• D
    module: add per-module param_lock · b51d23e4
    Dan Streetman 提交于
    Add a "param_lock" mutex to each module, and update params.c to use
    the correct built-in or module mutex while locking kernel params.
    Remove the kparam_block_sysfs_r/w() macros, replace them with direct
    calls to kernel_param_[un]lock(module).
    
    The kernel param code currently uses a single mutex to protect
    modification of any and all kernel params.  While this generally works,
    there is one specific problem with it; a module callback function
    cannot safely load another module, i.e. with request_module() or even
    with indirect calls such as crypto_has_alg().  If the module to be
    loaded has any of its params configured (e.g. with a /etc/modprobe.d/*
    config file), then the attempt will result in a deadlock between the
    first module param callback waiting for modprobe, and modprobe trying to
    lock the single kernel param mutex to set the new module's param.
    
    This fixes that by using per-module mutexes, so that each individual module
    is protected against concurrent changes in its own kernel params, but is
    not blocked by changes to other module params.  All built-in modules
    continue to use the built-in mutex, since they will always be loaded at
    runtime and references (e.g. request_module(), crypto_has_alg()) to them
    will never cause load-time param changing.
    
    This also simplifies the interface used by modules to block sysfs access
    to their params; while there are currently functions to block and unblock
    sysfs param access which are split up by read and write and expect a single
    kernel param to be passed, their actual operation is identical and applies
    to all params, not just the one passed to them; they simply lock and unlock
    the global param mutex.  They are replaced with direct calls to
    kernel_param_[un]lock(THIS_MODULE), which locks THIS_MODULE's param_lock, or
    if the module is built-in, it locks the built-in mutex.
    Suggested-by: NRusty Russell <rusty@rustcorp.com.au>
    Signed-off-by: NDan Streetman <ddstreet@ieee.org>
    Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
    b51d23e4
hostaudio_kern.c 7.6 KB
/*
 * Copyright (C) 2002 Steve Schmidtke
 * Licensed under the GPL
 */

#include <linux/fs.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sound.h>
#include <linux/soundcard.h>
#include <linux/mutex.h>
#include <asm/uaccess.h>
#include <init.h>
#include <os.h>

struct hostaudio_state {
	int fd;
};

struct hostmixer_state {
	int fd;
};

#define HOSTAUDIO_DEV_DSP "/dev/sound/dsp"
#define HOSTAUDIO_DEV_MIXER "/dev/sound/mixer"

/*
 * Changed either at boot time or module load time.  At boot, this is
 * single-threaded; at module load, multiple modules would each have
 * their own copy of these variables.
 */
static char *dsp = HOSTAUDIO_DEV_DSP;
static char *mixer = HOSTAUDIO_DEV_MIXER;

#define DSP_HELP \
"    This is used to specify the host dsp device to the hostaudio driver.\n" \
"    The default is \"" HOSTAUDIO_DEV_DSP "\".\n\n"

#define MIXER_HELP \
"    This is used to specify the host mixer device to the hostaudio driver.\n"\
"    The default is \"" HOSTAUDIO_DEV_MIXER "\".\n\n"

module_param(dsp, charp, 0644);
MODULE_PARM_DESC(dsp, DSP_HELP);
module_param(mixer, charp, 0644);
MODULE_PARM_DESC(mixer, MIXER_HELP);

#ifndef MODULE
static int set_dsp(char *name, int *add)
{
	dsp = name;
	return 0;
}

__uml_setup("dsp=", set_dsp, "dsp=<dsp device>\n" DSP_HELP);

static int set_mixer(char *name, int *add)
{
	mixer = name;
	return 0;
}

__uml_setup("mixer=", set_mixer, "mixer=<mixer device>\n" MIXER_HELP);
#endif

static DEFINE_MUTEX(hostaudio_mutex);

/* /dev/dsp file operations */

static ssize_t hostaudio_read(struct file *file, char __user *buffer,
			      size_t count, loff_t *ppos)
{
	struct hostaudio_state *state = file->private_data;
	void *kbuf;
	int err;

