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/*
* Copyright (C) 2015 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 "linker/arm/relative_patcher_arm_base.h"
#include "base/stl_util.h"
#include "compiled_method-inl.h"
#include "debug/method_debug_info.h"
#include "dex/dex_file_types.h"
#include "linker/linker_patch.h"
#include "linker/output_stream.h"
#include "oat.h"
#include "oat_quick_method_header.h"
namespace art {
namespace linker {
class ArmBaseRelativePatcher::ThunkData {
public:
ThunkData(ArrayRef<const uint8_t> code, const std::string& debug_name, uint32_t max_next_offset)
: code_(code),
debug_name_(debug_name),
offsets_(),
max_next_offset_(max_next_offset),
pending_offset_(0u) {
DCHECK(NeedsNextThunk()); // The data is constructed only when we expect to need the thunk.
}
ThunkData(ThunkData&& src) = default;
size_t CodeSize() const {
return code_.size();
}
ArrayRef<const uint8_t> GetCode() const {
return code_;
}
const std::string& GetDebugName() const {
return debug_name_;
}
bool NeedsNextThunk() const {
return max_next_offset_ != 0u;
}
uint32_t MaxNextOffset() const {
DCHECK(NeedsNextThunk());
return max_next_offset_;
}
void ClearMaxNextOffset() {
DCHECK(NeedsNextThunk());
max_next_offset_ = 0u;
}
void SetMaxNextOffset(uint32_t max_next_offset) {
DCHECK(!NeedsNextThunk());
max_next_offset_ = max_next_offset;
}
// Adjust the MaxNextOffset() down if needed to fit the code before the next thunk.
// Returns true if it was adjusted, false if the old value was kept.
bool MakeSpaceBefore(const ThunkData& next_thunk, size_t alignment) {
DCHECK(NeedsNextThunk());
DCHECK(next_thunk.NeedsNextThunk());
DCHECK_ALIGNED_PARAM(MaxNextOffset(), alignment);
DCHECK_ALIGNED_PARAM(next_thunk.MaxNextOffset(), alignment);
if (next_thunk.MaxNextOffset() - CodeSize() < MaxNextOffset()) {
max_next_offset_ = RoundDown(next_thunk.MaxNextOffset() - CodeSize(), alignment);
return true;
} else {
return false;
}
}
uint32_t ReserveOffset(size_t offset) {
DCHECK(NeedsNextThunk());
DCHECK_LE(offset, max_next_offset_);
max_next_offset_ = 0u; // The reserved offset should satisfy all pending references.
offsets_.push_back(offset);
return offset + CodeSize();
}
bool HasReservedOffset() const {
return !offsets_.empty();
}
uint32_t LastReservedOffset() const {
DCHECK(HasReservedOffset());
return offsets_.back();
}
bool HasPendingOffset() const {
return pending_offset_ != offsets_.size();
}
uint32_t GetPendingOffset() const {
DCHECK(HasPendingOffset());
return offsets_[pending_offset_];
}
void MarkPendingOffsetAsWritten() {
DCHECK(HasPendingOffset());
++pending_offset_;
}
bool HasWrittenOffset() const {
return pending_offset_ != 0u;
}
uint32_t LastWrittenOffset() const {
DCHECK(HasWrittenOffset());
return offsets_[pending_offset_ - 1u];
}
size_t IndexOfFirstThunkAtOrAfter(uint32_t offset) const {
size_t number_of_thunks = NumberOfThunks();
for (size_t i = 0; i != number_of_thunks; ++i) {
if (GetThunkOffset(i) >= offset) {
return i;
}
}
return number_of_thunks;
}
size_t NumberOfThunks() const {
return offsets_.size();
}
uint32_t GetThunkOffset(size_t index) const {
DCHECK_LT(index, NumberOfThunks());
return offsets_[index];
}
private:
const ArrayRef<const uint8_t> code_; // The code of the thunk.
const std::string debug_name_; // The debug name of the thunk.
std::vector<uint32_t> offsets_; // Offsets at which the thunk needs to be written.
uint32_t max_next_offset_; // The maximum offset at which the next thunk can be placed.
uint32_t pending_offset_; // The index of the next offset to write.
