// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright © 2017 Keith Packard <keithp@keithp.com>
 */
#include <linux/file.h>
#include <linux/uaccess.h>

#include <drm/drm_auth.h>
#include <drm/drm_crtc_helper.h>
#include <drm/drm_drv.h>
#include <drm/drm_file.h>
#include <drm/drm_lease.h>
#include <drm/drm_print.h>

#include "drm_crtc_internal.h"
#include "drm_internal.h"

/**
 * DOC: drm leasing
 *
 * DRM leases provide information about whether a DRM master may control a DRM
 * mode setting object. This enables the creation of multiple DRM masters that
 * manage subsets of display resources.
 *
 * The original DRM master of a device 'owns' the available drm resources. It
 * may create additional DRM masters and 'lease' resources which it controls
 * to the new DRM master. This gives the new DRM master control over the
 * leased resources until the owner revokes the lease, or the new DRM master
 * is closed. Some helpful terminology:
 *
 * - An 'owner' is a &struct drm_master that is not leasing objects from
 *   another &struct drm_master, and hence 'owns' the objects. The owner can be
 *   identified as the &struct drm_master for which &drm_master.lessor is NULL.
 *
 * - A 'lessor' is a &struct drm_master which is leasing objects to one or more
 *   other &struct drm_master. Currently, lessees are not allowed to
 *   create sub-leases, hence the lessor is the same as the owner.
 *
 * - A 'lessee' is a &struct drm_master which is leasing objects from some
 *   other &struct drm_master. Each lessee only leases resources from a single
 *   lessor recorded in &drm_master.lessor, and holds the set of objects that
 *   it is leasing in &drm_master.leases.
 *
 * - A 'lease' is a contract between the lessor and lessee that identifies
 *   which resources may be controlled by the lessee. All of the resources
 *   that are leased must be owned by or leased to the lessor, and lessors are
 *   not permitted to lease the same object to multiple lessees.
 *
 * The set of objects any &struct drm_master 'controls' is limited to the set
 * of objects it leases (for lessees) or all objects (for owners).
 *
 * Objects not controlled by a &struct drm_master cannot be modified through
 * the various state manipulating ioctls, and any state reported back to user
 * space will be edited to make them appear idle and/or unusable. For
 * instance, connectors always report 'disconnected', while encoders
 * report no possible crtcs or clones.
 *
 * Since each lessee may lease objects from a single lessor, display resource
 * leases form a tree of &struct drm_master. As lessees are currently not
 * allowed to create sub-leases, the tree depth is limited to 1. All of
 * these get activated simultaneously when the top level device owner changes
 * through the SETMASTER or DROPMASTER IOCTL, so &drm_device.master points to
 * the owner at the top of the lease tree (i.e. the &struct drm_master for which
 * &drm_master.lessor is NULL). The full list of lessees that are leasing
 * objects from the owner can be searched via the owner's
 * &drm_master.lessee_idr.
 */

#define drm_for_each_lessee(lessee, lessor) \
        list_for_each_entry((lessee), &(lessor)->lessees, lessee_list)

static uint64_t drm_lease_idr_object;

struct drm_master *drm_lease_owner(struct drm_master *master)
{
        while (master->lessor != NULL)
                master = master->lessor;
        return master;
}

static struct drm_master*
_drm_find_lessee(struct drm_master *master, int lessee_id)
{
        lockdep_assert_held(&master->dev->mode_config.idr_mutex);
        return idr_find(&drm_lease_owner(master)->lessee_idr, lessee_id);
}

static int _drm_lease_held_master(struct drm_master *master, int id)
{
        lockdep_assert_held(&master->dev->mode_config.idr_mutex);
        if (master->lessor)
                return idr_find(&master->leases, id) != NULL;
        return true;
}

/* Checks if the given object has been leased to some lessee of drm_master */
static bool _drm_has_leased(struct drm_master *master, int id)
{
        struct drm_master *lessee;

        lockdep_assert_held(&master->dev->mode_config.idr_mutex);
        drm_for_each_lessee(lessee, master)
                if (_drm_lease_held_master(lessee, id))
                        return true;
        return false;
}

