Re: Bug in i386_process_record?

Hui Zhu
2009-08-10T08:51:10Z

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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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---
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);