kernel/power/hibernate.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * kernel/power/hibernate.c - Hibernation (a.k.a suspend-to-disk) support.
 *
 * Copyright (c) 2003 Patrick Mochel
 * Copyright (c) 2003 Open Source Development Lab
 * Copyright (c) 2004 Pavel Machek <pavel@ucw.cz>
 * Copyright (c) 2009 Rafael J. Wysocki, Novell Inc.
 * Copyright (C) 2012 Bojan Smojver <bojan@rexursive.com>
 */

#define pr_fmt(fmt) "PM: hibernation: " fmt

#include <linux/export.h>
#include <linux/suspend.h>
#include <linux/reboot.h>
#include <linux/string.h>
#include <linux/device.h>
#include <linux/async.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/pm.h>
#include <linux/nmi.h>
#include <linux/console.h>
#include <linux/cpu.h>
#include <linux/freezer.h>
#include <linux/gfp.h>
#include <linux/syscore_ops.h>
#include <linux/ctype.h>
#include <linux/genhd.h>
#include <linux/ktime.h>
#include <linux/security.h>
#include <trace/events/power.h>

#include "power.h"

#define HIBERNATE_TWO 2
#define HIBERNATE_EIGHT 8
#define HIBERNATE_TEN 10
#define HIBERNATE_THIRTEEN 13
#define HIBERNATE_ONEHUNDRED 100
#define HIBERNATE_TWOHUNDREDFIFTYFIVE 255
#define HIBERNATE_TWOHUNDREDFIFTYSIX 256
#define HIBERNATE_ONETHOUSAND 1000
#define HIBERNATE_ONETHOUSANDTWENTYFOUR 1024
#define HIBERNATE_FIVETHOUSAND 5000

static int nocompress;
static int noresume;
static int nohibernate;
static int resume_wait;
static unsigned int resume_delay;
static char resume_file[HIBERNATE_TWOHUNDREDFIFTYSIX] = CONFIG_PM_STD_PARTITION;
dev_t swsusp_resume_device;
sector_t swsusp_resume_block;
__visible int in_suspend __nosavedata;

enum {
    HIBERNATION_INVALID,
    HIBERNATION_PLATFORM,
    HIBERNATION_SHUTDOWN,
    HIBERNATION_REBOOT,
#ifdef CONFIG_SUSPEND
    HIBERNATION_SUSPEND,
#endif
    HIBERNATION_TEST_RESUME,
    /* keep last */
    __HIBERNATION_AFTER_LAST
};
#define HIBERNATION_MAX (__HIBERNATION_AFTER_LAST - 1)
#define HIBERNATION_FIRST (HIBERNATION_INVALID + 1)

static int hibernation_mode = HIBERNATION_SHUTDOWN;

bool freezer_test_done;

static const struct platform_hibernation_ops *hibernation_ops;

static atomic_t hibernate_atomic = ATOMIC_INIT(1);

bool hibernate_acquire(void)
{
    return atomic_add_unless(&hibernate_atomic, -1, 0);
}

void hibernate_release(void)
{
    atomic_inc(&hibernate_atomic);
}

bool hibernation_available(void)
{
    return nohibernate == 0 && !security_locked_down(LOCKDOWN_HIBERNATION);
}

/**
 * hibernation_set_ops - Set the global hibernate operations.
 * @ops: Hibernation operations to use in subsequent hibernation transitions.
 */
void hibernation_set_ops(const struct platform_hibernation_ops *ops)
{
    if (ops && !(ops->begin && ops->end && ops->pre_snapshot && ops->prepare && ops->finish && ops->enter &&
                 ops->pre_restore && ops->restore_cleanup && ops->leave)) {
        WARN_ON(1);
        return;
    }
    lock_system_sleep();
    hibernation_ops = ops;
    if (ops) {
        hibernation_mode = HIBERNATION_PLATFORM;
    } else if (hibernation_mode == HIBERNATION_PLATFORM) {
        hibernation_mode = HIBERNATION_SHUTDOWN;
    }

    unlock_system_sleep();
}
EXPORT_SYMBOL_GPL(hibernation_set_ops);

static bool entering_platform_hibernation;

bool system_entering_hibernation(void)
{
    return entering_platform_hibernation;
}
EXPORT_SYMBOL(system_entering_hibernation);

#ifdef CONFIG_PM_DEBUG
static void hibernation_debug_sleep(void)
{
    pr_info("debug: Waiting for 5 seconds.\n");
    mdelay(HIBERNATE_FIVETHOUSAND);
}

static int hibernation_test(int level)
{
    if (pm_test_level == level) {
        hibernation_debug_sleep();
        return 1;
    }
    return 0;
}
#else  /* !CONFIG_PM_DEBUG */
static int hibernation_test(int level)
{
    return 0;
}
#endif /* !CONFIG_PM_DEBUG */

