/*
* Copyright (c) 2020-2022, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2023, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Badge.h>
#include <AK/Debug.h>
#include <AK/HashTable.h>
#include <AK/JsonArray.h>
#include <AK/JsonObject.h>
#include <AK/Platform.h>
#include <AK/StackInfo.h>
#include <AK/TemporaryChange.h>
#include <LibCore/ElapsedTimer.h>
#include <LibJS/Bytecode/Interpreter.h>
#include <LibJS/Heap/CellAllocator.h>
#include <LibJS/Heap/Handle.h>
#include <LibJS/Heap/Heap.h>
#include <LibJS/Heap/HeapBlock.h>
#include <LibJS/Runtime/Object.h>
#include <LibJS/Runtime/WeakContainer.h>
#include <LibJS/SafeFunction.h>
#include <setjmp.h>
#ifdef AK_OS_MINERVA
# include <minerva.h>
#endif
#ifdef HAS_ADDRESS_SANITIZER
# include <sanitizer/asan_interface.h>
#endif
namespace JS {
#ifdef AK_OS_MINERVA
static int gc_perf_string_id;
#endif
// NOTE: We keep a per-thread list of custom ranges. This hinges on the assumption that there is one JS VM per thread.
static __thread HashMap<FlatPtr*, size_t>* s_custom_ranges_for_conservative_scan = nullptr;
static __thread HashMap<FlatPtr*, SourceLocation*>* s_safe_function_locations = nullptr;
Heap::Heap(VM& vm)
: HeapBase(vm)
{
#ifdef AK_OS_MINERVA
auto gc_signpost_string = "Garbage collection"sv;
gc_perf_string_id = perf_register_string(gc_signpost_string.characters_without_null_termination(), gc_signpost_string.length());
#endif
static_assert(HeapBlock::min_possible_cell_size <= 32, "Heap Cell tracking uses too much data!");
m_size_based_cell_allocators.append(make<CellAllocator>(64));
m_size_based_cell_allocators.append(make<CellAllocator>(96));
m_size_based_cell_allocators.append(make<CellAllocator>(128));
m_size_based_cell_allocators.append(make<CellAllocator>(256));
m_size_based_cell_allocators.append(make<CellAllocator>(512));
m_size_based_cell_allocators.append(make<CellAllocator>(1024));
m_size_based_cell_allocators.append(make<CellAllocator>(3072));
}
Heap::~Heap()
{
vm().string_cache().clear();
vm().byte_string_cache().clear();
collect_garbage(CollectionType::CollectEverything);
}
void Heap::will_allocate(size_t size)
{
if (should_collect_on_every_allocation()) {
m_allocated_bytes_since_last_gc = 0;
collect_garbage();
} else if (m_allocated_bytes_since_last_gc + size > m_gc_bytes_threshold) {
m_allocated_bytes_since_last_gc = 0;
collect_garbage();
}
m_allocated_bytes_since_last_gc += size;
}
static void add_possible_value(HashMap<FlatPtr, HeapRoot>& possible_pointers, FlatPtr data, HeapRoot origin, FlatPtr min_block_address, FlatPtr max_block_address)
{
if constexpr (sizeof(FlatPtr*) == sizeof(Value)) {
// Because Value stores pointers in non-canonical form we have to check if the top bytes
// match any pointer-backed tag, in that case we have to extract the pointer to its
// canonical form and add that as a possible pointer.
FlatPtr possible_pointer;
if ((data & SHIFTED_IS_CELL_PATTERN) == SHIFTED_IS_CELL_PATTERN)
possible_pointer = Value::extract_pointer_bits(data);
else
possible_pointer = data;
if (possible_pointer < min_block_address || possible_pointer > max_block_address)
return;
possible_pointers.set(possible_pointer, move(origin));
} else {
static_assert((sizeof(Value) % sizeof(FlatPtr*)) == 0);
if (data < min_block_address || data > max_block_address)
return;
// In the 32-bit case we will look at the top and bottom part of Value separately we just
// add both the upper and lower bytes as possible pointers.
