selftest/powerpc: Add test for sigreturn in transaction

Ensure that kernel is throwing away the suspended transaction when
sigreturn() is called otherwise it if fails to restore the signal
frame's TM SPRS.
Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Reviewed-by: Cyril Bur <cyrilbur@gmail.com>
[mpe: Add have_htm() check, minor formatting, add SPDX tag]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

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)
+	$(SIGNAL_CONTEXT_CHK_TESTS) tm-sigreturn
 
 include ../../lib.mk
 

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

+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright 2015, Laurent Dufour, IBM Corp.
+ *
+ * Test the kernel's signal returning code to check reclaim is done if the
+ * sigreturn() is called while in a transaction (suspended since active is
+ * already dropped trough the system call path).
+ *
+ * The kernel must discard the transaction when entering sigreturn, since
+ * restoring the potential TM SPRS from the signal frame is requiring to not be
+ * in a transaction.
+ */
+
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "tm.h"
+#include "utils.h"
+
+
+void handler(int sig)
+{
+	uint64_t ret;
+
+	asm __volatile__(
+		"li             3,1             ;"
+		"tbegin.                        ;"
+		"beq            1f              ;"
+		"li             3,0             ;"
+		"tsuspend.                      ;"
+		"1:                             ;"
+		"std%X[ret]     3, %[ret]       ;"
+		: [ret] "=m"(ret)
+		:
+		: "memory", "3", "cr0");
+
+	if (ret)
+		exit(1);
+
+	/*
+	 * We return from the signal handle while in a suspended transaction
+	 */
+}
+
+
+int tm_sigreturn(void)
+{
+	struct sigaction sa;
+	uint64_t ret = 0;
+
+	SKIP_IF(!have_htm());
+
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_handler = handler;
+	sigemptyset(&sa.sa_mask);
+
+	if (sigaction(SIGSEGV, &sa, NULL))
+		exit(1);
+
+	asm __volatile__(
+		"tbegin.                        ;"
+		"beq            1f              ;"
+		"li             3,0             ;"
+		"std            3,0(3)          ;" /* trigger SEGV */
+		"li             3,1             ;"
+		"std%X[ret]     3,%[ret]        ;"
+		"tend.                          ;"
+		"b              2f              ;"
+		"1:                             ;"
+		"li             3,2             ;"
+		"std%X[ret]     3,%[ret]        ;"
+		"2:                             ;"
+		: [ret] "=m"(ret)
+		:
+		: "memory", "3", "cr0");
+
+	if (ret != 2)
+		exit(1);
+
+	exit(0);
+}
+
+int main(void)
+{
+	return test_harness(tm_sigreturn, "tm_sigreturn");
+}