Improved Dwarf v5 support

[emeryberger]

DWARF 5 Rangelist Support for libelfin

This change adds support for DWARF 5 range lists (DW_FORM::rnglistx with .debug_rnglists section) to libelfin.

Problem

DWARF 5 binaries use a new format for range lists that differs from DWARF 4:

• DWARF 4: Uses DW_FORM::sec_offset pointing directly into .debug_ranges
• DWARF 5: Uses DW_FORM::rnglistx as an index into .debug_rnglists, with entries encoded using DW_RLE_* opcodes

This caused a value_type_mismatch exception when attempting to parse DWARF 5 range lists:

cannot read value::type::rangelist as sec_offset

Changes

dwarf/data.hh

Added DW_RLE enum for DWARF 5 range list entry encodings (Section 7.25):

enum class DW_RLE : ubyte
{
    end_of_list    = 0x00,
    base_addressx  = 0x01,
    startx_endx    = 0x02,
    startx_length  = 0x03,
    offset_pair    = 0x04,
    base_address   = 0x05,
    start_end      = 0x06,
    start_length   = 0x07,
};

dwarf/dwarf++.hh

• Added rnglists to section_type enum
• Added is_dwarf5 parameter to rangelist constructor and rangelist::iterator

dwarf/elf.cc

Added section name mapping:

{".debug_rnglists", section_type::rnglists},

dwarf/value.cc

Updated as_rangelist() to handle DW_FORM::rnglistx:

• Reads the ULEB128 index from the attribute
• Parses the .debug_rnglists header (unit_length, version, addr_size, segment_selector_size, offset_entry_count)
• Looks up the offset in the offsets table
• Returns a rangelist configured for DWARF 5 parsing

dwarf/rangelist.cc

Updated rangelist::iterator::operator++() to support both formats:

• DWARF 4: Pairs of addresses with special base address entries
• DWARF 5: DW_RLE_* encoded entries including:
  • DW_RLE_end_of_list - terminates the list
  • DW_RLE_offset_pair - two ULEB128 offsets from base
  • DW_RLE_base_address - sets new base address
  • DW_RLE_start_end - two full addresses
  • DW_RLE_start_length - address + ULEB128 length

dwarf/to_string.cc

Added to_string(DW_RLE v) for debug output.

Limitations

The following DW_RLE_* entries that require .debug_addr lookups are parsed but skipped:

• DW_RLE_base_addressx
• DW_RLE_startx_endx
• DW_RLE_startx_length

Full support would require passing the compilation unit's .debug_addr base to the rangelist iterator.

Testing

Verified with a DWARF 5 binary compiled with g++ -gdwarf-5. The profiler now successfully parses range lists and generates valid profiles.