selftests/x86/vm86: Fix entry_from_vm86 test on 64-bit kernels

The test failed due to an oversight on my part when run on a
64-bit kernel.  vm86 isn't expected to work at all, and I
mistakenly failed one part of the test because no signal was
delivered.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/502c8bef877b33fe4943885ded6125dfcc7892db.1438205722.git.luto@kernel.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

tools/testing/selftests/x86/entry_from_vm86.c

@@ -105,7 +105,8 @@ extern unsigned char vmcode[], end_vmcode[];
 extern unsigned char vmcode_bound[], vmcode_sysenter[], vmcode_syscall[],
 	vmcode_sti[], vmcode_int3[], vmcode_int80[];
 
-static void do_test(struct vm86plus_struct *v86, unsigned long eip,
+/* Returns false if the test was skipped. */
+static bool do_test(struct vm86plus_struct *v86, unsigned long eip,
 		    unsigned int rettype, unsigned int retarg,
 		    const char *text)
 {
@@ -117,7 +118,7 @@ static void do_test(struct vm86plus_struct *v86, unsigned long eip,
 
 	if (ret == -1 && errno == ENOSYS) {
 		printf("[SKIP]\tvm86 not supported\n");
-		return;
+		return false;
 	}
 
 	if (VM86_TYPE(ret) == VM86_INTx) {
@@ -154,6 +155,8 @@ static void do_test(struct vm86plus_struct *v86, unsigned long eip,
 		printf("[FAIL]\tIncorrect return reason\n");
 		nerrs++;
 	}
+
+	return true;
 }
 
 int main(void)
@@ -219,8 +222,8 @@ int main(void)
 	v86.regs.ss = 0;
 	sethandler(SIGSEGV, sighandler, 0);
 	got_signal = 0;
-	do_test(&v86, 0, VM86_SIGNAL, 0, "Execute null pointer");
-	if (!got_signal) {
+	if (do_test(&v86, 0, VM86_SIGNAL, 0, "Execute null pointer") &&
+	    !got_signal) {
 		printf("[FAIL]\tDid not receive SIGSEGV\n");
 		nerrs++;
 	}