Re: [PATCH] Test case of emulating multibyte NOP

["李春奇 <Arthur Chunqi Li>" <yzt356@gmail.com>]

On Thu, Jun 6, 2013 at 3:02 PM, Gleb Natapov <gleb@redhat.com> wrote:
> On Thu, Jun 06, 2013 at 02:49:14PM +0800, 李春奇 <Arthur Chunqi Li> wrote:
>> On Thu, Jun 6, 2013 at 1:40 PM, Gleb Natapov <gleb@redhat.com> wrote:
>> > On Thu, Jun 06, 2013 at 12:28:16AM +0800, 李春奇 <Arthur Chunqi Li> wrote:
>> >> On Thu, Jun 6, 2013 at 12:13 AM, Gleb Natapov <gleb@redhat.com> wrote:
>> >> > This time the email is perfect :)
>> >> >
>> >> > On Thu, Jun 06, 2013 at 12:02:52AM +0800, Arthur Chunqi Li wrote:
>> >> >> Add multibyte NOP test case to kvm-unit-tests. This version adds test cases into x86/realmode.c. This can test one of bugs when booting RHEL5.9 64-bit.
>> >> >>
>> >> >> Signed-off-by: Arthur Chunqi Li <yzt356@gmail.com>
>> >> >> ---
>> >> >>  x86/realmode.c |   24 ++++++++++++++++++++++++
>> >> >>  1 file changed, 24 insertions(+)
>> >> >>
>> >> >> diff --git a/x86/realmode.c b/x86/realmode.c
>> >> >> index 981be08..e103ca6 100644
>> >> >> --- a/x86/realmode.c
>> >> >> +++ b/x86/realmode.c
>> >> >> @@ -1504,6 +1504,29 @@ static void test_fninit(void)
>> >> >>       report("fninit", 0, fsw == 0 && (fcw & 0x103f) == 0x003f);
>> >> >>  }
>> >> >>
>> >> >> +static void test_nopl(void)
>> >> >> +{
>> >> >> +     MK_INSN(nopl1, ".byte 0x90\n\r"); // 1 byte nop
>> >> >> +     MK_INSN(nopl2, ".byte 0x66, 0x90\n\r"); // 2 bytes nop
>> >> >> +     MK_INSN(nopl3, ".byte 0x0f, 0x1f, 0x00\n\r"); // 3 bytes nop
>> >> >> +     MK_INSN(nopl4, ".byte 0x0f, 0x1f, 0x40, 0x00\n\r"); // 4 bytes nop
>> >> > But all nops below that are not supported in 16 bit mode. You can
>> >> > disassemble realmode.elf in 16bit node (objdump -z -d -mi8086
>> >> > x86/realmode.elf) and check yourself. Lets not complicate things for now
>> >> > and test only those that are easy to test.
>> >> Yes. But what if a 7-bytes nop runs in 16bit mode? Just the same as
>> >> https://bugzilla.redhat.com/show_bug.cgi?id=967652
>> >>
>> > It cannot. In 16 bit mode it is decoded as two instructions:
>> >        0f 1f 80 00 00          nopw   0x0(%bx,%si)
>> >        00 00                   add    %al,(%bx,%si)
>> >
>> OK, I will just test the first four nop instructions. Should I commit
>> another patch?
>>
> Yes, all others will have to go into emulator.c.
You mean I need also add another test for nopl5~nop9 in emulator.c
with the "trick" emulator mode?
I will commit a modified one for realmode.c since some other works
should be done in emulator.c.

>
>> Arthur.
>>
>> >> DR6=00000000ffff0ff0 DR7=0000000000000400
>> >> EFER=0000000000000500
>> >> Code=00 00 e9 50 ff ff ff 00 00 00 00 85 d2 74 20 45 31 c0 31 c9 <0f>
>> >> 1f 80 00 00 00 00 0f b6 04 31 41 83 c0 01 88 04 39 48 83 c1 01 41 39
>> >> d0 75 ec 48 89 f8
>> >>
>> >> The error code is "0f 1f 80 00 00 00 00", which is a 7-bytes nop. Will
>> >> the emulator runs well in that case when booting RHEL5.9 64-bit?
>> >>
>> >> Arthur
>> >>
>> >>
>> >> >
>> >> >> +     MK_INSN(nopl5, ".byte 0x0f, 0x1f, 0x44, 0x00, 0x00\n\r"); // 5 bytes nop
>> >> >> +     MK_INSN(nopl6, ".byte 0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00\n\r"); // 6 bytes nop
>> >> >> +     MK_INSN(nopl7, ".byte 0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00\n\r"); // 7 bytes nop
>> >> >> +     MK_INSN(nopl8, ".byte 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00\n\r"); // 8 bytes nop
>> >> >> +     MK_INSN(nopl9, ".byte 0x66, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00\n\r"); // 9 bytes nop
>> >> >> +     exec_in_big_real_mode(&insn_nopl1);
>> >> >> +     exec_in_big_real_mode(&insn_nopl2);
>> >> >> +     exec_in_big_real_mode(&insn_nopl3);
>> >> >> +     exec_in_big_real_mode(&insn_nopl4);
>> >> >> +     exec_in_big_real_mode(&insn_nopl5);
>> >> >> +     exec_in_big_real_mode(&insn_nopl6);
>> >> >> +     exec_in_big_real_mode(&insn_nopl7);
>> >> >> +     exec_in_big_real_mode(&insn_nopl8);
>> >> >> +     exec_in_big_real_mode(&insn_nopl9);
>> >> >> +     report("nopl", 0, 1);
>> >> >> +}
>> >> >> +
>> >> >>  void realmode_start(void)
>> >> >>  {
>> >> >>       test_null();
>> >> >> @@ -1548,6 +1571,7 @@ void realmode_start(void)
>> >> >>       test_xlat();
>> >> >>       test_salc();
>> >> >>       test_fninit();
>> >> >> +     test_nopl();
>> >> >>
>> >> >>       exit(0);
>> >> >>  }
>> >> >> --
>> >> >> 1.7.9.5
>> >> >
>> >> > --
>> >> >                         Gleb.
>> >
>> > --
>> >                         Gleb.
>
> --
>                         Gleb.



--
Arthur Chunqi Li
Department of Computer Science
School of EECS
Peking University
Beijing, China