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[gdb/symtab] Fix bad compile unit index complaint

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I noticed this code in dw2_debug_names_iterator::next:
...
        case DW_IDX_compile_unit:
          /* Don't crash on bad data.  */
          if (ull >= per_bfd->all_comp_units.size ())
            {
              complaint (_(".debug_names entry has bad CU index %s"
                           " [in module %s]"),
                         pulongest (ull),
                         objfile_name (objfile));
              continue;
            }
          per_cu = per_bfd->get_cu (ull);
          break;
...

This code used to DTRT, before we started keeping both CUs and TUs in
all_comp_units.

Fix by using "per_bfd->all_comp_units.size () - per_bfd->tu_stats.nr_tus"
instead.

It's hard to produce a test-case for this, but let's try at least to trigger
the complaint somehow.  We start out by creating an exec with .debug_types and
.debug_names:
...
$ gcc -g ~/hello.c -fdebug-types-section
$ gdb-add-index -dwarf-5 a.out
...
and verify that we don't see any complaints:
...
$ gdb -q -batch -iex "set complaints 100" ./a.out
...

We look at the CU and TU table using readelf -w and conclude that we have
nr_cus == 6 and nr_tus == 1.

Now override ull in dw2_debug_names_iterator::next for the DW_IDX_compile_unit
case to 6, and we have:
...
$ gdb -q -batch -iex "set complaints 100" ./a.out
During symbol reading: .debug_names entry has bad CU index 6 [in module a.out]
...

After this, it still crashes because this code in
dw2_debug_names_iterator::next:
...
  /* Skip if already read in.  */
  if (m_per_objfile->symtab_set_p (per_cu))
    goto again;
...
is called with per_cu == nullptr.

Fix this by skipping the entry if per_cu == nullptr.

Now revert the fix and observe that the complaint disappears, so we've
confirmed that the fix is required.

A somewhat similar issue for .gdb_index in dw2_symtab_iter_next has been filed
as PR29367.

Tested on x86_64-linux, with native and target board cc-with-debug-names.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29336
This commit is contained in:
Tom de Vries 2022-07-21 13:05:39 +02:00
parent ea09fe9259
commit 2fe9a3c41f
1 changed files with 17 additions and 9 deletions
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26
gdb/dwarf2/read.c
View file

@ -4970,15 +4970,19 @@ dw2_debug_names_iterator::next ()
switch (attr.dw_idx)
{
case DW_IDX_compile_unit:
/* Don't crash on bad data. */
if (ull >= per_bfd->all_comp_units.size ())
{
complaint (_(".debug_names entry has bad CU index %s"
" [in module %s]"),
pulongest (ull),
objfile_name (objfile));
continue;
}
{
/* Don't crash on bad data. */
int nr_cus = (per_bfd->all_comp_units.size ()
- per_bfd->tu_stats.nr_tus);
if (ull >= nr_cus)
{
complaint (_(".debug_names entry has bad CU index %s"
" [in module %s]"),
pulongest (ull),
objfile_name (objfile));
continue;
}
}
per_cu = per_bfd->get_cu (ull);
break;
case DW_IDX_type_unit:
@ -5016,6 +5020,10 @@ dw2_debug_names_iterator::next ()
}
}
/* Skip if we couldn't find a valid CU/TU index. */
if (per_cu == nullptr)
goto again;
/* Skip if already read in. */
if (m_per_objfile->symtab_set_p (per_cu))
goto again;