/*
 * Copyright (C) 2013-2021 Canonical, Ltd.
 * Copyright (C) 2022-2026 Colin Ian King.
 *
 * 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.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 */
#include "stress-ng.h"
#include "core-mmap.h"
#include "core-put.h"
#include "core-signal.h"

static const stress_help_t help[] = {
	{ NULL,	"fault N",	"start N workers producing page faults" },
	{ NULL,	"fault-ops N",	"stop after N page fault bogo operations" },
	{ NULL,	NULL,		NULL }
};

#if defined(HAVE_SIGLONGJMP)

static sigjmp_buf jmp_env;
static volatile bool do_jmp = true;
static volatile int die_signum = -1;

/*
 *  stress_segvhandler()
 *	SEGV handler
 */
static void MLOCKED_TEXT stress_segvhandler(int signum)
{
	die_signum = signum;

	stress_signal_siglongjmp_flag(signum, jmp_env, 1, &do_jmp);
}

/*
 *  stress_fault()
 *	stress min and max page faulting
 */
static int stress_fault(stress_args_t *args)
{
#if defined(HAVE_GETRUSAGE) &&		\
    defined(RUSAGE_SELF) &&		\
    defined(HAVE_RUSAGE_RU_MINFLT)
	struct rusage usage;
#endif
	char filename[PATH_MAX];
	int ret;
	CLOBBERED int i;
	char *start;
	char *end;
	const size_t len = stress_exec_text_addr(&start, &end);
	const size_t page_size = args->page_size;
#if defined(SHIM_POSIX_FADV_DONTNEED) &&	\
    defined(HAVE_POSIX_FADVISE)
	const size_t file_size = page_size * 64;
#endif
	uint8_t buffer[page_size];
	void *mapto;
#if defined(HAVE_GETRUSAGE) &&		\
    defined(RUSAGE_SELF) &&		\
    defined(HAVE_RUSAGE_RU_MINFLT)
	double t1 = 0.0;
	double t2 = 0.0;
	double dt;
#endif
	CLOBBERED double duration = 0.0;
	CLOBBERED double count = 0.0;
	CLOBBERED int rc = EXIT_SUCCESS;

	stress_uint8rnd4(buffer, page_size);

	ret = stress_fs_temp_dir_make_args(args);
	if (ret < 0)
		return stress_exit_status(-ret);

	(void)stress_fs_temp_filename_args(args,
		filename, sizeof(filename), stress_mwc32());

	if (stress_signal_handler(args->name, SIGSEGV, stress_segvhandler, NULL) < 0)
		return EXIT_FAILURE;
	if (stress_signal_handler(args->name, SIGBUS, stress_segvhandler, NULL) < 0)
		return EXIT_FAILURE;

	mapto = mmap(NULL, page_size, PROT_READ,
		MAP_ANONYMOUS | MAP_SHARED, -1, 0);
	if (mapto != MAP_FAILED)
		stress_memory_anon_name_set(mapto, page_size, "mapping-ro-page");

	stress_proc_state_set(args->name, STRESS_STATE_SYNC_WAIT);
	stress_sync_start_wait(args);
	stress_proc_state_set(args->name, STRESS_STATE_RUN);

#if defined(HAVE_GETRUSAGE) &&		\
    defined(RUSAGE_SELF) &&		\
    defined(HAVE_RUSAGE_RU_MINFLT)
	t1 = stress_time_now();
#endif
	i = 0;
	do {
		int fd = -1;
		uint8_t *ptr;
		volatile uint8_t *vptr;
		double t;

		ret = sigsetjmp(jmp_env, 1);
		if (ret) {
			do_jmp = false;
			pr_fail("%s: unexpected %s, terminating early\n",
				args->name, stress_signal_str(die_signum));
			rc = EXIT_FAILURE;
			break;
		}

		fd = open(filename, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
		if (fd < 0) {
			if ((errno == ENOSPC) || (errno == ENOMEM))
				continue;	/* Try again */
			pr_fail("%s: open '%s' failed, errno=%d (%s)\n",
				args->name, filename, errno, strerror(errno));
			rc = EXIT_FAILURE;
			break;
		}

redo:
		if (stress_continue_flag() && (write(fd, buffer, sizeof(buffer)) < 0)) {
			if ((errno == EAGAIN) || (errno == EINTR))
				goto redo;
			if (errno == ENOSPC) {
				(void)close(fd);
				continue;
			}
			(void)close(fd);
			pr_fail("%s: write failed, errno=%d (%s)\n",
				args->name, errno, strerror(errno));
			rc = EXIT_FAILURE;
			break;
		}
#if defined(SHIM_POSIX_FADV_DONTNEED) &&	\
    defined(HAVE_POSIX_FADVISE)
		/* Force major page faults */
		(void)shim_fdatasync(fd);
		(void)posix_fadvise(fd, 0, file_size, SHIM_POSIX_FADV_DONTNEED);
#endif
		ret = sigsetjmp(jmp_env, 1);
		if (ret) {
			if (UNLIKELY(!stress_continue(args)))
				do_jmp = false;
			if (fd != -1)
				(void)close(fd);
			goto next;
		}

