[kvm-unit-tests PATCH] x86: Test single stepping with emulated instructions

[kvm-unit-tests PATCH] x86: Test single stepping with emulated instructions

[Kyle Huey]

This test checks that single stepping through CPUID and RDMSR works.
Both instructions trigger VM exits and are emulated by the hypervisor.

Signed-off-by: Kyle Huey <khuey@kylehuey.com>
---
 x86/debug.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/x86/debug.c b/x86/debug.c
index d04de23..fb1fb0d 100644
--- a/x86/debug.c
+++ b/x86/debug.c
@@ -107,16 +107,47 @@ hw_bp2:
 		"popf\n\t"
 		: "=g" (start) : : "rax");
 	report("single step",
 	       n == 3 &&
 	       bp_addr[0] == start+1+6 && dr6[0] == 0xffff4ff0 &&
 	       bp_addr[1] == start+1+6+1 && dr6[1] == 0xffff4ff0 &&
 	       bp_addr[2] == start+1+6+1+1 && dr6[2] == 0xffff4ff0);
 
+	/*
+	 * cpuid and rdmsr (among others) trigger VM exits and are then
+	 * emulated. Test that single stepping works on emulated instructions.
+	 */
+	n = 0;
+	set_dr6(0);
+	asm volatile(
+		"pushf\n\t"
+		"pop %%rax\n\t"
+		"or $(1<<8),%%rax\n\t"
+		"push %%rax\n\t"
+		"lea (%%rip),%0\n\t"
+		"popf\n\t"
+		"and $~(1<<8),%%rax\n\t"
+		"push %%rax\n\t"
+		"xor %%rax,%%rax\n\t"
+		"cpuid\n\t"
+		"movl $0x1a0,%%ecx\n\t"
+		"rdmsr\n\t"
+		"popf\n\t"
+		: "=g" (start) : : "rax", "ebx", "ecx", "edx");
+	report("single step emulated instructions",
+	       n == 7 &&
+	       bp_addr[0] == start+1+6 && dr6[0] == 0xffff4ff0 &&
+	       bp_addr[1] == start+1+6+1 && dr6[1] == 0xffff4ff0 &&
+	       bp_addr[2] == start+1+6+1+3 && dr6[2] == 0xffff4ff0 &&
+	       bp_addr[3] == start+1+6+1+3+2 && dr6[3] == 0xffff4ff0 &&
+	       bp_addr[4] == start+1+6+1+3+2+5 && dr6[4] == 0xffff4ff0 &&
+	       bp_addr[5] == start+1+6+1+3+2+5+2 && dr6[4] == 0xffff4ff0 &&
+	       bp_addr[6] == start+1+6+1+3+2+5+2+1 && dr6[4] == 0xffff4ff0);
+
 	n = 0;
 	set_dr1((void *)&value);
 	set_dr7(0x00d0040a);
 
 	asm volatile(
 		"mov $42,%%rax\n\t"
 		"mov %%rax,%0\n\t"
 		: "=m" (value) : : "rax");
-- 
2.10.2

Re: [kvm-unit-tests PATCH] x86: Test single stepping with emulated instructions

[Radim Krčmář]

2016-11-27 20:19-0800, Kyle Huey:
> This test checks that single stepping through CPUID and RDMSR works.
> Both instructions trigger VM exits and are emulated by the hypervisor.
> 
> Signed-off-by: Kyle Huey <khuey@kylehuey.com>
> ---
> diff --git a/x86/debug.c b/x86/debug.c
> @@ -107,16 +107,47 @@ hw_bp2:
>  		"popf\n\t"
>  		: "=g" (start) : : "rax");
>  	report("single step",
>  	       n == 3 &&
>  	       bp_addr[0] == start+1+6 && dr6[0] == 0xffff4ff0 &&
>  	       bp_addr[1] == start+1+6+1 && dr6[1] == 0xffff4ff0 &&
>  	       bp_addr[2] == start+1+6+1+1 && dr6[2] == 0xffff4ff0);
>  
> +	/*
> +	 * cpuid and rdmsr (among others) trigger VM exits and are then
> +	 * emulated. Test that single stepping works on emulated instructions.
> +	 */
> +	n = 0;
> +	set_dr6(0);
> +	asm volatile(
> +		"pushf\n\t"
> +		"pop %%rax\n\t"
> +		"or $(1<<8),%%rax\n\t"
> +		"push %%rax\n\t"
> +		"lea (%%rip),%0\n\t"
> +		"popf\n\t"
> +		"and $~(1<<8),%%rax\n\t"
> +		"push %%rax\n\t"
> +		"xor %%rax,%%rax\n\t"
> +		"cpuid\n\t"
> +		"movl $0x1a0,%%ecx\n\t"
> +		"rdmsr\n\t"
> +		"popf\n\t"
> +		: "=g" (start) : : "rax", "ebx", "ecx", "edx");
> +	report("single step emulated instructions",
> +	       n == 7 &&
> +	       bp_addr[0] == start+1+6 && dr6[0] == 0xffff4ff0 &&
> +	       bp_addr[1] == start+1+6+1 && dr6[1] == 0xffff4ff0 &&
> +	       bp_addr[2] == start+1+6+1+3 && dr6[2] == 0xffff4ff0 &&
> +	       bp_addr[3] == start+1+6+1+3+2 && dr6[3] == 0xffff4ff0 &&
> +	       bp_addr[4] == start+1+6+1+3+2+5 && dr6[4] == 0xffff4ff0 &&
> +	       bp_addr[5] == start+1+6+1+3+2+5+2 && dr6[4] == 0xffff4ff0 &&
> +	       bp_addr[6] == start+1+6+1+3+2+5+2+1 && dr6[4] == 0xffff4ff0);

You probably wanted to check dr6[5] and dr6[6] too, I will fix that
while applying.

Thanks.