/**
 * platform_begin - Call platform to start hibernation.
 * @platform_mode: Whether or not to use the platform driver.
 */
static int platform_begin(int platform_mode)
{
    return (platform_mode && hibernation_ops) ? hibernation_ops->begin(PMSG_FREEZE) : 0;
}

/**
 * platform_end - Call platform to finish transition to the working state.
 * @platform_mode: Whether or not to use the platform driver.
 */
static void platform_end(int platform_mode)
{
    if (platform_mode && hibernation_ops) {
        hibernation_ops->end();
    }
}

/**
 * platform_pre_snapshot - Call platform to prepare the machine for hibernation.
 * @platform_mode: Whether or not to use the platform driver.
 *
 * Use the platform driver to prepare the system for creating a hibernate image,
 * if so configured, and return an error code if that fails.
 */

static int platform_pre_snapshot(int platform_mode)
{
    return (platform_mode && hibernation_ops) ? hibernation_ops->pre_snapshot() : 0;
}

/**
 * platform_leave - Call platform to prepare a transition to the working state.
 * @platform_mode: Whether or not to use the platform driver.
 *
 * Use the platform driver prepare to prepare the machine for switching to the
 * normal mode of operation.
 *
 * This routine is called on one CPU with interrupts disabled.
 */
static void platform_leave(int platform_mode)
{
    if (platform_mode && hibernation_ops) {
        hibernation_ops->leave();
    }
}

/**
 * platform_finish - Call platform to switch the system to the working state.
 * @platform_mode: Whether or not to use the platform driver.
 *
 * Use the platform driver to switch the machine to the normal mode of
 * operation.
 *
 * This routine must be called after platform_prepare().
 */
static void platform_finish(int platform_mode)
{
    if (platform_mode && hibernation_ops) {
        hibernation_ops->finish();
    }
}

/**
 * platform_pre_restore - Prepare for hibernate image restoration.
 * @platform_mode: Whether or not to use the platform driver.
 *
 * Use the platform driver to prepare the system for resume from a hibernation
 * image.
 *
 * If the restore fails after this function has been called,
 * platform_restore_cleanup() must be called.
 */
static int platform_pre_restore(int platform_mode)
{
    return (platform_mode && hibernation_ops) ? hibernation_ops->pre_restore() : 0;
}

/**
 * platform_restore_cleanup - Switch to the working state after failing restore.
 * @platform_mode: Whether or not to use the platform driver.
 *
 * Use the platform driver to switch the system to the normal mode of operation
 * after a failing restore.
 *
 * If platform_pre_restore() has been called before the failing restore, this
 * function must be called too, regardless of the result of
 * platform_pre_restore().
 */
static void platform_restore_cleanup(int platform_mode)
{
    if (platform_mode && hibernation_ops) {
        hibernation_ops->restore_cleanup();
    }
}

/**
 * platform_recover - Recover from a failure to suspend devices.
 * @platform_mode: Whether or not to use the platform driver.
 */
static void platform_recover(int platform_mode)
{
    if (platform_mode && hibernation_ops && hibernation_ops->recover) {
        hibernation_ops->recover();
    }
}

/**
 * swsusp_show_speed - Print time elapsed between two events during hibernation.
 * @start: Starting event.
 * @stop: Final event.
 * @nr_pages: Number of memory pages processed between @start and @stop.
 * @msg: Additional diagnostic message to print.
 */
void swsusp_show_speed(ktime_t start, ktime_t stop, unsigned nr_pages, char *msg)
{
    ktime_t diff;
    u64 elapsed_centisecs64;
    unsigned int centisecs;
    unsigned int k;
    unsigned int kps;

    diff = ktime_sub(stop, start);
    elapsed_centisecs64 = ktime_divns(diff, HIBERNATE_TEN * NSEC_PER_MSEC);
    centisecs = elapsed_centisecs64;
    if (centisecs == 0) {
        centisecs = 1; /* avoid div-by-zero */
    }
    k = nr_pages * (PAGE_SIZE / HIBERNATE_ONETHOUSANDTWENTYFOUR);
    kps = (k * HIBERNATE_ONEHUNDRED) / centisecs;
    pr_info("%s %u kbytes in %u.%02u seconds (%u.%02u MB/s)\n", msg, k, centisecs / HIBERNATE_ONEHUNDRED,
            centisecs % HIBERNATE_ONEHUNDRED, kps / HIBERNATE_ONETHOUSAND,
            (kps % HIBERNATE_ONETHOUSAND) / HIBERNATE_TEN);
}

