// SPDX-License-Identifier: GPL-2.0

#include <linux/types.h>
#include <linux/kconfig.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/highmem.h>
#include <linux/umh.h>
#include <linux/sysctl.h>
#include <linux/vmalloc.h>

#include "fallback.h"
#include "firmware.h"

/*
 * firmware fallback mechanism
 */

extern struct firmware_fallback_config fw_fallback_config;

/* These getters are vetted to use int properly */
static inline int __firmware_loading_timeout(void)
{
        return fw_fallback_config.loading_timeout;
}

/* These setters are vetted to use int properly */
static void __fw_fallback_set_timeout(int timeout)
{
        fw_fallback_config.loading_timeout = timeout;
}

/*
 * use small loading timeout for caching devices' firmware because all these
 * firmware images have been loaded successfully at lease once, also system is
 * ready for completing firmware loading now. The maximum size of firmware in
 * current distributions is about 2M bytes, so 10 secs should be enough.
 */
void fw_fallback_set_cache_timeout(void)
{
        fw_fallback_config.old_timeout = __firmware_loading_timeout();
        __fw_fallback_set_timeout(10);
}

/* Restores the timeout to the value last configured during normal operation */
void fw_fallback_set_default_timeout(void)
{
        __fw_fallback_set_timeout(fw_fallback_config.old_timeout);
}

static long firmware_loading_timeout(void)
{
        return __firmware_loading_timeout() > 0 ?
                __firmware_loading_timeout() * HZ : MAX_JIFFY_OFFSET;
}

static inline bool fw_sysfs_done(struct fw_priv *fw_priv)
{
        return __fw_state_check(fw_priv, FW_STATUS_DONE);
}

static inline bool fw_sysfs_loading(struct fw_priv *fw_priv)
{
        return __fw_state_check(fw_priv, FW_STATUS_LOADING);
}

static inline int fw_sysfs_wait_timeout(struct fw_priv *fw_priv,  long timeout)
{
        return __fw_state_wait_common(fw_priv, timeout);
}

struct fw_sysfs {
        bool nowait;
        struct device dev;
        struct fw_priv *fw_priv;
        struct firmware *fw;
};

static struct fw_sysfs *to_fw_sysfs(struct device *dev)
{
        return container_of(dev, struct fw_sysfs, dev);
}

static void __fw_load_abort(struct fw_priv *fw_priv)
{
        /*
         * There is a small window in which user can write to 'loading'
         * between loading done and disappearance of 'loading'
         */
        if (fw_sysfs_done(fw_priv))
                return;

        list_del_init(&fw_priv->pending_list);
        fw_state_aborted(fw_priv);
}

static void fw_load_abort(struct fw_sysfs *fw_sysfs)
{
        struct fw_priv *fw_priv = fw_sysfs->fw_priv;

        __fw_load_abort(fw_priv);
}

static LIST_HEAD(pending_fw_head);

void kill_pending_fw_fallback_reqs(bool only_kill_custom)
{
        struct fw_priv *fw_priv;
        struct fw_priv *next;

        mutex_lock(&fw_lock);
        list_for_each_entry_safe(fw_priv, next, &pending_fw_head,
                                 pending_list) {
                if (!fw_priv->need_uevent || !only_kill_custom)
                         __fw_load_abort(fw_priv);
        }
        mutex_unlock(&fw_lock);
}

static ssize_t timeout_show(struct class *class, struct class_attribute *attr,
                            char *buf)
{
        return sprintf(buf, "%d\n", __firmware_loading_timeout());
}

/**
 * firmware_timeout_store() - set number of seconds to wait for firmware
 * @class: device class pointer
 * @attr: device attribute pointer
 * @buf: buffer to scan for timeout value
 * @count: number of bytes in @buf
 *
 *      Sets the number of seconds to wait for the firmware.  Once
 *      this expires an error will be returned to the driver and no
 *      firmware will be provided.
 *
 *      Note: zero means 'wait forever'.
 **/
static ssize_t timeout_store(struct class *class, struct class_attribute *attr,
                             const char *buf, size_t count)
{
        int tmp_loading_timeout = simple_strtol(buf, NULL, 10);

        if (tmp_loading_timeout < 0)
                tmp_loading_timeout = 0;

