Re: Bug in i386_process_record?

[Hui Zhu <teawater at gmail dot com>]

On Thu, Aug 27, 2009 at 07:45, Michael Snyder<msnyder@vmware.com> wrote:
> Hui Zhu wrote:
>>
>> On Wed, Aug 26, 2009 at 02:42, Eli Zaretskii<eliz@gnu.org> wrote:
>>>>
>>>> From: Hui Zhu <teawater@gmail.com>
>>>> Date: Tue, 25 Aug 2009 13:02:44 +0800
>>>> Cc: msnyder@vmware.com, gdb-patches@sourceware.org
>>>>
>>>> It seems that the segment (It is not the section) ?registers in x86
>>>> protect mode is just help MMU to get the physical address. ?It's
>>>> transparent for the user level program.
>>>
>>> It's transparent if $es and $ds have the same value (which they
>>> usually do, AFAIK).
>>>
>>>> What do you think about remove this warning from this patch?
>>>
>>> I would indeed do that, if we find that $es and $ds have the same
>>> values. ?Assuming that someone who knows Linux better than I do
>>> confirms that these two registers hold the same selector when a normal
>>> application is running in user mode.
>>>
>>
>> Thanks for remind me. ?We cannot get the value of each segment
>> register, but we can get each segment register point to. ?So if the
>> value of segment registers, it's means that the value of them is same.
>>
>> I add some code about it:
>> ? ? ? ? ?regcache_raw_read_unsigned (ir.regcache,
>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?ir.regmap[X86_RECORD_ES_REGNUM],
>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?&es);
>> ? ? ? ? ?regcache_raw_read_unsigned (ir.regcache,
>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?ir.regmap[X86_RECORD_DS_REGNUM],
>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?&ds);
>> ? ? ? ? ?if (ir.aflag && (es != ds))
>> ? ? ? ? ? ?{
>>
>> After that, we will not get the warning because the es is same with ds
>> in user level.
>>
>> What do you think about it?
>
> I think it is the best version I have seen so far.
> And it seems to follow the conclusions of the discussion.
> And I've tested it, and it seems to work.
>
> I would say wait until end-of-business Friday, and
> if there are no more comments, check it in!
>
> Michael
>

OK.

Thanks,
Hui

>> 2009-08-26 ?Hui Zhu ?<teawater@gmail.com>
>>
>> ? ? ? ?* i386-tdep.c (i386_process_record): Fix the error of string
>> ? ? ? ?ops instructions's handler.
>> ---
>> ?i386-tdep.c | ? 69
>> ++++++++++++++++++++++++++++--------------------------------
>> ?1 file changed, 33 insertions(+), 36 deletions(-)
>>
>> --- a/i386-tdep.c
>> +++ b/i386-tdep.c
>> @@ -4441,50 +4441,47 @@ reswitch:
>> ? ? ? /* insS */
>> ? ? case 0x6c:
>> ? ? case 0x6d:
>> - ? ? ?if ((opcode & 1) == 0)
>> - ? ? ? ir.ot = OT_BYTE;
>> - ? ? ?else
>> - ? ? ? ir.ot = ir.dflag + OT_WORD;
>> ? ? ? regcache_raw_read_unsigned (ir.regcache,
>> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?ir.regmap[X86_RECORD_REDI_REGNUM],
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?ir.regmap[X86_RECORD_RECX_REGNUM],
>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? &tmpulongest);
>> - ? ? ?if (!ir.aflag)
>> - ? ? ? ?{
>> - ? ? ? ? ?tmpulongest &= 0xffff;
>> - ? ? ? ? ?/* addr += ((uint32_t) read_register (I386_ES_REGNUM)) << 4; */
>> - ? ? ? ? ?if (record_debug)
>> - ? ? ? ? ? ?printf_unfiltered (_("Process record ignores the memory
>> change "
>> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? "of instruction at address 0x%s because
>> "
>> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? "it can't get the value of the segment "
>> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? "register.\n"),
>> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? paddress (gdbarch, ir.addr));
>> - ? ? ? ?}
>> - ? ? ?if (prefixes & (PREFIX_REPZ | PREFIX_REPNZ))
>> + ? ? ?if (tmpulongest)
>> ? ? ? ? {
>> - ? ? ? ? ?ULONGEST count, eflags;
>> + ? ? ? ? ?ULONGEST es, ds;
>> +
>> + ? ? ? ? ?if ((opcode & 1) == 0)
>> + ? ? ? ? ? ir.ot = OT_BYTE;
>> + ? ? ? ? ?else
>> + ? ? ? ? ? ir.ot = ir.dflag + OT_WORD;
>> ? ? ? ? ? regcache_raw_read_unsigned (ir.regcache,
>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ir.regmap[X86_RECORD_REDI_REGNUM],
>> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?&count);
>> - ? ? ? ? ?if (!ir.aflag)
>> - ? ? ? ? ? ?count &= 0xffff;
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?&tmpulongest);
>> +
>> ? ? ? ? ? regcache_raw_read_unsigned (ir.regcache,
>> -
>> ?ir.regmap[X86_RECORD_EFLAGS_REGNUM],
>> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?&eflags);
>> - ? ? ? ? ?if ((eflags >> 10) & 0x1)
>> - ? ? ? ? ? ?tmpulongest -= (count - 1) * (1 << ir.ot);
>> - ? ? ? ? ?if (record_arch_list_add_mem (tmpulongest, count * (1 <<
>> ir.ot)))
>> - ? ? ? ? ? ?return -1;
>> - ? ? ? ? ?I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_RECX_REGNUM);
>> - ? ? ? ?}
>> - ? ? ?else
>> - ? ? ? ?{
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?ir.regmap[X86_RECORD_ES_REGNUM],
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?&es);
>> + ? ? ? ? ?regcache_raw_read_unsigned (ir.regcache,
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?ir.regmap[X86_RECORD_DS_REGNUM],
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?&ds);
>> + ? ? ? ? ?if (ir.aflag && (es != ds))
>> + ? ? ? ? ? ?{
>> + ? ? ? ? ? ? ?/* addr += ((uint32_t) read_register (I386_ES_REGNUM)) <<
>> 4; */
>> + ? ? ? ? ? ? ?if (record_debug)
>> + ? ? ? ? ? ? ? ?printf_unfiltered (_("Process record ignores the memory "
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?"change of instruction at address
>> 0x%s "
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?"because it can't get the value of
>> the "
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?"ES segment register.\n"),
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? paddress (gdbarch, ir.addr));
>> + ? ? ? ? ? ?}
>> +
>> + ? ? ? ? ?if (prefixes & (PREFIX_REPZ | PREFIX_REPNZ))
>> + ? ? ? ? ? ?I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_RECX_REGNUM);
>> ? ? ? ? ? if (record_arch_list_add_mem (tmpulongest, 1 << ir.ot))
>> ? ? ? ? ? ? return -1;
>> - ? ? ? ?}
>> - ? ? ?if (opcode == 0xa4 || opcode == 0xa5)
>> - ? ? ? ?I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_RESI_REGNUM);
>> - ? ? ?I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_REDI_REGNUM);
>> - ? ? ?I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_EFLAGS_REGNUM);
>> + ? ? ? ? ?if (opcode == 0xa4 || opcode == 0xa5)
>> + ? ? ? ? ? ?I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_RESI_REGNUM);
>> + ? ? ? ? ?I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_REDI_REGNUM);
>> + ? ? ? ? ?I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_EFLAGS_REGNUM);
>> + ? ? ? }
>> ? ? ? break;
>>
>> ? ? ? /* cmpsS */
>
>