Re: [PATCH] Test case of emulating multibyte NOP

[Gleb Natapov <gleb@redhat.com>]

On Thu, Jun 06, 2013 at 03:22:59PM +0800, 李春奇 <Arthur Chunqi Li> wrote:
> On Thu, Jun 6, 2013 at 3:17 PM, 李春奇 <Arthur Chunqi Li> <yzt356@gmail.com> wrote:
> > 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.
> Since we need to place some relevant codes in emulator.c, why don't we
> place all the tests in emulator.c?
> 
We can place those 4 in both. I do not always run all tests so it is
nice to cover as much as possible in both.

--
			Gleb.