#ifdef DEBUG
	printk(KERN_DEBUG "hostaudio: read called, count = %d\n", count);
#endif

	kbuf = kmalloc(count, GFP_KERNEL);
	if (kbuf == NULL)
		return -ENOMEM;

	err = os_read_file(state->fd, kbuf, count);
	if (err < 0)
		goto out;

	if (copy_to_user(buffer, kbuf, err))
		err = -EFAULT;

out:
	kfree(kbuf);
	return err;
}

static ssize_t hostaudio_write(struct file *file, const char __user *buffer,
			       size_t count, loff_t *ppos)
{
	struct hostaudio_state *state = file->private_data;
	void *kbuf;
	int err;

#ifdef DEBUG
	printk(KERN_DEBUG "hostaudio: write called, count = %d\n", count);
#endif

	kbuf = kmalloc(count, GFP_KERNEL);
	if (kbuf == NULL)
		return -ENOMEM;

	err = -EFAULT;
	if (copy_from_user(kbuf, buffer, count))
		goto out;

	err = os_write_file(state->fd, kbuf, count);
	if (err < 0)
		goto out;
	*ppos += err;

 out:
	kfree(kbuf);
	return err;
}

static unsigned int hostaudio_poll(struct file *file,
				   struct poll_table_struct *wait)
{
	unsigned int mask = 0;

#ifdef DEBUG
	printk(KERN_DEBUG "hostaudio: poll called (unimplemented)\n");
#endif

	return mask;
}

static long hostaudio_ioctl(struct file *file,
			   unsigned int cmd, unsigned long arg)
{
	struct hostaudio_state *state = file->private_data;
	unsigned long data = 0;
	int err;

#ifdef DEBUG
	printk(KERN_DEBUG "hostaudio: ioctl called, cmd = %u\n", cmd);
#endif
	switch(cmd){
	case SNDCTL_DSP_SPEED:
	case SNDCTL_DSP_STEREO:
	case SNDCTL_DSP_GETBLKSIZE:
	case SNDCTL_DSP_CHANNELS:
	case SNDCTL_DSP_SUBDIVIDE:
	case SNDCTL_DSP_SETFRAGMENT:
		if (get_user(data, (int __user *) arg))
			return -EFAULT;
		break;
	default:
		break;
	}

	err = os_ioctl_generic(state->fd, cmd, (unsigned long) &data);

	switch(cmd){
	case SNDCTL_DSP_SPEED:
	case SNDCTL_DSP_STEREO:
	case SNDCTL_DSP_GETBLKSIZE:
	case SNDCTL_DSP_CHANNELS:
	case SNDCTL_DSP_SUBDIVIDE:
	case SNDCTL_DSP_SETFRAGMENT:
		if (put_user(data, (int __user *) arg))
			return -EFAULT;
		break;
	default:
		break;
	}

	return err;
}

static int hostaudio_open(struct inode *inode, struct file *file)
{
	struct hostaudio_state *state;
	int r = 0, w = 0;
	int ret;

#ifdef DEBUG
	kernel_param_lock(THIS_MODULE);
	printk(KERN_DEBUG "hostaudio: open called (host: %s)\n", dsp);
	kernel_param_unlock(THIS_MODULE);
#endif

	state = kmalloc(sizeof(struct hostaudio_state), GFP_KERNEL);
	if (state == NULL)
		return -ENOMEM;

	if (file->f_mode & FMODE_READ)
		r = 1;
	if (file->f_mode & FMODE_WRITE)
		w = 1;

	kernel_param_lock(THIS_MODULE);
	mutex_lock(&hostaudio_mutex);
	ret = os_open_file(dsp, of_set_rw(OPENFLAGS(), r, w), 0);
	mutex_unlock(&hostaudio_mutex);
	kernel_param_unlock(THIS_MODULE);

	if (ret < 0) {
		kfree(state);
		return ret;
	}
	state->fd = ret;
	file->private_data = state;
	return 0;
}

static int hostaudio_release(struct inode *inode, struct file *file)
{
	struct hostaudio_state *state = file->private_data;