__weak int arch_resume_nosmt(void)
{
    return 0;
}

/**
 * create_image - Create a hibernation image.
 * @platform_mode: Whether or not to use the platform driver.
 *
 * Execute device drivers' "late" and "noirq" freeze callbacks, create a
 * hibernation image and run the drivers' "noirq" and "early" thaw callbacks.
 *
 * Control reappears in this routine after the subsequent restore.
 */
static int create_image(int platform_mode)
{
    int error;

    error = dpm_suspend_end(PMSG_FREEZE);
    if (error) {
        pr_err("Some devices failed to power down, aborting\n");
        return error;
    }

    error = platform_pre_snapshot(platform_mode);
    if (error || hibernation_test(TEST_PLATFORM)) {
        goto Platform_finish;
    }

    error = suspend_disable_secondary_cpus();
    if (error || hibernation_test(TEST_CPUS)) {
        goto Enable_cpus;
    }

    local_irq_disable();

    system_state = SYSTEM_SUSPEND;

    error = syscore_suspend();
    if (error) {
        pr_err("Some system devices failed to power down, aborting\n");
        goto Enable_irqs;
    }

    if (hibernation_test(TEST_CORE) || pm_wakeup_pending()) {
        goto Power_up;
    }

    in_suspend = 1;
    save_processor_state();
    trace_suspend_resume(TPS("machine_suspend"), PM_EVENT_HIBERNATE, true);
    error = swsusp_arch_suspend();
    /* Restore control flow magically appears here */
    restore_processor_state();
    trace_suspend_resume(TPS("machine_suspend"), PM_EVENT_HIBERNATE, false);
    if (error) {
        pr_err("Error %d creating image\n", error);
    }

    if (!in_suspend) {
        events_check_enabled = false;
        clear_or_poison_free_pages();
    }

    platform_leave(platform_mode);

Power_up:
    syscore_resume();

Enable_irqs:
    system_state = SYSTEM_RUNNING;
    local_irq_enable();

Enable_cpus:
    suspend_enable_secondary_cpus();

    /* Allow architectures to do nosmt-specific post-resume dances */
    if (!in_suspend) {
        error = arch_resume_nosmt();
    }

Platform_finish:
    platform_finish(platform_mode);

    dpm_resume_start(in_suspend ? (error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE);

    return error;
}

/**
 * hibernation_snapshot - Quiesce devices and create a hibernation image.
 * @platform_mode: If set, use platform driver to prepare for the transition.
 *
 * This routine must be called with system_transition_mutex held.
 */
int hibernation_snapshot(int platform_mode)
{
    pm_message_t msg;
    int error;

    pm_suspend_clear_flags();
    error = platform_begin(platform_mode);
    if (error) {
        goto Close;
    }

    /* Preallocate image memory before shutting down devices. */
    error = hibernate_preallocate_memory();
    if (error) {
        goto Close;
    }

    error = freeze_kernel_threads();
    if (error) {
        goto Cleanup;
    }

    if (hibernation_test(TEST_FREEZER)) {
        /*
         * Indicate to the caller that we are returning due to a
         * successful freezer test.
         */
        freezer_test_done = true;
        goto Thaw;
    }

    error = dpm_prepare(PMSG_FREEZE);
    if (error) {
        dpm_complete(PMSG_RECOVER);
        goto Thaw;
    }

    suspend_console();
    pm_restrict_gfp_mask();

    error = dpm_suspend(PMSG_FREEZE);
    if (error || hibernation_test(TEST_DEVICES)) {
        platform_recover(platform_mode);
    } else {
        error = create_image(platform_mode);
    }

    /*
     * In the case that we call create_image() above, the control
     * returns here (1) after the image has been created or the
     * image creation has failed and (2) after a successful restore.
     */

    /* We may need to release the preallocated image pages here. */
    if (error || !in_suspend) {
        swsusp_free();
    }

    msg = in_suspend ? (error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE;
    dpm_resume(msg);

    if (error || !in_suspend) {
        pm_restore_gfp_mask();
    }

    resume_console();
    dpm_complete(msg);

Close:
    platform_end(platform_mode);
    return error;

Thaw:
    thaw_kernel_threads();
Cleanup:
    swsusp_free();
    platform_end(platform_mode);
    return error;
}

int __weak hibernate_resume_nonboot_cpu_disable(void)
{
    return suspend_disable_secondary_cpus();
}

