Optimize DWARF symbol lookup: Preprocessor CUs when they're first queried
This commit is contained in:
Jeremy
parent
cc0876dc94
commit
eb86ae2131
@ -8,6 +8,7 @@
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#include "../platform/error.hpp"
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#include "../platform/utils.hpp"
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#include <algorithm>
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#include <cstdint>
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#include <cstdio>
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#include <functional>
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@ -71,6 +72,9 @@ namespace libdwarf {
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die_object& operator=(const die_object&) = delete;
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die_object(die_object&& other) : dbg(other.dbg), die(other.die) {
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// done for finding mistakes, attempts to use the die_object after this should segfault
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// a valid use otherwise would be moved_from.get_sibling() which would get the next CU
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other.dbg = nullptr;
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other.die = nullptr;
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}
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@ -81,6 +85,14 @@ namespace libdwarf {
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return *this;
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}
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die_object clone() const {
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Dwarf_Off off = get_global_offset();
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Dwarf_Bool is_info = dwarf_get_die_infotypes_flag(die);
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Dwarf_Die die_copy = 0;
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CPPTRACE_VERIFY(dwarf_offdie_b(dbg, off, is_info, &die_copy, nullptr) == DW_DLV_OK);
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return {dbg, die_copy};
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}
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die_object get_child() const {
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Dwarf_Die child = nullptr;
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int ret = dwarf_child(
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@ -242,7 +254,12 @@ namespace libdwarf {
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}
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// ranges code based on libdwarf-addr2line
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int dwarf5_ranges(Dwarf_Die cu_die, Dwarf_Addr *lowest, Dwarf_Addr *highest) const {
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int dwarf5_ranges(
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Dwarf_Die cu_die,
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Dwarf_Addr *lowest,
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Dwarf_Addr *highest,
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std::vector<std::pair<Dwarf_Addr, Dwarf_Addr>>* ranges_vec // TODO: Super hacky
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) const {
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Dwarf_Unsigned offset = 0;
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Dwarf_Attribute attr = 0;
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Dwarf_Half attrform = 0;
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@ -315,6 +332,9 @@ namespace libdwarf {
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case DW_RLE_start_end:
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case DW_RLE_startx_length:
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case DW_RLE_start_length:
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if(ranges_vec) {
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ranges_vec->push_back({cooked1, cooked2});
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}
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if(cooked1 < *lowest) {
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*lowest = cooked1;
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}
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@ -335,7 +355,13 @@ namespace libdwarf {
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}
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// ranges code based on libdwarf-addr2line
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int dwarf4_ranges(Dwarf_Die cu_die, Dwarf_Addr cu_lowpc, Dwarf_Addr *lowest, Dwarf_Addr *highest) const {
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int dwarf4_ranges(
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Dwarf_Die cu_die,
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Dwarf_Addr cu_lowpc,
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Dwarf_Addr *lowest,
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Dwarf_Addr *highest,
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std::vector<std::pair<Dwarf_Addr, Dwarf_Addr>>* ranges_vec // TODO: Super hacky
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) const {
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Dwarf_Unsigned offset;
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Dwarf_Attribute attr = 0;
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int res = 0;
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@ -368,6 +394,9 @@ namespace libdwarf {
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Dwarf_Addr rng_lowpc, rng_highpc;
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rng_lowpc = baseaddr + cur->dwr_addr1;
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rng_highpc = baseaddr + cur->dwr_addr2;
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if(ranges_vec) {
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ranges_vec->push_back({rng_lowpc, rng_highpc});
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}
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if(rng_lowpc < *lowest) {
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*lowest = rng_lowpc;
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}
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@ -388,6 +417,37 @@ namespace libdwarf {
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}
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// pc_in_die code based on libdwarf-addr2line
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// TODO: Super hacky. And ugly code duplication.