/* Called with idr_mutex held */
bool _drm_lease_held(struct drm_file *file_priv, int id)
{
        bool ret;
        struct drm_master *master;

        if (!file_priv)
                return true;

        master = drm_file_get_master(file_priv);
        if (!master)
                return true;
        ret = _drm_lease_held_master(master, id);
        drm_master_put(&master);

        return ret;
}

bool drm_lease_held(struct drm_file *file_priv, int id)
{
        struct drm_master *master;
        bool ret;

        if (!file_priv)
                return true;

        master = drm_file_get_master(file_priv);
        if (!master)
                return true;
        if (!master->lessor) {
                ret = true;
                goto out;
        }
        mutex_lock(&master->dev->mode_config.idr_mutex);
        ret = _drm_lease_held_master(master, id);
        mutex_unlock(&master->dev->mode_config.idr_mutex);

out:
        drm_master_put(&master);
        return ret;
}

/*
 * Given a bitmask of crtcs to check, reconstructs a crtc mask based on the
 * crtcs which are visible through the specified file.
 */
uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in)
{
        struct drm_master *master;
        struct drm_device *dev;
        struct drm_crtc *crtc;
        int count_in, count_out;
        uint32_t crtcs_out = 0;

        if (!file_priv)
                return crtcs_in;

        master = drm_file_get_master(file_priv);
        if (!master)
                return crtcs_in;
        if (!master->lessor) {
                crtcs_out = crtcs_in;
                goto out;
        }
        dev = master->dev;

        count_in = count_out = 0;
        mutex_lock(&master->dev->mode_config.idr_mutex);
        list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
                if (_drm_lease_held_master(master, crtc->base.id)) {
                        uint32_t mask_in = 1ul << count_in;

                        if ((crtcs_in & mask_in) != 0) {
                                uint32_t mask_out = 1ul << count_out;

                                crtcs_out |= mask_out;
                        }
                        count_out++;
                }
                count_in++;
        }
        mutex_unlock(&master->dev->mode_config.idr_mutex);

out:
        drm_master_put(&master);
        return crtcs_out;
}

/*
 * Uses drm_master_create to allocate a new drm_master, then checks to
 * make sure all of the desired objects can be leased, atomically
 * leasing them to the new drmmaster.
 *
 *      ERR_PTR(-EACCES)        some other master holds the title to any object
 *      ERR_PTR(-ENOENT)        some object is not a valid DRM object for this device
 *      ERR_PTR(-EBUSY)         some other lessee holds title to this object
 *      ERR_PTR(-EEXIST)        same object specified more than once in the provided list
 *      ERR_PTR(-ENOMEM)        allocation failed
 */
static struct drm_master *drm_lease_create(struct drm_master *lessor, struct idr *leases)
{
        struct drm_device *dev = lessor->dev;
        int error;
        struct drm_master *lessee;
        int object;
        int id;
        void *entry;

        DRM_DEBUG_LEASE("lessor %d\n", lessor->lessee_id);

        lessee = drm_master_create(lessor->dev);
        if (!lessee) {
                DRM_DEBUG_LEASE("drm_master_create failed\n");
                return ERR_PTR(-ENOMEM);
        }

        mutex_lock(&dev->mode_config.idr_mutex);

        idr_for_each_entry(leases, entry, object) {
                error = 0;
                if (!idr_find(&dev->mode_config.object_idr, object))
                        error = -ENOENT;
                else if (_drm_has_leased(lessor, object))
                        error = -EBUSY;

                if (error != 0) {
                        DRM_DEBUG_LEASE("object %d failed %d\n", object, error);
                        goto out_lessee;
                }
        }