/**
 * resume_target_kernel - Restore system state from a hibernation image.
 * @platform_mode: Whether or not to use the platform driver.
 *
 * Execute device drivers' "noirq" and "late" freeze callbacks, restore the
 * contents of highmem that have not been restored yet from the image and run
 * the low-level code that will restore the remaining contents of memory and
 * switch to the just restored target kernel.
 */
static int resume_target_kernel(bool platform_mode)
{
    int error;

    error = dpm_suspend_end(PMSG_QUIESCE);
    if (error) {
        pr_err("Some devices failed to power down, aborting resume\n");
        return error;
    }

    error = platform_pre_restore(platform_mode);
    if (error) {
        goto Cleanup;
    }

    error = hibernate_resume_nonboot_cpu_disable();
    if (error) {
        goto Enable_cpus;
    }

    local_irq_disable();
    system_state = SYSTEM_SUSPEND;

    error = syscore_suspend();
    if (error) {
        goto Enable_irqs;
    }

    save_processor_state();
    error = restore_highmem();
    if (!error) {
        error = swsusp_arch_resume();
        /*
         * The code below is only ever reached in case of a failure.
         * Otherwise, execution continues at the place where
         * swsusp_arch_suspend() was called.
         */
        BUG_ON(!error);
        /*
         * This call to restore_highmem() reverts the changes made by
         * the previous one.
         */
        restore_highmem();
    }
    /*
     * The only reason why swsusp_arch_resume() can fail is memory being
     * very tight, so we have to free it as soon as we can to avoid
     * subsequent failures.
     */
    swsusp_free();
    restore_processor_state();
    touch_softlockup_watchdog();

    syscore_resume();

Enable_irqs:
    system_state = SYSTEM_RUNNING;
    local_irq_enable();

Enable_cpus:
    suspend_enable_secondary_cpus();

Cleanup:
    platform_restore_cleanup(platform_mode);

    dpm_resume_start(PMSG_RECOVER);

    return error;
}

/**
 * hibernation_restore - Quiesce devices and restore from a hibernation image.
 * @platform_mode: If set, use platform driver to prepare for the transition.
 *
 * This routine must be called with system_transition_mutex held.  If it is
 * successful, control reappears in the restored target kernel in
 * hibernation_snapshot().
 */
int hibernation_restore(int platform_mode)
{
    int error;

    pm_prepare_console();
    suspend_console();
    pm_restrict_gfp_mask();
    error = dpm_suspend_start(PMSG_QUIESCE);
    if (!error) {
        error = resume_target_kernel(platform_mode);
        /*
         * The above should either succeed and jump to the new kernel,
         * or return with an error. Otherwise things are just
         * undefined, so let's be paranoid.
         */
        BUG_ON(!error);
    }
    dpm_resume_end(PMSG_RECOVER);
    pm_restore_gfp_mask();
    resume_console();
    pm_restore_console();
    return error;
}

/**
 * hibernation_platform_enter - Power off the system using the platform driver.
 */
int hibernation_platform_enter(void)
{
    int error;

    if (!hibernation_ops) {
        return -ENOSYS;
    }

    /*
     * We have cancelled the power transition by running
     * hibernation_ops->finish() before saving the image, so we should let
     * the firmware know that we're going to enter the sleep state after all
     */
    error = hibernation_ops->begin(PMSG_HIBERNATE);
    if (error) {
        goto Close;
    }

    entering_platform_hibernation = true;
    suspend_console();
    error = dpm_suspend_start(PMSG_HIBERNATE);
    if (error) {
        if (hibernation_ops->recover) {
            hibernation_ops->recover();
        }
        goto Resume_devices;
    }

    error = dpm_suspend_end(PMSG_HIBERNATE);
    if (error) {
        goto Resume_devices;
    }

    error = hibernation_ops->prepare();
    if (error) {
        goto Platform_finish;
    }

    error = suspend_disable_secondary_cpus();
    if (error) {
        goto Enable_cpus;
    }

    local_irq_disable();
    system_state = SYSTEM_SUSPEND;
    syscore_suspend();
    if (pm_wakeup_pending()) {
        error = -EAGAIN;
        goto Power_up;
    }

    hibernation_ops->enter();
    /* We should never get here */
    while (1) {
        ;
    }

Power_up:
    syscore_resume();
    system_state = SYSTEM_RUNNING;
    local_irq_enable();

Enable_cpus:
    suspend_enable_secondary_cpus();

Platform_finish:
    hibernation_ops->finish();

    dpm_resume_start(PMSG_RESTORE);

Resume_devices:
    entering_platform_hibernation = false;
    dpm_resume_end(PMSG_RESTORE);
    resume_console();

