Re: [PATCH] kvm-unit-tests: Add test case for accessing bpl via modr/m

[Gleb Natapov <gleb@redhat.com>]

On Thu, Jun 06, 2013 at 01:03:44PM +0800, Arthur Chunqi Li wrote:
> Test access to %bpl via modr/m addressing mode. This case can test another bug in the boot of RHEL5.9 64-bit.
> 
We have growing number of instructions tests using the same tlb trick. I
think it is time to make the code more generic. Create a function that
receives instruction to check and all the tlb games will be done by that
function.

> Signed-off-by: Arthur Chunqi Li <yzt356@gmail.com>
> ---
>  x86/emulator.c |   41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/x86/emulator.c b/x86/emulator.c
> index 96576e5..3563971 100644
> --- a/x86/emulator.c
> +++ b/x86/emulator.c
> @@ -901,6 +901,45 @@ static void test_simplealu(u32 *mem)
>      report("test", *mem == 0x8400);
>  }
>  
> +static void test_bpl_modrm(uint64_t *mem, uint8_t *insn_page,
> +                       uint8_t *alt_insn_page, void *insn_ram)
> +{
> +	ulong *cr3 = (ulong *)read_cr3();
> +	uint16_t cx = 0;
> +
> +	// 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] = 0x66; // mov $0x4321, %cx
> +	insn_page[1] = 0xb9;
> +	insn_page[2] = 0x21;
> +	insn_page[3] = 0x43;
> +	insn_page[4] = 0x89; // mov %eax, (%rax)
> +	insn_page[5] = 0x00;
> +	insn_page[6] = 0x90; // nop
> +	// Place mov %cl, %bpl in alt_insn_page for emulator to execuate
> +	// If emulator mistaken addressing %bpl, %cl may be moved to %ch
> +	// %cx will be broken to 0x2121, not 0x4321
> +	alt_insn_page[4] = 0x40;
> +	alt_insn_page[5] = 0x88;
> +	alt_insn_page[6] = 0xcd;
> +
> +	// 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));
> +	asm volatile("":"=c"(cx));
Why not add the constrain to previous asm?

> +	report("access bpl in modr/m", cx == 0x4321);
> +}
> +
>  int main()
>  {
>  	void *mem;
> @@ -964,6 +1003,8 @@ int main()
>  
>  	test_string_io_mmio(mem);
>  
> +	test_bpl_modrm(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.