};
class ArmBaseRelativePatcher::PendingThunkComparator {
public:
bool operator()(const ThunkData* lhs, const ThunkData* rhs) const {
DCHECK(lhs->HasPendingOffset());
DCHECK(rhs->HasPendingOffset());
// The top of the heap is defined to contain the highest element and we want to pick
// the thunk with the smallest pending offset, so use the reverse ordering, i.e. ">".
return lhs->GetPendingOffset() > rhs->GetPendingOffset();
}
};
uint32_t ArmBaseRelativePatcher::ReserveSpace(uint32_t offset,
const CompiledMethod* compiled_method,
MethodReference method_ref) {
return ReserveSpaceInternal(offset, compiled_method, method_ref, 0u);
}
uint32_t ArmBaseRelativePatcher::ReserveSpaceEnd(uint32_t offset) {
// For multi-oat compilations (boot image), ReserveSpaceEnd() is called for each oat file.
// Since we do not know here whether this is the last file or whether the next opportunity
// to place thunk will be soon enough, we need to reserve all needed thunks now. Code for
// subsequent oat files can still call back to them.
if (!unprocessed_method_call_patches_.empty()) {
ResolveMethodCalls(offset, MethodReference(nullptr, dex::kDexNoIndex));
}
for (ThunkData* data : unreserved_thunks_) {
uint32_t thunk_offset = CompiledCode::AlignCode(offset, instruction_set_);
offset = data->ReserveOffset(thunk_offset);
}
unreserved_thunks_.clear();
// We also need to delay initiating the pending_thunks_ until the call to WriteThunks().
// Check that the `pending_thunks_.capacity()` indicates that no WriteThunks() has taken place.
DCHECK_EQ(pending_thunks_.capacity(), 0u);
return offset;
}
uint32_t ArmBaseRelativePatcher::WriteThunks(OutputStream* out, uint32_t offset) {
if (pending_thunks_.capacity() == 0u) {
if (thunks_.empty()) {
return offset;
}
// First call to WriteThunks(), prepare the thunks for writing.
pending_thunks_.reserve(thunks_.size());
for (auto& entry : thunks_) {
ThunkData* data = &entry.second;
if (data->HasPendingOffset()) {
pending_thunks_.push_back(data);
}
}
std::make_heap(pending_thunks_.begin(), pending_thunks_.end(), PendingThunkComparator());
}
uint32_t aligned_offset = CompiledMethod::AlignCode(offset, instruction_set_);
while (!pending_thunks_.empty() &&
pending_thunks_.front()->GetPendingOffset() == aligned_offset) {
// Write alignment bytes and code.
uint32_t aligned_code_delta = aligned_offset - offset;
if (aligned_code_delta != 0u && UNLIKELY(!WriteCodeAlignment(out, aligned_code_delta))) {
return 0u;
}
if (UNLIKELY(!WriteThunk(out, pending_thunks_.front()->GetCode()))) {
return 0u;
}
offset = aligned_offset + pending_thunks_.front()->CodeSize();
// Mark the thunk as written at the pending offset and update the `pending_thunks_` heap.
std::pop_heap(pending_thunks_.begin(), pending_thunks_.end(), PendingThunkComparator());
pending_thunks_.back()->MarkPendingOffsetAsWritten();
if (pending_thunks_.back()->HasPendingOffset()) {
std::push_heap(pending_thunks_.begin(), pending_thunks_.end(), PendingThunkComparator());
} else {
pending_thunks_.pop_back();
}
aligned_offset = CompiledMethod::AlignCode(offset, instruction_set_);
}
DCHECK(pending_thunks_.empty() || pending_thunks_.front()->GetPendingOffset() > aligned_offset);
return offset;
}
std::vector<debug::MethodDebugInfo> ArmBaseRelativePatcher::GenerateThunkDebugInfo(
uint32_t executable_offset) {
// For multi-oat compilation (boot image), `thunks_` records thunks for all oat files.
// To return debug info for the current oat file, we must ignore thunks before the
// `executable_offset` as they are in the previous oat files and this function must be
// called before reserving thunk positions for subsequent oat files.
size_t number_of_thunks = 0u;
for (auto&& entry : thunks_) {
const ThunkData& data = entry.second;
number_of_thunks += data.NumberOfThunks() - data.IndexOfFirstThunkAtOrAfter(executable_offset);
}
std::vector<debug::MethodDebugInfo> result;
result.reserve(number_of_thunks);
for (auto&& entry : thunks_) {
const ThunkData& data = entry.second;
size_t start = data.IndexOfFirstThunkAtOrAfter(executable_offset);
if (start == data.NumberOfThunks()) {
continue;
}
// Get the base name to use for the first occurrence of the thunk.
