ALSA: seq: Fix racy access for queue timer in proc read

[mirror_ubuntu-bionic-kernel.git] / sound / sound_core.c

/*
 *      Sound core.  This file is composed of two parts.  sound_class
 *      which is common to both OSS and ALSA and OSS sound core which
 *      is used OSS or emulation of it.
 */

/*
 * First, the common part.
 */
#include <linux/module.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/kdev_t.h>
#include <linux/major.h>
#include <sound/core.h>

#ifdef CONFIG_SOUND_OSS_CORE
static int __init init_oss_soundcore(void);
static void cleanup_oss_soundcore(void);
#else
static inline int init_oss_soundcore(void)      { return 0; }
static inline void cleanup_oss_soundcore(void)  { }
#endif

struct class *sound_class;
EXPORT_SYMBOL(sound_class);

MODULE_DESCRIPTION("Core sound module");
MODULE_AUTHOR("Alan Cox");
MODULE_LICENSE("GPL");

static char *sound_devnode(struct device *dev, umode_t *mode)
{
        if (MAJOR(dev->devt) == SOUND_MAJOR)
                return NULL;
        return kasprintf(GFP_KERNEL, "snd/%s", dev_name(dev));
}

static int __init init_soundcore(void)
{
        int rc;

        rc = init_oss_soundcore();
        if (rc)
                return rc;

        sound_class = class_create(THIS_MODULE, "sound");
        if (IS_ERR(sound_class)) {
                cleanup_oss_soundcore();
                return PTR_ERR(sound_class);
        }

        sound_class->devnode = sound_devnode;

        return 0;
}

static void __exit cleanup_soundcore(void)
{
        cleanup_oss_soundcore();
        class_destroy(sound_class);
}

subsys_initcall(init_soundcore);
module_exit(cleanup_soundcore);


#ifdef CONFIG_SOUND_OSS_CORE
/*
 *      OSS sound core handling. Breaks out sound functions to submodules
 *      
 *      Author:         Alan Cox <alan@lxorguk.ukuu.org.uk>
 *
 *      Fixes:
 *
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 *                         --------------------
 * 
 *      Top level handler for the sound subsystem. Various devices can
 *      plug into this. The fact they don't all go via OSS doesn't mean 
 *      they don't have to implement the OSS API. There is a lot of logic
 *      to keeping much of the OSS weight out of the code in a compatibility
 *      module, but it's up to the driver to rember to load it...
 *
 *      The code provides a set of functions for registration of devices
 *      by type. This is done rather than providing a single call so that
 *      we can hide any future changes in the internals (eg when we go to
 *      32bit dev_t) from the modules and their interface.
 *
 *      Secondly we need to allocate the dsp, dsp16 and audio devices as
 *      one. Thus we misuse the chains a bit to simplify this.
 *
 *      Thirdly to make it more fun and for 2.3.x and above we do all
 *      of this using fine grained locking.
 *
 *      FIXME: we have to resolve modules and fine grained load/unload
 *      locking at some point in 2.3.x.
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sound.h>
#include <linux/kmod.h>

#define SOUND_STEP 16

struct sound_unit
{
        int unit_minor;
        const struct file_operations *unit_fops;
        struct sound_unit *next;
        char name[32];
};

#ifdef CONFIG_SOUND_MSNDCLAS
extern int msnd_classic_init(void);
#endif
#ifdef CONFIG_SOUND_MSNDPIN
extern int msnd_pinnacle_init(void);
#endif

/*
 * By default, OSS sound_core claims full legacy minor range (0-255)
 * of SOUND_MAJOR to trap open attempts to any sound minor and
 * requests modules using custom sound-slot/service-* module aliases.
 * The only benefit of doing this is allowing use of custom module
 * aliases instead of the standard char-major-* ones.  This behavior
 * prevents alternative OSS implementation and is scheduled to be
 * removed.
 *
 * CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss kernel
 * parameter are added to allow distros and developers to try and
 * switch to alternative implementations without needing to rebuild
 * the kernel in the meantime.  If preclaim_oss is non-zero, the
 * kernel will behave the same as before.  All SOUND_MAJOR minors are
 * preclaimed and the custom module aliases along with standard chrdev
 * ones are emitted if a missing device is opened.  If preclaim_oss is
 * zero, sound_core only grabs what's actually in use and for missing
 * devices only the standard chrdev aliases are requested.
 *
 * All these clutters are scheduled to be removed along with
 * sound-slot/service-* module aliases.
 */
#ifdef CONFIG_SOUND_OSS_CORE_PRECLAIM
static int preclaim_oss = 1;
#else
static int preclaim_oss = 0;
#endif

module_param(preclaim_oss, int, 0444);

static int soundcore_open(struct inode *, struct file *);

static const struct file_operations soundcore_fops =
{
        /* We must have an owner or the module locking fails */
        .owner  = THIS_MODULE,
        .open   = soundcore_open,
        .llseek = noop_llseek,
};

