FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_firmware.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2005-2008, Sam Leffler <sam@errno.com>
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice unmodified, this list of conditions, and the following
     *    disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/12.0/sys/kern/subr_firmware.c 326271 2017-11-27 15:20:12Z pfg $");
    
    #include <sys/param.h>
    #include <sys/kernel.h>
    #include <sys/malloc.h>
    #include <sys/queue.h>
    #include <sys/taskqueue.h>
    #include <sys/systm.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/errno.h>
    #include <sys/linker.h>
    #include <sys/firmware.h>
    #include <sys/priv.h>
    #include <sys/proc.h>
    #include <sys/module.h>
    #include <sys/eventhandler.h>
    
    #include <sys/filedesc.h>
    #include <sys/vnode.h>
    
    /*
     * Loadable firmware support. See sys/sys/firmware.h and firmware(9)
     * form more details on the subsystem.
     *
     * 'struct firmware' is the user-visible part of the firmware table.
     * Additional internal information is stored in a 'struct priv_fw'
     * (currently a static array). A slot is in use if FW_INUSE is true:
     */
    
    #define FW_INUSE(p)     ((p)->file != NULL || (p)->fw.name != NULL)
    
    /*
     * fw.name != NULL when an image is registered; file != NULL for
     * autoloaded images whose handling has not been completed.
     *
     * The state of a slot evolves as follows:
     *      firmware_register       -->  fw.name = image_name
     *      (autoloaded image)      -->  file = module reference
     *      firmware_unregister     -->  fw.name = NULL
     *      (unloadentry complete)  -->  file = NULL
     *
     * In order for the above to work, the 'file' field must remain
     * unchanged in firmware_unregister().
     *
     * Images residing in the same module are linked to each other
     * through the 'parent' argument of firmware_register().
     * One image (typically, one with the same name as the module to let
     * the autoloading mechanism work) is considered the parent image for
     * all other images in the same module. Children affect the refcount
     * on the parent image preventing improper unloading of the image itself.
     */
    
    struct priv_fw {
            int             refcnt;         /* reference count */
    
            /*
             * parent entry, see above. Set on firmware_register(),
             * cleared on firmware_unregister().
             */
            struct priv_fw  *parent;
    
            int             flags;  /* record FIRMWARE_UNLOAD requests */
    #define FW_UNLOAD       0x100
    
            /*
             * 'file' is private info managed by the autoload/unload code.
             * Set at the end of firmware_get(), cleared only in the
             * firmware_unload_task, so the latter can depend on its value even
             * while the lock is not held.
            */
           linker_file_t   file;   /* module file, if autoloaded */
   
           /*
            * 'fw' is the externally visible image information.
            * We do not make it the first field in priv_fw, to avoid the
            * temptation of casting pointers to each other.
            * Use PRIV_FW(fw) to get a pointer to the cointainer of fw.
            * Beware, PRIV_FW does not work for a NULL pointer.
            */
           struct firmware fw;     /* externally visible information */
   };
   
   /*
    * PRIV_FW returns the pointer to the container of struct firmware *x.
    * Cast to intptr_t to override the 'const' attribute of x
    */
   #define PRIV_FW(x)      ((struct priv_fw *)             \
           ((intptr_t)(x) - offsetof(struct priv_fw, fw)) )
   
   /*
    * At the moment we use a static array as backing store for the registry.
    * Should we move to a dynamic structure, keep in mind that we cannot
    * reallocate the array because pointers are held externally.
    * A list may work, though.
    */
   #define FIRMWARE_MAX    50
   static struct priv_fw firmware_table[FIRMWARE_MAX];
   
   /*
    * Firmware module operations are handled in a separate task as they
    * might sleep and they require directory context to do i/o.
    */
   static struct taskqueue *firmware_tq;
   static struct task firmware_unload_task;
   
   /*
    * This mutex protects accesses to the firmware table.
    */
   static struct mtx firmware_mtx;
   MTX_SYSINIT(firmware, &firmware_mtx, "firmware table", MTX_DEF);
   
