Re: Bug in i386_process_record?

Hui Zhu
2009-08-27T13:48:58Z

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On Thu, Aug 27, 2009 at 09:43, Hui Zhu<teawater@gmail.com> wrote:
> On Thu, Aug 27, 2009 at 08:28, Michael Snyder<msnyder@vmware.com> wrote:
>> Michael Snyder 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!
>>
>> Hui,
>>
>> Do you think you could add some new tests to i386-reverse.exp,
>> to verify the string instructions?
>>
>> Thanks,
>> Michael
>>
>
> OK. I will do it.
>
> Thanks,
> Hui
>

Hi Michael,

I make a patch to add the test for string insn.

Please help me review it.

Thanks,
Hui

2009-08-27 Hui Zhu <teawater@gmail.com>

* gdb.reverse/i386-reverse.c (string_insn_tests): New function.
(main): Call "string_insn_tests".

---
testsuite/gdb.reverse/i386-reverse.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

--- a/testsuite/gdb.reverse/i386-reverse.c
+++ b/testsuite/gdb.reverse/i386-reverse.c
@@ -38,9 +38,25 @@ inc_dec_tests (void)
asm ("dec %edi");
} /* end inc_dec_tests */

+void
+string_insn_tests (void)
+{
+ register char x asm("ax");
+ char *dstp = (char *) 1;
+ int d0;
+ int len = 0;
+
+ asm volatile("rep\n"
+ "stosb" /* %0, %2, %3 */ :
+ "=D" (dstp), "=c" (d0) :
+ "0" (dstp), "1" (len), "a" (x) :
+ "memory");
+}
+
int
main ()
{
inc_dec_tests ();
+ string_insn_tests ();
return 0; /* end of main */
}

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---
testsuite/gdb.reverse/i386-reverse.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

--- a/testsuite/gdb.reverse/i386-reverse.c
+++ b/testsuite/gdb.reverse/i386-reverse.c
@@ -38,9 +38,25 @@ inc_dec_tests (void)
asm ("dec %edi");
} /* end inc_dec_tests */

+void
+string_insn_tests (void)
+{
+ register char x asm("ax");
+ char *dstp = (char *) 1;
+ int d0;
+ int len = 0;
+
+ asm volatile("rep\n"
+ "stosb" /* %0, %2, %3 */ :
+ "=D" (dstp), "=c" (d0) :
+ "0" (dstp), "1" (len), "a" (x) :
+ "memory");
+}
+
int
main ()
{
inc_dec_tests ();
+ string_insn_tests ();
return 0; /* end of main */
}