Caching and optimization work for dwarf
This commit is contained in:
Jeremy
parent
59b5e80256
commit
93dde93802
@ -264,7 +264,9 @@ namespace libdwarf {
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template<typename F>
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void dwarf5_ranges(F callback) const {
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Dwarf_Attribute attr = 0;
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VERIFY(wrap(dwarf_attr, die, DW_AT_ranges, &attr) == DW_DLV_OK);
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if(wrap(dwarf_attr, die, DW_AT_ranges, &attr) != DW_DLV_OK) {
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return;
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}
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auto attrwrapper = raii_wrap(attr, [] (Dwarf_Attribute attr) { dwarf_dealloc_attribute(attr); });
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Dwarf_Unsigned offset = get_ranges_offset(attr);
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Dwarf_Half form = 0;
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@ -413,7 +415,17 @@ namespace libdwarf {
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std::vector<std::pair<Dwarf_Addr, Dwarf_Addr>> get_rangelist_entries(int version) const {
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std::vector<std::pair<Dwarf_Addr, Dwarf_Addr>> vec;
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dwarf_ranges(version, nullopt, [&vec] (Dwarf_Addr low, Dwarf_Addr high) {
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// Simple coalescing optimization:
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// Sometimes the range list entries are really continuous: [100, 200), [200, 300)
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// Other times there's just one byte of separation [300, 399), [400, 500)
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// Those are the main two cases I've observed.
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// This will not catch all cases, presumably, as the range lists aren't sorted. But compilers/linkers
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// seem to like to emit the ranges in sorted order.
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if(!vec.empty() && low - vec.back().second <= 1) {
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vec.back().second = high;
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} else {
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vec.push_back({low, high});
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}
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return true;
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});
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return vec;
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@ -457,12 +469,26 @@ namespace libdwarf {
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Dwarf_Addr high;
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};
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struct cu_entry {
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die_object die;
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Dwarf_Half dwversion;
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Dwarf_Addr low;
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Dwarf_Addr high;
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};
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struct dwarf_resolver {
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std::string obj_path;
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Dwarf_Debug dbg = nullptr;
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bool ok = false;
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// .debug_aranges cache
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Dwarf_Arange* aranges = nullptr;
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Dwarf_Signed arange_count = 0;
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// Map from CU -> Line context
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std::unordered_map<Dwarf_Off, line_context> line_contexts;
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// Map from CU -> Sorted subprograms vector
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std::unordered_map<Dwarf_Off, std::vector<subprogram_entry>> subprograms_cache;
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// Vector of ranges and their corresponding CU offsets
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std::vector<cu_entry> cu_cache;
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// Exists only for cleaning up an awful mach-o hack
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std::string tmp_object_path;
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@ -544,6 +570,26 @@ namespace libdwarf {
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ok = false;
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PANIC("Unknown return code from dwarf_init_path");
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}
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if(ok) {
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// Check for .debug_aranges for fast lookup
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wrap(dwarf_get_aranges, dbg, &aranges, &arange_count);
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}
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if(ok && !aranges) {
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walk_compilation_units([this] (const die_object& cu_die) {
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Dwarf_Half offset_size = 0;
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Dwarf_Half dwversion = 0;
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dwarf_get_version_of_die(cu_die.get(), &dwversion, &offset_size);
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auto ranges_vec = cu_die.get_rangelist_entries(dwversion);
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for(auto range : ranges_vec) {
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cu_cache.push_back({ cu_die.clone(), dwversion, range.first, range.second });
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}
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return true;
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});
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std::sort(cu_cache.begin(), cu_cache.end(), [] (const cu_entry& a, const cu_entry& b) {
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return a.low < b.low;
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});
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}
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}
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CPPTRACE_FORCE_NO_INLINE_FOR_PROFILING
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@ -555,6 +601,10 @@ namespace libdwarf {
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}
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// subprograms_cache needs to be destroyed before dbg otherwise there will be another use after free
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subprograms_cache.clear();
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if(aranges) {
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dwarf_dealloc(dbg, aranges, DW_DLA_LIST);
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}
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cu_cache.clear();
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dwarf_finish(dbg);
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// cleanup awful mach-o hack
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if(!tmp_object_path.empty()) {
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@ -564,17 +614,20 @@ namespace libdwarf {
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// walk die list, callback is called on each die and should return true to
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// continue traversal
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void walk_die_list(
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// returns true if traversal should continue
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bool walk_die_list(
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const die_object& die,
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std::function<bool(const die_object&)> fn
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) {
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// TODO: Refactor so there is only one fn call
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bool continue_traversal = true;
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if(fn(die)) {
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die_object current = die.get_sibling();
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while(current) {
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if(fn(current)) {
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current = current.get_sibling();
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} else {
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continue_traversal = false;
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break;
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}
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}