   /*
    * Helper function to lookup a name.
    * As a side effect, it sets the pointer to a free slot, if any.
    * This way we can concentrate most of the registry scanning in
    * this function, which makes it easier to replace the registry
    * with some other data structure.
    */
   static struct priv_fw *
   lookup(const char *name, struct priv_fw **empty_slot)
   {
           struct priv_fw *fp = NULL;
           struct priv_fw *dummy;
           int i;
   
           if (empty_slot == NULL)
                   empty_slot = &dummy;
           *empty_slot = NULL;
           for (i = 0; i < FIRMWARE_MAX; i++) {
                   fp = &firmware_table[i];
                   if (fp->fw.name != NULL && strcasecmp(name, fp->fw.name) == 0)
                           break;
                   else if (!FW_INUSE(fp))
                           *empty_slot = fp;
           }
           return (i < FIRMWARE_MAX ) ? fp : NULL;
   }
   
   /*
    * Register a firmware image with the specified name.  The
    * image name must not already be registered.  If this is a
    * subimage then parent refers to a previously registered
    * image that this should be associated with.
    */
   const struct firmware *
   firmware_register(const char *imagename, const void *data, size_t datasize,
       unsigned int version, const struct firmware *parent)
   {
           struct priv_fw *match, *frp;
           char *str;
   
           str = strdup(imagename, M_TEMP);
   
           mtx_lock(&firmware_mtx);
           /*
            * Do a lookup to make sure the name is unique or find a free slot.
            */
           match = lookup(imagename, &frp);
           if (match != NULL) {
                   mtx_unlock(&firmware_mtx);
                   printf("%s: image %s already registered!\n",
                           __func__, imagename);
                   free(str, M_TEMP);
                   return NULL;
           }
           if (frp == NULL) {
                   mtx_unlock(&firmware_mtx);
                   printf("%s: cannot register image %s, firmware table full!\n",
                       __func__, imagename);
                   free(str, M_TEMP);
                   return NULL;
           }
           bzero(frp, sizeof(*frp));       /* start from a clean record */
           frp->fw.name = str;
           frp->fw.data = data;
           frp->fw.datasize = datasize;
           frp->fw.version = version;
           if (parent != NULL)
                   frp->parent = PRIV_FW(parent);
           mtx_unlock(&firmware_mtx);
           if (bootverbose)
                   printf("firmware: '%s' version %u: %zu bytes loaded at %p\n",
                       imagename, version, datasize, data);
           return &frp->fw;
   }
   
   /*
    * Unregister/remove a firmware image.  If there are outstanding
    * references an error is returned and the image is not removed
    * from the registry.
    */
   int
   firmware_unregister(const char *imagename)
   {
           struct priv_fw *fp;
           int err;
   
           mtx_lock(&firmware_mtx);
           fp = lookup(imagename, NULL);
           if (fp == NULL) {
                   /*
                    * It is ok for the lookup to fail; this can happen
                    * when a module is unloaded on last reference and the
                    * module unload handler unregister's each of its
                    * firmware images.
                    */
                   err = 0;
           } else if (fp->refcnt != 0) {   /* cannot unregister */
                   err = EBUSY;
           } else {
                   linker_file_t x = fp->file;     /* save value */
   
                   /*
                    * Clear the whole entry with bzero to make sure we
                    * do not forget anything. Then restore 'file' which is
                    * non-null for autoloaded images.
                    */
                   free((void *) (uintptr_t) fp->fw.name, M_TEMP);
                   bzero(fp, sizeof(struct priv_fw));
                   fp->file = x;
                   err = 0;
           }
           mtx_unlock(&firmware_mtx);
           return err;
   }
   
   static void
   loadimage(void *arg, int npending)
   {
           struct thread *td = curthread;
           char *imagename = arg;
           struct priv_fw *fp;
           linker_file_t result;
           int error;
   
           /* synchronize with the thread that dispatched us */
           mtx_lock(&firmware_mtx);
           mtx_unlock(&firmware_mtx);
   
           if (td->td_proc->p_fd->fd_rdir == NULL) {
                   printf("%s: root not mounted yet, no way to load image\n",
                       imagename);
                   goto done;
           }
           error = linker_reference_module(imagename, NULL, &result);
           if (error != 0) {
                   printf("%s: could not load firmware image, error %d\n",
                       imagename, error);
                   goto done;
           }
   
           mtx_lock(&firmware_mtx);
           fp = lookup(imagename, NULL);
           if (fp == NULL || fp->file != NULL) {
                   mtx_unlock(&firmware_mtx);
                   if (fp == NULL)
                           printf("%s: firmware image loaded, "
                               "but did not register\n", imagename);
                   (void) linker_release_module(imagename, NULL, NULL);
                   goto done;
           }
           fp->file = result;      /* record the module identity */
           mtx_unlock(&firmware_mtx);
   done:
           wakeup_one(imagename);          /* we're done */
   }
   