#ifdef DEBUG
	printk(KERN_DEBUG "hostaudio: release called\n");
#endif
	os_close_file(state->fd);
	kfree(state);

	return 0;
}

/* /dev/mixer file operations */

static long hostmixer_ioctl_mixdev(struct file *file,
				  unsigned int cmd, unsigned long arg)
{
	struct hostmixer_state *state = file->private_data;

#ifdef DEBUG
	printk(KERN_DEBUG "hostmixer: ioctl called\n");
#endif

	return os_ioctl_generic(state->fd, cmd, arg);
}

static int hostmixer_open_mixdev(struct inode *inode, struct file *file)
{
	struct hostmixer_state *state;
	int r = 0, w = 0;
	int ret;

#ifdef DEBUG
	printk(KERN_DEBUG "hostmixer: open called (host: %s)\n", mixer);
#endif

	state = kmalloc(sizeof(struct hostmixer_state), GFP_KERNEL);
	if (state == NULL)
		return -ENOMEM;

	if (file->f_mode & FMODE_READ)
		r = 1;
	if (file->f_mode & FMODE_WRITE)
		w = 1;

	kernel_param_lock(THIS_MODULE);
	mutex_lock(&hostaudio_mutex);
	ret = os_open_file(mixer, of_set_rw(OPENFLAGS(), r, w), 0);
	mutex_unlock(&hostaudio_mutex);
	kernel_param_unlock(THIS_MODULE);

	if (ret < 0) {
		kernel_param_lock(THIS_MODULE);
		printk(KERN_ERR "hostaudio_open_mixdev failed to open '%s', "
		       "err = %d\n", dsp, -ret);
		kernel_param_unlock(THIS_MODULE);
		kfree(state);
		return ret;
	}

	file->private_data = state;
	return 0;
}

static int hostmixer_release(struct inode *inode, struct file *file)
{
	struct hostmixer_state *state = file->private_data;

#ifdef DEBUG
	printk(KERN_DEBUG "hostmixer: release called\n");
#endif

	os_close_file(state->fd);
	kfree(state);

	return 0;
}

/* kernel module operations */

static const struct file_operations hostaudio_fops = {
	.owner          = THIS_MODULE,
	.llseek         = no_llseek,
	.read           = hostaudio_read,
	.write          = hostaudio_write,
	.poll           = hostaudio_poll,
	.unlocked_ioctl	= hostaudio_ioctl,
	.mmap           = NULL,
	.open           = hostaudio_open,
	.release        = hostaudio_release,
};

static const struct file_operations hostmixer_fops = {
	.owner          = THIS_MODULE,
	.llseek         = no_llseek,
	.unlocked_ioctl	= hostmixer_ioctl_mixdev,
	.open           = hostmixer_open_mixdev,
	.release        = hostmixer_release,
};

struct {
	int dev_audio;
	int dev_mixer;
} module_data;

MODULE_AUTHOR("Steve Schmidtke");
MODULE_DESCRIPTION("UML Audio Relay");
MODULE_LICENSE("GPL");

static int __init hostaudio_init_module(void)
{
	kernel_param_lock(THIS_MODULE);
	printk(KERN_INFO "UML Audio Relay (host dsp = %s, host mixer = %s)\n",
	       dsp, mixer);
	kernel_param_unlock(THIS_MODULE);

	module_data.dev_audio = register_sound_dsp(&hostaudio_fops, -1);
	if (module_data.dev_audio < 0) {
		printk(KERN_ERR "hostaudio: couldn't register DSP device!\n");
		return -ENODEV;
	}

	module_data.dev_mixer = register_sound_mixer(&hostmixer_fops, -1);
	if (module_data.dev_mixer < 0) {
		printk(KERN_ERR "hostmixer: couldn't register mixer "
		       "device!\n");
		unregister_sound_dsp(module_data.dev_audio);
		return -ENODEV;
	}

	return 0;
}

static void __exit hostaudio_cleanup_module (void)
{
	unregister_sound_mixer(module_data.dev_mixer);
	unregister_sound_dsp(module_data.dev_audio);
}

module_init(hostaudio_init_module);
module_exit(hostaudio_cleanup_module);