        __fw_fallback_set_timeout(tmp_loading_timeout);

        return count;
}
static CLASS_ATTR_RW(timeout);

static struct attribute *firmware_class_attrs[] = {
        &class_attr_timeout.attr,
        NULL,
};
ATTRIBUTE_GROUPS(firmware_class);

static void fw_dev_release(struct device *dev)
{
        struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);

        kfree(fw_sysfs);
}

static int do_firmware_uevent(struct fw_sysfs *fw_sysfs, struct kobj_uevent_env *env)
{
        if (add_uevent_var(env, "FIRMWARE=%s", fw_sysfs->fw_priv->fw_name))
                return -ENOMEM;
        if (add_uevent_var(env, "TIMEOUT=%i", __firmware_loading_timeout()))
                return -ENOMEM;
        if (add_uevent_var(env, "ASYNC=%d", fw_sysfs->nowait))
                return -ENOMEM;

        return 0;
}

static int firmware_uevent(struct device *dev, struct kobj_uevent_env *env)
{
        struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);
        int err = 0;

        mutex_lock(&fw_lock);
        if (fw_sysfs->fw_priv)
                err = do_firmware_uevent(fw_sysfs, env);
        mutex_unlock(&fw_lock);
        return err;
}

static struct class firmware_class = {
        .name           = "firmware",
        .class_groups   = firmware_class_groups,
        .dev_uevent     = firmware_uevent,
        .dev_release    = fw_dev_release,
};

int register_sysfs_loader(void)
{
        return class_register(&firmware_class);
}

void unregister_sysfs_loader(void)
{
        class_unregister(&firmware_class);
}

static ssize_t firmware_loading_show(struct device *dev,
                                     struct device_attribute *attr, char *buf)
{
        struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);
        int loading = 0;

        mutex_lock(&fw_lock);
        if (fw_sysfs->fw_priv)
                loading = fw_sysfs_loading(fw_sysfs->fw_priv);
        mutex_unlock(&fw_lock);

        return sprintf(buf, "%d\n", loading);
}

/**
 * firmware_loading_store() - set value in the 'loading' control file
 * @dev: device pointer
 * @attr: device attribute pointer
 * @buf: buffer to scan for loading control value
 * @count: number of bytes in @buf
 *
 *      The relevant values are:
 *
 *       1: Start a load, discarding any previous partial load.
 *       0: Conclude the load and hand the data to the driver code.
 *      -1: Conclude the load with an error and discard any written data.
 **/
static ssize_t firmware_loading_store(struct device *dev,
                                      struct device_attribute *attr,
                                      const char *buf, size_t count)
{
        struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);
        struct fw_priv *fw_priv;
        ssize_t written = count;
        int loading = simple_strtol(buf, NULL, 10);

        mutex_lock(&fw_lock);
        fw_priv = fw_sysfs->fw_priv;
        if (fw_state_is_aborted(fw_priv))
                goto out;

        switch (loading) {
        case 1:
                /* discarding any previous partial load */
                if (!fw_sysfs_done(fw_priv)) {
                        fw_free_paged_buf(fw_priv);
                        fw_state_start(fw_priv);
                }
                break;
        case 0:
                if (fw_sysfs_loading(fw_priv)) {
                        int rc;

                        /*
                         * Several loading requests may be pending on
                         * one same firmware buf, so let all requests
                         * see the mapped 'buf->data' once the loading
                         * is completed.
                         * */
                        rc = fw_map_paged_buf(fw_priv);
                        if (rc)
                                dev_err(dev, "%s: map pages failed\n",
                                        __func__);
                        else
                                rc = security_kernel_post_read_file(NULL,
                                                fw_priv->data, fw_priv->size,
                                                READING_FIRMWARE);