   /*
    * Lookup and potentially load the specified firmware image.
    * If the firmware is not found in the registry, try to load a kernel
    * module named as the image name.
    * If the firmware is located, a reference is returned. The caller must
    * release this reference for the image to be eligible for removal/unload.
    */
   const struct firmware *
   firmware_get(const char *imagename)
   {
           struct task fwload_task;
           struct thread *td;
           struct priv_fw *fp;
   
           mtx_lock(&firmware_mtx);
           fp = lookup(imagename, NULL);
           if (fp != NULL)
                   goto found;
           /*
            * Image not present, try to load the module holding it.
            */
           td = curthread;
           if (priv_check(td, PRIV_FIRMWARE_LOAD) != 0 ||
               securelevel_gt(td->td_ucred, 0) != 0) {
                   mtx_unlock(&firmware_mtx);
                   printf("%s: insufficient privileges to "
                       "load firmware image %s\n", __func__, imagename);
                   return NULL;
           }
           /* 
            * Defer load to a thread with known context.  linker_reference_module
            * may do filesystem i/o which requires root & current dirs, etc.
            * Also we must not hold any mtx's over this call which is problematic.
            */
           if (!cold) {
                   TASK_INIT(&fwload_task, 0, loadimage, __DECONST(void *,
                       imagename));
                   taskqueue_enqueue(firmware_tq, &fwload_task);
                   msleep(__DECONST(void *, imagename), &firmware_mtx, 0,
                       "fwload", 0);
           }
           /*
            * After attempting to load the module, see if the image is registered.
            */
           fp = lookup(imagename, NULL);
           if (fp == NULL) {
                   mtx_unlock(&firmware_mtx);
                   return NULL;
           }
   found:                          /* common exit point on success */
           if (fp->refcnt == 0 && fp->parent != NULL)
                   fp->parent->refcnt++;
           fp->refcnt++;
           mtx_unlock(&firmware_mtx);
           return &fp->fw;
   }
   
   /*
    * Release a reference to a firmware image returned by firmware_get.
    * The caller may specify, with the FIRMWARE_UNLOAD flag, its desire
    * to release the resource, but the flag is only advisory.
    *
    * If this is the last reference to the firmware image, and this is an
    * autoloaded module, wake up the firmware_unload_task to figure out
    * what to do with the associated module.
    */
   void
   firmware_put(const struct firmware *p, int flags)
   {
           struct priv_fw *fp = PRIV_FW(p);
   
           mtx_lock(&firmware_mtx);
           fp->refcnt--;
           if (fp->refcnt == 0) {
                   if (fp->parent != NULL)
                           fp->parent->refcnt--;
                   if (flags & FIRMWARE_UNLOAD)
                           fp->flags |= FW_UNLOAD;
                   if (fp->file)
                           taskqueue_enqueue(firmware_tq, &firmware_unload_task);
           }
           mtx_unlock(&firmware_mtx);
   }
   
   /*
    * Setup directory state for the firmware_tq thread so we can do i/o.
    */
   static void
   set_rootvnode(void *arg, int npending)
   {
   
           pwd_ensure_dirs();
   
           free(arg, M_TEMP);
   }
   
   /*
    * Event handler called on mounting of /; bounce a task
    * into the task queue thread to setup it's directories.
    */
   static void
   firmware_mountroot(void *arg)
   {
           struct task *setroot_task;
   
           setroot_task = malloc(sizeof(struct task), M_TEMP, M_NOWAIT);
           if (setroot_task != NULL) {
                   TASK_INIT(setroot_task, 0, set_rootvnode, setroot_task);
                   taskqueue_enqueue(firmware_tq, setroot_task);
           } else
                   printf("%s: no memory for task!\n", __func__);
   }
   EVENTHANDLER_DEFINE(mountroot, firmware_mountroot, NULL, 0);
   
