Re: [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>]

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
>>