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From: Hui Zhu <teawater@gmail.com>
Date: Sun, 16 Aug 2009 16:12:00 -0000
Message-ID: <daef60380908160846w57db2c7frcac0409a7ae8d73e@mail.gmail.com>
Subject: Re: Bug in i386_process_record?
To: Michael Snyder <msnyder@vmware.com>
Cc: gdb-patches ml <gdb-patches@sourceware.org>
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On Tue, Aug 11, 2009 at 14:19, Hui Zhu<teawater@gmail.com> wrote:
> On Tue, Aug 11, 2009 at 05:57, Michael Snyder <msnyder@vmware.com> wrote:
>>
>> Yes, this seems to be better. =A0It records only 4 bytes each time
>> it is called.
>>
>> But there seems to be still an off-by-one error? =A0With the test
>> program that I provided, we call memset with an argument of
>> 1024, but we actually record 1025 bytes... this code gets hit
>> 257 times, with the last time recording only 1 byte.
>>
>>
>
> Hi Michael,
>
> This issue is because:
>
> 0xb7edf4e7 <memset+55>: rep stos %eax,%es:(%edi)
> 0xb7edf4e9 <memset+57>: mov =A0 =A0%edx,%ecx
> 0xb7edf4eb <memset+59>: rep stos %al,%es:(%edi)
> 0xb7edf4ed <memset+61>: mov =A0 =A00x8(%esp),%eax
> 0xb7edf4f1 <memset+65>: pop =A0 =A0%edi
>
> If the memcpy size is not align with 4, it will handle by second rep stos.
> Then rep stos will not execute if %ecx is 0.
> i386_process_record doesn't check %ecx, so it get this error.
>
> I make a new patch for it. =A0Please help me review it.
>
> Thanks,
> Hui
>
> 2009-08-11 =A0Hui Zhu =A0<teawater@gmail.com>
>
> =A0 =A0 =A0 =A0* record.c (i386_process_record): Remove some error code.
>
> ---
> =A0i386-tdep.c | =A0 61 +++++++++++++++++++++++--------------------------=
-----------
> =A01 file changed, 24 insertions(+), 37 deletions(-)
>
> --- a/i386-tdep.c
> +++ b/i386-tdep.c
> @@ -4441,50 +4441,37 @@ reswitch:
> =A0 =A0 =A0 /* insS */
> =A0 =A0 case 0x6c:
> =A0 =A0 case 0x6d:
> - =A0 =A0 =A0if ((opcode & 1) =3D=3D 0)
> - =A0 =A0 =A0 ir.ot =3D OT_BYTE;
> - =A0 =A0 =A0else
> - =A0 =A0 =A0 ir.ot =3D ir.dflag + OT_WORD;
> =A0 =A0 =A0 regcache_raw_read_unsigned (ir.regcache,
> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0ir.r=
egmap[X86_RECORD_REDI_REGNUM],
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0ir.r=
egmap[X86_RECORD_RECX_REGNUM],
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 &tmpu=
longest);
> - =A0 =A0 =A0if (!ir.aflag)
> - =A0 =A0 =A0 =A0{
> - =A0 =A0 =A0 =A0 =A0tmpulongest &=3D 0xffff;
> - =A0 =A0 =A0 =A0 =A0/* addr +=3D ((uint32_t) read_register (I386_ES_REGN=
UM)) << 4; */
> - =A0 =A0 =A0 =A0 =A0if (record_debug)
> - =A0 =A0 =A0 =A0 =A0 =A0printf_unfiltered (_("Process record ignores the=
 memory change "
> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "of ins=
truction at address 0x%s because "
> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "it can=
't get the value of the segment "
> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "regist=
er.\n"),
> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 paddress (g=
dbarch, ir.addr));
> - =A0 =A0 =A0 =A0}
> - =A0 =A0 =A0if (prefixes & (PREFIX_REPZ | PREFIX_REPNZ))
