selftests/powerpc: Add test to check if TM is disabled when it must be

@@ -20,3 +20,4 @@ tm-unavailable
 tm-trap
 tm-sigreturn
 tm-poison
+tm-no-tm

@@ -5,7 +5,7 @@ SIGNAL_CONTEXT_CHK_TESTS := tm-signal-context-chk-gpr tm-signal-context-chk-fpu
 TEST_GEN_PROGS := tm-resched-dscr tm-syscall tm-signal-msr-resv tm-signal-stack \
 	tm-vmxcopy tm-fork tm-tar tm-tmspr tm-vmx-unavail tm-unavailable tm-trap \
 	$(SIGNAL_CONTEXT_CHK_TESTS) tm-sigreturn tm-signal-sigreturn-nt \
-	tm-signal-context-force-tm tm-poison tm-signal-pagefault
+	tm-signal-context-force-tm tm-poison tm-signal-pagefault tm-no-tm
 
 TEST_FILES := settings
 

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2020, Gustavo Romero, IBM Corp.
+ *
+ * This test checks if when TM is not supported by the OS indeed it's not
+ * possible to start a TM transaction. Moreover, when trying to start a new
+ * transaction the user gets an illegal instruction, which is the correct
+ * behavior in that case, instead of any other signal, like SIGSEGV etc.
+ *
+ * Since firmware can change the TM instruction behavior in many ways, it's good
+ * to have a test to check if TM is properly disabled when the OS advertises
+ * that TM is not available in userspace.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+
+#include "utils.h"
+#include "tm.h"
+
+void illegal_signal_handler(int signo_notused, siginfo_t *si_notused, void *uc_notused)
+{
+	exit(EXIT_SUCCESS);
+}
+
+int tm_no_tm_test(void)
+{
+	struct sigaction illegal_sa;
+
+	SKIP_IF(have_htm());
+
+	illegal_sa.sa_flags = SA_SIGINFO;
+	illegal_sa.sa_sigaction = illegal_signal_handler;
+
+	sigaction(SIGILL, &illegal_sa, NULL);
+
+	/* It must cause a SIGILL since TM is not supported by the OS */
+	asm("tbegin.;");
+
+	return EXIT_FAILURE;
+}
+
+int main(int argc, char **argv)
+{
+	return test_harness(tm_no_tm_test, "tm_no_tm_test");
+}