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std::vector<std::pair<Dwarf_Addr, Dwarf_Addr>> get_pc_range(int version) const {
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int ret;
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Dwarf_Addr cu_lowpc = 0xffffffffffffffff;
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Dwarf_Addr cu_highpc = 0;
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enum Dwarf_Form_Class highpc_cls;
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Dwarf_Addr lowest = 0xffffffffffffffff;
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Dwarf_Addr highest = 0;
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ret = dwarf_lowpc(die, &cu_lowpc, nullptr);
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if(ret == DW_DLV_OK) {
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ret = dwarf_highpc_b(die, &cu_highpc,
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nullptr, &highpc_cls, nullptr);
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if(ret == DW_DLV_OK) {
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if(highpc_cls == DW_FORM_CLASS_CONSTANT) {
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cu_highpc += cu_lowpc;
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}
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return {{cu_lowpc, cu_highpc}};
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}
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}
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std::vector<std::pair<Dwarf_Addr, Dwarf_Addr>> ranges;
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if(version >= 5) {
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ret = dwarf5_ranges(die, &lowest, &highest, &ranges);
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} else {
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ret = dwarf4_ranges(die, cu_lowpc, &lowest, &highest, &ranges);
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}
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return ranges;
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//return {lowest, highest};
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}
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Dwarf_Bool pc_in_die(int version, Dwarf_Addr pc) const {
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int ret;
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Dwarf_Addr cu_lowpc = 0xffffffffffffffff;
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@ -413,9 +473,9 @@ namespace libdwarf {
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}
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}
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if(version >= 5) {
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ret = dwarf5_ranges(die, &lowest, &highest);
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ret = dwarf5_ranges(die, &lowest, &highest, nullptr);
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} else {
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ret = dwarf4_ranges(die, cu_lowpc, &lowest, &highest);
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ret = dwarf4_ranges(die, cu_lowpc, &lowest, &highest, nullptr);
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}
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if(pc >= lowest && pc < highest) {
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return true;
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@ -444,10 +504,17 @@ namespace libdwarf {
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Dwarf_Line_Context ctx;
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};
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struct subprogram_entry {
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die_object die;
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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;
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std::unordered_map<Dwarf_Off, line_context> line_contexts;
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std::unordered_map<Dwarf_Off, std::vector<subprogram_entry>> subprograms_cache;
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CPPTRACE_FORCE_NO_INLINE
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dwarf_resolver(const std::string& object_path) {
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@ -479,9 +546,13 @@ namespace libdwarf {
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CPPTRACE_FORCE_NO_INLINE
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~dwarf_resolver() {
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// TODO: Maybe redundant since dwarf_finish(dbg); will clean up the line stuff anyway but may as well just
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// for thoroughness
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for(auto& entry : line_contexts) {
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dwarf_srclines_dealloc_b(entry.second.ctx);
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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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dwarf_finish(dbg);
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}
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@ -583,7 +654,7 @@ namespace libdwarf {
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// returns true if this call found the symbol
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CPPTRACE_FORCE_NO_INLINE
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bool retrieve_symbol(
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bool retrieve_symbol_walk(
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const die_object& die,
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Dwarf_Addr pc,
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Dwarf_Half dwversion,
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@ -624,7 +695,7 @@ namespace libdwarf {
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}
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auto child = die.get_child();
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if(child) {
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if(retrieve_symbol(child, pc, dwversion, frame)) {
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if(retrieve_symbol_walk(child, pc, dwversion, frame)) {
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found = true;
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return false;
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}
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@ -640,6 +711,91 @@ namespace libdwarf {
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return found;
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}
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CPPTRACE_FORCE_NO_INLINE
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void preprocess_subprograms(
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const die_object& die,
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Dwarf_Half dwversion,
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std::vector<subprogram_entry>& vec
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) {
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walk_die_list(
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die,
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[this, dwversion, &vec] (const die_object& die) {
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//die.print();
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switch(die.get_tag()) {
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case DW_TAG_subprogram:
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{
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auto ranges_vec = die.get_pc_range(dwversion);
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// TODO: Feels super inefficient and some day should maybe use an interval tree.
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for(auto range : ranges_vec) {
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vec.push_back({ die.clone(), range.first, range.second });
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}
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}
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break;
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case DW_TAG_namespace:
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case DW_TAG_structure_type:
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case DW_TAG_class_type:
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case DW_TAG_module:
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case DW_TAG_imported_module:
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case DW_TAG_compile_unit:
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{
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auto child = die.get_child();
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if(child) {
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preprocess_subprograms(child, dwversion, vec);
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}
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}
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break;
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default:
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break;
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}
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return true;
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}
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);
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}
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CPPTRACE_FORCE_NO_INLINE
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void retrieve_symbol(
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const die_object& cu_die,
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Dwarf_Addr pc,
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Dwarf_Half dwversion,
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stacktrace_frame& frame
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) {
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//retrieve_symbol_walk(std::move(cu_die), pc, dwversion, frame);
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//return;
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auto off = cu_die.get_global_offset();
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auto it = subprograms_cache.find(off);
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if(it == subprograms_cache.end()) {
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std::vector<subprogram_entry> vec;
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preprocess_subprograms(cu_die, dwversion, vec);
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std::sort(vec.begin(), vec.end(), [] (const subprogram_entry& a, const subprogram_entry& b) {
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return a.low < b.low;
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});
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subprograms_cache.emplace(off, std::move(vec));
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it = subprograms_cache.find(off);
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}
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auto& vec = it->second;
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//fprintf(stderr, "%llu\n", vec.size());
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auto vec_it = std::lower_bound(
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vec.begin(),
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vec.end(),
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pc,
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[] (const subprogram_entry& entry, Dwarf_Addr pc) {
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//fprintf(stderr, "%llx %llx\n", entry.low, 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 == vec.end()) {
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return;
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}
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if(vec_it != vec.begin()) {
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vec_it--;
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}
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if(vec_it->die.pc_in_die(dwversion, pc)) {
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retrieve_symbol_for_subprogram(vec_it->die, pc, dwversion, frame);
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}
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}
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void handle_line(Dwarf_Line line, stacktrace_frame& frame) {
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char what[] = "??";
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char * linesrc = what;
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@ -759,6 +915,9 @@ namespace libdwarf {
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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 p = cu_die.get_pc_range(dwversion);
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//cu_die.print();
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//fprintf(stderr, " %llx, %llx\n", p.first, p.second);
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if(trace_dwarf) {
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fprintf(stderr, "CU: %d %s\n", dwversion, cu_die.get_name().c_str());
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}
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@ -786,6 +945,7 @@ namespace libdwarf {
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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 = dwarf_next_cu_header_d(
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dbg,
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