// SPDX-License-Identifier: GPL-2.0-only
/*
 * Handle extern requests for shutdown, reboot and sysrq
 */

#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/reboot.h>
#include <linux/sysrq.h>
#include <linux/stop_machine.h>
#include <linux/suspend.h>
#include <linux/freezer.h>
#include <linux/syscore_ops.h>
#include <linux/export.h>

#include <xen/xen.h>
#include <xen/xenbus.h>
#include <xen/grant_table.h>
#include <xen/events.h>
#include <xen/hvc-console.h>
#include <xen/page.h>
#include <xen/xen-ops.h>

#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>

enum shutdown_state {
        SHUTDOWN_INVALID = -1,
        SHUTDOWN_POWEROFF = 0,
        SHUTDOWN_SUSPEND = 2,
        /* Code 3 is SHUTDOWN_CRASH, which we don't use because the domain can only
           report a crash, not be instructed to crash!
           HALT is the same as POWEROFF, as far as we're concerned.  The tools use
           the distinction when we return the reason code to them.  */
         SHUTDOWN_HALT = 4,
};

/* Ignore multiple shutdown requests. */
static enum shutdown_state shutting_down = SHUTDOWN_INVALID;

struct suspend_info {
        int cancelled;
};

static RAW_NOTIFIER_HEAD(xen_resume_notifier);

void xen_resume_notifier_register(struct notifier_block *nb)
{
        raw_notifier_chain_register(&xen_resume_notifier, nb);
}
EXPORT_SYMBOL_GPL(xen_resume_notifier_register);

#ifdef CONFIG_HIBERNATE_CALLBACKS
static int xen_suspend(void *data)
{
        struct suspend_info *si = data;
        int err;

        BUG_ON(!irqs_disabled());

        err = syscore_suspend();
        if (err) {
                pr_err("%s: system core suspend failed: %d\n", __func__, err);
                return err;
        }

        gnttab_suspend();
        xen_manage_runstate_time(-1);
        xen_arch_pre_suspend();

        si->cancelled = HYPERVISOR_suspend(xen_pv_domain()
                                           ? virt_to_gfn(xen_start_info)
                                           : 0);

        xen_arch_post_suspend(si->cancelled);
        xen_manage_runstate_time(si->cancelled ? 1 : 0);
        gnttab_resume();

        if (!si->cancelled) {
                xen_irq_resume();
                xen_timer_resume();
        }

        syscore_resume();

        return 0;
}

static void do_suspend(void)
{
        int err;
        struct suspend_info si;

        shutting_down = SHUTDOWN_SUSPEND;

        if (!mutex_trylock(&system_transition_mutex))
        {
                pr_err("%s: failed to take system_transition_mutex\n", __func__);
                goto out;
        }

        err = freeze_processes();
        if (err) {
                pr_err("%s: freeze processes failed %d\n", __func__, err);
                goto out_unlock;
        }

        err = freeze_kernel_threads();
        if (err) {
                pr_err("%s: freeze kernel threads failed %d\n", __func__, err);
                goto out_thaw;
        }

        err = dpm_suspend_start(PMSG_FREEZE);
        if (err) {
                pr_err("%s: dpm_suspend_start %d\n", __func__, err);
                goto out_resume_end;
        }

        printk(KERN_DEBUG "suspending xenstore...\n");
        xs_suspend();

        err = dpm_suspend_end(PMSG_FREEZE);
        if (err) {
                pr_err("dpm_suspend_end failed: %d\n", err);
                si.cancelled = 0;
                goto out_resume;
        }

        xen_arch_suspend();

        si.cancelled = 1;

        err = stop_machine(xen_suspend, &si, cpumask_of(0));

        /* Resume console as early as possible. */
        if (!si.cancelled)
                xen_console_resume();

        raw_notifier_call_chain(&xen_resume_notifier, 0, NULL);

        xen_arch_resume();

        dpm_resume_start(si.cancelled ? PMSG_THAW : PMSG_RESTORE);

        if (err) {
                pr_err("failed to start xen_suspend: %d\n", err);
                si.cancelled = 1;
        }

out_resume:
        if (!si.cancelled)
                xs_resume();
        else
                xs_suspend_cancel();

out_resume_end:
        dpm_resume_end(si.cancelled ? PMSG_THAW : PMSG_RESTORE);

out_thaw:
        thaw_processes();
out_unlock:
        mutex_unlock(&system_transition_mutex);
out:
        shutting_down = SHUTDOWN_INVALID;
}
#endif  /* CONFIG_HIBERNATE_CALLBACKS */

struct shutdown_handler {
#define SHUTDOWN_CMD_SIZE 11
        const char command[SHUTDOWN_CMD_SIZE];
        bool flag;
        void (*cb)(void);
};

static int poweroff_nb(struct notifier_block *cb, unsigned long code, void *unused)
{
        switch (code) {
        case SYS_DOWN:
        case SYS_HALT:
        case SYS_POWER_OFF:
                shutting_down = SHUTDOWN_POWEROFF;
                break;
        default:
                break;
        }
        return NOTIFY_DONE;
}
static void do_poweroff(void)
{
        switch (system_state) {
        case SYSTEM_BOOTING:
        case SYSTEM_SCHEDULING:
                orderly_poweroff(true);
                break;
        case SYSTEM_RUNNING:
                orderly_poweroff(false);
                break;
        default:
                /* Don't do it when we are halting/rebooting. */
                pr_info("Ignoring Xen toolstack shutdown.\n");
                break;
        }
}

