// SPDX-License-Identifier: GPL-2.0+
/*
 * xen console driver interface to hvc_console.c
 *
 * (c) 2007 Gerd Hoffmann <kraxel@suse.de>
 */

#include <linux/console.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/irq.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/list.h>
#include <linux/serial_core.h>

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

#include <xen/xen.h>
#include <xen/interface/xen.h>
#include <xen/hvm.h>
#include <xen/grant_table.h>
#include <xen/page.h>
#include <xen/events.h>
#include <xen/interface/io/console.h>
#include <xen/interface/sched.h>
#include <xen/hvc-console.h>
#include <xen/xenbus.h>

#include "hvc_console.h"

#define HVC_COOKIE   0x58656e /* "Xen" in hex */

struct xencons_info {
        struct list_head list;
        struct xenbus_device *xbdev;
        struct xencons_interface *intf;
        unsigned int evtchn;
        XENCONS_RING_IDX out_cons;
        unsigned int out_cons_same;
        struct hvc_struct *hvc;
        int irq;
        int vtermno;
        grant_ref_t gntref;
        spinlock_t ring_lock;
};

static LIST_HEAD(xenconsoles);
static DEFINE_SPINLOCK(xencons_lock);

/* ------------------------------------------------------------------ */

static bool xen_console_io = false;
static int __initdata opt_console_io = -1;

static int __init parse_xen_console_io(char *arg)
{
        bool val;
        int ret;

        ret = kstrtobool(arg, &val);
        if (ret == 0)
                opt_console_io = (int)val;

        return ret;
}
early_param("xen_console_io", parse_xen_console_io);

static struct xencons_info *vtermno_to_xencons(int vtermno)
{
        struct xencons_info *entry, *ret = NULL;
        unsigned long flags;

        spin_lock_irqsave(&xencons_lock, flags);
        if (list_empty(&xenconsoles)) {
                spin_unlock_irqrestore(&xencons_lock, flags);
                return NULL;
        }

        list_for_each_entry(entry, &xenconsoles, list) {
                if (entry->vtermno == vtermno) {
                        ret  = entry;
                        break;
                }
        }
        spin_unlock_irqrestore(&xencons_lock, flags);

        return ret;
}

static inline int xenbus_devid_to_vtermno(int devid)
{
        return devid + HVC_COOKIE;
}

static inline void notify_daemon(struct xencons_info *cons)
{
        /* Use evtchn: this is called early, before irq is set up. */
        notify_remote_via_evtchn(cons->evtchn);
}

static ssize_t __write_console(struct xencons_info *xencons,
                               const u8 *data, size_t len)
{
        XENCONS_RING_IDX cons, prod;
        struct xencons_interface *intf = xencons->intf;
        unsigned long flags;
        size_t sent = 0;

        spin_lock_irqsave(&xencons->ring_lock, flags);
        cons = intf->out_cons;
        prod = intf->out_prod;
        mb();                   /* update queue values before going on */

        if ((prod - cons) > sizeof(intf->out)) {
                spin_unlock_irqrestore(&xencons->ring_lock, flags);
                pr_err_once("xencons: Illegal ring page indices");
                return -EINVAL;
        }

        while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
                intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++];

        wmb();                  /* write ring before updating pointer */
        intf->out_prod = prod;
        spin_unlock_irqrestore(&xencons->ring_lock, flags);

        if (sent)
                notify_daemon(xencons);
        return sent;
}

static ssize_t domU_write_console(uint32_t vtermno, const u8 *data, size_t len)
{
        struct xencons_info *cons = vtermno_to_xencons(vtermno);
        size_t ret = len;

        if (cons == NULL)
                return -EINVAL;

        /*
         * Make sure the whole buffer is emitted, polling if
         * necessary.  We don't ever want to rely on the hvc daemon
         * because the most interesting console output is when the
         * kernel is crippled.
         */
        while (len) {
                ssize_t sent = __write_console(cons, data, len);

                if (sent < 0)
                        return sent;

                data += sent;
                len -= sent;

                if (unlikely(len))
                        HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
        }

        return ret;
}

static ssize_t domU_read_console(uint32_t vtermno, u8 *buf, size_t len)
{
        struct xencons_interface *intf;
        XENCONS_RING_IDX cons, prod;
        struct xencons_info *xencons = vtermno_to_xencons(vtermno);
        unsigned int eoiflag = 0;
        unsigned long flags;
        size_t recv = 0;

        if (xencons == NULL)
                return -EINVAL;
        intf = xencons->intf;

        spin_lock_irqsave(&xencons->ring_lock, flags);
        cons = intf->in_cons;
        prod = intf->in_prod;
        mb();                   /* get pointers before reading ring */

        if ((prod - cons) > sizeof(intf->in)) {
                spin_unlock_irqrestore(&xencons->ring_lock, flags);
                pr_err_once("xencons: Illegal ring page indices");
                return -EINVAL;
        }

        while (cons != prod && recv < len)
                buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];

        mb();                   /* read ring before consuming */
        intf->in_cons = cons;

