Re: [PING 4][PATCH PR gdb/18071] TLS variables can't be resolved on aarch64-linux-gnu

Weimin Pan
2018-02-06T01:21:56Z

On 1/23/2018 5:11 PM, Weimin Pan wrote:
> 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));
>>>
>>
>