> + =A0 =A0 =A0if (tmpulongest)
> =A0 =A0 =A0 =A0 {
> - =A0 =A0 =A0 =A0 =A0ULONGEST count, eflags;
> + =A0 =A0 =A0 =A0 =A0if ((opcode & 1) =3D=3D 0)
> + =A0 =A0 =A0 =A0 =A0 ir.ot =3D OT_BYTE;
> + =A0 =A0 =A0 =A0 =A0else
> + =A0 =A0 =A0 =A0 =A0 ir.ot =3D ir.dflag + OT_WORD;
> =A0 =A0 =A0 =A0 =A0 regcache_raw_read_unsigned (ir.regcache,
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 ir.regmap[X86_RECORD_REDI_REGNUM],
> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0&count);
> - =A0 =A0 =A0 =A0 =A0if (!ir.aflag)
> - =A0 =A0 =A0 =A0 =A0 =A0count &=3D 0xffff;
> - =A0 =A0 =A0 =A0 =A0regcache_raw_read_unsigned (ir.regcache,
> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0ir.regmap[X86_RECORD_EFLAGS_REGNUM],
> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0&eflags);
> - =A0 =A0 =A0 =A0 =A0if ((eflags >> 10) & 0x1)
> - =A0 =A0 =A0 =A0 =A0 =A0tmpulongest -=3D (count - 1) * (1 << ir.ot);
> - =A0 =A0 =A0 =A0 =A0if (record_arch_list_add_mem (tmpulongest, count * (=
1 << ir.ot)))
> - =A0 =A0 =A0 =A0 =A0 =A0return -1;
> - =A0 =A0 =A0 =A0 =A0I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_RECX_REGNU=
M);
> - =A0 =A0 =A0 =A0}
> - =A0 =A0 =A0else
> - =A0 =A0 =A0 =A0{
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0&tmpulongest);
> + =A0 =A0 =A0 =A0 =A0if (ir.aflag)
> + =A0 =A0 =A0 =A0 =A0 =A0{
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0/* addr +=3D ((uint32_t) read_register (I386=
_ES_REGNUM)) << 4; */
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0if (record_debug)
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0printf_unfiltered (_("Process record ign=
ores the
> memory change "
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 "of instruction at address 0x%s because "
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 "it can't get the value of the segment "
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 "register.\n"),
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 pad=
dress (gdbarch, ir.addr));
> + =A0 =A0 =A0 =A0 =A0 =A0}
> + =A0 =A0 =A0 =A0 =A0if (prefixes & (PREFIX_REPZ | PREFIX_REPNZ))
> + =A0 =A0 =A0 =A0 =A0 =A0I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_RECX_R=
EGNUM);
> =A0 =A0 =A0 =A0 =A0 if (record_arch_list_add_mem (tmpulongest, 1 << ir.ot=
))
> =A0 =A0 =A0 =A0 =A0 =A0 return -1;
> - =A0 =A0 =A0 =A0}
> - =A0 =A0 =A0if (opcode =3D=3D 0xa4 || opcode =3D=3D 0xa5)
> - =A0 =A0 =A0 =A0I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_RESI_REGNUM);
> - =A0 =A0 =A0I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_REDI_REGNUM);
> - =A0 =A0 =A0I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_EFLAGS_REGNUM);
> + =A0 =A0 =A0 =A0 =A0if (opcode =3D=3D 0xa4 || opcode =3D=3D 0xa5)
> + =A0 =A0 =A0 =A0 =A0 =A0I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_RESI_R=
EGNUM);
> + =A0 =A0 =A0 =A0 =A0I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_REDI_REGNU=
M);
> + =A0 =A0 =A0 =A0 =A0I386_RECORD_ARCH_LIST_ADD_REG (X86_RECORD_EFLAGS_REG=
NUM);
> + =A0 =A0 =A0 }
> =A0 =A0 =A0 break;
>
> =A0 =A0 =A0 /* cmpsS */
>