static void do_reboot(void)
{
        shutting_down = SHUTDOWN_POWEROFF; /* ? */
        orderly_reboot();
}

static const struct shutdown_handler shutdown_handlers[] = {
        { "poweroff",   true,   do_poweroff },
        { "halt",       false,  do_poweroff },
        { "reboot",     true,   do_reboot   },
#ifdef CONFIG_HIBERNATE_CALLBACKS
        { "suspend",    true,   do_suspend  },
#endif
};

static void shutdown_handler(struct xenbus_watch *watch,
                             const char *path, const char *token)
{
        char *str;
        struct xenbus_transaction xbt;
        int err;
        int idx;

        if (shutting_down != SHUTDOWN_INVALID)
                return;

 again:
        err = xenbus_transaction_start(&xbt);
        if (err)
                return;

        str = (char *)xenbus_read(xbt, "control", "shutdown", NULL);
        /* Ignore read errors and empty reads. */
        if (XENBUS_IS_ERR_READ(str)) {
                xenbus_transaction_end(xbt, 1);
                return;
        }

        for (idx = 0; idx < ARRAY_SIZE(shutdown_handlers); idx++) {
                if (strcmp(str, shutdown_handlers[idx].command) == 0)
                        break;
        }

        /* Only acknowledge commands which we are prepared to handle. */
        if (idx < ARRAY_SIZE(shutdown_handlers))
                xenbus_write(xbt, "control", "shutdown", "");

        err = xenbus_transaction_end(xbt, 0);
        if (err == -EAGAIN) {
                kfree(str);
                goto again;
        }

        if (idx < ARRAY_SIZE(shutdown_handlers)) {
                shutdown_handlers[idx].cb();
        } else {
                pr_info("Ignoring shutdown request: %s\n", str);
                shutting_down = SHUTDOWN_INVALID;
        }

        kfree(str);
}

#ifdef CONFIG_MAGIC_SYSRQ
static void sysrq_handler(struct xenbus_watch *watch, const char *path,
                          const char *token)
{
        char sysrq_key = '\0';
        struct xenbus_transaction xbt;
        int err;

 again:
        err = xenbus_transaction_start(&xbt);
        if (err)
                return;
        err = xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key);
        if (err < 0) {
                /*
                 * The Xenstore watch fires directly after registering it and
                 * after a suspend/resume cycle. So ENOENT is no error but
                 * might happen in those cases. ERANGE is observed when we get
                 * an empty value (''), this happens when we acknowledge the
                 * request by writing '\0' below.
                 */
                if (err != -ENOENT && err != -ERANGE)
                        pr_err("Error %d reading sysrq code in control/sysrq\n",
                               err);
                xenbus_transaction_end(xbt, 1);
                return;
        }

        if (sysrq_key != '\0') {
                err = xenbus_printf(xbt, "control", "sysrq", "%c", '\0');
                if (err) {
                        pr_err("%s: Error %d writing sysrq in control/sysrq\n",
                               __func__, err);
                        xenbus_transaction_end(xbt, 1);
                        return;
                }
        }

        err = xenbus_transaction_end(xbt, 0);
        if (err == -EAGAIN)
                goto again;

        if (sysrq_key != '\0')
                handle_sysrq(sysrq_key);
}

static struct xenbus_watch sysrq_watch = {
        .node = "control/sysrq",
        .callback = sysrq_handler
};
#endif

static struct xenbus_watch shutdown_watch = {
        .node = "control/shutdown",
        .callback = shutdown_handler
};

static struct notifier_block xen_reboot_nb = {
        .notifier_call = poweroff_nb,
};

static int setup_shutdown_watcher(void)
{
        int err;
        int idx;
#define FEATURE_PATH_SIZE (SHUTDOWN_CMD_SIZE + sizeof("feature-"))
        char node[FEATURE_PATH_SIZE];

        err = register_xenbus_watch(&shutdown_watch);
        if (err) {
                pr_err("Failed to set shutdown watcher\n");
                return err;
        }


#ifdef CONFIG_MAGIC_SYSRQ
        err = register_xenbus_watch(&sysrq_watch);
        if (err) {
                pr_err("Failed to set sysrq watcher\n");
                return err;
        }
#endif

        for (idx = 0; idx < ARRAY_SIZE(shutdown_handlers); idx++) {
                if (!shutdown_handlers[idx].flag)
                        continue;
                snprintf(node, FEATURE_PATH_SIZE, "feature-%s",
                         shutdown_handlers[idx].command);
                err = xenbus_printf(XBT_NIL, "control", node, "%u", 1);
                if (err) {
                        pr_err("%s: Error %d writing %s\n", __func__,
                                err, node);
                        return err;
                }
        }

        return 0;
}

static int shutdown_event(struct notifier_block *notifier,
                          unsigned long event,
                          void *data)
{
        setup_shutdown_watcher();
        return NOTIFY_DONE;
}

int xen_setup_shutdown_event(void)
{
        static struct notifier_block xenstore_notifier = {
                .notifier_call = shutdown_event
        };

        if (!xen_domain())
                return -ENODEV;
        register_xenstore_notifier(&xenstore_notifier);
        register_reboot_notifier(&xen_reboot_nb);

        return 0;
}
EXPORT_SYMBOL_GPL(xen_setup_shutdown_event);

subsys_initcall(xen_setup_shutdown_event);