libdw: Parse DWARF package file index sections

libdw: Parse DWARF package file index sections

The .debug_cu_index and .debug_tu_index sections in DWARF package files
are basically hash tables mapping a unit's 8 byte signature to an offset
and size in each section used by that unit [1].  Add support for parsing
and doing lookups in the index sections.

We look up a unit in the index when we intern it and cache its hash
table row in Dwarf_CU.  Then, a new function, dwarf_cu_dwp_section_info,
can be used to look up the section offsets and sizes for a unit.  This
will mostly be used internally in libdw, but it will also be needed in
static inline functions shared with eu-readelf.  Additionally, making it
public it makes dwp support much easier for external tools that do their
own low-level parsing of DWARF information, like drgn [2].

1: https://gcc.gnu.org/wiki/DebugFissionDWP#Format_of_the_CU_and_TU_Index_Sections
2: https://github.com/osandov/drgn

	* libdw/dwarf.h: Add DW_SECT_TYPES.
	* libdw/libdwP.h (Dwarf): Add cu_index and tu_index.
	(Dwarf_CU): Add dwp_row.
	(Dwarf_Package_Index): New type.
	(__libdw_dwp_find_unit): New declaration.
	(dwarf_cu_dwp_section_info): New INTDECL.
	Add DWARF_E_UNKNOWN_SECTION.
	* libdw/Makefile.am (libdw_a_SOURCES): Add
	dwarf_cu_dwp_section_info.c.
	* libdw/dwarf_end.c (dwarf_end): Free dwarf->cu_index and
	dwarf->tu_index.
	* libdw/dwarf_error.c (errmsgs): Add DWARF_E_UNKNOWN_SECTION.
	* libdw/libdw.h (dwarf_cu_dwp_section_info): New declaration.
	* libdw/libdw.map (ELFUTILS_0.190): Add
	dwarf_cu_dwp_section_info.
	* libdw/libdw_findcu.c (__libdw_intern_next_unit): Call
	__libdw_dwp_find_unit, and use it to adjust abbrev_offset and
	assign newp->dwp_row.
	* libdw/dwarf_cu_dwp_section_info.c: New file.
	* tests/Makefile.am (check_PROGRAMS): Add cu-dwp-section-info.
	(TESTS): Add run-cu-dwp-section-info.sh
	(EXTRA_DIST): Add run-cu-dwp-section-info.sh and new test files.
	(cu_dwp_section_info_LDADD): New variable.
	* tests/cu-dwp-section-info.c: New test.
	* tests/run-cu-dwp-section-info.sh: New test.
	* tests/testfile-dwp-4-strict.bz2: New test file.
	* tests/testfile-dwp-4-strict.dwp.bz2: New test file.
	* tests/testfile-dwp-4.bz2: New test file.
	* tests/testfile-dwp-4.dwp.bz2: New test file.
	* tests/testfile-dwp-5.bz2: New test file.
	* tests/testfile-dwp-5.dwp.bz2: New test file.
	* tests/testfile-dwp.source: New file.

Signed-off-by: Omar Sandoval <osandov@fb.com>