possible_pointers.set(data, move(origin));
}
}
void Heap::find_min_and_max_block_addresses(FlatPtr& min_address, FlatPtr& max_address)
{
min_address = explode_byte(0xff);
max_address = 0;
for (auto& allocator : m_all_cell_allocators) {
min_address = min(min_address, allocator.min_block_address());
max_address = max(max_address, allocator.max_block_address() + HeapBlockBase::block_size);
}
}
template<typename Callback>
static void for_each_cell_among_possible_pointers(HashTable<HeapBlock*> const& all_live_heap_blocks, HashMap<FlatPtr, HeapRoot>& possible_pointers, Callback callback)
{
for (auto possible_pointer : possible_pointers.keys()) {
if (!possible_pointer)
continue;
auto* possible_heap_block = HeapBlock::from_cell(reinterpret_cast<Cell const*>(possible_pointer));
if (!all_live_heap_blocks.contains(possible_heap_block))
continue;
if (auto* cell = possible_heap_block->cell_from_possible_pointer(possible_pointer)) {
callback(cell, possible_pointer);
}
}
}
class GraphConstructorVisitor final : public Cell::Visitor {
public:
explicit GraphConstructorVisitor(Heap& heap, HashMap<Cell*, HeapRoot> const& roots)
: m_heap(heap)
{
m_heap.find_min_and_max_block_addresses(m_min_block_address, m_max_block_address);
m_heap.for_each_block([&](auto& block) {
m_all_live_heap_blocks.set(&block);
return IterationDecision::Continue;
});
m_work_queue.ensure_capacity(roots.size());
for (auto& [root, root_origin] : roots) {
auto& graph_node = m_graph.ensure(bit_cast<FlatPtr>(root));
graph_node.class_name = root->class_name();
graph_node.root_origin = root_origin;
m_work_queue.append(*root);
}
}
virtual void visit_impl(Cell& cell) override
{
if (m_node_being_visited)
m_node_being_visited->edges.set(reinterpret_cast<FlatPtr>(&cell));
if (m_graph.get(reinterpret_cast<FlatPtr>(&cell)).has_value())
return;
m_work_queue.append(cell);
}
virtual void visit_possible_values(ReadonlyBytes bytes) override
{
HashMap<FlatPtr, HeapRoot> possible_pointers;
auto* raw_pointer_sized_values = reinterpret_cast<FlatPtr const*>(bytes.data());
for (size_t i = 0; i < (bytes.size() / sizeof(FlatPtr)); ++i)
add_possible_value(possible_pointers, raw_pointer_sized_values[i], HeapRoot { .type = HeapRoot::Type::HeapFunctionCapturedPointer }, m_min_block_address, m_max_block_address);
for_each_cell_among_possible_pointers(m_all_live_heap_blocks, possible_pointers, [&](Cell* cell, FlatPtr) {
if (m_node_being_visited)
m_node_being_visited->edges.set(reinterpret_cast<FlatPtr>(cell));
if (m_graph.get(reinterpret_cast<FlatPtr>(&cell)).has_value())
return;
m_work_queue.append(*cell);
});
}
void visit_all_cells()
{
while (!m_work_queue.is_empty()) {
auto cell = m_work_queue.take_last();
m_node_being_visited = &m_graph.ensure(bit_cast<FlatPtr>(cell.ptr()));
m_node_being_visited->class_name = cell->class_name();
cell->visit_edges(*this);
m_node_being_visited = nullptr;
}
}
AK::JsonObject dump()
{
auto graph = AK::JsonObject();
for (auto& it : m_graph) {
AK::JsonArray edges;
for (auto const& value : it.value.edges) {
edges.must_append(ByteString::formatted("{}", value));
}
auto node = AK::JsonObject();
if (it.value.root_origin.has_value()) {
auto type = it.value.root_origin->type;
auto location = it.value.root_origin->location;
switch (type) {
case HeapRoot::Type::Handle:
node.set("root"sv, ByteString::formatted("Handle {} {}:{}", location->function_name(), location->filename(), location->line_number()));
break;
case HeapRoot::Type::MarkedVector:
node.set("root"sv, "MarkedVector");
break;
case HeapRoot::Type::RegisterPointer:
node.set("root"sv, "RegisterPointer");
break;
case HeapRoot::Type::StackPointer:
node.set("root"sv, "StackPointer");
break;
case HeapRoot::Type::VM:
node.set("root"sv, "VM");
break;
case HeapRoot::Type::SafeFunction:
node.set("root"sv, ByteString::formatted("SafeFunction {} {}:{}", location->function_name(), location->filename(), location->line_number()));
break;
default:
VERIFY_NOT_REACHED();