const std::string& base_name = data.GetDebugName();
for (size_t i = start, num = data.NumberOfThunks(); i != num; ++i) {
debug::MethodDebugInfo info = {};
if (i == 0u) {
info.custom_name = base_name;
} else {
// Add a disambiguating tag for subsequent identical thunks. Since the `thunks_`
// keeps records also for thunks in previous oat files, names based on the thunk
// index shall be unique across the whole multi-oat output.
info.custom_name = base_name + "_" + std::to_string(i);
}
info.isa = instruction_set_;
info.is_code_address_text_relative = true;
info.code_address = data.GetThunkOffset(i) - executable_offset;
info.code_size = data.CodeSize();
result.push_back(std::move(info));
}
}
return result;
}
ArmBaseRelativePatcher::ArmBaseRelativePatcher(RelativePatcherThunkProvider* thunk_provider,
RelativePatcherTargetProvider* target_provider,
InstructionSet instruction_set)
: thunk_provider_(thunk_provider),
target_provider_(target_provider),
instruction_set_(instruction_set),
thunks_(),
unprocessed_method_call_patches_(),
method_call_thunk_(nullptr),
pending_thunks_() {
}
ArmBaseRelativePatcher::~ArmBaseRelativePatcher() {
// All work done by member destructors.
}
uint32_t ArmBaseRelativePatcher::ReserveSpaceInternal(uint32_t offset,
const CompiledMethod* compiled_method,
MethodReference method_ref,
uint32_t max_extra_space) {
// Adjust code size for extra space required by the subclass.
uint32_t max_code_size = compiled_method->GetQuickCode().size() + max_extra_space;
uint32_t code_offset;
uint32_t next_aligned_offset;
while (true) {
code_offset = compiled_method->AlignCode(offset + sizeof(OatQuickMethodHeader));
next_aligned_offset = compiled_method->AlignCode(code_offset + max_code_size);
if (unreserved_thunks_.empty() ||
unreserved_thunks_.front()->MaxNextOffset() >= next_aligned_offset) {
break;
}
ThunkData* thunk = unreserved_thunks_.front();
if (thunk == method_call_thunk_) {
ResolveMethodCalls(code_offset, method_ref);
// This may have changed `method_call_thunk_` data, so re-check if we need to reserve.
if (unreserved_thunks_.empty() ||
unreserved_thunks_.front()->MaxNextOffset() >= next_aligned_offset) {
break;
}
// We need to process the new `front()` whether it's still the `method_call_thunk_` or not.
thunk = unreserved_thunks_.front();
}
unreserved_thunks_.pop_front();
uint32_t thunk_offset = CompiledCode::AlignCode(offset, instruction_set_);
offset = thunk->ReserveOffset(thunk_offset);
if (thunk == method_call_thunk_) {
// All remaining method call patches will be handled by this thunk.
DCHECK(!unprocessed_method_call_patches_.empty());
DCHECK_LE(thunk_offset - unprocessed_method_call_patches_.front().GetPatchOffset(),
MaxPositiveDisplacement(GetMethodCallKey()));
unprocessed_method_call_patches_.clear();
}
}
// Process patches and check that adding thunks for the current method did not push any
// thunks (previously existing or newly added) before `next_aligned_offset`. This is
// essentially a check that we never compile a method that's too big. The calls or branches
// from the method should be able to reach beyond the end of the method and over any pending
// thunks. (The number of different thunks should be relatively low and their code short.)
ProcessPatches(compiled_method, code_offset);
CHECK(unreserved_thunks_.empty() ||
unreserved_thunks_.front()->MaxNextOffset() >= next_aligned_offset);
return offset;
}
uint32_t ArmBaseRelativePatcher::CalculateMethodCallDisplacement(uint32_t patch_offset,
uint32_t target_offset) {
DCHECK(method_call_thunk_ != nullptr);
// Unsigned arithmetic with its well-defined overflow behavior is just fine here.
uint32_t displacement = target_offset - patch_offset;
uint32_t max_positive_displacement = MaxPositiveDisplacement(GetMethodCallKey());
uint32_t max_negative_displacement = MaxNegativeDisplacement(GetMethodCallKey());
// NOTE: With unsigned arithmetic we do mean to use && rather than || below.
if (displacement > max_positive_displacement && displacement < -max_negative_displacement) {
// Unwritten thunks have higher offsets, check if it's within range.
