selftests/powerpc: Add checks for transactional sigreturn

This is a new test case that creates a signal and starts a suspended
transaction inside the signal handler.

It returns from the signal handler with the CPU at suspended state, but
without setting user context MSR Transaction State (TS) field.

The kernel signal handler code should be able to handle this discrepancy
instead of crashing.

This code could be compiled and used to test 32 and 64-bits signal
handlers.

Signed-off-by: Breno Leitao <[email protected]>
Signed-off-by: Gustavo Romero <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>

tools/testing/selftests/powerpc/tm/.gitignore

@@ -11,6 +11,7 @@ tm-signal-context-chk-fpu
 tm-signal-context-chk-gpr
 tm-signal-context-chk-vmx
 tm-signal-context-chk-vsx
+tm-signal-sigreturn-nt
 tm-vmx-unavail
 tm-unavailable
 tm-trap

tools/testing/selftests/powerpc/tm/Makefile

@@ -4,7 +4,7 @@ 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
+	$(SIGNAL_CONTEXT_CHK_TESTS) tm-sigreturn tm-signal-sigreturn-nt
 
 top_srcdir = ../../../../..
 include ../../lib.mk

tools/testing/selftests/powerpc/tm/tm-signal-sigreturn-nt.c

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2018, Breno Leitao, Gustavo Romero, IBM Corp.
+ *
+ * A test case that creates a signal and starts a suspended transaction
+ * inside the signal handler.
+ *
+ * It returns from the signal handler with the CPU at suspended state, but
+ * without setting usercontext MSR Transaction State (TS) fields.
+ */
+
+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <signal.h>
+
+#include "utils.h"
+
+void trap_signal_handler(int signo, siginfo_t *si, void *uc)
+{
+	ucontext_t *ucp = (ucontext_t *) uc;
+
+	asm("tbegin.; tsuspend.;");
+
+	/* Skip 'trap' instruction if it succeed */
+	ucp->uc_mcontext.regs->nip += 4;
+}
+
+int tm_signal_sigreturn_nt(void)
+{
+	struct sigaction trap_sa;
+
+	trap_sa.sa_flags = SA_SIGINFO;
+	trap_sa.sa_sigaction = trap_signal_handler;
+
+	sigaction(SIGTRAP, &trap_sa, NULL);
+
+	raise(SIGTRAP);
+
+	return EXIT_SUCCESS;
+}
+
+int main(int argc, char **argv)
+{
+	test_harness(tm_signal_sigreturn_nt, "tm_signal_sigreturn_nt");
+}
+