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PR23425, unresolved symbol diagnostic

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dwarf2.c code reasonably assumes that debug info is local to a file,
an assumption now violated by gcc, resulting in "DWARF error: invalid
abstract instance DIE ref" or wrong details when attempting to print
linker error messages with file, function and line reported.

This is because find_abstract_instance is only prepared to handle
DW_FORM_ref_addr when the .debug_info section referenced is in the
current file.  When that isn't the case, relocations to access another
file's .debug_info will typically be against a symbol defined at the
start of that .debug_info section, plus an addend.  Since the dwarf2.c
code only considers the current file's debug info, that symbol will be
undefined, resolving to zero.  In effect the ref_addr will wrongly
resolve to the current file's .debug_info.

This patch avoids the problem by treating relocations in debug
sections against undefined symbols in a similar manner to the way
relocations against symbols defined in discarded sections are
resolved.  They result in a zero value (except in .debug_ranges)
regardless of the addend.

	PR 23425
	* reloc.c (bfd_generic_get_relocated_section_contents): Zero reloc
	fields in debug sections when reloc is against an undefined symbol
	and called from bfd_simple_get_relocated_section_contents or
	similar.
	* dwarf2.c (find_abstract_instance): Return true for zero offset
	DW_FORM_ref_addr without returning values.
This commit is contained in:
Alan Modra 2018-09-11 23:50:15 +09:30
parent 556059dd13
commit a4cd947aca
3 changed files with 25 additions and 2 deletions
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10
bfd/ChangeLog
View File

@ -1,3 +1,13 @@
2018-09-14 Alan Modra <amodra@gmail.com>
PR 23425
* reloc.c (bfd_generic_get_relocated_section_contents): Zero reloc
fields in debug sections when reloc is against an undefined symbol
and called from bfd_simple_get_relocated_section_contents or
similar.
* dwarf2.c (find_abstract_instance): Return true for zero offset
DW_FORM_ref_addr without returning values.
2018-09-06 Alan Modra <amodra@gmail.com>
PR 23570

4
bfd/dwarf2.c
View File

@ -2837,7 +2837,9 @@ find_abstract_instance (struct comp_unit * unit,
info_ptr = unit->stash->info_ptr_memory;
info_ptr_end = unit->stash->info_ptr_end;
total = info_ptr_end - info_ptr;
if (!die_ref || die_ref >= total)
if (!die_ref)
return TRUE;
else if (die_ref >= total)
{
_bfd_error_handler
(_("DWARF error: invalid abstract instance DIE ref"));

13
bfd/reloc.c
View File

@ -8259,7 +8259,18 @@ bfd_generic_get_relocated_section_contents (bfd *abfd,
goto error_return;
}
if (symbol->section && discarded_section (symbol->section))
/* Zap reloc field when the symbol is from a discarded
section, ignoring any addend. Do the same when called
from bfd_simple_get_relocated_section_contents for
undefined symbols in debug sections. This is to keep
debug info reasonably sane, in particular so that
DW_FORM_ref_addr to another file's .debug_info isn't
confused with an offset into the current file's
.debug_info. */
if ((symbol->section != NULL && discarded_section (symbol->section))
|| (symbol->section == bfd_und_section_ptr
&& (input_section->flags & SEC_DEBUGGING) != 0
&& link_info->input_bfds == link_info->output_bfd))
{
bfd_byte *p;
static reloc_howto_type none_howto