Re: PATCH: PR gdb/13969: GDBserver doesn't check unsupported binary

["H.J. Lu" <hjl.tools@gmail.com>]

On Thu, Apr 12, 2012 at 6:09 AM, Pedro Alves <palves@redhat.com> wrote:
> On 04/11/2012 08:16 PM, H.J. Lu wrote:
>
>> 2012-04-11  H.J. Lu  <hongjiu.lu@intel.com>
>>
>>       PR gdb/13969
>>       * linux-low.c (linux_pid_exe_is_elf_64_file): Also return the
>>       e_machine field.
>>       (linux_qxfer_libraries_svr4): Update call to elf_64_file_p.
>>
>>       * linux-low.h (linux_pid_exe_is_elf_64_file): Updated.
>>
>>       * linux-x86-low.c (linux_is_64bit): New.
>
>
> I don't see a new linux_is_64bit symbol in the patch.

Removed.

>>       (x86_arch_setup): Check if GDBserver is compatible with
>>       process.
>
>
> These all all logically related changes.  Please drop the empty lines.

Done.

>
>> --- a/gdb/gdbserver/linux-x86-low.c
>
>> +++ b/gdb/gdbserver/linux-x86-low.c
>> @@ -1106,17 +1106,28 @@ x86_linux_process_qsupported (const char *query)
>>  static void
>>  x86_arch_setup (void)
>>  {
>> -#ifdef __x86_64__
>>    int pid = pid_of (get_thread_lwp (current_inferior));
>> -  int use_64bit = linux_pid_exe_is_elf_64_file (pid);
>> +  unsigned int machine;
>> +  int use_64bit = linux_pid_exe_is_elf_64_file (pid, &machine);
>>
>> +  if (sizeof (void *) == 4)
>> +    {
>> +      if (use_64bit > 0)
>> +     error (_("Can't debug 64-bit process with 32-bit GDBserver"));
>> +#ifndef __x86_64__
>> +      else if (machine == EM_X86_64)
>> +     error (_("Can't debug x86-64 process with 32-bit GDBserver"));
>> +#endif
>> +    }
>> +
>> +#ifdef __x86_64__
>>    if (use_64bit < 0)
>
>
> Please rename use_64bit to something like is_elf64.  The code reads
> now a bit confusingly with "use_64bit".  Okay with that change,
> and the ChangeLog entry fixed.

Done.  I checked in the updated patch.

> I assume there's no kernel limitation that would prevent a x32
> gdbserver from debugging a 64-bit process?
>

It doesn't work since x32 is a 32-bit process.  Although x32
GDBserver can get registers of 64-bit process, it can't handle
64-bit address in 64b-bit process, like setting break points.

-- 
H.J.