/*
* Copyright (C) 2014 The Android Open Source Project
*
* 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 "verified_method.h"
#include <algorithm>
#include <memory>
#include <vector>
#include "base/logging.h"
#include "base/stl_util.h"
#include "dex_file.h"
#include "dex_instruction.h"
#include "dex_instruction-inl.h"
#include "base/mutex.h"
#include "base/mutex-inl.h"
#include "mirror/art_method.h"
#include "mirror/art_method-inl.h"
#include "mirror/class.h"
#include "mirror/class-inl.h"
#include "mirror/dex_cache.h"
#include "mirror/dex_cache-inl.h"
#include "mirror/object.h"
#include "mirror/object-inl.h"
#include "verifier/dex_gc_map.h"
#include "verifier/method_verifier.h"
#include "verifier/method_verifier-inl.h"
#include "verifier/register_line.h"
#include "verifier/register_line-inl.h"
namespace art {
const VerifiedMethod* VerifiedMethod::Create(verifier::MethodVerifier* method_verifier,
bool compile) {
std::unique_ptr<VerifiedMethod> verified_method(new VerifiedMethod);
if (compile) {
/* Generate a register map. */
if (!verified_method->GenerateGcMap(method_verifier)) {
CHECK(method_verifier->HasFailures());
return nullptr; // Not a real failure, but a failure to encode.
}
if (kIsDebugBuild) {
VerifyGcMap(method_verifier, verified_method->dex_gc_map_);
}
// TODO: move this out when DEX-to-DEX supports devirtualization.
if (method_verifier->HasVirtualOrInterfaceInvokes()) {
verified_method->GenerateDevirtMap(method_verifier);
}
}
if (method_verifier->HasCheckCasts()) {
verified_method->GenerateSafeCastSet(method_verifier);
}
return verified_method.release();
}
const MethodReference* VerifiedMethod::GetDevirtTarget(uint32_t dex_pc) const {
auto it = devirt_map_.find(dex_pc);
return (it != devirt_map_.end()) ? &it->second : nullptr;
}
bool VerifiedMethod::IsSafeCast(uint32_t pc) const {
return std::binary_search(safe_cast_set_.begin(), safe_cast_set_.end(), pc);
}
bool VerifiedMethod::GenerateGcMap(verifier::MethodVerifier* method_verifier) {
DCHECK(dex_gc_map_.empty());
size_t num_entries, ref_bitmap_bits, pc_bits;
ComputeGcMapSizes(method_verifier, &num_entries, &ref_bitmap_bits, &pc_bits);
// There's a single byte to encode the size of each bitmap.
if (ref_bitmap_bits >= (8 /* bits per byte */ * 8192 /* 13-bit size */ )) {
// TODO: either a better GC map format or per method failures
method_verifier->Fail(verifier::VERIFY_ERROR_BAD_CLASS_HARD)
<< "Cannot encode GC map for method with " << ref_bitmap_bits << " registers";
return false;
}
size_t ref_bitmap_bytes = (ref_bitmap_bits + 7) / 8;
// There are 2 bytes to encode the number of entries.
if (num_entries >= 65536) {
// TODO: Either a better GC map format or per method failures.
method_verifier->Fail(verifier::VERIFY_ERROR_BAD_CLASS_HARD)
<< "Cannot encode GC map for method with " << num_entries << " entries";
return false;
}
size_t pc_bytes;
verifier::RegisterMapFormat format;
if (pc_bits <= 8) {
format = verifier::kRegMapFormatCompact8;
pc_bytes = 1;
} else if (pc_bits <= 16) {
format = verifier::kRegMapFormatCompact16;
pc_bytes = 2;
} else {
// TODO: Either a better GC map format or per method failures.
method_verifier->Fail(verifier::VERIFY_ERROR_BAD_CLASS_HARD)
<< "Cannot encode GC map for method with "
<< (1 << pc_bits) << " instructions (number is rounded up to nearest power of 2)";
return false;
}
size_t table_size = ((pc_bytes + ref_bitmap_bytes) * num_entries) + 4;
dex_gc_map_.reserve(table_size);
// Write table header.
dex_gc_map_.push_back(format | ((ref_bitmap_bytes & ~0xFF) >> 5));
dex_gc_map_.push_back(ref_bitmap_bytes & 0xFF);
dex_gc_map_.push_back(num_entries & 0xFF);
dex_gc_map_.push_back((num_entries >> 8) & 0xFF);
// Write table data.