        /*
         * When to mark interrupt having been spurious:
         * - there was no new data to be read, and
         * - the backend did not consume some output bytes, and
         * - the previous round with no read data didn't see consumed bytes
         *   (we might have a race with an interrupt being in flight while
         *   updating xencons->out_cons, so account for that by allowing one
         *   round without any visible reason)
         */
        if (intf->out_cons != xencons->out_cons) {
                xencons->out_cons = intf->out_cons;
                xencons->out_cons_same = 0;
        }
        if (!recv && xencons->out_cons_same++ > 1) {
                eoiflag = XEN_EOI_FLAG_SPURIOUS;
        }
        spin_unlock_irqrestore(&xencons->ring_lock, flags);

        if (recv) {
                notify_daemon(xencons);
        }

        xen_irq_lateeoi(xencons->irq, eoiflag);

        return recv;
}

static const struct hv_ops domU_hvc_ops = {
        .get_chars = domU_read_console,
        .put_chars = domU_write_console,
        .notifier_add = notifier_add_irq,
        .notifier_del = notifier_del_irq,
        .notifier_hangup = notifier_hangup_irq,
};

static ssize_t dom0_read_console(uint32_t vtermno, u8 *buf, size_t len)
{
        return HYPERVISOR_console_io(CONSOLEIO_read, len, buf);
}

/*
 * Either for a dom0 to write to the system console, or a domU with a
 * debug version of Xen
 */
static ssize_t dom0_write_console(uint32_t vtermno, const u8 *str, size_t len)
{
        int rc = HYPERVISOR_console_io(CONSOLEIO_write, len, (u8 *)str);
        if (rc < 0)
                return rc;

        return len;
}

static const struct hv_ops dom0_hvc_ops = {
        .get_chars = dom0_read_console,
        .put_chars = dom0_write_console,
        .notifier_add = notifier_add_irq,
        .notifier_del = notifier_del_irq,
        .notifier_hangup = notifier_hangup_irq,
};

static int xen_hvm_console_init(void)
{
        int r;
        uint64_t v = 0;
        unsigned long gfn, flags;
        struct xencons_info *info;

        if (!xen_hvm_domain())
                return -ENODEV;

        info = vtermno_to_xencons(HVC_COOKIE);
        if (!info) {
                info = kzalloc_obj(struct xencons_info);
                if (!info)
                        return -ENOMEM;
                spin_lock_init(&info->ring_lock);
        } else if (info->intf != NULL) {
                /* already configured */
                return 0;
        }
        /*
         * If the toolstack (or the hypervisor) hasn't set these values, the
         * default value is 0. Even though gfn = 0 and evtchn = 0 are
         * theoretically correct values, in practice they never are and they
         * mean that a legacy toolstack hasn't initialized the pv console correctly.
         */
        r = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &v);
        if (r < 0 || v == 0)
                goto err;
        info->evtchn = v;
        v = 0;
        r = hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v);
        if (r < 0 || v == 0)
                goto err;
        gfn = v;
        info->intf = memremap(gfn << XEN_PAGE_SHIFT, XEN_PAGE_SIZE, MEMREMAP_WB);
        if (info->intf == NULL)
                goto err;
        info->vtermno = HVC_COOKIE;

        spin_lock_irqsave(&xencons_lock, flags);
        list_add_tail(&info->list, &xenconsoles);
        spin_unlock_irqrestore(&xencons_lock, flags);

        return 0;
err:
        kfree(info);
        return -ENODEV;
}

static int xencons_info_pv_init(struct xencons_info *info, int vtermno)
{
        spin_lock_init(&info->ring_lock);
        info->evtchn = xen_start_info->console.domU.evtchn;
        /* GFN == MFN for PV guest */
        info->intf = gfn_to_virt(xen_start_info->console.domU.mfn);
        info->vtermno = vtermno;

        list_add_tail(&info->list, &xenconsoles);