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@ -582,6 +635,7 @@ namespace libdwarf {
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if(dump_dwarf) {
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fprintf(stderr, "End walk_die_list\n");
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}
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return continue_traversal;
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}
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// walk die list, recursing into children, callback is called on each die
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@ -591,21 +645,66 @@ namespace libdwarf {
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const die_object& die,
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std::function<bool(const die_object&)> fn
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) {
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bool continue_traversal = true;
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walk_die_list(
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return walk_die_list(
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die,
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[this, &fn, &continue_traversal](const die_object& die) {
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[this, &fn](const die_object& die) {
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auto child = die.get_child();
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if(child) {
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if(!walk_die_list_recursive(child, fn)) {
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continue_traversal = false;
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return false;
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}
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}
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return fn(die);
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}
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);
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return continue_traversal;
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}
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// walk all CU's in a dbg, callback is called on each die and should return true to
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// continue traversal
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void walk_compilation_units(std::function<bool(const die_object&)> fn) {
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// libdwarf keeps track of where it is in the file, dwarf_next_cu_header_d is statefull
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Dwarf_Unsigned next_cu_header;
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Dwarf_Half header_cu_type;
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while(true) {
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int ret = wrap(
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dwarf_next_cu_header_d,
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dbg,
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true,
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nullptr,
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nullptr,
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nullptr,
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nullptr,
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nullptr,
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nullptr,
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nullptr,
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nullptr,
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&next_cu_header,
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&header_cu_type
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);
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if(ret == DW_DLV_NO_ENTRY) {
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if(dump_dwarf) {
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fprintf(stderr, "End walk_dbg\n");
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}
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return;
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}
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if(ret != DW_DLV_OK) {
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PANIC("Unexpected return code from dwarf_next_cu_header_d");
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return;
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}
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// 0 passed as the die to the first call of dwarf_siblingof_b immediately after dwarf_next_cu_header_d
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// to fetch the cu die
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die_object cu_die(dbg, nullptr);
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cu_die = cu_die.get_sibling();
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if(!cu_die) {
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if(dump_dwarf) {
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fprintf(stderr, "End walk_compilation_units\n");
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}
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return;
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}
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if(!walk_die_list(cu_die, fn)) {
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break;
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}
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}
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}
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void retrieve_symbol_for_subprogram(
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@ -868,20 +967,40 @@ namespace libdwarf {
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}
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CPPTRACE_FORCE_NO_INLINE_FOR_PROFILING
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void walk_compilation_units(Dwarf_Addr pc, stacktrace_frame& frame) {
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// 0 passed as the die to the first call of dwarf_siblingof_b immediately after dwarf_next_cu_header_d
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// to fetch the cu die
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die_object cu_die(dbg, nullptr);
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cu_die = cu_die.get_sibling();
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if(!cu_die) {
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void lookup_pc(
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Dwarf_Addr pc,
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stacktrace_frame& frame
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) {
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if(dump_dwarf) {
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fprintf(stderr, "End walk_compilation_units\n");
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fprintf(stderr, "%s\n", obj_path.c_str());
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fprintf(stderr, "%llx\n", to_ull(pc));
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}
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return;
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// Check for .debug_aranges for fast lookup
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if(aranges) {
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// Try to find pc in aranges
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Dwarf_Arange arange;
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if(wrap(dwarf_get_arange, aranges, arange_count, pc, &arange) == DW_DLV_OK) {
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// Address in table, load CU die
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Dwarf_Off cu_die_offset;
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VERIFY(wrap(dwarf_get_cu_die_offset, arange, &cu_die_offset) == DW_DLV_OK);
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Dwarf_Die raw_die;
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// Setting is_info = true for now, assuming in .debug_info rather than .debug_types
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VERIFY(wrap(dwarf_offdie_b, dbg, cu_die_offset, true, &raw_die) == DW_DLV_OK);
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die_object cu_die(dbg, raw_die);
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Dwarf_Half offset_size = 0;
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Dwarf_Half dwversion = 0;
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VERIFY(dwarf_get_version_of_die(cu_die.get(), &dwversion, &offset_size) == DW_DLV_OK);
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if(trace_dwarf) {
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fprintf(stderr, "Found CU in aranges\n");
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cu_die.print();
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}
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walk_die_list(
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cu_die,
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[this, &frame, pc] (const die_object& cu_die) {
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retrieve_line_info(cu_die, pc, frame); // no offset for line info