/*
 *      Low level list operator. Scan the ordered list, find a hole and
 *      join into it. Called with the lock asserted
 */

static int __sound_insert_unit(struct sound_unit * s, struct sound_unit **list, const struct file_operations *fops, int index, int low, int top)
{
        int n=low;

        if (index < 0) {        /* first free */

                while (*list && (*list)->unit_minor<n)
                        list=&((*list)->next);

                while(n<top)
                {
                        /* Found a hole ? */
                        if(*list==NULL || (*list)->unit_minor>n)
                                break;
                        list=&((*list)->next);
                        n+=SOUND_STEP;
                }

                if(n>=top)
                        return -ENOENT;
        } else {
                n = low+(index*16);
                while (*list) {
                        if ((*list)->unit_minor==n)
                                return -EBUSY;
                        if ((*list)->unit_minor>n)
                                break;
                        list=&((*list)->next);
                }
        }       
                
        /*
         *      Fill it in
         */
         
        s->unit_minor=n;
        s->unit_fops=fops;
        
        /*
         *      Link it
         */
         
        s->next=*list;
        *list=s;
        
        
        return n;
}

/*
 *      Remove a node from the chain. Called with the lock asserted
 */
 
static struct sound_unit *__sound_remove_unit(struct sound_unit **list, int unit)
{
        while(*list)
        {
                struct sound_unit *p=*list;
                if(p->unit_minor==unit)
                {
                        *list=p->next;
                        return p;
                }
                list=&(p->next);
        }
        printk(KERN_ERR "Sound device %d went missing!\n", unit);
        return NULL;
}

/*
 *      This lock guards the sound loader list.
 */

static DEFINE_SPINLOCK(sound_loader_lock);

/*
 *      Allocate the controlling structure and add it to the sound driver
 *      list. Acquires locks as needed
 */

static int sound_insert_unit(struct sound_unit **list, const struct file_operations *fops, int index, int low, int top, const char *name, umode_t mode, struct device *dev)
{
        struct sound_unit *s = kmalloc(sizeof(*s), GFP_KERNEL);
        int r;

        if (!s)
                return -ENOMEM;

        spin_lock(&sound_loader_lock);
retry:
        r = __sound_insert_unit(s, list, fops, index, low, top);
        spin_unlock(&sound_loader_lock);
        
        if (r < 0)
                goto fail;
        else if (r < SOUND_STEP)
                sprintf(s->name, "sound/%s", name);
        else
                sprintf(s->name, "sound/%s%d", name, r / SOUND_STEP);

        if (!preclaim_oss) {
                /*
                 * Something else might have grabbed the minor.  If
                 * first free slot is requested, rescan with @low set
                 * to the next unit; otherwise, -EBUSY.
                 */
                r = __register_chrdev(SOUND_MAJOR, s->unit_minor, 1, s->name,
                                      &soundcore_fops);
                if (r < 0) {
                        spin_lock(&sound_loader_lock);
                        __sound_remove_unit(list, s->unit_minor);
                        if (index < 0) {
                                low = s->unit_minor + SOUND_STEP;
                                goto retry;
                        }
                        spin_unlock(&sound_loader_lock);
                        r = -EBUSY;
                        goto fail;
                }
        }

        device_create(sound_class, dev, MKDEV(SOUND_MAJOR, s->unit_minor),
                      NULL, "%s", s->name+6);
        return s->unit_minor;

fail:
        kfree(s);
        return r;
}

/*
 *      Remove a unit. Acquires locks as needed. The drivers MUST have
 *      completed the removal before their file operations become
 *      invalid.
 */
        
static void sound_remove_unit(struct sound_unit **list, int unit)
{
        struct sound_unit *p;

        spin_lock(&sound_loader_lock);
        p = __sound_remove_unit(list, unit);
        spin_unlock(&sound_loader_lock);
        if (p) {
                if (!preclaim_oss)
                        __unregister_chrdev(SOUND_MAJOR, p->unit_minor, 1,
                                            p->name);
                device_destroy(sound_class, MKDEV(SOUND_MAJOR, p->unit_minor));
                kfree(p);
        }
}