Close:
    hibernation_ops->end();

    return error;
}

/**
 * power_down - Shut the machine down for hibernation.
 *
 * Use the platform driver, if configured, to put the system into the sleep
 * state corresponding to hibernation, or try to power it off or reboot,
 * depending on the value of hibernation_mode.
 */
static void power_down(void)
{
#ifdef CONFIG_SUSPEND
    int error;

    if (hibernation_mode == HIBERNATION_SUSPEND) {
        error = suspend_devices_and_enter(PM_SUSPEND_MEM);
        if (error) {
            hibernation_mode = hibernation_ops ? HIBERNATION_PLATFORM : HIBERNATION_SHUTDOWN;
        } else {
            /* Restore swap signature. */
            error = swsusp_unmark();
            if (error) {
                pr_err("Swap will be unusable! Try swapon -a.\n");
            }

            return;
        }
    }
#endif

    switch (hibernation_mode) {
        case HIBERNATION_REBOOT:
            kernel_restart(NULL);
            break;
        case HIBERNATION_PLATFORM:
            hibernation_platform_enter();
            fallthrough;
        case HIBERNATION_SHUTDOWN:
            if (pm_power_off) {
                kernel_power_off();
            }
            break;
    }
    kernel_halt();
    /*
     * Valid image is on the disk, if we continue we risk serious data
     * corruption after resume.
     */
    pr_crit("Power down manually\n");
    while (1) {
        cpu_relax();
    }
}

static int load_image_and_restore(void)
{
    int error;
    unsigned int flags;

    pm_pr_dbg("Loading hibernation image.\n");

    lock_device_hotplug();
    error = create_basic_memory_bitmaps();
    if (error) {
        goto Unlock;
    }

    error = swsusp_read(&flags);
    swsusp_close(FMODE_READ | FMODE_EXCL);
    if (!error) {
        error = hibernation_restore(flags & SF_PLATFORM_MODE);
    }

    pr_err("Failed to load image, recovering.\n");
    swsusp_free();
    free_basic_memory_bitmaps();
Unlock:
    unlock_device_hotplug();

    return error;
}

/**
 * hibernate - Carry out system hibernation, including saving the image.
 */
int hibernate(void)
{
    bool snapshot_test = false;
    int error;

    if (!hibernation_available()) {
        pm_pr_dbg("Hibernation not available.\n");
        return -EPERM;
    }

    lock_system_sleep();
    /* The snapshot device should not be opened while we're running */
    if (!hibernate_acquire()) {
        error = -EBUSY;
        goto Unlock;
    }

    pr_info("hibernation entry\n");
    pm_prepare_console();
    error = pm_notifier_call_chain_robust(PM_HIBERNATION_PREPARE, PM_POST_HIBERNATION);
    if (error) {
        goto Restore;
    }

    ksys_sync_helper();

    error = freeze_processes();
    if (error) {
        goto Exit;
    }

    lock_device_hotplug();
    /* Allocate memory management structures */
    error = create_basic_memory_bitmaps();
    if (error) {
        goto Thaw;
    }

    error = hibernation_snapshot(hibernation_mode == HIBERNATION_PLATFORM);
    if (error || freezer_test_done) {
        goto Free_bitmaps;
    }

    if (in_suspend) {
        unsigned int flags = 0;

        if (hibernation_mode == HIBERNATION_PLATFORM) {
            flags |= SF_PLATFORM_MODE;
        }
        if (nocompress) {
            flags |= SF_NOCOMPRESS_MODE;
        } else {
            flags |= SF_CRC32_MODE;
        }

        pm_pr_dbg("Writing hibernation image.\n");
        error = swsusp_write(flags);
        swsusp_free();
        if (!error) {
            if (hibernation_mode == HIBERNATION_TEST_RESUME) {
                snapshot_test = true;
            } else {
                power_down();
            }
        }
        in_suspend = 0;
        pm_restore_gfp_mask();
    } else {
        pm_pr_dbg("Hibernation image restored successfully.\n");
    }

Free_bitmaps:
    free_basic_memory_bitmaps();
Thaw:
    unlock_device_hotplug();
    if (snapshot_test) {
        pm_pr_dbg("Checking hibernation image\n");
        error = swsusp_check();
        if (!error) {
            error = load_image_and_restore();
        }
    }
    thaw_processes();

