Re: [PING 3][PATCH PR gdb/18071] TLS variables can't be resolved on aarch64-linux-gnu

Weimin Pan
2018-01-24T01:11:22Z

While this problem shows up in aarch64, the fix is actually
in gdb core. Pedro, would you please review the patch when
you get a chance?

Thanks.

On 1/11/2018 4:32 PM, Wei-min Pan wrote:
>
> On 11/15/2017 5:51 PM, Wei-min Pan wrote:
>>
>> On 11/2/2017 8:32 AM, Weimin Pan wrote:
>>> Running the test case with upstream gdb shows two failures:
>>>
>>> (1) Receiving different error messages when printing TLS variable
>>> before
>>> Â Â Â Â  program runs - because the ARM compiler does not emit dwarf
>>> attribute
>>> Â Â Â Â  DW_AT_location for TLS, the result is expected and the baseline
>>> may
>>> Â Â Â Â  need to be changed for aarch64.
>>>
>>> (2) Using "info address" command on C++ static TLS object resulted in
>>> Â Â Â Â  "symbol unresolved" error - below is a snippet from the test case:
>>>
>>> class K {
>>> Â  public:
>>> Â Â  static __thread int another_thread_local;
>>> };
>>>
>>> __thread int K::another_thread_local;
>>>
>>> (gdb) info address K::another_thread_local
>>> Symbol "K::another_thread_local" is unresolved.
>>>
>>> This patch contains fix for (2).
>>>
>>> Function info_address_command() handles the "info address" command and
>>> calls lookup_minimal_symbol_and_objfile() to find sym's symbol entry in
>>> mininal symbol table if SYMBOL_COMPUTED_OPS (sym) is false. Problem is
>>> that function lookup_minimal_symbol_and_objfile() only looked up an
>>> objfile's minsym ordinary hash table, not its demangled hash table,
>>> which
>>> was the reason why the C++ name was not found.
>>>
>>> The fix is to call lookup_minimal_symbol(), which already looks up
>>> entries
>>> in both minsym's hash tables, to find names when traversing the
>>> object file
>>> list in lookup_minimal_symbol_and_objfile().
>>>
>>> Tested in both aarch64-linux-gnu and amd64-linux-gnu. No regressions.
>>> ---
>>> Â  gdb/ChangeLog |Â Â Â  5 +++++
>>> Â  gdb/minsyms.c |Â Â  17 +++--------------
>>> Â  2 files changed, 8 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
>>> index 4b292e0..2f630bc 100644
>>> --- a/gdb/ChangeLog
>>> +++ b/gdb/ChangeLog
>>> @@ -1,3 +1,8 @@
>>> +2017-11-01Â  Weimin PanÂ  <weimin.pan@oracle.com>
>>> +
>>> +Â Â Â  * minsyms.c (lookup_minimal_symbol_and_objfile): Use
>>> +Â Â Â  lookup_minimal_symbol() to find symbol entry.
>>> +
>>> Â  2017-10-27Â  Keith SeitzÂ  <keiths@redhat.com>
>>> Â  Â Â Â Â Â  * breakpoint.c (print_breakpoint_location): Use the symbol
>>> saved
>>> diff --git a/gdb/minsyms.c b/gdb/minsyms.c
>>> index 37edbd8..4edd8b1 100644
>>> --- a/gdb/minsyms.c
>>> +++ b/gdb/minsyms.c
>>> @@ -881,23 +881,12 @@ lookup_minimal_symbol_and_objfile (const char
>>> *name)
>>> Â  {
>>> Â Â Â  struct bound_minimal_symbol result;
>>> Â Â Â  struct objfile *objfile;
>>> -Â  unsigned int hash = msymbol_hash (name) % MINIMAL_SYMBOL_HASH_SIZE;
>>> Â  Â Â Â  ALL_OBJFILES (objfile)
>>> Â Â Â Â Â  {
>>> -Â Â Â Â Â  struct minimal_symbol *msym;
>>> -
>>> -Â Â Â Â Â  for (msym = objfile->per_bfd->msymbol_hash[hash];
>>> -Â Â Â Â Â Â  msym != NULL;
>>> -Â Â Â Â Â Â  msym = msym->hash_next)
>>> -Â Â Â  {
>>> -Â Â Â Â Â  if (strcmp (MSYMBOL_LINKAGE_NAME (msym), name) == 0)
>>> -Â Â Â Â Â Â Â  {
>>> -Â Â Â Â Â Â Â Â Â  result.minsym = msym;
>>> -Â Â Â Â Â Â Â Â Â  result.objfile = objfile;
>>> -Â Â Â Â Â Â Â Â Â  return result;
>>> -Â Â Â Â Â Â Â  }
>>> -Â Â Â  }
>>> +Â Â Â Â Â  result = lookup_minimal_symbol (name, NULL, objfile);
>>> +Â Â Â Â Â  if (result.minsym != NULL)
>>> +Â Â Â Â Â Â Â  return result;
>>> Â Â Â Â Â  }
>>> Â  Â Â Â  memset (&result, 0, sizeof (result));
>>
>