		/*
		 * Removing file here causes major fault when we touch
		 * ptr later
		 */
		if (i & 1)
			(void)shim_unlink(filename);
		ptr = (uint8_t *)mmap(NULL, page_size, PROT_READ | PROT_WRITE,
			MAP_SHARED, fd, 0);
		if (ptr == MAP_FAILED) {
			if ((errno == EAGAIN) ||
			    (errno == ENOMEM) ||
			    (errno == ENFILE)) {
				(void)close(fd);
				goto next;
			}
			pr_err("%s: mmap of a page failed%s, errno=%d (%s)\n",
				args->name, stress_memory_free_get(),
				errno, strerror(errno));
			(void)close(fd);
			break;

		}
		vptr = (volatile uint8_t *)ptr;
		stress_put_uint8(*vptr);

		(void)close(fd);
		t = stress_time_now();
		*vptr = 0xff;		/* Cause the page fault */
		duration += stress_time_now() - t;
		count += 1.0;

		stress_memory_anon_name_set(ptr, page_size, "page-fault-major");

#if defined(HAVE_MADVISE) &&	\
    defined(MADV_DONTNEED)
		if (madvise((void *)ptr, page_size, MADV_DONTNEED) == 0) {
			t = stress_time_now();
			*vptr ^= 0xff;	/* Cause the page fault */
			duration += stress_time_now() - t;
			count += 1.0;
		}
#endif

#if defined(HAVE_MADVISE) &&	\
    defined(MADV_PAGEOUT)
		if (madvise((void *)ptr, page_size, MADV_PAGEOUT) == 0) {
			t = stress_time_now();
			*vptr ^= 0xff;	/* Cause the page fault */
			duration += stress_time_now() - t;
			count += 1.0;
		}
#endif
		stress_put_uint8(*vptr);

		if (stress_munmap_force((void *)ptr, page_size) < 0) {
			pr_err("%s: munmap failed, errno=%d (%s)\n",
				args->name, errno, strerror(errno));
			break;
		}

next:
		/* Remove file on-non major fault case */
		if (!(i & 1))
			(void)shim_unlink(filename);

		/*
		 *  Force a minor page fault by remapping an existing
		 *  page in the text segment onto page mapto and then
		 *  force reading a byte from the start of the page.
		 */
		if (len > (page_size << 1)) {
			if (mapto != MAP_FAILED) {
				ptr = (uint8_t *)mmap(mapto, page_size, PROT_READ,
					MAP_ANONYMOUS | MAP_SHARED, -1, 0);
				if (ptr != MAP_FAILED) {
					stress_put_uint8(*ptr);
					stress_memory_anon_name_set(ptr, page_size, "page-fault-minor");
#if defined(HAVE_MADVISE) &&	\
    defined(MADV_DONTNEED)
					if (madvise((void *)ptr, page_size, MADV_DONTNEED) == 0) {
						t = stress_time_now();
						stress_put_uint8(*ptr);
						duration += stress_time_now() - t;
						count += 1.0;
					}
#endif
					(void)stress_munmap_force((void *)ptr, page_size);
				}
			}
		}
		i++;
		stress_bogo_inc(args);
	} while (stress_continue(args));

	(void)stress_signal_default_handler(SIGBUS);
	(void)stress_signal_default_handler(SIGSEGV);

#if defined(HAVE_GETRUSAGE) &&		\
    defined(RUSAGE_SELF) &&		\
    defined(HAVE_RUSAGE_RU_MINFLT)
	t2 = stress_time_now();
#endif
	/* Clean up, most times this is redundant */

	stress_proc_state_set(args->name, STRESS_STATE_DEINIT);

	if (mapto != MAP_FAILED)
		(void)munmap(mapto, page_size);
	(void)shim_unlink(filename);
	(void)stress_fs_temp_dir_rm_args(args);

#if defined(HAVE_GETRUSAGE) &&		\
    defined(RUSAGE_SELF) &&		\
    defined(HAVE_RUSAGE_RU_MINFLT)
	if (!shim_getrusage(RUSAGE_SELF, &usage)) {
		pr_dbg("%s: page faults: minor: %ld, major: %ld\n",
			args->name, usage.ru_minflt, usage.ru_majflt);
	}
	dt = t2 - t1;
	if (dt > 0.0) {
		double average_duration;

		stress_metrics_set(args, "minor page faults per sec",
			(double)usage.ru_minflt / dt, STRESS_METRIC_HARMONIC_MEAN);
		stress_metrics_set(args, "major page faults per sec",
			(double)usage.ru_majflt / dt, STRESS_METRIC_HARMONIC_MEAN);
		average_duration = (count > 0.0) ? duration / count : 0.0;
		stress_metrics_set(args, "nanosecs per page fault",
			average_duration * STRESS_DBL_NANOSECOND, STRESS_METRIC_HARMONIC_MEAN);
	}
#endif
	return rc;
}

static const stress_exercises_t exercises[] = {
	STRESS_EX_FEATURE("io-read"),
	STRESS_EX_FEATURE("io-write"),

	STRESS_EX_SYSCALL("mmap"),
	STRESS_EX_SYSCALL("munmap"),
#if defined(HAVE_MADVISE) &&	\
    (defined(MADV_DONTNEED) || defined(MADV_PAGEOUT))
	STRESS_EX_SYSCALL("madvise"),
#endif
	STRESS_EX_END,
};

const stressor_info_t stress_fault_info = {
	.stressor = stress_fault,
	.classifier = CLASS_INTERRUPT | CLASS_OS,
	.help = help,
	.exercises = exercises,
};

#else

const stressor_info_t stress_fault_info = {
	.stressor = stress_unimplemented,
	.classifier = CLASS_INTERRUPT | CLASS_OS,
	.help = help,
	.unimplemented_reason = "built without siglongjmp support"
};

#endif
