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- // SPDX-License-Identifier: GPL-2.0
- #include <linux/types.h>
- #include <linux/kconfig.h>
- #include <linux/list.h>
- #include <linux/security.h>
- #include <linux/umh.h>
- #include <linux/sysctl.h>
- #include <linux/module.h>
- #include "fallback.h"
- #include "firmware.h"
- /*
- * firmware fallback mechanism
- */
- /*
- * 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 int fw_sysfs_wait_timeout(struct fw_priv *fw_priv, long timeout)
- {
- return __fw_state_wait_common(fw_priv, timeout);
- }
- 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);
- }
- /**
- * fw_load_sysfs_fallback() - load a firmware via the sysfs fallback mechanism
- * @fw_sysfs: firmware sysfs information for the firmware to load
- * @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, 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);
- if (fw_state_is_aborted(fw_priv)) {
- mutex_unlock(&fw_lock);
- retval = -EINTR;
- goto out;
- }
- list_add(&fw_priv->pending_list, &pending_fw_head);
- mutex_unlock(&fw_lock);
- if (fw_priv->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 && retval != -ENOENT) {
- 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 if (fw_priv->is_paged_buf && !fw_priv->data)
- retval = -ENOMEM;
- out:
- 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,
- u32 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, timeout);
- if (!ret)
- ret = assign_fw(firmware, device);
- out_unlock:
- usermodehelper_read_unlock();
- return ret;
- }
- static bool fw_force_sysfs_fallback(u32 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(u32 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_SYSFS))
- return false;
- /* Also permit LSMs and IMA to fail firmware sysfs fallback */
- ret = security_kernel_load_data(LOADING_FIRMWARE, true);
- 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, as defined by
- * &enum fw_opt
- * @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 is false we check if the internal API caller set the
- * @FW_OPT_NOFALLBACK_SYSFS flag, if so it would also disable the fallback
- * mechanism. A system may want to enforce 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,
- u32 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);
- }
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