Re: [PATCH] Test case of multibyte NOP in emulation mode

[Gleb Natapov <gleb@redhat.com>]

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 <yzt356@gmail.com>
> ---
>  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.