[PATCH v2 3/4] libdw: Apply DWARF package file section offsets where appropriate

[Mark Wielaard]

Hi Omar,

On Wed, 2023-12-06 at 01:22 -0800, Omar Sandoval wrote:
> The final piece of DWARF package file support is that offsets have to be
> interpreted relative to the section offset from the package index.
> .debug_abbrev.dwo is already covered, so sprinkle around calls to
> dwarf_cu_dwp_section_info for the remaining sections: .debug_line.dwo,
> .debug_loclists.dwo/.debug_loc.dwo, .debug_str_offsets.dwo,
> .debug_macro.dwo/.debug_macinfo.dwo, and .debug_rnglists.dwo.  With all
> of that in place, we can finally test various libdw functions on dwp
> files.

So the offsets for DW_SECT_INFO, DW_SECT_TYPES and DW_SECT_ABBREV were
already taken into account when setting up a cu from a dwp.

With this patch __libdw_cu_str_off_base/str_offsets_base_off handles
DW_SECT_STR_OFFSETS which is used in dwarf_formstring and
dwarf_getmacros.

__libdw_cu_ranges_base handles DW_SECT_RNGLISTS, which is used by
dwarf_ranges. And __libdw_formptr has a special case for
DW_FORM_sec_offset for IDX_debug_ranges && version < 5 && unit_type ==
DW_UT_split_compile to also uses __libdw_cu_ranges_base.

__libdw_cu_locs_base handles DW_SECT_LOCLISTS which is used in
dwarf_getlocation through initial_offset. I do wonder why the special
case in __libdw_formptr isn't needed here too.

dwarf_getmacros handles DW_SECT_MACRO through get_offset_from. And when
the macros need to refer to the line table, it also handles
DW_SECT_LINE.

Don't we also need to handle DW_SECT_LINE in dwarf_getsrclines and
dwarf_next_lines when looking for DW_AT_stmt_list?

> 	* libdw/dwarf_getmacros.c (get_macinfo_table): Call
> 	dwarf_cu_dwp_section_info and add offset to line_offset.
> 	(get_offset_from): Call dwarf_cu_dwp_section_info and add offset
> 	to *retp.
> 	* libdw/libdwP.h (str_offsets_base_off): Call
> 	dwarf_cu_dwp_section_info and add offset.
> 	(__libdw_cu_ranges_base): Ditto.
> 	(__libdw_cu_locs_base): Ditto.
> 	* libdw/dwarf_getlocation.c (initial_offset): Call
> 	dwarf_cu_dwp_section_info and add offset to start_offset.
> 	* tests/run-varlocs.sh: Check testfile-dwp-5 and testfile-dwp-4.
> 	* tests/run-all-dwarf-ranges.sh: Check testfile-dwp-5 and
> 	testfile-dwp-4.
> 	* tests/run-dwarf-getmacros.sh: Check testfile-dwp-5 and
> 	testfile-dwp-4-strict.
> 	* tests/run-get-units-split.sh: Check testfile-dwp-5,
> 	testfile-dwp-4, and testfile-dwp-4-strict.

The code and tests look good. run-varlocs.sh seems good, which seems to
confirm DW_SECT_LOCLISTS is handled correctly (but why doesn't it need
a hack similar to ranges in __libdw_formptr?).

We might want to add a test for run-next-lines.sh and run-next-
files.sh?

Thanks,

Mark