"Only Function, Private and Workgroup storage classes are "
"supported at present.");
// Add a new global variable to the module, zero-initializing it if
// it has Private storage class, and noting that its pointee value is
// irrelevant.
ApplyTransformation(TransformationAddGlobalVariable(
fresh_variable_id, param->type_id(), storage_class,
storage_class == SpvStorageClassPrivate
? FindOrCreateZeroConstant(pointee_type_id, false)
: 0,
true));
}
}
return result;
}
} // namespace fuzz
} // namespace spvtools
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