const DexFile::CodeItem* code_item = method_verifier->CodeItem();
for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
if (method_verifier->GetInstructionFlags(i).IsCompileTimeInfoPoint()) {
dex_gc_map_.push_back(i & 0xFF);
if (pc_bytes == 2) {
dex_gc_map_.push_back((i >> 8) & 0xFF);
}
verifier::RegisterLine* line = method_verifier->GetRegLine(i);
line->WriteReferenceBitMap(dex_gc_map_, ref_bitmap_bytes);
}
}
DCHECK_EQ(dex_gc_map_.size(), table_size);
return true;
}
void VerifiedMethod::VerifyGcMap(verifier::MethodVerifier* method_verifier,
const std::vector<uint8_t>& data) {
// Check that for every GC point there is a map entry, there aren't entries for non-GC points,
// that the table data is well formed and all references are marked (or not) in the bitmap.
verifier::DexPcToReferenceMap map(&data[0]);
DCHECK_EQ(data.size(), map.RawSize());
size_t map_index = 0;
const DexFile::CodeItem* code_item = method_verifier->CodeItem();
for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
const uint8_t* reg_bitmap = map.FindBitMap(i, false);
if (method_verifier->GetInstructionFlags(i).IsCompileTimeInfoPoint()) {
DCHECK_LT(map_index, map.NumEntries());
DCHECK_EQ(map.GetDexPc(map_index), i);
DCHECK_EQ(map.GetBitMap(map_index), reg_bitmap);
map_index++;
verifier::RegisterLine* line = method_verifier->GetRegLine(i);
for (size_t j = 0; j < code_item->registers_size_; j++) {
if (line->GetRegisterType(j).IsNonZeroReferenceTypes()) {
DCHECK_LT(j / 8, map.RegWidth());
DCHECK_EQ((reg_bitmap[j / 8] >> (j % 8)) & 1, 1);
} else if ((j / 8) < map.RegWidth()) {
DCHECK_EQ((reg_bitmap[j / 8] >> (j % 8)) & 1, 0);
} else {
// If a register doesn't contain a reference then the bitmap may be shorter than the line.
}
}
} else {
DCHECK(reg_bitmap == NULL);
}
}
}
void VerifiedMethod::ComputeGcMapSizes(verifier::MethodVerifier* method_verifier,
size_t* gc_points, size_t* ref_bitmap_bits,
size_t* log2_max_gc_pc) {
size_t local_gc_points = 0;
size_t max_insn = 0;
size_t max_ref_reg = -1;
const DexFile::CodeItem* code_item = method_verifier->CodeItem();
for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
if (method_verifier->GetInstructionFlags(i).IsCompileTimeInfoPoint()) {
local_gc_points++;
max_insn = i;
verifier::RegisterLine* line = method_verifier->GetRegLine(i);
max_ref_reg = line->GetMaxNonZeroReferenceReg(max_ref_reg);
}
}
*gc_points = local_gc_points;
*ref_bitmap_bits = max_ref_reg + 1; // If max register is 0 we need 1 bit to encode (ie +1).
size_t i = 0;
while ((1U << i) <= max_insn) {
i++;
}
*log2_max_gc_pc = i;
}
void VerifiedMethod::GenerateDevirtMap(verifier::MethodVerifier* method_verifier) {
// It is risky to rely on reg_types for sharpening in cases of soft
// verification, we might end up sharpening to a wrong implementation. Just abort.
if (method_verifier->HasFailures()) {
return;
}
const DexFile::CodeItem* code_item = method_verifier->CodeItem();
const uint16_t* insns = code_item->insns_;
const Instruction* inst = Instruction::At(insns);
const Instruction* end = Instruction::At(insns + code_item->insns_size_in_code_units_);
for (; inst < end; inst = inst->Next()) {
bool is_virtual = (inst->Opcode() == Instruction::INVOKE_VIRTUAL) ||
(inst->Opcode() == Instruction::INVOKE_VIRTUAL_RANGE);
bool is_interface = (inst->Opcode() == Instruction::INVOKE_INTERFACE) ||
(inst->Opcode() == Instruction::INVOKE_INTERFACE_RANGE);
if (!is_interface && !is_virtual) {
continue;
}
// Get reg type for register holding the reference to the object that will be dispatched upon.