}
}
node.set("class_name"sv, it.value.class_name);
node.set("edges"sv, edges);
graph.set(ByteString::number(it.key), node);
}
return graph;
}
private:
struct GraphNode {
Optional<HeapRoot> root_origin;
StringView class_name;
HashTable<FlatPtr> edges {};
};
GraphNode* m_node_being_visited { nullptr };
Vector<NonnullGCPtr<Cell>> m_work_queue;
HashMap<FlatPtr, GraphNode> m_graph;
Heap& m_heap;
HashTable<HeapBlock*> m_all_live_heap_blocks;
FlatPtr m_min_block_address;
FlatPtr m_max_block_address;
};
AK::JsonObject Heap::dump_graph()
{
HashMap<Cell*, HeapRoot> roots;
gather_roots(roots);
GraphConstructorVisitor visitor(*this, roots);
visitor.visit_all_cells();
return visitor.dump();
}
void Heap::collect_garbage(CollectionType collection_type, bool print_report)
{
VERIFY(!m_collecting_garbage);
TemporaryChange change(m_collecting_garbage, true);
#ifdef AK_OS_MINERVA
static size_t global_gc_counter = 0;
perf_event(PERF_EVENT_SIGNPOST, gc_perf_string_id, global_gc_counter++);
#endif
Core::ElapsedTimer collection_measurement_timer;
if (print_report)
collection_measurement_timer.start();
if (collection_type == CollectionType::CollectGarbage) {
if (m_gc_deferrals) {
m_should_gc_when_deferral_ends = true;
return;
}
HashMap<Cell*, HeapRoot> roots;
gather_roots(roots);
mark_live_cells(roots);
}
finalize_unmarked_cells();
sweep_dead_cells(print_report, collection_measurement_timer);
}
void Heap::gather_roots(HashMap<Cell*, HeapRoot>& roots)
{
vm().gather_roots(roots);
gather_conservative_roots(roots);
for (auto& handle : m_handles)
roots.set(handle.cell(), HeapRoot { .type = HeapRoot::Type::Handle, .location = &handle.source_location() });
for (auto& vector : m_marked_vectors)
vector.gather_roots(roots);
if constexpr (HEAP_DEBUG) {
dbgln("gather_roots:");
for (auto* root : roots.keys())
dbgln(" + {}", root);
}
}
#ifdef HAS_ADDRESS_SANITIZER
NO_SANITIZE_ADDRESS void Heap::gather_asan_fake_stack_roots(HashMap<FlatPtr, HeapRoot>& possible_pointers, FlatPtr addr, FlatPtr min_block_address, FlatPtr max_block_address)
{
void* begin = nullptr;
void* end = nullptr;
void* real_stack = __asan_addr_is_in_fake_stack(__asan_get_current_fake_stack(), reinterpret_cast<void*>(addr), &begin, &end);
if (real_stack != nullptr) {
for (auto* real_stack_addr = reinterpret_cast<void const* const*>(begin); real_stack_addr < end; ++real_stack_addr) {
void const* real_address = *real_stack_addr;
if (real_address == nullptr)
continue;
add_possible_value(possible_pointers, reinterpret_cast<FlatPtr>(real_address), HeapRoot { .type = HeapRoot::Type::StackPointer }, min_block_address, max_block_address);
}
}
}
#else
void Heap::gather_asan_fake_stack_roots(HashMap<FlatPtr, HeapRoot>&, FlatPtr, FlatPtr, FlatPtr)
{
}
#endif
NO_SANITIZE_ADDRESS void Heap::gather_conservative_roots(HashMap<Cell*, HeapRoot>& roots)
{
FlatPtr dummy;
dbgln_if(HEAP_DEBUG, "gather_conservative_roots:");
jmp_buf buf {};
setjmp(buf);
HashMap<FlatPtr, HeapRoot> possible_pointers;
auto* raw_jmp_buf = reinterpret_cast<FlatPtr const*>(buf);
FlatPtr min_block_address, max_block_address;
find_min_and_max_block_addresses(min_block_address, max_block_address);
for (size_t i = 0; i < ((size_t)sizeof(buf)) / sizeof(FlatPtr); ++i)
add_possible_value(possible_pointers, raw_jmp_buf[i], HeapRoot { .type = HeapRoot::Type::RegisterPointer }, min_block_address, max_block_address);
auto stack_reference = bit_cast<FlatPtr>(&dummy);
auto& stack_info = m_vm.stack_info();
for (FlatPtr stack_address = stack_reference; stack_address < stack_info.top(); stack_address += sizeof(FlatPtr)) {
auto data = *reinterpret_cast<FlatPtr*>(stack_address);
add_possible_value(possible_pointers, data, HeapRoot { .type = HeapRoot::Type::StackPointer }, min_block_address, max_block_address);
gather_asan_fake_stack_roots(possible_pointers, data, min_block_address, max_block_address);
}
// NOTE: If we have any custom ranges registered, scan those as well.