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retrieve_symbol(cu_die, pc, dwversion, frame);
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}
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} else {
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if(false) { // TODO: Proper condition
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// walk for the cu and go from there
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walk_compilation_units([this, pc, &frame] (const die_object& cu_die) {
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Dwarf_Half offset_size = 0;
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Dwarf_Half dwversion = 0;
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dwarf_get_version_of_die(cu_die.get(), &dwversion, &offset_size);
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@ -906,89 +1025,33 @@ namespace libdwarf {
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return false;
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}
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return true;
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});
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} else {
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// look up the cu
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auto vec_it = std::lower_bound(
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cu_cache.begin(),
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cu_cache.end(),
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pc,
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[] (const cu_entry& entry, Dwarf_Addr pc) {
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return entry.low < pc;
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}
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);
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// vec_it is first >= pc
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// we want first <= pc
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if(vec_it != cu_cache.begin()) {
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vec_it--;
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}
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CPPTRACE_FORCE_NO_INLINE_FOR_PROFILING
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void walk_dbg(Dwarf_Addr pc, stacktrace_frame& frame) {
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// libdwarf keeps track of where it is in the file, dwarf_next_cu_header_d is statefull
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Dwarf_Unsigned next_cu_header;
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Dwarf_Half header_cu_type;
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//fprintf(stderr, "-----------------\n");
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while(true) {
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int ret = wrap(
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dwarf_next_cu_header_d,
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dbg,
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true,
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nullptr,
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nullptr,
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nullptr,
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nullptr,
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nullptr,
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nullptr,
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nullptr,
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nullptr,
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&next_cu_header,
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&header_cu_type
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);
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if(ret == DW_DLV_NO_ENTRY) {
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if(dump_dwarf) {
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fprintf(stderr, "End walk_dbg\n");
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}
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return;
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}
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if(ret != DW_DLV_OK) {
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PANIC("Unexpected return code from dwarf_next_cu_header_d");
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return;
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}
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walk_compilation_units(pc, frame);
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}
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}
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CPPTRACE_FORCE_NO_INLINE_FOR_PROFILING
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void lookup_pc(
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Dwarf_Addr pc,
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stacktrace_frame& frame
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) {
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if(dump_dwarf) {
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fprintf(stderr, "%s\n", obj_path.c_str());
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fprintf(stderr, "%llx\n", to_ull(pc));
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}
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// Check for .debug_aranges for fast lookup
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Dwarf_Arange* aranges;
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Dwarf_Signed arange_count;
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if(wrap(dwarf_get_aranges, dbg, &aranges, &arange_count) == DW_DLV_OK) {
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auto aranges_wrapper = raii_wrap(
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aranges,
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[this] (Dwarf_Arange* aranges) { dwarf_dealloc(dbg, aranges, DW_DLA_LIST); }
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);
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// Try to find pc in aranges
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Dwarf_Arange arange;
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if(wrap(dwarf_get_arange, aranges, arange_count, pc, &arange) == DW_DLV_OK) {
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auto arange_wrapper = raii_wrap(
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arange,
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[this] (Dwarf_Arange arange) { dwarf_dealloc(dbg, arange, DW_DLA_ARANGE); }
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);
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// Address in table, load CU die
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Dwarf_Off cu_die_offset;
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VERIFY(wrap(dwarf_get_cu_die_offset, arange, &cu_die_offset) == DW_DLV_OK);
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Dwarf_Die raw_die;
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// Setting is_info = true for now, assuming in .debug_info rather than .debug_types
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VERIFY(wrap(dwarf_offdie_b, dbg, cu_die_offset, true, &raw_die) == DW_DLV_OK);
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die_object cu_die(dbg, raw_die);
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Dwarf_Half offset_size = 0;
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Dwarf_Half dwversion = 0;
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VERIFY(dwarf_get_version_of_die(cu_die.get(), &dwversion, &offset_size) == DW_DLV_OK);
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if(trace_dwarf) {
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fprintf(stderr, "Found CU in aranges\n");
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cu_die.print();
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}
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retrieve_line_info(cu_die, pc, frame); // no offset for line info
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retrieve_symbol(cu_die, pc, dwversion, frame);
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// If the vector has been empty this can happen
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if(vec_it != cu_cache.end()) {
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//vec_it->die.print();
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if(vec_it->die.pc_in_die(vec_it->dwversion, pc)) {
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retrieve_line_info(vec_it->die, pc, frame); // no offset for line info
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retrieve_symbol(vec_it->die, pc, vec_it->dwversion, frame);
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}
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} else {
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walk_dbg(pc, frame);
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ASSERT(cu_cache.size() == 0, "Vec should be empty?");
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}
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}
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}
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}
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