[PATCH] Lookup the JIT descriptor symbol first to avoid finding the PLT entry of the breakpoint in the wrong object file.

Yichao Yu yyc1992@gmail.com
Fri Feb 24 19:01:00 GMT 2017


Ping again.

On Sun, Feb 5, 2017 at 7:46 PM, Yichao Yu <yyc1992@gmail.com> wrote:
> Ping. Can anyone please review this? Or is there a better place to post this?
>
> On Thu, Jan 26, 2017 at 3:31 PM, Yichao Yu <yyc1992@gmail.com> wrote:
>> On Thu, Jan 26, 2017 at 3:24 PM, Yichao Yu <yyc1992@gmail.com> wrote:
>>> Fix 20633
>>
>>
>> ..... I don't use git send-mail very often and missed the chance to
>> type more comments....
>>
>> The link to the bug report is
>> https://sourceware.org/bugzilla/show_bug.cgi?id=20633 . I think
>> ideally the interface should find all the global and local symbols and
>> breakpoint on all of them since there isn't an agreement on who will
>> provide it AFAICT (and for example,a process can load multiple copies
>> of statically linked LLVM each providing a jit debugging interface).
>> However, I'm not really sure what's the right function to use for that
>> and it'll probably be a much bigger change so I went for this smaller
>> change that fixes the original issue.
>>
>> Not sure how this should be tested....... =(
>>
>>> ---
>>>  gdb/jit.c | 17 ++++++++++-------
>>>  1 file changed, 10 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/gdb/jit.c b/gdb/jit.c
>>> index 158d6d8..d6eb800 100644
>>> --- a/gdb/jit.c
>>> +++ b/gdb/jit.c
>>> @@ -1051,18 +1051,21 @@ jit_breakpoint_re_set_internal (struct gdbarch *gdbarch,
>>>    if (ps_data->objfile == NULL)
>>>      {
>>>        /* Lookup the registration symbol.  If it is missing, then we
>>> -        assume we are not attached to a JIT.  */
>>> -      reg_symbol = lookup_minimal_symbol_and_objfile (jit_break_name);
>>> -      if (reg_symbol.minsym == NULL
>>> -         || BMSYMBOL_VALUE_ADDRESS (reg_symbol) == 0)
>>> -       return 1;
>>> +        assume we are not attached to a JIT.
>>> +        Lookup the descriptor first since looking up the breakpoint might
>>> +        return a PLT entry in the wrong file.  */
>>>
>>> -      desc_symbol = lookup_minimal_symbol (jit_descriptor_name, NULL,
>>> -                                          reg_symbol.objfile);
>>> +      desc_symbol = lookup_minimal_symbol_and_objfile (jit_descriptor_name);
>>>        if (desc_symbol.minsym == NULL
>>>           || BMSYMBOL_VALUE_ADDRESS (desc_symbol) == 0)
>>>         return 1;
>>>
>>> +      reg_symbol = lookup_minimal_symbol (jit_break_name, NULL,
>>> +                                         desc_symbol.objfile);
>>> +      if (reg_symbol.minsym == NULL
>>> +         || BMSYMBOL_VALUE_ADDRESS (reg_symbol) == 0)
>>> +       return 1;
>>> +
>>>        objf_data = get_jit_objfile_data (reg_symbol.objfile);
>>>        objf_data->register_code = reg_symbol.minsym;
>>>        objf_data->descriptor = desc_symbol.minsym;
>>> --
>>> 2.10.2
>>>



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