Re: [PING 5][PATCH PR gdb/18071] TLS variables can't be resolved on aarch64-linux-gnu

Weimin Pan
2018-03-06T01:21:18Z

On 2/5/2018 5:21 PM, Weimin Pan wrote:
> 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));
>>>>
>>>
>>
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