        return 0;
}

static int xen_pv_console_init(void)
{
        struct xencons_info *info;
        unsigned long flags;

        if (!xen_pv_domain())
                return -ENODEV;

        if (!xen_start_info->console.domU.evtchn)
                return -ENODEV;

        info = vtermno_to_xencons(HVC_COOKIE);
        if (!info) {
                info = kzalloc_obj(struct xencons_info);
                if (!info)
                        return -ENOMEM;
        } else if (info->intf != NULL) {
                /* already configured */
                return 0;
        }
        spin_lock_irqsave(&xencons_lock, flags);
        xencons_info_pv_init(info, HVC_COOKIE);
        spin_unlock_irqrestore(&xencons_lock, flags);

        return 0;
}

static int xen_initial_domain_console_init(void)
{
        struct xencons_info *info;
        unsigned long flags;

        if (!xen_console_io)
                return -ENODEV;

        info = vtermno_to_xencons(HVC_COOKIE);
        if (!info) {
                info = kzalloc_obj(struct xencons_info);
                if (!info)
                        return -ENOMEM;
                spin_lock_init(&info->ring_lock);
        }

        info->irq = bind_virq_to_irq(VIRQ_CONSOLE, 0, false);
        info->vtermno = HVC_COOKIE;

        spin_lock_irqsave(&xencons_lock, flags);
        list_add_tail(&info->list, &xenconsoles);
        spin_unlock_irqrestore(&xencons_lock, flags);

        return 0;
}

static void xen_console_update_evtchn(struct xencons_info *info)
{
        if (xen_hvm_domain()) {
                uint64_t v = 0;
                int err;

                err = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &v);
                if (!err && v)
                        info->evtchn = v;
        } else
                info->evtchn = xen_start_info->console.domU.evtchn;
}

void xen_console_resume(void)
{
        struct xencons_info *info = vtermno_to_xencons(HVC_COOKIE);
        if (info != NULL && info->irq) {
                if (!xen_console_io)
                        xen_console_update_evtchn(info);
                rebind_evtchn_irq(info->evtchn, info->irq);
        }
}

#ifdef CONFIG_HVC_XEN_FRONTEND
static void xencons_disconnect_backend(struct xencons_info *info)
{
        if (info->hvc != NULL)
                hvc_remove(info->hvc);
        info->hvc = NULL;
        if (info->irq > 0) {
                evtchn_put(info->evtchn);
                info->irq = 0;
                info->evtchn = 0;
        }
        /* evtchn_put() will also close it so this is only an error path */
        if (info->evtchn > 0)
                xenbus_free_evtchn(info->xbdev, info->evtchn);
        info->evtchn = 0;
        if (info->gntref > 0)
                gnttab_free_grant_references(info->gntref);
        info->gntref = 0;
}

static void xencons_free(struct xencons_info *info)
{
        free_page((unsigned long)info->intf);
        info->intf = NULL;
        info->vtermno = 0;
        kfree(info);
}

static int xen_console_remove(struct xencons_info *info)
{
        unsigned long flags;

        xencons_disconnect_backend(info);
        spin_lock_irqsave(&xencons_lock, flags);
        list_del(&info->list);
        spin_unlock_irqrestore(&xencons_lock, flags);
        if (info->xbdev != NULL)
                xencons_free(info);
        else {
                if (xen_hvm_domain())
                        iounmap(info->intf);
                kfree(info);
        }
        return 0;
}

static void xencons_remove(struct xenbus_device *dev)
{
        xen_console_remove(dev_get_drvdata(&dev->dev));
}

static int xencons_connect_backend(struct xenbus_device *dev,
                                  struct xencons_info *info)
{
        int ret, evtchn, devid, ref, irq;
        struct xenbus_transaction xbt;
        grant_ref_t gref_head;

        ret = xenbus_alloc_evtchn(dev, &evtchn);
        if (ret)
                return ret;
        info->evtchn = evtchn;
        irq = bind_evtchn_to_irq_lateeoi(evtchn);
        if (irq < 0)
                return irq;
        info->irq = irq;
        devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
        info->hvc = hvc_alloc(xenbus_devid_to_vtermno(devid),
                        irq, &domU_hvc_ops, 256);
        if (IS_ERR(info->hvc))
                return PTR_ERR(info->hvc);
        ret = gnttab_alloc_grant_references(1, &gref_head);
        if (ret < 0)
                return ret;
        info->gntref = gref_head;
        ref = gnttab_claim_grant_reference(&gref_head);
        if (ref < 0)
                return ref;
        gnttab_grant_foreign_access_ref(ref, info->xbdev->otherend_id,
                                        virt_to_gfn(info->intf), 0);