    /* Don't bother checking whether freezer_test_done is true */
    freezer_test_done = false;
Exit:
    pm_notifier_call_chain(PM_POST_HIBERNATION);
Restore:
    pm_restore_console();
    hibernate_release();
Unlock:
    unlock_system_sleep();
    pr_info("hibernation exit\n");

    return error;
}

/**
 * hibernate_quiet_exec - Execute a function with all devices frozen.
 * @func: Function to execute.
 * @data: Data pointer to pass to @func.
 *
 * Return the @func return value or an error code if it cannot be executed.
 */
int hibernate_quiet_exec(int (*func)(void *data), void *data)
{
    int error;

    lock_system_sleep();

    if (!hibernate_acquire()) {
        error = -EBUSY;
        goto unlock;
    }

    pm_prepare_console();

    error = pm_notifier_call_chain_robust(PM_HIBERNATION_PREPARE, PM_POST_HIBERNATION);
    if (error) {
        goto restore;
    }

    error = freeze_processes();
    if (error) {
        goto exit;
    }

    lock_device_hotplug();

    pm_suspend_clear_flags();

    error = platform_begin(true);
    if (error) {
        goto thaw;
    }

    error = freeze_kernel_threads();
    if (error) {
        goto thaw;
    }

    error = dpm_prepare(PMSG_FREEZE);
    if (error) {
        goto dpm_complete;
    }

    suspend_console();

    error = dpm_suspend(PMSG_FREEZE);
    if (error) {
        goto dpm_resume;
    }

    error = dpm_suspend_end(PMSG_FREEZE);
    if (error) {
        goto dpm_resume;
    }

    error = platform_pre_snapshot(true);
    if (error) {
        goto skip;
    }

    error = func(data);

skip:
    platform_finish(true);

    dpm_resume_start(PMSG_THAW);

dpm_resume:
    dpm_resume(PMSG_THAW);

    resume_console();

dpm_complete:
    dpm_complete(PMSG_THAW);

    thaw_kernel_threads();

thaw:
    platform_end(true);

    unlock_device_hotplug();

    thaw_processes();

exit:
    pm_notifier_call_chain(PM_POST_HIBERNATION);

restore:
    pm_restore_console();

    hibernate_release();

unlock:
    unlock_system_sleep();

    return error;
}
EXPORT_SYMBOL_GPL(hibernate_quiet_exec);

/**
 * software_resume - Resume from a saved hibernation image.
 *
 * This routine is called as a late initcall, when all devices have been
 * discovered and initialized already.
 *
 * The image reading code is called to see if there is a hibernation image
 * available for reading.  If that is the case, devices are quiesced and the
 * contents of memory is restored from the saved image.
 *
 * If this is successful, control reappears in the restored target kernel in
 * hibernation_snapshot() which returns to hibernate().  Otherwise, the routine
 * attempts to recover gracefully and make the kernel return to the normal mode
 * of operation.
 */
static int software_resume(void)
{
    int error;

    /*
     * If the user said "noresume".. bail out early.
     */
    if (noresume || !hibernation_available()) {
        return 0;
    }

    /*
     * name_to_dev_t() below takes a sysfs buffer mutex when sysfs
     * is configured into the kernel. Since the regular hibernate
     * trigger path is via sysfs which takes a buffer mutex before
     * calling hibernate functions (which take system_transition_mutex)
     * this can cause lockdep to complain about a possible ABBA deadlock
     * which cannot happen since we're in the boot code here and
     * sysfs can't be invoked yet. Therefore, we use a subclass
     * here to avoid lockdep complaining.
     */
    mutex_lock_nested(&system_transition_mutex, SINGLE_DEPTH_NESTING);

    if (swsusp_resume_device) {
        goto Check_image;
    }

    if (!strlen(resume_file)) {
        error = -ENOENT;
        goto Unlock;
    }

    pm_pr_dbg("Checking hibernation image partition %s\n", resume_file);

    if (resume_delay) {
        pr_info("Waiting %dsec before reading resume device ...\n", resume_delay);
        ssleep(resume_delay);
    }

    /* Check if the device is there */
    swsusp_resume_device = name_to_dev_t(resume_file);
    if (!swsusp_resume_device) {
        /*
         * Some device discovery might still be in progress; we need
         * to wait for this to finish.
         */
        wait_for_device_probe();

        if (resume_wait) {
            while ((swsusp_resume_device = name_to_dev_t(resume_file)) == 0) {
                msleep(HIBERNATE_TEN);
            }
            async_synchronize_full();
        }

        swsusp_resume_device = name_to_dev_t(resume_file);
        if (!swsusp_resume_device) {
            error = -ENODEV;
            goto Unlock;
        }
    }

Check_image:
    pm_pr_dbg("Hibernation image partition %d:%d present\n", MAJOR(swsusp_resume_device), MINOR(swsusp_resume_device));

    pm_pr_dbg("Looking for hibernation image.\n");
    error = swsusp_check();
    if (error) {
        goto Unlock;
    }

