subr_firmware.c

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/*-
 * 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("$BSDSUniX$");

#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;

        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);
                return NULL;
        }
        if (frp == NULL) {
                mtx_unlock(&firmware_mtx);
                printf("%s: cannot register image %s, firmware table full!\n",
                    __func__, imagename);
                return NULL;
        }
        bzero(frp, sizeof(*frp));       /* start from a clean record */
        frp->fw.name = imagename;
        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 it's
                 * 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.
                 */
                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)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;

        FILEDESC_XLOCK(p->p_fd);
        if (p->p_fd->fd_cdir == NULL) {
                p->p_fd->fd_cdir = rootvnode;
                VREF(rootvnode);
        }
        if (p->p_fd->fd_rdir == NULL) {
                p->p_fd->fd_rdir = rootvnode;
                VREF(rootvnode);
        }
        FILEDESC_XUNLOCK(p->p_fd);

        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);