 again:
        ret = xenbus_transaction_start(&xbt);
        if (ret) {
                xenbus_dev_fatal(dev, ret, "starting transaction");
                return ret;
        }
        ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", ref);
        if (ret)
                goto error_xenbus;
        ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
                            evtchn);
        if (ret)
                goto error_xenbus;
        ret = xenbus_transaction_end(xbt, 0);
        if (ret) {
                if (ret == -EAGAIN)
                        goto again;
                xenbus_dev_fatal(dev, ret, "completing transaction");
                return ret;
        }

        xenbus_switch_state(dev, XenbusStateInitialised);
        return 0;

 error_xenbus:
        xenbus_transaction_end(xbt, 1);
        xenbus_dev_fatal(dev, ret, "writing xenstore");
        return ret;
}

static int xencons_probe(struct xenbus_device *dev,
                                  const struct xenbus_device_id *id)
{
        int ret, devid;
        struct xencons_info *info;
        unsigned long flags;

        devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
        if (devid == 0)
                return -ENODEV;

        info = kzalloc_obj(struct xencons_info);
        if (!info)
                return -ENOMEM;
        spin_lock_init(&info->ring_lock);
        dev_set_drvdata(&dev->dev, info);
        info->xbdev = dev;
        info->vtermno = xenbus_devid_to_vtermno(devid);
        info->intf = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
        if (!info->intf)
                goto error_nomem;

        ret = xencons_connect_backend(dev, info);
        if (ret < 0)
                goto error;
        spin_lock_irqsave(&xencons_lock, flags);
        list_add_tail(&info->list, &xenconsoles);
        spin_unlock_irqrestore(&xencons_lock, flags);

        return 0;

 error_nomem:
        ret = -ENOMEM;
        xenbus_dev_fatal(dev, ret, "allocating device memory");
 error:
        xencons_disconnect_backend(info);
        xencons_free(info);
        return ret;
}

static int xencons_resume(struct xenbus_device *dev)
{
        struct xencons_info *info = dev_get_drvdata(&dev->dev);

        xencons_disconnect_backend(info);
        memset(info->intf, 0, XEN_PAGE_SIZE);
        return xencons_connect_backend(dev, info);
}

static void xencons_backend_changed(struct xenbus_device *dev,
                                   enum xenbus_state backend_state)
{
        switch (backend_state) {
        case XenbusStateReconfiguring:
        case XenbusStateReconfigured:
        case XenbusStateInitialising:
        case XenbusStateInitialised:
        case XenbusStateUnknown:
                break;

        case XenbusStateInitWait:
                break;

        case XenbusStateConnected:
                xenbus_switch_state(dev, XenbusStateConnected);
                break;

        case XenbusStateClosed:
                if (dev->state == XenbusStateClosed)
                        break;
                fallthrough;    /* Missed the backend's CLOSING state */
        case XenbusStateClosing: {
                struct xencons_info *info = dev_get_drvdata(&dev->dev);

                /*
                 * Don't tear down the evtchn and grant ref before the other
                 * end has disconnected, but do stop userspace from trying
                 * to use the device before we allow the backend to close.
                 */
                if (info->hvc) {
                        hvc_remove(info->hvc);
                        info->hvc = NULL;
                }

                xenbus_frontend_closed(dev);
                break;
        }
        }
}

static const struct xenbus_device_id xencons_ids[] = {
        { "console" },
        { "" }
};

static struct xenbus_driver xencons_driver = {
        .name = "xenconsole",
        .ids = xencons_ids,
        .probe = xencons_probe,
        .remove = xencons_remove,
        .resume = xencons_resume,
        .otherend_changed = xencons_backend_changed,
        .not_essential = true,
};
#endif /* CONFIG_HVC_XEN_FRONTEND */

static int __init xen_hvc_init(void)
{
        int r;
        struct xencons_info *info;
        const struct hv_ops *ops;

        if (!xen_domain())
                return -ENODEV;

        if (xen_console_io) {
                ops = &dom0_hvc_ops;
                r = xen_initial_domain_console_init();
                if (r < 0)
                        goto register_fe;
                info = vtermno_to_xencons(HVC_COOKIE);
        } else {
                ops = &domU_hvc_ops;
                if (xen_hvm_domain())
                        r = xen_hvm_console_init();
                else
                        r = xen_pv_console_init();
                if (r < 0)
                        goto register_fe;

