Re: Bug in i386_process_record

[Hui Zhu <teawater at gmail dot com>]

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
>>
>>
>