selftests: breakpoint: add step_after_suspend_test

Commit e56d82a11617 ("arm64: cpu hotplug: ensure we mask out
CPU_TASKS_FROZEN in notifiers") fixed a long-standing ARM64 bug that
broke single-stepping after a suspend/resume cycle. Add a kernel
selftest to make sure this doesn't regress or affect other platforms.

Signed-off-by: Greg Hackmann <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/breakpoints/Makefile

···
 TEST_PROGS := breakpoint_test
 endif
 
+TEST_PROGS += step_after_suspend_test
+
 all: $(TEST_PROGS)
 
 include ../lib.mk
 
 clean:
-	rm -fr breakpoint_test
+	rm -fr breakpoint_test step_after_suspend_test

tools/testing/selftests/breakpoints/step_after_suspend_test.c

···
+/*
+ * Copyright (C) 2016 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/ptrace.h>
+#include <sys/stat.h>
+#include <sys/timerfd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include "../kselftest.h"
+
+void child(int cpu)
+{
+	cpu_set_t set;
+
+	CPU_ZERO(&set);
+	CPU_SET(cpu, &set);
+	if (sched_setaffinity(0, sizeof(set), &set) != 0) {
+		perror("sched_setaffinity() failed");
+		_exit(1);
+	}
+
+	if (ptrace(PTRACE_TRACEME, 0, NULL, NULL) != 0) {
+		perror("ptrace(PTRACE_TRACEME) failed");
+		_exit(1);
+	}
+
+	if (raise(SIGSTOP) != 0) {
+		perror("raise(SIGSTOP) failed");
+		_exit(1);
+	}
+
+	_exit(0);
+}
+
+bool run_test(int cpu)
+{
+	int status;
+	pid_t pid = fork();
+	pid_t wpid;
+
+	if (pid < 0) {
+		perror("fork() failed");
+		return false;
+	}
+	if (pid == 0)
+		child(cpu);
+
+	wpid = waitpid(pid, &status, __WALL);
+	if (wpid != pid) {
+		perror("waitpid() failed");
+		return false;
+	}
+	if (!WIFSTOPPED(status)) {
+		printf("child did not stop\n");
+		return false;
+	}
+	if (WSTOPSIG(status) != SIGSTOP) {
+		printf("child did not stop with SIGSTOP\n");
+		return false;
+	}
+
+	if (ptrace(PTRACE_SINGLESTEP, pid, NULL, NULL) < 0) {
+		if (errno == EIO) {
+			printf("ptrace(PTRACE_SINGLESTEP) not supported on this architecture\n");
+			ksft_exit_skip();
+		}
+		perror("ptrace(PTRACE_SINGLESTEP) failed");
+		return false;
+	}
+
+	wpid = waitpid(pid, &status, __WALL);
+	if (wpid != pid) {
+		perror("waitpid() failed");
+		return false;
+	}
+	if (WIFEXITED(status)) {
+		printf("child did not single-step\n");
+		return false;
+	}
+	if (!WIFSTOPPED(status)) {
+		printf("child did not stop\n");
+		return false;
+	}
+	if (WSTOPSIG(status) != SIGTRAP) {
+		printf("child did not stop with SIGTRAP\n");
+		return false;
+	}
+
+	if (ptrace(PTRACE_CONT, pid, NULL, NULL) < 0) {
+		perror("ptrace(PTRACE_CONT) failed");
+		return false;
+	}
+
+	wpid = waitpid(pid, &status, __WALL);
+	if (wpid != pid) {
+		perror("waitpid() failed");
+		return false;
+	}
+	if (!WIFEXITED(status)) {
+		printf("child did not exit after PTRACE_CONT\n");
+		return false;
+	}
+
+	return true;
+}
+
+void suspend(void)
+{
+	int power_state_fd;
+	struct sigevent event = {};
+	int timerfd;
+	int err;
+	struct itimerspec spec = {};
+
+	power_state_fd = open("/sys/power/state", O_RDWR);
+	if (power_state_fd < 0) {
+		perror("open(\"/sys/power/state\") failed (is this test running as root?)");
+		ksft_exit_fail();
+	}
+
+	timerfd = timerfd_create(CLOCK_BOOTTIME_ALARM, 0);
+	if (timerfd < 0) {
+		perror("timerfd_create() failed");
+		ksft_exit_fail();
+	}
+
+	spec.it_value.tv_sec = 5;
+	err = timerfd_settime(timerfd, 0, &spec, NULL);
+	if (err < 0) {
+		perror("timerfd_settime() failed");
+		ksft_exit_fail();
+	}
+
+	if (write(power_state_fd, "mem", strlen("mem")) != strlen("mem")) {
+		perror("entering suspend failed");
+		ksft_exit_fail();
+	}
+
+	close(timerfd);
+	close(power_state_fd);
+}
+
+int main(int argc, char **argv)
+{
+	int opt;
+	bool do_suspend = true;
+	bool succeeded = true;
+	cpu_set_t available_cpus;
+	int err;
+	int cpu;
+
+	while ((opt = getopt(argc, argv, "n")) != -1) {
+		switch (opt) {
+		case 'n':
+			do_suspend = false;
+			break;
+		default:
+			printf("Usage: %s [-n]\n", argv[0]);
+			printf("        -n: do not trigger a suspend/resume cycle before the test\n");
+			return -1;
+		}
+	}
+
+	if (do_suspend)
+		suspend();
+
+	err = sched_getaffinity(0, sizeof(available_cpus), &available_cpus);
+	if (err < 0) {
+		perror("sched_getaffinity() failed");
+		ksft_exit_fail();
+	}
+
+	for (cpu = 0; cpu < CPU_SETSIZE; cpu++) {
+		bool test_success;
+
+		if (!CPU_ISSET(cpu, &available_cpus))
+			continue;
+
+		test_success = run_test(cpu);
+		printf("CPU %d: ", cpu);
+		if (test_success) {
+			printf("[OK]\n");
+			ksft_inc_pass_cnt();
+		} else {
+			printf("[FAILED]\n");
+			ksft_inc_fail_cnt();
+			succeeded = false;
+		}
+	}
+
+	ksft_print_cnts();
+	if (succeeded)
+		ksft_exit_pass();
+	else
+		ksft_exit_fail();
+}