        /* Insert the new lessee into the tree */
        id = idr_alloc(&(drm_lease_owner(lessor)->lessee_idr), lessee, 1, 0, GFP_KERNEL);
        if (id < 0) {
                error = id;
                goto out_lessee;
        }

        lessee->lessee_id = id;
        lessee->lessor = drm_master_get(lessor);
        list_add_tail(&lessee->lessee_list, &lessor->lessees);

        /* Move the leases over */
        lessee->leases = *leases;
        DRM_DEBUG_LEASE("new lessee %d %p, lessor %d %p\n", lessee->lessee_id, lessee, lessor->lessee_id, lessor);

        mutex_unlock(&dev->mode_config.idr_mutex);
        return lessee;

out_lessee:
        mutex_unlock(&dev->mode_config.idr_mutex);

        drm_master_put(&lessee);

        return ERR_PTR(error);
}

void drm_lease_destroy(struct drm_master *master)
{
        struct drm_device *dev = master->dev;

        mutex_lock(&dev->mode_config.idr_mutex);

        DRM_DEBUG_LEASE("drm_lease_destroy %d\n", master->lessee_id);

        /* This master is referenced by all lessees, hence it cannot be destroyed
         * until all of them have been
         */
        WARN_ON(!list_empty(&master->lessees));

        /* Remove this master from the lessee idr in the owner */
        if (master->lessee_id != 0) {
                DRM_DEBUG_LEASE("remove master %d from device list of lessees\n", master->lessee_id);
                idr_remove(&(drm_lease_owner(master)->lessee_idr), master->lessee_id);
        }

        /* Remove this master from any lessee list it may be on */
        list_del(&master->lessee_list);

        mutex_unlock(&dev->mode_config.idr_mutex);

        if (master->lessor) {
                /* Tell the master to check the lessee list */
                drm_sysfs_lease_event(dev);
                drm_master_put(&master->lessor);
        }

        DRM_DEBUG_LEASE("drm_lease_destroy done %d\n", master->lessee_id);
}

static void _drm_lease_revoke(struct drm_master *top)
{
        int object;
        void *entry;
        struct drm_master *master = top;

        lockdep_assert_held(&top->dev->mode_config.idr_mutex);

        /*
         * Walk the tree starting at 'top' emptying all leases. Because
         * the tree is fully connected, we can do this without recursing
         */
        for (;;) {
                DRM_DEBUG_LEASE("revoke leases for %p %d\n", master, master->lessee_id);

                /* Evacuate the lease */
                idr_for_each_entry(&master->leases, entry, object)
                        idr_remove(&master->leases, object);

                /* Depth-first list walk */

                /* Down */
                if (!list_empty(&master->lessees)) {
                        master = list_first_entry(&master->lessees, struct drm_master, lessee_list);
                } else {
                        /* Up */
                        while (master != top && master == list_last_entry(&master->lessor->lessees, struct drm_master, lessee_list))
                                master = master->lessor;

                        if (master == top)
                                break;

                        /* Over */
                        master = list_next_entry(master, lessee_list);
                }
        }
}

void drm_lease_revoke(struct drm_master *top)
{
        mutex_lock(&top->dev->mode_config.idr_mutex);
        _drm_lease_revoke(top);
        mutex_unlock(&top->dev->mode_config.idr_mutex);
}

static int validate_lease(struct drm_device *dev,
                          int object_count,
                          struct drm_mode_object **objects,
                          bool universal_planes)
{
        int o;
        int has_crtc = -1;
        int has_connector = -1;
        int has_plane = -1;