/*
 *      Allocations
 *
 *      0       *16             Mixers
 *      1       *8              Sequencers
 *      2       *16             Midi
 *      3       *16             DSP
 *      4       *16             SunDSP
 *      5       *16             DSP16
 *      6       --              sndstat (obsolete)
 *      7       *16             unused
 *      8       --              alternate sequencer (see above)
 *      9       *16             raw synthesizer access
 *      10      *16             unused
 *      11      *16             unused
 *      12      *16             unused
 *      13      *16             unused
 *      14      *16             unused
 *      15      *16             unused
 */

static struct sound_unit *chains[SOUND_STEP];

/**
 *      register_sound_special_device - register a special sound node
 *      @fops: File operations for the driver
 *      @unit: Unit number to allocate
 *      @dev: device pointer
 *
 *      Allocate a special sound device by minor number from the sound
 *      subsystem.
 *
 *      Return: The allocated number is returned on success. On failure,
 *      a negative error code is returned.
 */
 
int register_sound_special_device(const struct file_operations *fops, int unit,
                                  struct device *dev)
{
        const int chain = unit % SOUND_STEP;
        int max_unit = 256;
        const char *name;
        char _name[16];

        switch (chain) {
            case 0:
                name = "mixer";
                break;
            case 1:
                name = "sequencer";
                if (unit >= SOUND_STEP)
                        goto __unknown;
                max_unit = unit + 1;
                break;
            case 2:
                name = "midi";
                break;
            case 3:
                name = "dsp";
                break;
            case 4:
                name = "audio";
                break;
            case 5:
                name = "dspW";
                break;
            case 8:
                name = "sequencer2";
                if (unit >= SOUND_STEP)
                        goto __unknown;
                max_unit = unit + 1;
                break;
            case 9:
                name = "dmmidi";
                break;
            case 10:
                name = "dmfm";
                break;
            case 12:
                name = "adsp";
                break;
            case 13:
                name = "amidi";
                break;
            case 14:
                name = "admmidi";
                break;
            default:
                {
                    __unknown:
                        sprintf(_name, "unknown%d", chain);
                        if (unit >= SOUND_STEP)
                                strcat(_name, "-");
                        name = _name;
                }
                break;
        }
        return sound_insert_unit(&chains[chain], fops, -1, unit, max_unit,
                                 name, S_IRUSR | S_IWUSR, dev);
}
 
EXPORT_SYMBOL(register_sound_special_device);

int register_sound_special(const struct file_operations *fops, int unit)
{
        return register_sound_special_device(fops, unit, NULL);
}

EXPORT_SYMBOL(register_sound_special);

/**
 *      register_sound_mixer - register a mixer device
 *      @fops: File operations for the driver
 *      @dev: Unit number to allocate
 *
 *      Allocate a mixer device. Unit is the number of the mixer requested.
 *      Pass -1 to request the next free mixer unit.
 *
 *      Return: On success, the allocated number is returned. On failure,
 *      a negative error code is returned.
 */

int register_sound_mixer(const struct file_operations *fops, int dev)
{
        return sound_insert_unit(&chains[0], fops, dev, 0, 128,
                                 "mixer", S_IRUSR | S_IWUSR, NULL);
}

EXPORT_SYMBOL(register_sound_mixer);

/**
 *      register_sound_midi - register a midi device
 *      @fops: File operations for the driver
 *      @dev: Unit number to allocate
 *
 *      Allocate a midi device. Unit is the number of the midi device requested.
 *      Pass -1 to request the next free midi unit.
 *
 *      Return: On success, the allocated number is returned. On failure,
 *      a negative error code is returned.
 */

int register_sound_midi(const struct file_operations *fops, int dev)
{
        return sound_insert_unit(&chains[2], fops, dev, 2, 130,
                                 "midi", S_IRUSR | S_IWUSR, NULL);
}

EXPORT_SYMBOL(register_sound_midi);

/*
 *      DSP's are registered as a triple. Register only one and cheat
 *      in open - see below.
 */
 
/**
 *      register_sound_dsp - register a DSP device
 *      @fops: File operations for the driver
 *      @dev: Unit number to allocate
 *
 *      Allocate a DSP device. Unit is the number of the DSP requested.
 *      Pass -1 to request the next free DSP unit.
 *
 *      This function allocates both the audio and dsp device entries together
 *      and will always allocate them as a matching pair - eg dsp3/audio3
 *
 *      Return: On success, the allocated number is returned. On failure,
 *      a negative error code is returned.
 */

int register_sound_dsp(const struct file_operations *fops, int dev)
{
        return sound_insert_unit(&chains[3], fops, dev, 3, 131,
                                 "dsp", S_IWUSR | S_IRUSR, NULL);
}