                        /*
                         * Same logic as fw_load_abort, only the DONE bit
                         * is ignored and we set ABORT only on failure.
                         */
                        list_del_init(&fw_priv->pending_list);
                        if (rc) {
                                fw_state_aborted(fw_priv);
                                written = rc;
                        } else {
                                fw_state_done(fw_priv);
                        }
                        break;
                }
                /* fallthrough */
        default:
                dev_err(dev, "%s: unexpected value (%d)\n", __func__, loading);
                /* fallthrough */
        case -1:
                fw_load_abort(fw_sysfs);
                break;
        }
out:
        mutex_unlock(&fw_lock);
        return written;
}

static DEVICE_ATTR(loading, 0644, firmware_loading_show, firmware_loading_store);

static void firmware_rw_data(struct fw_priv *fw_priv, char *buffer,
                           loff_t offset, size_t count, bool read)
{
        if (read)
                memcpy(buffer, fw_priv->data + offset, count);
        else
                memcpy(fw_priv->data + offset, buffer, count);
}

static void firmware_rw(struct fw_priv *fw_priv, char *buffer,
                        loff_t offset, size_t count, bool read)
{
        while (count) {
                void *page_data;
                int page_nr = offset >> PAGE_SHIFT;
                int page_ofs = offset & (PAGE_SIZE-1);
                int page_cnt = min_t(size_t, PAGE_SIZE - page_ofs, count);

                page_data = kmap(fw_priv->pages[page_nr]);

                if (read)
                        memcpy(buffer, page_data + page_ofs, page_cnt);
                else
                        memcpy(page_data + page_ofs, buffer, page_cnt);

                kunmap(fw_priv->pages[page_nr]);
                buffer += page_cnt;
                offset += page_cnt;
                count -= page_cnt;
        }
}

static ssize_t firmware_data_read(struct file *filp, struct kobject *kobj,
                                  struct bin_attribute *bin_attr,
                                  char *buffer, loff_t offset, size_t count)
{
        struct device *dev = kobj_to_dev(kobj);
        struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);
        struct fw_priv *fw_priv;
        ssize_t ret_count;

        mutex_lock(&fw_lock);
        fw_priv = fw_sysfs->fw_priv;
        if (!fw_priv || fw_sysfs_done(fw_priv)) {
                ret_count = -ENODEV;
                goto out;
        }
        if (offset > fw_priv->size) {
                ret_count = 0;
                goto out;
        }
        if (count > fw_priv->size - offset)
                count = fw_priv->size - offset;

        ret_count = count;

        if (fw_priv->data)
                firmware_rw_data(fw_priv, buffer, offset, count, true);
        else
                firmware_rw(fw_priv, buffer, offset, count, true);

out:
        mutex_unlock(&fw_lock);
        return ret_count;
}

static int fw_realloc_pages(struct fw_sysfs *fw_sysfs, int min_size)
{
        int err;

        err = fw_grow_paged_buf(fw_sysfs->fw_priv,
                                PAGE_ALIGN(min_size) >> PAGE_SHIFT);
        if (err)
                fw_load_abort(fw_sysfs);
        return err;
}

/**
 * firmware_data_write() - write method for firmware
 * @filp: open sysfs file
 * @kobj: kobject for the device
 * @bin_attr: bin_attr structure
 * @buffer: buffer being written
 * @offset: buffer offset for write in total data store area
 * @count: buffer size
 *
 *      Data written to the 'data' attribute will be later handed to
 *      the driver as a firmware image.
 **/
static ssize_t firmware_data_write(struct file *filp, struct kobject *kobj,
                                   struct bin_attribute *bin_attr,
                                   char *buffer, loff_t offset, size_t count)
{
        struct device *dev = kobj_to_dev(kobj);
        struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);
        struct fw_priv *fw_priv;
        ssize_t retval;

        if (!capable(CAP_SYS_RAWIO))
                return -EPERM;

        mutex_lock(&fw_lock);
        fw_priv = fw_sysfs->fw_priv;
        if (!fw_priv || fw_sysfs_done(fw_priv)) {
                retval = -ENODEV;
                goto out;
        }

