text: /*
   * linux/kernel/power/user.c
   *
   * This file provides the user space interface for software suspend/resume.
   *
   * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
   *
   * This file is released under the GPLv2.
   *
   */
  
  #include <linux/suspend.h>
  #include <linux/syscalls.h>
  #include <linux/reboot.h>
  #include <linux/string.h>
  #include <linux/device.h>
  #include <linux/miscdevice.h>
  #include <linux/mm.h>
  #include <linux/swap.h>
  #include <linux/swapops.h>
  #include <linux/pm.h>
  #include <linux/fs.h>
  #include <linux/compat.h>
  #include <linux/console.h>
  #include <linux/cpu.h>
  #include <linux/freezer.h>
  
  #include <asm/uaccess.h>
  
  #include "power.h"
  
  
  #define SNAPSHOT_MINOR	231
  
  static struct snapshot_data {
  	struct snapshot_handle handle;
  	int swap;
  	int mode;
  	bool frozen;
  	bool ready;
  	bool platform_support;
  	bool free_bitmaps;
  } snapshot_state;
  
  atomic_t snapshot_device_available = ATOMIC_INIT(1);
  
  static int snapshot_open(struct inode *inode, struct file *filp)
  {
  	struct snapshot_data *data;
  	int error, nr_calls = 0;
  
  	if (!hibernation_available())
  		return -EPERM;
  
  	lock_system_sleep();
  
  	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
  		error = -EBUSY;
  		goto Unlock;
  	}
  
  	if ((filp->f_flags & O_ACCMODE) == O_RDWR) {
  		atomic_inc(&snapshot_device_available);
  		error = -ENOSYS;
  		goto Unlock;
  	}
  	nonseekable_open(inode, filp);
  	data = &snapshot_state;
  	filp->private_data = data;
  	memset(&data->handle, 0, sizeof(struct snapshot_handle));
  	if ((filp->f_flags & O_ACCMODE) == O_RDONLY) {
  		/* Hibernating.  The image device should be accessible. */
  		data->swap = swsusp_resume_device ?
  			swap_type_of(swsusp_resume_device, 0, NULL) : -1;
  		data->mode = O_RDONLY;
  		data->free_bitmaps = false;
  		error = __pm_notifier_call_chain(PM_HIBERNATION_PREPARE, -1, &nr_calls);
  		if (error)
  			__pm_notifier_call_chain(PM_POST_HIBERNATION, --nr_calls, NULL);
  	} else {
  		/*
  		 * Resuming.  We may need to wait for the image device to
  		 * appear.
  		 */
  		wait_for_device_probe();
  
  		data->swap = -1;
  		data->mode = O_WRONLY;
  		error = __pm_notifier_call_chain(PM_RESTORE_PREPARE, -1, &nr_calls);
  		if (!error) {
  			error = create_basic_memory_bitmaps();
  			data->free_bitmaps = !error;
  		} else
  			nr_calls--;
  
  		if (error)
  			__pm_notifier_call_chain(PM_POST_RESTORE, nr_calls, NULL);
  	}
  	if (error)
  		atomic_inc(&snapshot_device_available);
  
  	data->frozen = false;
  	data->ready = false;
  	data->platform_support = false;
  
   Unlock:
  	unlock_system_sleep();
  
  	return error;
  }
  
  static int snapshot_release(struct inode *inode, struct file *filp)
  {
  	struct snapshot_data *data;
  
  	lock_system_sleep();
  
  	swsusp_free();
  	data = filp->private_data;
  	free_all_swap_pages(data->swap);
  	if (data->frozen) {
  		pm_restore_gfp_mask();
  		free_basic_memory_bitmaps();
  		thaw_processes();
  	} else if (data->free_bitmaps) {
  		free_basic_memory_bitmaps();
  	}
  	pm_notifier_call_chain(data->mode == O_RDONLY ?
  			PM_POST_HIBERNATION : PM_POST_RESTORE);
  	atomic_inc(&snapshot_device_available);
  
  	unlock_system_sleep();
  
  	return 0;
  }
  
  static ssize_t snapshot_read(struct file *filp, char __user *buf,
                               size_t count, loff_t *offp)
  {
  	struct snapshot_data *data;
  	ssize_t res;
  	loff_t pg_offp = *offp & ~PAGE_MASK;
  
  	lock_system_sleep();
  
  	data = filp->private_data;
  	if (!data->ready) {
  		res = -ENODATA;
  		goto Unlock;
  	}
  	if (!pg_offp) { /* on page boundary? */
  		res = snapshot_read_next(&data->handle);
  		if (res <= 0)
  			goto Unlock;
  	} else {
  		res = PAGE_SIZE - pg_offp;
  	}
  
  	res = simple_read_from_buffer(buf, count, &pg_offp,
  			data_of(data->handle), res);
  	if (res > 0)
  		*offp += res;
  