DCHECK(!method_call_thunk_->HasPendingOffset() ||
method_call_thunk_->GetPendingOffset() > patch_offset);
if (method_call_thunk_->HasPendingOffset() &&
method_call_thunk_->GetPendingOffset() - patch_offset <= max_positive_displacement) {
displacement = method_call_thunk_->GetPendingOffset() - patch_offset;
} else {
// We must have a previous thunk then.
DCHECK(method_call_thunk_->HasWrittenOffset());
DCHECK_LT(method_call_thunk_->LastWrittenOffset(), patch_offset);
displacement = method_call_thunk_->LastWrittenOffset() - patch_offset;
DCHECK_GE(displacement, -max_negative_displacement);
}
}
return displacement;
}
uint32_t ArmBaseRelativePatcher::GetThunkTargetOffset(const ThunkKey& key, uint32_t patch_offset) {
auto it = thunks_.find(key);
CHECK(it != thunks_.end());
const ThunkData& data = it->second;
if (data.HasWrittenOffset()) {
uint32_t offset = data.LastWrittenOffset();
DCHECK_LT(offset, patch_offset);
if (patch_offset - offset <= MaxNegativeDisplacement(key)) {
return offset;
}
}
DCHECK(data.HasPendingOffset());
uint32_t offset = data.GetPendingOffset();
DCHECK_GT(offset, patch_offset);
DCHECK_LE(offset - patch_offset, MaxPositiveDisplacement(key));
return offset;
}
ArmBaseRelativePatcher::ThunkKey ArmBaseRelativePatcher::GetMethodCallKey() {
return ThunkKey(ThunkType::kMethodCall);
}
ArmBaseRelativePatcher::ThunkKey ArmBaseRelativePatcher::GetBakerThunkKey(
const LinkerPatch& patch) {
DCHECK_EQ(patch.GetType(), LinkerPatch::Type::kBakerReadBarrierBranch);
return ThunkKey(ThunkType::kBakerReadBarrier,
patch.GetBakerCustomValue1(),
patch.GetBakerCustomValue2());
}
void ArmBaseRelativePatcher::ProcessPatches(const CompiledMethod* compiled_method,
uint32_t code_offset) {
for (const LinkerPatch& patch : compiled_method->GetPatches()) {
uint32_t patch_offset = code_offset + patch.LiteralOffset();
ThunkKey key(static_cast<ThunkType>(-1));
ThunkData* old_data = nullptr;
if (patch.GetType() == LinkerPatch::Type::kCallRelative) {
key = GetMethodCallKey();
unprocessed_method_call_patches_.emplace_back(patch_offset, patch.TargetMethod());
if (method_call_thunk_ == nullptr) {
uint32_t max_next_offset = CalculateMaxNextOffset(patch_offset, key);
auto it = thunks_.Put(key, ThunkDataForPatch(patch, max_next_offset));
method_call_thunk_ = &it->second;
AddUnreservedThunk(method_call_thunk_);
} else {
old_data = method_call_thunk_;
}
} else if (patch.GetType() == LinkerPatch::Type::kBakerReadBarrierBranch) {
key = GetBakerThunkKey(patch);
auto lb = thunks_.lower_bound(key);
if (lb == thunks_.end() || thunks_.key_comp()(key, lb->first)) {
uint32_t max_next_offset = CalculateMaxNextOffset(patch_offset, key);
auto it = thunks_.PutBefore(lb, key, ThunkDataForPatch(patch, max_next_offset));
AddUnreservedThunk(&it->second);
} else {
old_data = &lb->second;
}
}
if (old_data != nullptr) {
// Shared path where an old thunk may need an update.
DCHECK(key.GetType() != static_cast<ThunkType>(-1));
DCHECK(!old_data->HasReservedOffset() || old_data->LastReservedOffset() < patch_offset);
if (old_data->NeedsNextThunk()) {
// Patches for a method are ordered by literal offset, so if we still need to place
// this thunk for a previous patch, that thunk shall be in range for this patch.
