selftests/powerpc: Add checks for transactional FPUs in signal contexts

If a thread receives a signal while transactional the kernel creates a
second context to show the transactional state of the process. This
test loads some known values and waits for a signal and confirms that
the expected values are in the signal context.
Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/tm/Makefile

-SIGNAL_CONTEXT_CHK_TESTS := tm-signal-context-chk-gpr
+SIGNAL_CONTEXT_CHK_TESTS := tm-signal-context-chk-gpr tm-signal-context-chk-fpu
 
 TEST_PROGS := tm-resched-dscr tm-syscall tm-signal-msr-resv tm-signal-stack \
 	tm-vmxcopy tm-fork tm-tar tm-tmspr $(SIGNAL_CONTEXT_CHK_TESTS)

tools/testing/selftests/powerpc/tm/tm-signal-context-chk-fpu.c

+/*
+ * Copyright 2016, Cyril Bur, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ *
+ * Test the kernel's signal frame code.
+ *
+ * The kernel sets up two sets of ucontexts if the signal was to be
+ * delivered while the thread was in a transaction.
+ * Expected behaviour is that the checkpointed state is in the user
+ * context passed to the signal handler. The speculated state can be
+ * accessed with the uc_link pointer.
+ *
+ * The rationale for this is that if TM unaware code (which linked
+ * against TM libs) installs a signal handler it will not know of the
+ * speculative nature of the 'live' registers and may infer the wrong
+ * thing.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include <altivec.h>
+
+#include "utils.h"
+#include "tm.h"
+
+#define MAX_ATTEMPT 500000
+
+#define NV_FPU_REGS 18
+
+long tm_signal_self_context_load(pid_t pid, long *gprs, double *fps, vector int *vms, vector int *vss);
+
+/* Be sure there are 2x as many as there are NV FPU regs (2x18) */
+static double fps[] = {
+	 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
+	-1,-2,-3,-4,-5,-6,-7,-8,-9,-10,-11,-12,-13,-14,-15,-16,-17,-18
+};
+
+static sig_atomic_t fail;
+
+static void signal_usr1(int signum, siginfo_t *info, void *uc)
+{
+	int i;
+	ucontext_t *ucp = uc;
+	ucontext_t *tm_ucp = ucp->uc_link;
+
+	for (i = 0; i < NV_FPU_REGS && !fail; i++) {
+		fail = (ucp->uc_mcontext.fp_regs[i + 14] != fps[i]);
+		fail |= (tm_ucp->uc_mcontext.fp_regs[i + 14] != fps[i + NV_FPU_REGS]);
+		if (fail)
+			printf("Failed on %d FP %g or %g\n", i, ucp->uc_mcontext.fp_regs[i + 14], tm_ucp->uc_mcontext.fp_regs[i + 14]);
+	}
+}
+
+static int tm_signal_context_chk_fpu()
+{
+	struct sigaction act;
+	int i;
+	long rc;
+	pid_t pid = getpid();
+
+	SKIP_IF(!have_htm());
+
+	act.sa_sigaction = signal_usr1;
+	sigemptyset(&act.sa_mask);
+	act.sa_flags = SA_SIGINFO;
+	if (sigaction(SIGUSR1, &act, NULL) < 0) {
+		perror("sigaction sigusr1");
+		exit(1);
+	}
+
+	i = 0;
+	while (i < MAX_ATTEMPT && !fail) {
+		rc = tm_signal_self_context_load(pid, NULL, fps, NULL, NULL);
+		FAIL_IF(rc != pid);
+		i++;
+	}
+
+	return fail;
+}
+
+int main(void)
+{
+	return test_harness(tm_signal_context_chk_fpu, "tm_signal_context_chk_fpu");
+}