                info = vtermno_to_xencons(HVC_COOKIE);
                info->irq = bind_evtchn_to_irq_lateeoi(info->evtchn);
        }
        if (info->irq < 0)
                info->irq = 0; /* NO_IRQ */
        else
                irq_set_noprobe(info->irq);

        info->hvc = hvc_alloc(HVC_COOKIE, info->irq, ops, 256);
        if (IS_ERR(info->hvc)) {
                unsigned long flags;

                r = PTR_ERR(info->hvc);
                spin_lock_irqsave(&xencons_lock, flags);
                list_del(&info->list);
                spin_unlock_irqrestore(&xencons_lock, flags);
                if (info->irq)
                        evtchn_put(info->evtchn);
                kfree(info);
                return r;
        }

        r = 0;
 register_fe:
#ifdef CONFIG_HVC_XEN_FRONTEND
        r = xenbus_register_frontend(&xencons_driver);
#endif
        return r;
}
device_initcall(xen_hvc_init);

static int __init xen_cons_init(void)
{
        const struct hv_ops *ops;

        xen_console_io = opt_console_io >= 0 ? opt_console_io :
                                               xen_initial_domain();

        if (!xen_domain())
                return 0;

        if (xen_console_io)
                ops = &dom0_hvc_ops;
        else {
                int r;
                ops = &domU_hvc_ops;

                if (xen_hvm_domain())
                        r = xen_hvm_console_init();
                else
                        r = xen_pv_console_init();
                if (r < 0)
                        return r;
        }

        hvc_instantiate(HVC_COOKIE, 0, ops);
        return 0;
}
console_initcall(xen_cons_init);

#ifdef CONFIG_X86
static void xen_hvm_early_write(uint32_t vtermno, const char *str, int len)
{
        if (xen_cpuid_base())
                outsb(0xe9, str, len);
}
#else
static void xen_hvm_early_write(uint32_t vtermno, const char *str, int len) { }
#endif

#ifdef CONFIG_EARLY_PRINTK
static int __init xenboot_console_setup(struct console *console, char *string)
{
        static struct xencons_info xenboot;

        if (xen_initial_domain() || !xen_pv_domain())
                return 0;

        return xencons_info_pv_init(&xenboot, 0);
}

static void xenboot_write_console(struct console *console, const char *string,
                                  unsigned len)
{
        unsigned int linelen, off = 0;
        const char *pos;

        if (dom0_write_console(0, string, len) >= 0)
                return;

        if (!xen_pv_domain()) {
                xen_hvm_early_write(0, string, len);
                return;
        }

        if (domU_write_console(0, "(early) ", 8) < 0)
                return;
        while (off < len && NULL != (pos = strchr(string+off, '\n'))) {
                linelen = pos-string+off;
                if (off + linelen > len)
                        break;
                domU_write_console(0, string+off, linelen);
                domU_write_console(0, "\r\n", 2);
                off += linelen + 1;
        }
        if (off < len)
                domU_write_console(0, string+off, len-off);
}

struct console xenboot_console = {
        .name           = "xenboot",
        .write          = xenboot_write_console,
        .setup          = xenboot_console_setup,
        .flags          = CON_PRINTBUFFER | CON_BOOT | CON_ANYTIME,
        .index          = -1,
};
#endif  /* CONFIG_EARLY_PRINTK */

void xen_raw_console_write(const char *str)
{
        ssize_t len = strlen(str);
        int rc = 0;

        if (xen_domain()) {
                rc = dom0_write_console(0, str, len);
                if (rc != -ENOSYS || !xen_hvm_domain())
                        return;
        }
        xen_hvm_early_write(0, str, len);
}

void xen_raw_printk(const char *fmt, ...)
{
        static char buf[512];
        va_list ap;

        va_start(ap, fmt);
        vsnprintf(buf, sizeof(buf), fmt, ap);
        va_end(ap);

        xen_raw_console_write(buf);
}

static void xenboot_earlycon_write(struct console *console,
                                  const char *string,
                                  unsigned len)
{
        dom0_write_console(0, string, len);
}

static int __init xenboot_earlycon_setup(struct earlycon_device *device,
                                            const char *opt)
{
        device->con->write = xenboot_earlycon_write;
        return 0;
}
EARLYCON_DECLARE(xenboot, xenboot_earlycon_setup);