        /* we want to confirm that there is at least one crtc, plane
           connector object. */

        for (o = 0; o < object_count; o++) {
                if (objects[o]->type == DRM_MODE_OBJECT_CRTC && has_crtc == -1) {
                        has_crtc = o;
                }
                if (objects[o]->type == DRM_MODE_OBJECT_CONNECTOR && has_connector == -1)
                        has_connector = o;

                if (universal_planes) {
                        if (objects[o]->type == DRM_MODE_OBJECT_PLANE && has_plane == -1)
                                has_plane = o;
                }
        }
        if (has_crtc == -1 || has_connector == -1)
                return -EINVAL;
        if (universal_planes && has_plane == -1)
                return -EINVAL;
        return 0;
}

static int fill_object_idr(struct drm_device *dev,
                           struct drm_file *lessor_priv,
                           struct idr *leases,
                           int object_count,
                           u32 *object_ids)
{
        struct drm_mode_object **objects;
        u32 o;
        int ret;
        bool universal_planes = READ_ONCE(lessor_priv->universal_planes);

        objects = kcalloc(object_count, sizeof(struct drm_mode_object *),
                          GFP_KERNEL);
        if (!objects)
                return -ENOMEM;

        /* step one - get references to all the mode objects
           and check for validity. */
        for (o = 0; o < object_count; o++) {
                objects[o] = drm_mode_object_find(dev, lessor_priv,
                                                  object_ids[o],
                                                  DRM_MODE_OBJECT_ANY);
                if (!objects[o]) {
                        ret = -ENOENT;
                        goto out_free_objects;
                }

                if (!drm_mode_object_lease_required(objects[o]->type)) {
                        DRM_DEBUG_KMS("invalid object for lease\n");
                        ret = -EINVAL;
                        goto out_free_objects;
                }
        }

        ret = validate_lease(dev, object_count, objects, universal_planes);
        if (ret) {
                DRM_DEBUG_LEASE("lease validation failed\n");
                goto out_free_objects;
        }

        /* add their IDs to the lease request - taking into account
           universal planes */
        for (o = 0; o < object_count; o++) {
                struct drm_mode_object *obj = objects[o];
                u32 object_id = objects[o]->id;

                DRM_DEBUG_LEASE("Adding object %d to lease\n", object_id);

                /*
                 * We're using an IDR to hold the set of leased
                 * objects, but we don't need to point at the object's
                 * data structure from the lease as the main object_idr
                 * will be used to actually find that. Instead, all we
                 * really want is a 'leased/not-leased' result, for
                 * which any non-NULL pointer will work fine.
                 */
                ret = idr_alloc(leases, &drm_lease_idr_object , object_id, object_id + 1, GFP_KERNEL);
                if (ret < 0) {
                        DRM_DEBUG_LEASE("Object %d cannot be inserted into leases (%d)\n",
                                        object_id, ret);
                        goto out_free_objects;
                }
                if (obj->type == DRM_MODE_OBJECT_CRTC && !universal_planes) {
                        struct drm_crtc *crtc = obj_to_crtc(obj);

                        ret = idr_alloc(leases, &drm_lease_idr_object, crtc->primary->base.id, crtc->primary->base.id + 1, GFP_KERNEL);
                        if (ret < 0) {
                                DRM_DEBUG_LEASE("Object primary plane %d cannot be inserted into leases (%d)\n",
                                                object_id, ret);
                                goto out_free_objects;
                        }
                        if (crtc->cursor) {
                                ret = idr_alloc(leases, &drm_lease_idr_object, crtc->cursor->base.id, crtc->cursor->base.id + 1, GFP_KERNEL);
                                if (ret < 0) {
                                        DRM_DEBUG_LEASE("Object cursor plane %d cannot be inserted into leases (%d)\n",
                                                        object_id, ret);
                                        goto out_free_objects;
                                }
                        }
                }
        }

        ret = 0;
out_free_objects:
        for (o = 0; o < object_count; o++) {
                if (objects[o])
                        drm_mode_object_put(objects[o]);
        }
        kfree(objects);
        return ret;
}

/*
 * The master associated with the specified file will have a lease
 * created containing the objects specified in the ioctl structure.
 * A file descriptor will be allocated for that and returned to the
 * application.
 */
int drm_mode_create_lease_ioctl(struct drm_device *dev,
                                void *data, struct drm_file *lessor_priv)
{
        struct drm_mode_create_lease *cl = data;
        size_t object_count;
        int ret = 0;
        struct idr leases;
        struct drm_master *lessor;
        struct drm_master *lessee = NULL;
        struct file *lessee_file = NULL;
        struct file *lessor_file = lessor_priv->filp;
        struct drm_file *lessee_priv;
        int fd = -1;
        uint32_t *object_ids;