DCHECK_LE(old_data->MaxNextOffset(), CalculateMaxNextOffset(patch_offset, key));
} else {
if (!old_data->HasReservedOffset() ||
patch_offset - old_data->LastReservedOffset() > MaxNegativeDisplacement(key)) {
old_data->SetMaxNextOffset(CalculateMaxNextOffset(patch_offset, key));
AddUnreservedThunk(old_data);
}
}
}
}
}
void ArmBaseRelativePatcher::AddUnreservedThunk(ThunkData* data) {
DCHECK(data->NeedsNextThunk());
size_t index = unreserved_thunks_.size();
while (index != 0u && data->MaxNextOffset() < unreserved_thunks_[index - 1u]->MaxNextOffset()) {
--index;
}
unreserved_thunks_.insert(unreserved_thunks_.begin() + index, data);
// We may need to update the max next offset(s) if the thunk code would not fit.
size_t alignment = GetInstructionSetAlignment(instruction_set_);
if (index + 1u != unreserved_thunks_.size()) {
// Note: Ignore the return value as we need to process previous thunks regardless.
data->MakeSpaceBefore(*unreserved_thunks_[index + 1u], alignment);
}
// Make space for previous thunks. Once we find a pending thunk that does
// not need an adjustment, we can stop.
while (index != 0u && unreserved_thunks_[index - 1u]->MakeSpaceBefore(*data, alignment)) {
--index;
data = unreserved_thunks_[index];
}
}
void ArmBaseRelativePatcher::ResolveMethodCalls(uint32_t quick_code_offset,
MethodReference method_ref) {
DCHECK(!unreserved_thunks_.empty());
DCHECK(!unprocessed_method_call_patches_.empty());
DCHECK(method_call_thunk_ != nullptr);
uint32_t max_positive_displacement = MaxPositiveDisplacement(GetMethodCallKey());
uint32_t max_negative_displacement = MaxNegativeDisplacement(GetMethodCallKey());
// Process as many patches as possible, stop only on unresolved targets or calls too far back.
while (!unprocessed_method_call_patches_.empty()) {
MethodReference target_method = unprocessed_method_call_patches_.front().GetTargetMethod();
uint32_t patch_offset = unprocessed_method_call_patches_.front().GetPatchOffset();
DCHECK(!method_call_thunk_->HasReservedOffset() ||
method_call_thunk_->LastReservedOffset() <= patch_offset);
if (!method_call_thunk_->HasReservedOffset() ||
patch_offset - method_call_thunk_->LastReservedOffset() > max_negative_displacement) {
// No previous thunk in range, check if we can reach the target directly.
if (target_method == method_ref) {
DCHECK_GT(quick_code_offset, patch_offset);
if (quick_code_offset - patch_offset > max_positive_displacement) {
break;
}
} else {
auto result = target_provider_->FindMethodOffset(target_method);
if (!result.first) {
break;
}
uint32_t target_offset = result.second - CompiledCode::CodeDelta(instruction_set_);
if (target_offset >= patch_offset) {
DCHECK_LE(target_offset - patch_offset, max_positive_displacement);
} else if (patch_offset - target_offset > max_negative_displacement) {
break;
}
}
}
unprocessed_method_call_patches_.pop_front();
}
if (!unprocessed_method_call_patches_.empty()) {
// Try to adjust the max next offset in `method_call_thunk_`. Do this conservatively only if
// the thunk shall be at the end of the `unreserved_thunks_` to avoid dealing with overlaps.
uint32_t new_max_next_offset =
unprocessed_method_call_patches_.front().GetPatchOffset() + max_positive_displacement;
if (new_max_next_offset >
unreserved_thunks_.back()->MaxNextOffset() + unreserved_thunks_.back()->CodeSize()) {
method_call_thunk_->ClearMaxNextOffset();
method_call_thunk_->SetMaxNextOffset(new_max_next_offset);
if (method_call_thunk_ != unreserved_thunks_.back()) {
RemoveElement(unreserved_thunks_, method_call_thunk_);
unreserved_thunks_.push_back(method_call_thunk_);
}
}
} else {
// We have resolved all method calls, we do not need a new thunk anymore.
method_call_thunk_->ClearMaxNextOffset();
RemoveElement(unreserved_thunks_, method_call_thunk_);
}
}
inline uint32_t ArmBaseRelativePatcher::CalculateMaxNextOffset(uint32_t patch_offset,
const ThunkKey& key) {
return RoundDown(patch_offset + MaxPositiveDisplacement(key),
GetInstructionSetAlignment(instruction_set_));
}
inline ArmBaseRelativePatcher::ThunkData ArmBaseRelativePatcher::ThunkDataForPatch(
const LinkerPatch& patch, uint32_t max_next_offset) {
ArrayRef<const uint8_t> code;
std::string debug_name;
thunk_provider_->GetThunkCode(patch, &code, &debug_name);
DCHECK(!code.empty());
return ThunkData(code, debug_name, max_next_offset);
}
} // namespace linker
} // namespace art