LibDebug: Use DW_AT_ranges to get address ranges of DIEs

Previously, we only supported DIEs with a contiguous address ranges and
ignored ones with a non-contiguous set of ranges.

We now check if a DIE has the DW_AT_ranges attribute, and if it does we
parse its range list.

This improves the quality of our backtraces - we previously missed many
inlined function calls because their DIEs had non-contigues address
ranges.

2 files changed, 18 insertions, 2 deletions

diff --git a/Userland/Libraries/LibDebug/Dwarf/DwarfInfo.cpp b/Userland/Libraries/LibDebug/Dwarf/DwarfInfo.cpp
index 1195edaa9e..8f36efa31e 100644
--- a/Userland/Libraries/LibDebug/Dwarf/DwarfInfo.cpp
+++ b/Userland/Libraries/LibDebug/Dwarf/DwarfInfo.cpp
@@ -5,6 +5,7 @@
  */
 
 #include "DwarfInfo.h"
+#include "AddressRanges.h"
 #include "AttributeValue.h"
 #include "CompilationUnit.h"
 
@@ -21,6 +22,7 @@ DwarfInfo::DwarfInfo(ELF::Image const& elf)
     m_debug_strings_data = section_data(".debug_str"sv);
     m_debug_line_data = section_data(".debug_line"sv);
     m_debug_line_strings_data = section_data(".debug_line_str"sv);
+    m_debug_range_lists_data = section_data(".debug_rnglists"sv);
 
     populate_compilation_units();
 }
@@ -241,8 +243,20 @@ void DwarfInfo::build_cached_dies() const
         m_cached_dies_by_range.insert(range.start_address, DIEAndRange { die, range });
         m_cached_dies_by_offset.insert(die.offset(), die);
     };
-    auto get_ranges_of_die = [](DIE const& die) -> Vector<DIERange> {
-        // TODO support DW_AT_ranges (appears when range is non-contiguous)
+    auto get_ranges_of_die = [this](DIE const& die) -> Vector<DIERange> {
+        auto ranges = die.get_attribute(Attribute::Ranges);
+        if (ranges.has_value()) {
+            // TODO Support DW_FORM_rnglistx
+            if (ranges->form != AttributeDataForm::SecOffset)
+                return {};
+            auto offset = ranges->data.as_addr;
+            AddressRanges address_ranges(debug_range_lists_data(), offset, die.compilation_unit());
+            Vector<DIERange> entries;
+            address_ranges.for_each_range([&entries](auto range) {
+                entries.empend(range.start, range.end);
+            });
+            return entries;
+        }
 
         auto start = die.get_attribute(Attribute::LowPc);
         auto end = die.get_attribute(Attribute::HighPc);
diff --git a/Userland/Libraries/LibDebug/Dwarf/DwarfInfo.h b/Userland/Libraries/LibDebug/Dwarf/DwarfInfo.h
index 105cebde29..24f7e9a2d3 100644
--- a/Userland/Libraries/LibDebug/Dwarf/DwarfInfo.h
+++ b/Userland/Libraries/LibDebug/Dwarf/DwarfInfo.h
@@ -30,6 +30,7 @@ public:
     ReadonlyBytes abbreviation_data() const { return m_abbreviation_data; }
     ReadonlyBytes debug_strings_data() const { return m_debug_strings_data; }
     ReadonlyBytes debug_line_strings_data() const { return m_debug_line_strings_data; }
+    ReadonlyBytes debug_range_lists_data() const { return m_debug_range_lists_data; }
 
     template<typename Callback>
     void for_each_compilation_unit(Callback) const;
@@ -58,6 +59,7 @@ private:
     ReadonlyBytes m_debug_strings_data;
     ReadonlyBytes m_debug_line_data;
     ReadonlyBytes m_debug_line_strings_data;
+    ReadonlyBytes m_debug_range_lists_data;
 
     NonnullOwnPtrVector<Dwarf::CompilationUnit> m_compilation_units;