        /* Can't lease without MODESET */
        if (!drm_core_check_feature(dev, DRIVER_MODESET))
                return -EOPNOTSUPP;

        if (cl->flags && (cl->flags & ~(O_CLOEXEC | O_NONBLOCK))) {
                DRM_DEBUG_LEASE("invalid flags\n");
                return -EINVAL;
        }

        lessor = drm_file_get_master(lessor_priv);
        /* Do not allow sub-leases */
        if (lessor->lessor) {
                DRM_DEBUG_LEASE("recursive leasing not allowed\n");
                ret = -EINVAL;
                goto out_lessor;
        }

        object_count = cl->object_count;

        /* Handle leased objects, if any */
        idr_init(&leases);
        if (object_count != 0) {
                object_ids = memdup_user(u64_to_user_ptr(cl->object_ids),
                                         array_size(object_count, sizeof(__u32)));
                if (IS_ERR(object_ids)) {
                        ret = PTR_ERR(object_ids);
                        idr_destroy(&leases);
                        goto out_lessor;
                }

                /* fill and validate the object idr */
                ret = fill_object_idr(dev, lessor_priv, &leases,
                                      object_count, object_ids);
                kfree(object_ids);
                if (ret) {
                        DRM_DEBUG_LEASE("lease object lookup failed: %i\n", ret);
                        idr_destroy(&leases);
                        goto out_lessor;
                }
        }

        /* Allocate a file descriptor for the lease */
        fd = get_unused_fd_flags(cl->flags & (O_CLOEXEC | O_NONBLOCK));
        if (fd < 0) {
                idr_destroy(&leases);
                ret = fd;
                goto out_lessor;
        }

        DRM_DEBUG_LEASE("Creating lease\n");
        /* lessee will take the ownership of leases */
        lessee = drm_lease_create(lessor, &leases);

        if (IS_ERR(lessee)) {
                ret = PTR_ERR(lessee);
                idr_destroy(&leases);
                goto out_leases;
        }

        /* Clone the lessor file to create a new file for us */
        DRM_DEBUG_LEASE("Allocating lease file\n");
        lessee_file = file_clone_open(lessor_file);
        if (IS_ERR(lessee_file)) {
                ret = PTR_ERR(lessee_file);
                goto out_lessee;
        }

        lessee_priv = lessee_file->private_data;
        /* Change the file to a master one */
        drm_master_put(&lessee_priv->master);
        lessee_priv->master = lessee;
        lessee_priv->is_master = 1;
        lessee_priv->authenticated = 1;

        /* Pass fd back to userspace */
        DRM_DEBUG_LEASE("Returning fd %d id %d\n", fd, lessee->lessee_id);
        cl->fd = fd;
        cl->lessee_id = lessee->lessee_id;

        /* Hook up the fd */
        fd_install(fd, lessee_file);

        drm_master_put(&lessor);
        DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl succeeded\n");
        return 0;

out_lessee:
        drm_master_put(&lessee);

out_leases:
        put_unused_fd(fd);

out_lessor:
        drm_master_put(&lessor);
        DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl failed: %d\n", ret);
        return ret;
}

int drm_mode_list_lessees_ioctl(struct drm_device *dev,
                               void *data, struct drm_file *lessor_priv)
{
        struct drm_mode_list_lessees *arg = data;
        __u32 __user *lessee_ids = (__u32 __user *) (uintptr_t) (arg->lessees_ptr);
        __u32 count_lessees = arg->count_lessees;
        struct drm_master *lessor, *lessee;
        int count;
        int ret = 0;

        if (arg->pad)
                return -EINVAL;