uint32_t dex_pc = inst->GetDexPc(insns);
verifier::RegisterLine* line = method_verifier->GetRegLine(dex_pc);
bool is_range = (inst->Opcode() == Instruction::INVOKE_VIRTUAL_RANGE) ||
(inst->Opcode() == Instruction::INVOKE_INTERFACE_RANGE);
verifier::RegType&
reg_type(line->GetRegisterType(is_range ? inst->VRegC_3rc() : inst->VRegC_35c()));
if (!reg_type.HasClass()) {
// We will compute devirtualization information only when we know the Class of the reg type.
continue;
}
mirror::Class* reg_class = reg_type.GetClass();
if (reg_class->IsInterface()) {
// We can't devirtualize when the known type of the register is an interface.
continue;
}
if (reg_class->IsAbstract() && !reg_class->IsArrayClass()) {
// We can't devirtualize abstract classes except on arrays of abstract classes.
continue;
}
mirror::ArtMethod* abstract_method = method_verifier->GetDexCache()->GetResolvedMethod(
is_range ? inst->VRegB_3rc() : inst->VRegB_35c());
if (abstract_method == NULL) {
// If the method is not found in the cache this means that it was never found
// by ResolveMethodAndCheckAccess() called when verifying invoke_*.
continue;
}
// Find the concrete method.
mirror::ArtMethod* concrete_method = NULL;
if (is_interface) {
concrete_method = reg_type.GetClass()->FindVirtualMethodForInterface(abstract_method);
}
if (is_virtual) {
concrete_method = reg_type.GetClass()->FindVirtualMethodForVirtual(abstract_method);
}
if (concrete_method == NULL || concrete_method->IsAbstract()) {
// In cases where concrete_method is not found, or is abstract, continue to the next invoke.
continue;
}
if (reg_type.IsPreciseReference() || concrete_method->IsFinal() ||
concrete_method->GetDeclaringClass()->IsFinal()) {
// If we knew exactly the class being dispatched upon, or if the target method cannot be
// overridden record the target to be used in the compiler driver.
MethodReference concrete_ref(
concrete_method->GetDeclaringClass()->GetDexCache()->GetDexFile(),
concrete_method->GetDexMethodIndex());
devirt_map_.Put(dex_pc, concrete_ref);
}
}
}
void VerifiedMethod::GenerateSafeCastSet(verifier::MethodVerifier* method_verifier) {
/*
* Walks over the method code and adds any cast instructions in which
* the type cast is implicit to a set, which is used in the code generation
* to elide these casts.
*/
if (method_verifier->HasFailures()) {
return;
}
const DexFile::CodeItem* code_item = method_verifier->CodeItem();
const Instruction* inst = Instruction::At(code_item->insns_);
const Instruction* end = Instruction::At(code_item->insns_ +
code_item->insns_size_in_code_units_);
for (; inst < end; inst = inst->Next()) {
Instruction::Code code = inst->Opcode();
if ((code == Instruction::CHECK_CAST) || (code == Instruction::APUT_OBJECT)) {
uint32_t dex_pc = inst->GetDexPc(code_item->insns_);
const verifier::RegisterLine* line = method_verifier->GetRegLine(dex_pc);
bool is_safe_cast = false;
if (code == Instruction::CHECK_CAST) {
verifier::RegType& reg_type(line->GetRegisterType(inst->VRegA_21c()));
verifier::RegType& cast_type =
method_verifier->ResolveCheckedClass(inst->VRegB_21c());
is_safe_cast = cast_type.IsStrictlyAssignableFrom(reg_type);
} else {
verifier::RegType& array_type(line->GetRegisterType(inst->VRegB_23x()));
// We only know its safe to assign to an array if the array type is precise. For example,
// an Object[] can have any type of object stored in it, but it may also be assigned a
// String[] in which case the stores need to be of Strings.
if (array_type.IsPreciseReference()) {
verifier::RegType& value_type(line->GetRegisterType(inst->VRegA_23x()));
verifier::RegType& component_type = method_verifier->GetRegTypeCache()
->GetComponentType(array_type, method_verifier->GetClassLoader());
is_safe_cast = component_type.IsStrictlyAssignableFrom(value_type);
}
}
if (is_safe_cast) {
// Verify ordering for push_back() to the sorted vector.
DCHECK(safe_cast_set_.empty() || safe_cast_set_.back() < dex_pc);
safe_cast_set_.push_back(dex_pc);
}
}
}
}
} // namespace art