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Re: Bug in i386_process_record?


Oops, I will try to find it out.

Thanks,
Hui

On Tue, Aug 11, 2009 at 05:57, Michael Snyder<msnyder@vmware.com> wrote:
> Yes, this seems to be better. ?It records only 4 bytes each time
> it is called.
>
> But there seems to be still an off-by-one error? ?With 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.
>
>
>
> Hui Zhu wrote:
>>
>> On Fri, Aug 7, 2009 at 11:39, Michael Snyder<msnyder@vmware.com> wrote:
>>>
>>> Hi Hui,
>>>
>>> While experimenting with your dump/load commands, I think I discovered
>>> a bug in i386_process_record, in the handling of the "string ops"
>>> and the "rep" prefix. ?Looks like we are saving the same data over
>>> and over in the log.
>>>
>>> This was made using the attached sample program.
>>>
>>> ?(gdb) break main
>>> ? Breakpoint 1 at 0x80483c4: file memrange-reverse.c, line 29.
>>> ?(gdb) run
>>> ? Starting program:
>>> ? Breakpoint 1, main ()
>>> ? 29 ? ? ? ?memset (blob1, 'a', sizeof (blob1));
>>> ?(gdb) record
>>> ?(gdb) next
>>> ? 30 ? ? ? ?blob1[sizeof (blob1) - 1] = '\0';
>>> ?(gdb) record dump
>>> ? Saving recording to file 'rec.27255'
>>> ? Writing 4-byte magic cookie RECORD_FILE_MAGIC (0x26070920)
>>> ?[...]
>>> ?Writing register 7 val 0x0000000008049684 (1 plus 8 plus 16 bytes)
>>> ?Writing memory 0x08049680 (1 plus 8 plus 8 bytes plus 1024 bytes)
>>> ?Writing register 1 val 0x00000000000000ff (1 plus 8 plus 16 bytes)
>>> ?Writing register 8 val 0x0000000000587be7 (1 plus 8 plus 16 bytes)
>>> ?Writing record_end (1 byte)
>>> ?Writing register 7 val 0x0000000008049688 (1 plus 8 plus 16 bytes)
>>> ?Writing memory 0x08049684 (1 plus 8 plus 8 bytes plus 1020 bytes)
>>> ?Writing register 1 val 0x00000000000000fe (1 plus 8 plus 16 bytes)
>>> ?Writing register 8 val 0x0000000000587be7 (1 plus 8 plus 16 bytes)
>>> ?Writing record_end (1 byte)
>>> ?Writing register 7 val 0x000000000804968c (1 plus 8 plus 16 bytes)
>>> ?Writing memory 0x08049688 (1 plus 8 plus 8 bytes plus 1016 bytes)
>>> ?Writing register 1 val 0x00000000000000fd (1 plus 8 plus 16 bytes)
>>> ?Writing register 8 val 0x0000000000587be7 (1 plus 8 plus 16 bytes)
>>> ?Writing record_end (1 byte)
>>> ?Writing register 7 val 0x0000000008049690 (1 plus 8 plus 16 bytes)
>>> ?Writing memory 0x0804968c (1 plus 8 plus 8 bytes plus 1012 bytes)
>>> ?Writing register 1 val 0x00000000000000fc (1 plus 8 plus 16 bytes)
>>> ?Writing register 8 val 0x0000000000587be7 (1 plus 8 plus 16 bytes)
>>> ?Writing record_end (1 byte)
>>> ?Writing register 7 val 0x0000000008049694 (1 plus 8 plus 16 bytes)
>>> ?Writing memory 0x08049690 (1 plus 8 plus 8 bytes plus 1008 bytes)
>>> ?Writing register 1 val 0x00000000000000fb (1 plus 8 plus 16 bytes)
>>> ?Writing register 8 val 0x0000000000587be7 (1 plus 8 plus 16 bytes)
>>> ?Writing record_end (1 byte)
>>> ?Writing register 7 val 0x0000000008049698 (1 plus 8 plus 16 bytes)
>>> ?Writing memory 0x08049694 (1 plus 8 plus 8 bytes plus 1004 bytes)
>>> ?Writing register 1 val 0x00000000000000fa (1 plus 8 plus 16 bytes)
>>> ?Writing register 8 val 0x0000000000587be7 (1 plus 8 plus 16 bytes)
>>> ?Writing record_end (1 byte)
>>> ?Writing register 7 val 0x000000000804969c (1 plus 8 plus 16 bytes)
>>> ?Writing memory 0x08049698 (1 plus 8 plus 8 bytes plus 1000 bytes)
>>> ?Writing register 1 val 0x00000000000000f9 (1 plus 8 plus 16 bytes)
>>> ?Writing register 8 val 0x0000000000587be7 (1 plus 8 plus 16 bytes)
>>> ?Writing record_end (1 byte)
>>> ?Writing register 7 val 0x00000000080496a0 (1 plus 8 plus 16 bytes)
>>> ?Writing memory 0x0804969c (1 plus 8 plus 8 bytes plus 996 bytes)
>>> ?Writing register 1 val 0x00000000000000f8 (1 plus 8 plus 16 bytes)
>>> ?Writing register 8 val 0x0000000000587be7 (1 plus 8 plus 16 bytes)
>>> ?[...]
>>>
>>> Altogether there were 256 duplicate entries, each one is
>>> four bytes shorter than the previous one.
>>>
>>>
>>
>> Hi Michael,
>>
>> I reproduce about issue. ?This is because "i386_process_record" record
>> rep string insn is not right.
>> I make a patch for it.
>>
>> Please help me review it.
>>
>> Thanks,
>> Hui
>>
>> 2009-08-10 ?Hui Zhu ?<teawater@gmail.com>
>>
>> ? ? ? ?* record.c (i386_process_record): Remove some error code.
>>
>> ---
>> ?i386-tdep.c | ? 27 ++++-----------------------
>> ?1 file changed, 4 insertions(+), 23 deletions(-)
>>
>> --- a/i386-tdep.c
>> +++ b/i386-tdep.c
>> @@ -4448,9 +4448,8 @@ reswitch:
>> ? ? ? regcache_raw_read_unsigned (ir.regcache,
>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ir.regmap[X86_RECORD_REDI_REGNUM],
>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? &tmpulongest);
>> - ? ? ?if (!ir.aflag)
>> + ? ? ?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
>> "
>> @@ -4460,27 +4459,9 @@ reswitch:
>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?paddress (gdbarch, ir.addr));
>> ? ? ? ? }
>> ? ? ? if (prefixes & (PREFIX_REPZ | PREFIX_REPNZ))
>> - ? ? ? ?{
>> - ? ? ? ? ?ULONGEST count, eflags;
>> - ? ? ? ? ?regcache_raw_read_unsigned (ir.regcache,
>> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?ir.regmap[X86_RECORD_REDI_REGNUM],
>> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?&count);
>> - ? ? ? ? ?if (!ir.aflag)
>> - ? ? ? ? ? ?count &= 0xffff;
>> - ? ? ? ? ?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
>> - ? ? ? ?{
>> - ? ? ? ? ?if (record_arch_list_add_mem (tmpulongest, 1 << ir.ot))
>> - ? ? ? ? ? ?return -1;
>> - ? ? ? ?}
>> + ? ? ? ?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);
>
>


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