        /* Can't lease without MODESET */
        if (!drm_core_check_feature(dev, DRIVER_MODESET))
                return -EOPNOTSUPP;

        lessor = drm_file_get_master(lessor_priv);
        DRM_DEBUG_LEASE("List lessees for %d\n", lessor->lessee_id);

        mutex_lock(&dev->mode_config.idr_mutex);

        count = 0;
        drm_for_each_lessee(lessee, lessor) {
                /* Only list un-revoked leases */
                if (!idr_is_empty(&lessee->leases)) {
                        if (count_lessees > count) {
                                DRM_DEBUG_LEASE("Add lessee %d\n", lessee->lessee_id);
                                ret = put_user(lessee->lessee_id, lessee_ids + count);
                                if (ret)
                                        break;
                        }
                        count++;
                }
        }

        DRM_DEBUG_LEASE("Lessor leases to %d\n", count);
        if (ret == 0)
                arg->count_lessees = count;

        mutex_unlock(&dev->mode_config.idr_mutex);
        drm_master_put(&lessor);

        return ret;
}

/* Return the list of leased objects for the specified lessee */
int drm_mode_get_lease_ioctl(struct drm_device *dev,
                             void *data, struct drm_file *lessee_priv)
{
        struct drm_mode_get_lease *arg = data;
        __u32 __user *object_ids = (__u32 __user *) (uintptr_t) (arg->objects_ptr);
        __u32 count_objects = arg->count_objects;
        struct drm_master *lessee;
        struct idr *object_idr;
        int count;
        void *entry;
        int object;
        int ret = 0;

        if (arg->pad)
                return -EINVAL;

        /* Can't lease without MODESET */
        if (!drm_core_check_feature(dev, DRIVER_MODESET))
                return -EOPNOTSUPP;

        lessee = drm_file_get_master(lessee_priv);
        DRM_DEBUG_LEASE("get lease for %d\n", lessee->lessee_id);

        mutex_lock(&dev->mode_config.idr_mutex);

        if (lessee->lessor == NULL)
                /* owner can use all objects */
                object_idr = &lessee->dev->mode_config.object_idr;
        else
                /* lessee can only use allowed object */
                object_idr = &lessee->leases;

        count = 0;
        idr_for_each_entry(object_idr, entry, object) {
                if (count_objects > count) {
                        DRM_DEBUG_LEASE("adding object %d\n", object);
                        ret = put_user(object, object_ids + count);
                        if (ret)
                                break;
                }
                count++;
        }

        DRM_DEBUG("lease holds %d objects\n", count);
        if (ret == 0)
                arg->count_objects = count;

        mutex_unlock(&dev->mode_config.idr_mutex);
        drm_master_put(&lessee);

        return ret;
}

/*
 * This removes all of the objects from the lease without
 * actually getting rid of the lease itself; that way all
 * references to it still work correctly
 */
int drm_mode_revoke_lease_ioctl(struct drm_device *dev,
                                void *data, struct drm_file *lessor_priv)
{
        struct drm_mode_revoke_lease *arg = data;
        struct drm_master *lessor;
        struct drm_master *lessee;
        int ret = 0;

        DRM_DEBUG_LEASE("revoke lease for %d\n", arg->lessee_id);

        /* Can't lease without MODESET */
        if (!drm_core_check_feature(dev, DRIVER_MODESET))
                return -EOPNOTSUPP;

        lessor = drm_file_get_master(lessor_priv);
        mutex_lock(&dev->mode_config.idr_mutex);

        lessee = _drm_find_lessee(lessor, arg->lessee_id);

        /* No such lessee */
        if (!lessee) {
                ret = -ENOENT;
                goto fail;
        }

        /* Lease is not held by lessor */
        if (lessee->lessor != lessor) {
                ret = -EACCES;
                goto fail;
        }

        _drm_lease_revoke(lessee);

fail:
        mutex_unlock(&dev->mode_config.idr_mutex);
        drm_master_put(&lessor);

        return ret;
}