Re: Bug in i386_process_record?

Hui Zhu
2009-08-26T02:59:06Z

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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?

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 */

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---
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 */