// This is where JS::SafeFunction closures get marked.
if (s_custom_ranges_for_conservative_scan) {
for (auto& custom_range : *s_custom_ranges_for_conservative_scan) {
for (size_t i = 0; i < (custom_range.value / sizeof(FlatPtr)); ++i) {
auto safe_function_location = s_safe_function_locations->get(custom_range.key);
add_possible_value(possible_pointers, custom_range.key[i], HeapRoot { .type = HeapRoot::Type::SafeFunction, .location = *safe_function_location }, min_block_address, max_block_address);
}
}
}
for (auto& vector : m_conservative_vectors) {
for (auto possible_value : vector.possible_values()) {
add_possible_value(possible_pointers, possible_value, HeapRoot { .type = HeapRoot::Type::ConservativeVector }, min_block_address, max_block_address);
}
}
HashTable<HeapBlock*> all_live_heap_blocks;
for_each_block([&](auto& block) {
all_live_heap_blocks.set(&block);
return IterationDecision::Continue;
});
for_each_cell_among_possible_pointers(all_live_heap_blocks, possible_pointers, [&](Cell* cell, FlatPtr possible_pointer) {
if (cell->state() == Cell::State::Live) {
dbgln_if(HEAP_DEBUG, " ?-> {}", (void const*)cell);
roots.set(cell, *possible_pointers.get(possible_pointer));
} else {
dbgln_if(HEAP_DEBUG, " #-> {}", (void const*)cell);
}
});
}
class MarkingVisitor final : public Cell::Visitor {
public:
explicit MarkingVisitor(Heap& heap, HashMap<Cell*, HeapRoot> const& roots)
: m_heap(heap)
{
m_heap.find_min_and_max_block_addresses(m_min_block_address, m_max_block_address);
m_heap.for_each_block([&](auto& block) {
m_all_live_heap_blocks.set(&block);
return IterationDecision::Continue;
});
for (auto* root : roots.keys()) {
visit(root);
}
}
virtual void visit_impl(Cell& cell) override
{
if (cell.is_marked())
return;
dbgln_if(HEAP_DEBUG, " ! {}", &cell);
cell.set_marked(true);
m_work_queue.append(cell);
}
virtual void visit_possible_values(ReadonlyBytes bytes) override
{
HashMap<FlatPtr, HeapRoot> possible_pointers;
auto* raw_pointer_sized_values = reinterpret_cast<FlatPtr const*>(bytes.data());
for (size_t i = 0; i < (bytes.size() / sizeof(FlatPtr)); ++i)
add_possible_value(possible_pointers, raw_pointer_sized_values[i], HeapRoot { .type = HeapRoot::Type::HeapFunctionCapturedPointer }, m_min_block_address, m_max_block_address);
for_each_cell_among_possible_pointers(m_all_live_heap_blocks, possible_pointers, [&](Cell* cell, FlatPtr) {
if (cell->is_marked())
return;
if (cell->state() != Cell::State::Live)
return;
cell->set_marked(true);
m_work_queue.append(*cell);
});
}
void mark_all_live_cells()
{
while (!m_work_queue.is_empty()) {
m_work_queue.take_last()->visit_edges(*this);
}
}
private:
Heap& m_heap;
Vector<NonnullGCPtr<Cell>> m_work_queue;
HashTable<HeapBlock*> m_all_live_heap_blocks;
FlatPtr m_min_block_address;
FlatPtr m_max_block_address;
};
void Heap::mark_live_cells(HashMap<Cell*, HeapRoot> const& roots)
{
dbgln_if(HEAP_DEBUG, "mark_live_cells:");
MarkingVisitor visitor(*this, roots);
visitor.mark_all_live_cells();
for (auto& inverse_root : m_uprooted_cells)
inverse_root->set_marked(false);
m_uprooted_cells.clear();
}
bool Heap::cell_must_survive_garbage_collection(Cell const& cell)
{
if (!cell.overrides_must_survive_garbage_collection({}))
return false;
return cell.must_survive_garbage_collection();
}
void Heap::finalize_unmarked_cells()
{
for_each_block([&](auto& block) {
block.template for_each_cell_in_state<Cell::State::Live>([](Cell* cell) {
if (!cell->is_marked() && !cell_must_survive_garbage_collection(*cell))
cell->finalize();
});
return IterationDecision::Continue;
});
}
void Heap::sweep_dead_cells(bool print_report, Core::ElapsedTimer const& measurement_timer)
{
dbgln_if(HEAP_DEBUG, "sweep_dead_cells:");
Vector<HeapBlock*, 32> empty_blocks;