   /*
    * The body of the task in charge of unloading autoloaded modules
    * that are not needed anymore.
    * Images can be cross-linked so we may need to make multiple passes,
    * but the time we spend in the loop is bounded because we clear entries
    * as we touch them.
    */
   static void
   unloadentry(void *unused1, int unused2)
   {
           int limit = FIRMWARE_MAX;
           int i;  /* current cycle */
   
           mtx_lock(&firmware_mtx);
           /*
            * Scan the table. limit is set to make sure we make another
            * full sweep after matching an entry that requires unloading.
            */
           for (i = 0; i < limit; i++) {
                   struct priv_fw *fp;
                   int err;
   
                   fp = &firmware_table[i % FIRMWARE_MAX];
                   if (fp->fw.name == NULL || fp->file == NULL ||
                       fp->refcnt != 0 || (fp->flags & FW_UNLOAD) == 0)
                           continue;
   
                   /*
                    * Found an entry. Now:
                    * 1. bump up limit to make sure we make another full round;
                    * 2. clear FW_UNLOAD so we don't try this entry again.
                    * 3. release the lock while trying to unload the module.
                    * 'file' remains set so that the entry cannot be reused
                    * in the meantime (it also means that fp->file will
                    * not change while we release the lock).
                    */
                   limit = i + FIRMWARE_MAX;       /* make another full round */
                   fp->flags &= ~FW_UNLOAD;        /* do not try again */
   
                   mtx_unlock(&firmware_mtx);
                   err = linker_release_module(NULL, NULL, fp->file);
                   mtx_lock(&firmware_mtx);
   
                   /*
                    * We rely on the module to call firmware_unregister()
                    * on unload to actually release the entry.
                    * If err = 0 we can drop our reference as the system
                    * accepted it. Otherwise unloading failed (e.g. the
                    * module itself gave an error) so our reference is
                    * still valid.
                    */
                   if (err == 0)
                           fp->file = NULL; 
           }
           mtx_unlock(&firmware_mtx);
   }
   
   /*
    * Module glue.
    */
   static int
   firmware_modevent(module_t mod, int type, void *unused)
   {
           struct priv_fw *fp;
           int i, err;
   
           switch (type) {
           case MOD_LOAD:
                   TASK_INIT(&firmware_unload_task, 0, unloadentry, NULL);
                   firmware_tq = taskqueue_create("taskqueue_firmware", M_WAITOK,
                       taskqueue_thread_enqueue, &firmware_tq);
                   /* NB: use our own loop routine that sets up context */
                   (void) taskqueue_start_threads(&firmware_tq, 1, PWAIT,
                       "firmware taskq");
                   if (rootvnode != NULL) {
                           /* 
                            * Root is already mounted so we won't get an event;
                            * simulate one here.
                            */
                           firmware_mountroot(NULL);
                   }
                   return 0;
   
           case MOD_UNLOAD:
                   /* request all autoloaded modules to be released */
                   mtx_lock(&firmware_mtx);
                   for (i = 0; i < FIRMWARE_MAX; i++) {
                           fp = &firmware_table[i];
                           fp->flags |= FW_UNLOAD;
                   }
                   mtx_unlock(&firmware_mtx);
                   taskqueue_enqueue(firmware_tq, &firmware_unload_task);
                   taskqueue_drain(firmware_tq, &firmware_unload_task);
                   err = 0;
                   for (i = 0; i < FIRMWARE_MAX; i++) {
                           fp = &firmware_table[i];
                           if (fp->fw.name != NULL) {
                                   printf("%s: image %p ref %d still active slot %d\n",
                                           __func__, fp->fw.name,
                                           fp->refcnt,  i);
                                   err = EINVAL;
                           }
                   }
                   if (err == 0)
                           taskqueue_free(firmware_tq);
                   return err;
           }
           return EINVAL;
   }
   
   static moduledata_t firmware_mod = {
           "firmware",
           firmware_modevent,
           NULL
   };
   DECLARE_MODULE(firmware, firmware_mod, SI_SUB_DRIVERS, SI_ORDER_FIRST);
   MODULE_VERSION(firmware, 1);

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