        if (fw_priv->data) {
                if (offset + count > fw_priv->allocated_size) {
                        retval = -ENOMEM;
                        goto out;
                }
                firmware_rw_data(fw_priv, buffer, offset, count, false);
                retval = count;
        } else {
                retval = fw_realloc_pages(fw_sysfs, offset + count);
                if (retval)
                        goto out;

                retval = count;
                firmware_rw(fw_priv, buffer, offset, count, false);
        }

        fw_priv->size = max_t(size_t, offset + count, fw_priv->size);
out:
        mutex_unlock(&fw_lock);
        return retval;
}

static struct bin_attribute firmware_attr_data = {
        .attr = { .name = "data", .mode = 0644 },
        .size = 0,
        .read = firmware_data_read,
        .write = firmware_data_write,
};

static struct attribute *fw_dev_attrs[] = {
        &dev_attr_loading.attr,
        NULL
};

static struct bin_attribute *fw_dev_bin_attrs[] = {
        &firmware_attr_data,
        NULL
};

static const struct attribute_group fw_dev_attr_group = {
        .attrs = fw_dev_attrs,
        .bin_attrs = fw_dev_bin_attrs,
};

static const struct attribute_group *fw_dev_attr_groups[] = {
        &fw_dev_attr_group,
        NULL
};

static struct fw_sysfs *
fw_create_instance(struct firmware *firmware, const char *fw_name,
                   struct device *device, enum fw_opt opt_flags)
{
        struct fw_sysfs *fw_sysfs;
        struct device *f_dev;

        fw_sysfs = kzalloc(sizeof(*fw_sysfs), GFP_KERNEL);
        if (!fw_sysfs) {
                fw_sysfs = ERR_PTR(-ENOMEM);
                goto exit;
        }

        fw_sysfs->nowait = !!(opt_flags & FW_OPT_NOWAIT);
        fw_sysfs->fw = firmware;
        f_dev = &fw_sysfs->dev;

        device_initialize(f_dev);
        dev_set_name(f_dev, "%s", fw_name);
        f_dev->parent = device;
        f_dev->class = &firmware_class;
        f_dev->groups = fw_dev_attr_groups;
exit:
        return fw_sysfs;
}

/**
 * fw_load_sysfs_fallback() - load a firmware via the sysfs fallback mechanism
 * @fw_sysfs: firmware sysfs information for the firmware to load
 * @opt_flags: flags of options, FW_OPT_*
 * @timeout: timeout to wait for the load
 *
 * In charge of constructing a sysfs fallback interface for firmware loading.
 **/
static int fw_load_sysfs_fallback(struct fw_sysfs *fw_sysfs,
                                  enum fw_opt opt_flags, long timeout)
{
        int retval = 0;
        struct device *f_dev = &fw_sysfs->dev;
        struct fw_priv *fw_priv = fw_sysfs->fw_priv;

        /* fall back on userspace loading */
        if (!fw_priv->data)
                fw_priv->is_paged_buf = true;

        dev_set_uevent_suppress(f_dev, true);

        retval = device_add(f_dev);
        if (retval) {
                dev_err(f_dev, "%s: device_register failed\n", __func__);
                goto err_put_dev;
        }

        mutex_lock(&fw_lock);
        list_add(&fw_priv->pending_list, &pending_fw_head);
        mutex_unlock(&fw_lock);

        if (opt_flags & FW_OPT_UEVENT) {
                fw_priv->need_uevent = true;
                dev_set_uevent_suppress(f_dev, false);
                dev_dbg(f_dev, "firmware: requesting %s\n", fw_priv->fw_name);
                kobject_uevent(&fw_sysfs->dev.kobj, KOBJ_ADD);
        } else {
                timeout = MAX_JIFFY_OFFSET;
        }

        retval = fw_sysfs_wait_timeout(fw_priv, timeout);
        if (retval < 0) {
                mutex_lock(&fw_lock);
                fw_load_abort(fw_sysfs);
                mutex_unlock(&fw_lock);
        }

        if (fw_state_is_aborted(fw_priv)) {
                if (retval == -ERESTARTSYS)
                        retval = -EINTR;
                else
                        retval = -EAGAIN;
        } else if (fw_priv->is_paged_buf && !fw_priv->data)
                retval = -ENOMEM;

