Bug in i386_process_record

[Hui Zhu]

I try to find the reason of 4 failures in machinestate.exp.

(gdb) PASS: gdb.reverse/machinestate.exp: forward to 33
print a

$16 = 0

(gdb) PASS: gdb.reverse/machinestate.exp: register var forward-breakpoint
reverse-step

32	  hide (a);	/* External function to defeat optimization.  */

(gdb) step

hide (x=0) at ../src/gdb/testsuite/gdb.reverse/ms1.c:25

25	}

(gdb) FAIL: gdb.reverse/machinestate.exp: step

I think the fail is because rs didn't step into hide.


Thanks,
Hui



On Mon, Aug 17, 2009 at 11:34, Hui Zhu<teawater@gmail.com> wrote:
> Hi Michael,
>
> I think this is not a bug.
>
> In "Intel® 64 and IA-32 Architectures Software Developer’s Manual
> Volume 2A: Instruction Set Reference, A-M" INC—Increment by 1, it
> said:"In 64-bit mode, INC r16 and INC r32 are not encodable (because
> opcodes 40H
> through 47H are REX prefixes)."
> And disas of machinestate is clear:
> (gdb) disas /m register_state
> Dump of assembler code for function register_state:
> 29      {
> 0x0000000000400488 <register_state+0>:  push   %rbp
> 0x0000000000400489 <register_state+1>:  mov    %rsp,%rbp
> 0x000000000040048c <register_state+4>:  push   %rbx
> 0x000000000040048d <register_state+5>:  sub    $0x8,%rsp
>
> 30        register int a = 0;
> 0x0000000000400491 <register_state+9>:  mov    $0x0,%ebx
>
> 31
> 32        hide (a);     /* External function to defeat optimization.  */
> 0x0000000000400496 <register_state+14>: mov    %ebx,%edi
> 0x0000000000400498 <register_state+16>: callq  0x400598 <hide>
>
> 33        a++;          /* register_state: set breakpoint here */
> 0x000000000040049d <register_state+21>: add    $0x1,%ebx
>
> 34        hide (a);     /* register post-change */
> 0x00000000004004a0 <register_state+24>: mov    %ebx,%edi
> 0x00000000004004a2 <register_state+26>: callq  0x400598 <hide>
>
> 35      }
> 0x00000000004004a7 <register_state+31>: add    $0x8,%rsp
> 0x00000000004004ab <register_state+35>: pop    %rbx
> 0x00000000004004ac <register_state+36>: leaveq
> 0x00000000004004ad <register_state+37>: retq
>
> End of assembler dump.
>
> In amd64, 0x40-0x47 will not be use to inv.
>
>
> Thanks,
> Hui
>
>
> On Mon, Aug 17, 2009 at 00:12, Hui Zhu<teawater@gmail.com> wrote:
>>        case 0x67:
>>          prefixes |= PREFIX_ADDR;
>>          break;
>>        case 0x40:
>>        case 0x41:
>>        case 0x42:
>>        case 0x43:
>>        case 0x44:
>>        case 0x45:
>>        case 0x46:
>>        case 0x47:
>>
>>      /* inv */
>>    case 0x40:
>>    case 0x41:
>>    case 0x42:
>>    case 0x43:
>>    case 0x44:
>>    case 0x45:
>>    case 0x46:
>>    case 0x47:
>>
>> Oops, I must make something wrong.  I need check the spec of amd64 clear.
>>
>> Thanks,
>> Hui
>>
>> On Sun, Aug 16, 2009 at 09:08, Michael Snyder<msnyder@vmware.com> wrote:
>>> Hi Hui,
>>>
>>> This line in i386-tdep.c causes 4 failures in machinestate.exp.
>>>
>>> diff -u -p -r1.283 i386-tdep.c
>>> --- i386-tdep.c 10 Aug 2009 03:02:39 -0000      1.283
>>> +++ i386-tdep.c 16 Aug 2009 01:07:48 -0000
>>> @@ -3283,7 +3283,7 @@ i386_process_record (struct gdbarch *gdb
>>>         case 0x40:
>>>         case 0x41:
>>>         case 0x42:
>>> -        case 0x43:
>>> +         //        case 0x43:
>>>         case 0x44:
>>>         case 0x45:
>>>         case 0x46:
>>>
>>> 0x43 is "inc %ebx", and this line causes it to be treated as a prefix,
>>> consuming the instruction without recording the register change.
>>>
>>> I don't want to change it myself, because I'm not sure what other
>>> side effects the change might have.  Could you fix it please?  ;-)
>>>
>>> Thanks,
>>> Michael
>>>
>>>
>>
>