    /* The snapshot device should not be opened while we're running */
    if (!hibernate_acquire()) {
        error = -EBUSY;
        swsusp_close(FMODE_READ | FMODE_EXCL);
        goto Unlock;
    }

    pr_info("resume from hibernation\n");
    pm_prepare_console();
    error = pm_notifier_call_chain_robust(PM_RESTORE_PREPARE, PM_POST_RESTORE);
    if (error) {
        goto Restore;
    }

    pm_pr_dbg("Preparing processes for hibernation restore.\n");
    error = freeze_processes();
    if (error) {
        swsusp_close(FMODE_READ | FMODE_EXCL);
        goto Finish;
    }

    error = freeze_kernel_threads();
    if (error) {
        thaw_processes();
        swsusp_close(FMODE_READ | FMODE_EXCL);
        goto Finish;
    }

    error = load_image_and_restore();
    thaw_processes();
Finish:
    pm_notifier_call_chain(PM_POST_RESTORE);
Restore:
    pm_restore_console();
    pr_info("resume failed (%d)\n", error);
    hibernate_release();
    /* For success case, the suspend path will release the lock */
Unlock:
    mutex_unlock(&system_transition_mutex);
    pm_pr_dbg("Hibernation image not present or could not be loaded.\n");
    return error;
}

late_initcall_sync(software_resume);

static const char *const hibernation_modes[] = {
    [HIBERNATION_PLATFORM] = "platform",       [HIBERNATION_SHUTDOWN] = "shutdown", [HIBERNATION_REBOOT] = "reboot",
#ifdef CONFIG_SUSPEND
    [HIBERNATION_SUSPEND] = "suspend",
#endif
    [HIBERNATION_TEST_RESUME] = "test_resume",
};

/*
 * /sys/power/disk - Control hibernation mode.
 *
 * Hibernation can be handled in several ways.  There are a few different ways
 * to put the system into the sleep state: using the platform driver (e.g. ACPI
 * or other hibernation_ops), powering it off or rebooting it (for testing
 * mostly).
 *
 * The sysfs file /sys/power/disk provides an interface for selecting the
 * hibernation mode to use.  Reading from this file causes the available modes
 * to be printed.  There are 3 modes that can be supported:
 *
 *    'platform'
 *    'shutdown'
 *    'reboot'
 *
 * If a platform hibernation driver is in use, 'platform' will be supported
 * and will be used by default.  Otherwise, 'shutdown' will be used by default.
 * The selected option (i.e. the one corresponding to the current value of
 * hibernation_mode) is enclosed by a square bracket.
 *
 * To select a given hibernation mode it is necessary to write the mode's
 * string representation (as returned by reading from /sys/power/disk) back
 * into /sys/power/disk.
 */

static ssize_t disk_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
{
    int i;
    char *start = buf;

    if (!hibernation_available()) {
        return sprintf(buf, "[disabled]\n");
    }

    for (i = HIBERNATION_FIRST; i <= HIBERNATION_MAX; i++) {
        if (!hibernation_modes[i]) {
            continue;
        }
        switch (i) {
            case HIBERNATION_SHUTDOWN:
            case HIBERNATION_REBOOT:
#ifdef CONFIG_SUSPEND
            case HIBERNATION_SUSPEND:
#endif
            case HIBERNATION_TEST_RESUME:
                break;
            case HIBERNATION_PLATFORM:
                if (hibernation_ops) {
                    break;
                }
                /* not a valid mode, continue with loop */
                continue;
            default:
                break;
        }
        if (i == hibernation_mode) {
            buf += sprintf(buf, "[%s] ", hibernation_modes[i]);
        } else {
            buf += sprintf(buf, "%s ", hibernation_modes[i]);
        }
    }
    buf += sprintf(buf, "\n");
    return buf - start;
}

static ssize_t disk_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t n)
{
    int error = 0;
    int i;
    int len;
    char *p;
    int mode = HIBERNATION_INVALID;

    if (!hibernation_available()) {
        return -EPERM;
    }

    p = memchr(buf, '\n', n);
    len = p ? p - buf : n;

    lock_system_sleep();
    for (i = HIBERNATION_FIRST; i <= HIBERNATION_MAX; i++) {
        if (len == strlen(hibernation_modes[i]) && !strncmp(buf, hibernation_modes[i], len)) {
            mode = i;
            break;
        }
    }
    if (mode != HIBERNATION_INVALID) {
        switch (mode) {
            case HIBERNATION_SHUTDOWN:
            case HIBERNATION_REBOOT:
#ifdef CONFIG_SUSPEND
            case HIBERNATION_SUSPEND:
#endif
            case HIBERNATION_TEST_RESUME:
                hibernation_mode = mode;
                break;
            case HIBERNATION_PLATFORM:
                if (hibernation_ops) {
                    hibernation_mode = mode;
                } else {
                    error = -EINVAL;
                }
            default:
                break;
        }
    } else {
        error = -EINVAL;
    }