        device_del(f_dev);
err_put_dev:
        put_device(f_dev);
        return retval;
}

static int fw_load_from_user_helper(struct firmware *firmware,
                                    const char *name, struct device *device,
                                    enum fw_opt opt_flags)
{
        struct fw_sysfs *fw_sysfs;
        long timeout;
        int ret;

        timeout = firmware_loading_timeout();
        if (opt_flags & FW_OPT_NOWAIT) {
                timeout = usermodehelper_read_lock_wait(timeout);
                if (!timeout) {
                        dev_dbg(device, "firmware: %s loading timed out\n",
                                name);
                        return -EBUSY;
                }
        } else {
                ret = usermodehelper_read_trylock();
                if (WARN_ON(ret)) {
                        dev_err(device, "firmware: %s will not be loaded\n",
                                name);
                        return ret;
                }
        }

        fw_sysfs = fw_create_instance(firmware, name, device, opt_flags);
        if (IS_ERR(fw_sysfs)) {
                ret = PTR_ERR(fw_sysfs);
                goto out_unlock;
        }

        fw_sysfs->fw_priv = firmware->priv;
        ret = fw_load_sysfs_fallback(fw_sysfs, opt_flags, timeout);

        if (!ret)
                ret = assign_fw(firmware, device, opt_flags);

out_unlock:
        usermodehelper_read_unlock();

        return ret;
}

static bool fw_force_sysfs_fallback(enum fw_opt opt_flags)
{
        if (fw_fallback_config.force_sysfs_fallback)
                return true;
        if (!(opt_flags & FW_OPT_USERHELPER))
                return false;
        return true;
}

static bool fw_run_sysfs_fallback(enum fw_opt opt_flags)
{
        int ret;

        if (fw_fallback_config.ignore_sysfs_fallback) {
                pr_info_once("Ignoring firmware sysfs fallback due to sysctl knob\n");
                return false;
        }

        if ((opt_flags & FW_OPT_NOFALLBACK))
                return false;

        /* Also permit LSMs and IMA to fail firmware sysfs fallback */
        ret = security_kernel_load_data(LOADING_FIRMWARE);
        if (ret < 0)
                return false;

        return fw_force_sysfs_fallback(opt_flags);
}

/**
 * firmware_fallback_sysfs() - use the fallback mechanism to find firmware
 * @fw: pointer to firmware image
 * @name: name of firmware file to look for
 * @device: device for which firmware is being loaded
 * @opt_flags: options to control firmware loading behaviour
 * @ret: return value from direct lookup which triggered the fallback mechanism
 *
 * This function is called if direct lookup for the firmware failed, it enables
 * a fallback mechanism through userspace by exposing a sysfs loading
 * interface. Userspace is in charge of loading the firmware through the sysfs
 * loading interface. This sysfs fallback mechanism may be disabled completely
 * on a system by setting the proc sysctl value ignore_sysfs_fallback to true.
 * If this false we check if the internal API caller set the @FW_OPT_NOFALLBACK
 * flag, if so it would also disable the fallback mechanism. A system may want
 * to enfoce the sysfs fallback mechanism at all times, it can do this by
 * setting ignore_sysfs_fallback to false and force_sysfs_fallback to true.
 * Enabling force_sysfs_fallback is functionally equivalent to build a kernel
 * with CONFIG_FW_LOADER_USER_HELPER_FALLBACK.
 **/
int firmware_fallback_sysfs(struct firmware *fw, const char *name,
                            struct device *device,
                            enum fw_opt opt_flags,
                            int ret)
{
        if (!fw_run_sysfs_fallback(opt_flags))
                return ret;

        if (!(opt_flags & FW_OPT_NO_WARN))
                dev_warn(device, "Falling back to sysfs fallback for: %s\n",
                                 name);
        else
                dev_dbg(device, "Falling back to sysfs fallback for: %s\n",
                                name);
        return fw_load_from_user_helper(fw, name, device, opt_flags);
}