Vector<HeapBlock*, 32> full_blocks_that_became_usable;
size_t collected_cells = 0;
size_t live_cells = 0;
size_t collected_cell_bytes = 0;
size_t live_cell_bytes = 0;
for_each_block([&](auto& block) {
bool block_has_live_cells = false;
bool block_was_full = block.is_full();
block.template for_each_cell_in_state<Cell::State::Live>([&](Cell* cell) {
if (!cell->is_marked() && !cell_must_survive_garbage_collection(*cell)) {
dbgln_if(HEAP_DEBUG, " ~ {}", cell);
block.deallocate(cell);
++collected_cells;
collected_cell_bytes += block.cell_size();
} else {
cell->set_marked(false);
block_has_live_cells = true;
++live_cells;
live_cell_bytes += block.cell_size();
}
});
if (!block_has_live_cells)
empty_blocks.append(&block);
else if (block_was_full != block.is_full())
full_blocks_that_became_usable.append(&block);
return IterationDecision::Continue;
});
for (auto& weak_container : m_weak_containers)
weak_container.remove_dead_cells({});
for (auto* block : empty_blocks) {
dbgln_if(HEAP_DEBUG, " - HeapBlock empty @ {}: cell_size={}", block, block->cell_size());
block->cell_allocator().block_did_become_empty({}, *block);
}
for (auto* block : full_blocks_that_became_usable) {
dbgln_if(HEAP_DEBUG, " - HeapBlock usable again @ {}: cell_size={}", block, block->cell_size());
block->cell_allocator().block_did_become_usable({}, *block);
}
if constexpr (HEAP_DEBUG) {
for_each_block([&](auto& block) {
dbgln(" > Live HeapBlock @ {}: cell_size={}", &block, block.cell_size());
return IterationDecision::Continue;
});
}
m_gc_bytes_threshold = live_cell_bytes > GC_MIN_BYTES_THRESHOLD ? live_cell_bytes : GC_MIN_BYTES_THRESHOLD;
if (print_report) {
Duration const time_spent = measurement_timer.elapsed_time();
size_t live_block_count = 0;
for_each_block([&](auto&) {
++live_block_count;
return IterationDecision::Continue;
});
dbgln("Garbage collection report");
dbgln("=============================================");
dbgln(" Time spent: {} ms", time_spent.to_milliseconds());
dbgln(" Live cells: {} ({} bytes)", live_cells, live_cell_bytes);
dbgln("Collected cells: {} ({} bytes)", collected_cells, collected_cell_bytes);
dbgln(" Live blocks: {} ({} bytes)", live_block_count, live_block_count * HeapBlock::block_size);
dbgln(" Freed blocks: {} ({} bytes)", empty_blocks.size(), empty_blocks.size() * HeapBlock::block_size);
dbgln("=============================================");
}
}
void Heap::defer_gc()
{
++m_gc_deferrals;
}
void Heap::undefer_gc()
{
VERIFY(m_gc_deferrals > 0);
--m_gc_deferrals;
if (!m_gc_deferrals) {
if (m_should_gc_when_deferral_ends)
collect_garbage();
m_should_gc_when_deferral_ends = false;
}
}
void Heap::uproot_cell(Cell* cell)
{
m_uprooted_cells.append(cell);
}
void register_safe_function_closure(void* base, size_t size, SourceLocation* location)
{
if (!s_custom_ranges_for_conservative_scan) {
// FIXME: This per-thread HashMap is currently leaked on thread exit.
s_custom_ranges_for_conservative_scan = new HashMap<FlatPtr*, size_t>;
}
if (!s_safe_function_locations) {
s_safe_function_locations = new HashMap<FlatPtr*, SourceLocation*>;
}
auto result = s_custom_ranges_for_conservative_scan->set(reinterpret_cast<FlatPtr*>(base), size);
VERIFY(result == AK::HashSetResult::InsertedNewEntry);
result = s_safe_function_locations->set(reinterpret_cast<FlatPtr*>(base), location);
VERIFY(result == AK::HashSetResult::InsertedNewEntry);
}
void unregister_safe_function_closure(void* base, size_t, SourceLocation*)
{
VERIFY(s_custom_ranges_for_conservative_scan);
bool did_remove_range = s_custom_ranges_for_conservative_scan->remove(reinterpret_cast<FlatPtr*>(base));
VERIFY(did_remove_range);
bool did_remove_location = s_safe_function_locations->remove(reinterpret_cast<FlatPtr*>(base));
VERIFY(did_remove_location);
}
}