    if (!error) {
        pm_pr_dbg("Hibernation mode set to '%s'\n", hibernation_modes[mode]);
    }
    unlock_system_sleep();
    return error ? error : n;
}

power_attr(disk);

static ssize_t resume_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
{
    return sprintf(buf, "%d:%d\n", MAJOR(swsusp_resume_device), MINOR(swsusp_resume_device));
}

static ssize_t resume_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t n)
{
    dev_t res;
    int len = n;
    char *name;

    if (len && buf[len - 1] == '\n') {
        len--;
    }
    name = kstrndup(buf, len, GFP_KERNEL);
    if (!name) {
        return -ENOMEM;
    }

    res = name_to_dev_t(name);
    kfree(name);
    if (!res) {
        return -EINVAL;
    }

    lock_system_sleep();
    swsusp_resume_device = res;
    unlock_system_sleep();
    pm_pr_dbg("Configured hibernation resume from disk to %u\n", swsusp_resume_device);
    noresume = 0;
    software_resume();
    return n;
}

power_attr(resume);

static ssize_t resume_offset_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
{
    return sprintf(buf, "%llu\n", (unsigned long long)swsusp_resume_block);
}

static ssize_t resume_offset_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t n)
{
    unsigned long long offset;
    int rc;

    rc = kstrtoull(buf, 0, &offset);
    if (rc) {
        return rc;
    }
    swsusp_resume_block = offset;

    return n;
}

power_attr(resume_offset);

static ssize_t image_size_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
{
    return sprintf(buf, "%lu\n", image_size);
}

static ssize_t image_size_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t n)
{
    unsigned long size;

    if (sscanf(buf, "%lu", &size) == 1) {
        image_size = size;
        return n;
    }

    return -EINVAL;
}

power_attr(image_size);

static ssize_t reserved_size_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
{
    return sprintf(buf, "%lu\n", reserved_size);
}

static ssize_t reserved_size_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t n)
{
    unsigned long size;

    if (sscanf(buf, "%lu", &size) == 1) {
        reserved_size = size;
        return n;
    }

    return -EINVAL;
}

power_attr(reserved_size);

static struct attribute *g[] = {
    &disk_attr.attr, &resume_offset_attr.attr, &resume_attr.attr, &image_size_attr.attr, &reserved_size_attr.attr, NULL,
};

static const struct attribute_group attr_group = {
    .attrs = g,
};

static int __init pm_disk_init(void)
{
    return sysfs_create_group(power_kobj, &attr_group);
}

core_initcall(pm_disk_init);

static int __init resume_setup(char *str)
{
    if (noresume) {
        return 1;
    }

    strncpy(resume_file, str, HIBERNATE_TWOHUNDREDFIFTYFIVE);
    return 1;
}

static int __init resume_offset_setup(char *str)
{
    unsigned long long offset;

    if (noresume) {
        return 1;
    }

    if (sscanf(str, "%llu", &offset) == 1) {
        swsusp_resume_block = offset;
    }

    return 1;
}

static int __init hibernate_setup(char *str)
{
    if (!strncmp(str, "noresume", HIBERNATE_EIGHT)) {
        noresume = 1;
    } else if (!strncmp(str, "nocompress", HIBERNATE_TEN)) {
        nocompress = 1;
    } else if (!strncmp(str, "no", HIBERNATE_TWO)) {
        noresume = 1;
        nohibernate = 1;
    } else if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX) && !strncmp(str, "protect_image", HIBERNATE_THIRTEEN)) {
        enable_restore_image_protection();
    }
    return 1;
}

static int __init noresume_setup(char *str)
{
    noresume = 1;
    return 1;
}

static int __init resumewait_setup(char *str)
{
    resume_wait = 1;
    return 1;
}

static int __init resumedelay_setup(char *str)
{
    int rc = kstrtouint(str, 0, &resume_delay);

    if (rc) {
        pr_warn("resumedelay: bad option string '%s'\n", str);
    }
    return 1;
}

static int __init nohibernate_setup(char *str)
{
    noresume = 1;
    nohibernate = 1;
    return 1;
}

__setup("noresume", noresume_setup);
__setup("resume_offset=", resume_offset_setup);
__setup("resume=", resume_setup);
__setup("hibernate=", hibernate_setup);
__setup("resumewait", resumewait_setup);
__setup("resumedelay=", resumedelay_setup);
__setup("nohibernate", nohibernate_setup);