Yes, that should be the point. x86/realmode.c is always running in
emulation mode. I added the testing here there but no error occurred.
I cannot find the reason.
The code is as follows added to x86/realmode.c
static void test_nopl(void)
{
MK_INSN(nopl, ".byte 0x0f, 0x1f, 0x00\n\r");
exec_in_big_real_mode(&insn_nopl);
report("nopl", 0, 1);
}
and I objdump from realmode.flat is as follows:
00006458 <insn_code_nopl>:
6458: 0f 1f 00 nopl (%eax)
But there cause no error when executing this insn. Why?
On Wed, Jun 5, 2013 at 2:42 PM, Gleb Natapov <[email protected]> wrote:
>
> On Wed, Jun 05, 2013 at 10:16:46AM +0800, 李春奇 <Arthur Chunqi Li> wrote:
> > Add multibyte NOP test case to kvm-unit-tests. This case can test one
> > of bugs when booting RHEL5.9 64-bit.
> >
> Adding the test to x86/realmode.c will be much easier.
>
> > Signed-off-by: Arthur Chunqi Li <[email protected]>
> > ---
> > x86/emulator.c | 33 +++++++++++++++++++++++++++++++++
> > 1 file changed, 33 insertions(+)
> >
> > diff --git a/x86/emulator.c b/x86/emulator.c
> > index 96576e5..f26c70f 100644
> > --- a/x86/emulator.c
> > +++ b/x86/emulator.c
> > @@ -901,6 +901,37 @@ static void test_simplealu(u32 *mem)
> > report("test", *mem == 0x8400);
> > }
> >
> > +static void test_nopl(uint64_t *mem, uint8_t *insn_page,
> > + uint8_t *alt_insn_page, void *insn_ram)
> > +{
> > + ulong *cr3 = (ulong *)read_cr3();
> > +
> > + // Pad with RET instructions
> > + memset(insn_page, 0xc3, 4096);
> > + memset(alt_insn_page, 0xc3, 4096);
> > + // Place a trapping instruction in the page to trigger a VMEXIT
> > + insn_page[0] = 0x89; // mov %eax, (%rax)
> > + insn_page[1] = 0x00;
> > + insn_page[2] = 0x90; // nop
> > + // Place nopl 0x0(%eax) in alt_insn_page for emulator to execuate
> > + alt_insn_page[0] = 0x0f; // nop DWORD ptr[EAX]
> > + alt_insn_page[1] = 0x1f;
> > + alt_insn_page[2] = 0x00;
> > +
> > + // Load the code TLB with insn_page, but point the page tables at
> > + // alt_insn_page (and keep the data TLB clear, for AMD decode assist).
> > + // This will make the CPU trap on the insn_page instruction but the
> > + // hypervisor will see alt_insn_page.
> > + install_page(cr3, virt_to_phys(insn_page), insn_ram);
> > + // Load code TLB
> > + invlpg(insn_ram);
> > + asm volatile("call *%0" : : "r"(insn_ram + 3));
> > + // Trap, let hypervisor emulate at alt_insn_page
> > + install_page(cr3, virt_to_phys(alt_insn_page), insn_ram);
> > + asm volatile("call *%0" : : "r"(insn_ram), "a"(mem));
> > + report("nopl", 1);
> > +}
> > +
> > int main()
> > {
> > void *mem;
> > @@ -964,6 +995,8 @@ int main()
> >
> > test_string_io_mmio(mem);
> >
> > + test_nopl(mem, insn_page, alt_insn_page, insn_ram);
> > +
> > printf("\nSUMMARY: %d tests, %d failures\n", tests, fails);
> > return fails ? 1 : 0;
> > }
> > --
> > 1.7.9.5
>
> --
> Gleb.
--
Arthur Chunqi Li
Department of Computer Science
School of EECS
Peking University
Beijing, China
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