[kvm-unit-tests PATCH v2 2/5] x86: emulator.c cleanup: Use ASM_TRY() for the UD_VECTOR cases

[Michal Luczaj <mhal@rbox.co>]

For #UD handling use ASM_TRY() instead of handle_exception().

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
---
v1 -> v2: Change `mov` to `movl` to silence the compiler warning

 x86/emulator.c | 42 ++++++++++++++++--------------------------
 1 file changed, 16 insertions(+), 26 deletions(-)

diff --git a/x86/emulator.c b/x86/emulator.c
index 769a049..96d3ccd 100644
--- a/x86/emulator.c
+++ b/x86/emulator.c
@@ -17,10 +17,8 @@
 
 static int exceptions;
 
-/* Forced emulation prefix, used to invoke the emulator unconditionally.  */
+/* Forced emulation prefix, used to invoke the emulator unconditionally. */
 #define KVM_FEP "ud2; .byte 'k', 'v', 'm';"
-#define KVM_FEP_LENGTH 5
-static int fep_available = 1;
 
 struct regs {
 	u64 rax, rbx, rcx, rdx;
@@ -1099,33 +1097,23 @@ static void test_simplealu(u32 *mem)
     report(*mem == 0x8400, "test");
 }
 
-static void illegal_movbe_handler(struct ex_regs *regs)
-{
-	extern char bad_movbe_cont;
-
-	++exceptions;
-	regs->rip = (ulong)&bad_movbe_cont;
-}
-
 static void test_illegal_movbe(void)
 {
+	unsigned int vector;
+
 	if (!this_cpu_has(X86_FEATURE_MOVBE)) {
-		report_skip("illegal movbe");
+		report_skip("MOVBE unsupported by CPU");
 		return;
 	}
 
-	exceptions = 0;
-	handle_exception(UD_VECTOR, illegal_movbe_handler);
-	asm volatile(".byte 0x0f; .byte 0x38; .byte 0xf0; .byte 0xc0;\n\t"
-		     " bad_movbe_cont:" : : : "rax");
-	report(exceptions == 1, "illegal movbe");
-	handle_exception(UD_VECTOR, 0);
-}
+	asm volatile(ASM_TRY("1f")
+		     ".byte 0x0f; .byte 0x38; .byte 0xf0; .byte 0xc0;\n\t"
+		     "1:"
+		     : : : "memory", "rax");
 
-static void record_no_fep(struct ex_regs *regs)
-{
-	fep_available = 0;
-	regs->rip += KVM_FEP_LENGTH;
+	vector = exception_vector();
+	report(vector == UD_VECTOR,
+	       "Wanted #UD on MOVBE with /reg, got vector = %u", vector);
 }
 
 int main(void)
@@ -1135,11 +1123,13 @@ int main(void)
 	void *insn_ram;
 	void *cross_mem;
 	unsigned long t1, t2;
+	int fep_available = 0;
 
 	setup_vm();
-	handle_exception(UD_VECTOR, record_no_fep);
-	asm(KVM_FEP "nop");
-	handle_exception(UD_VECTOR, 0);
+	asm volatile(ASM_TRY("1f")
+		     KVM_FEP "movl $1, %[fep_available]\n\t"
+		     "1:"
+		     : [fep_available] "=m" (fep_available) : : "memory");
 
 	mem = alloc_vpages(2);
 	install_page((void *)read_cr3(), IORAM_BASE_PHYS, mem);
-- 
2.37.1