EXPORT_SYMBOL(register_sound_dsp);

/**
 *      unregister_sound_special - unregister a special sound device
 *      @unit: unit number to allocate
 *
 *      Release a sound device that was allocated with
 *      register_sound_special(). The unit passed is the return value from
 *      the register function.
 */


void unregister_sound_special(int unit)
{
        sound_remove_unit(&chains[unit % SOUND_STEP], unit);
}
 
EXPORT_SYMBOL(unregister_sound_special);

/**
 *      unregister_sound_mixer - unregister a mixer
 *      @unit: unit number to allocate
 *
 *      Release a sound device that was allocated with register_sound_mixer().
 *      The unit passed is the return value from the register function.
 */

void unregister_sound_mixer(int unit)
{
        sound_remove_unit(&chains[0], unit);
}

EXPORT_SYMBOL(unregister_sound_mixer);

/**
 *      unregister_sound_midi - unregister a midi device
 *      @unit: unit number to allocate
 *
 *      Release a sound device that was allocated with register_sound_midi().
 *      The unit passed is the return value from the register function.
 */

void unregister_sound_midi(int unit)
{
        sound_remove_unit(&chains[2], unit);
}

EXPORT_SYMBOL(unregister_sound_midi);

/**
 *      unregister_sound_dsp - unregister a DSP device
 *      @unit: unit number to allocate
 *
 *      Release a sound device that was allocated with register_sound_dsp().
 *      The unit passed is the return value from the register function.
 *
 *      Both of the allocated units are released together automatically.
 */

void unregister_sound_dsp(int unit)
{
        sound_remove_unit(&chains[3], unit);
}


EXPORT_SYMBOL(unregister_sound_dsp);

static struct sound_unit *__look_for_unit(int chain, int unit)
{
        struct sound_unit *s;
        
        s=chains[chain];
        while(s && s->unit_minor <= unit)
        {
                if(s->unit_minor==unit)
                        return s;
                s=s->next;
        }
        return NULL;
}

static int soundcore_open(struct inode *inode, struct file *file)
{
        int chain;
        int unit = iminor(inode);
        struct sound_unit *s;
        const struct file_operations *new_fops = NULL;

        chain=unit&0x0F;
        if(chain==4 || chain==5)        /* dsp/audio/dsp16 */
        {
                unit&=0xF0;
                unit|=3;
                chain=3;
        }
        
        spin_lock(&sound_loader_lock);
        s = __look_for_unit(chain, unit);
        if (s)
                new_fops = fops_get(s->unit_fops);
        if (preclaim_oss && !new_fops) {
                spin_unlock(&sound_loader_lock);

                /*
                 *  Please, don't change this order or code.
                 *  For ALSA slot means soundcard and OSS emulation code
                 *  comes as add-on modules which aren't depend on
                 *  ALSA toplevel modules for soundcards, thus we need
                 *  load them at first.   [Jaroslav Kysela <perex@jcu.cz>]
                 */
                request_module("sound-slot-%i", unit>>4);
                request_module("sound-service-%i-%i", unit>>4, chain);

                /*
                 * sound-slot/service-* module aliases are scheduled
                 * for removal in favor of the standard char-major-*
                 * module aliases.  For the time being, generate both
                 * the legacy and standard module aliases to ease
                 * transition.
                 */
                if (request_module("char-major-%d-%d", SOUND_MAJOR, unit) > 0)
                        request_module("char-major-%d", SOUND_MAJOR);

                spin_lock(&sound_loader_lock);
                s = __look_for_unit(chain, unit);
                if (s)
                        new_fops = fops_get(s->unit_fops);
        }
        spin_unlock(&sound_loader_lock);
        if (new_fops) {
                /*
                 * We rely upon the fact that we can't be unloaded while the
                 * subdriver is there.
                 */
                int err = 0;
                replace_fops(file, new_fops);

                if (file->f_op->open)
                        err = file->f_op->open(inode,file);

                return err;
        }
        return -ENODEV;
}

MODULE_ALIAS_CHARDEV_MAJOR(SOUND_MAJOR);

static void cleanup_oss_soundcore(void)
{
        /* We have nothing to really do here - we know the lists must be
           empty */
        unregister_chrdev(SOUND_MAJOR, "sound");
}

static int __init init_oss_soundcore(void)
{
        if (preclaim_oss &&
            register_chrdev(SOUND_MAJOR, "sound", &soundcore_fops) < 0) {
                printk(KERN_ERR "soundcore: sound device already in use.\n");
                return -EBUSY;
        }

        return 0;
}

#endif /* CONFIG_SOUND_OSS_CORE */