   Unlock:
  	unlock_system_sleep();
  
  	return res;
  }
  
  static ssize_t snapshot_write(struct file *filp, const char __user *buf,
                                size_t count, loff_t *offp)
  {
  	struct snapshot_data *data;
  	ssize_t res;
  	loff_t pg_offp = *offp & ~PAGE_MASK;
  
  	lock_system_sleep();
  
  	data = filp->private_data;
  
  	if (!pg_offp) {
  		res = snapshot_write_next(&data->handle);
  		if (res <= 0)
  			goto unlock;
  	} else {
  		res = PAGE_SIZE - pg_offp;
  	}
  
  	res = simple_write_to_buffer(data_of(data->handle), res, &pg_offp,
  			buf, count);
  	if (res > 0)
  		*offp += res;
  unlock:
  	unlock_system_sleep();
  
  	return res;
  }
  
  static long snapshot_ioctl(struct file *filp, unsigned int cmd,
  							unsigned long arg)
  {
  	int error = 0;
  	struct snapshot_data *data;
  	loff_t size;
  	sector_t offset;
  
  	if (_IOC_TYPE(cmd) != SNAPSHOT_IOC_MAGIC)
  		return -ENOTTY;
  	if (_IOC_NR(cmd) > SNAPSHOT_IOC_MAXNR)
  		return -ENOTTY;
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	if (!mutex_trylock(&pm_mutex))
  		return -EBUSY;
  
  	lock_device_hotplug();
  	data = filp->private_data;
  
  	switch (cmd) {
  
  	case SNAPSHOT_FREEZE:
  		if (data->frozen)
  			break;
  
  		printk("Syncing filesystems ... ");
  		sys_sync();
  		printk("done.\n");
  
  		error = freeze_processes();
  		if (error)
  			break;
  
  		error = create_basic_memory_bitmaps();
  		if (error)
  			thaw_processes();
  		else
  			data->frozen = true;
  
  		break;
  
  	case SNAPSHOT_UNFREEZE:
  		if (!data->frozen || data->ready)
  			break;
  		pm_restore_gfp_mask();
  		free_basic_memory_bitmaps();
  		data->free_bitmaps = false;
  		thaw_processes();
  		data->frozen = false;
  		break;
  
  	case SNAPSHOT_CREATE_IMAGE:
  		if (data->mode != O_RDONLY || !data->frozen  || data->ready) {
  			error = -EPERM;
  			break;
  		}
  		pm_restore_gfp_mask();
  		error = hibernation_snapshot(data->platform_support);
  		if (!error) {
  			error = put_user(in_suspend, (int __user *)arg);
  			data->ready = !freezer_test_done && !error;
  			freezer_test_done = false;
  		}
  		break;
  
  	case SNAPSHOT_ATOMIC_RESTORE:
  		snapshot_write_finalize(&data->handle);
  		if (data->mode != O_WRONLY || !data->frozen ||
  		    !snapshot_image_loaded(&data->handle)) {
  			error = -EPERM;
  			break;
  		}
  		error = hibernation_restore(data->platform_support);
  		break;
  
  	case SNAPSHOT_FREE:
  		swsusp_free();
  		memset(&data->handle, 0, sizeof(struct snapshot_handle));
  		data->ready = false;
  		/*
  		 * It is necessary to thaw kernel threads here, because
  		 * SNAPSHOT_CREATE_IMAGE may be invoked directly after
  		 * SNAPSHOT_FREE.  In that case, if kernel threads were not
  		 * thawed, the preallocation of memory carried out by
  		 * hibernation_snapshot() might run into problems (i.e. it
  		 * might fail or even deadlock).
  		 */
  		thaw_kernel_threads();
  		break;
  
  	case SNAPSHOT_PREF_IMAGE_SIZE:
  		image_size = arg;
  		break;
  
  	case SNAPSHOT_GET_IMAGE_SIZE:
  		if (!data->ready) {
  			error = -ENODATA;
  			break;
  		}
  		size = snapshot_get_image_size();
  		size <<= PAGE_SHIFT;
  		error = put_user(size, (loff_t __user *)arg);
  		break;
  
  	case SNAPSHOT_AVAIL_SWAP_SIZE:
  		size = count_swap_pages(data->swap, 1);
  		size <<= PAGE_SHIFT;
  		error = put_user(size, (loff_t __user *)arg);
  		break;
  
  	case SNAPSHOT_ALLOC_SWAP_PAGE:
  		if (data->swap < 0 || data->swap >= MAX_SWAPFILES) {
  			error = -ENODEV;
  			break;
  		}
  		offset = alloc_swapdev_block(data->swap);
  		if (offset) {
  			offset <<= PAGE_SHIFT;
  			error = put_user(offset, (loff_t __user *)arg);
  		} else {
  			error = -ENOSPC;
  		}
  		break;
  
  	case SNAPSHOT_FREE_SWAP_PAGES:
  		if (data->swap < 0 || data->swap >= MAX_SWAPFILES) {
  			error = -ENODEV;
  			break;
  		}
  		free_all_swap_pages(data->swap);
  		break;
  
  	case SNAPSHOT_S2RAM:
  		if (!data->frozen) {
  			error = -EPERM;
  			break;
  		}
  		/*
  		 * Tasks are frozen and the notifiers have been called with
  		 * PM_HIBERNATION_PREPARE
  		 */
  		error = suspend_devices_and_enter(PM_SUSPEND_MEM);
  		data->ready = false;
  		break;
  
  	case SNAPSHOT_PLATFORM_SUPPORT:
  		data->platform_support = !!arg;
  		break;
  
  	case SNAPSHOT_POWER_OFF:
  		if (data->platform_support)
  			error = hibernation_platform_enter();
  		break;
  
  	case SNAPSHOT_SET_SWAP_AREA:
  		if (swsusp_swap_in_use()) {
  			error = -EPERM;
  		} else {
  			struct resume_swap_area swap_area;
  			dev_t swdev;
  
  			error = copy_from_user(&swap_area, (void __user *)arg,
  					sizeof(struct resume_swap_area));
  			if (error) {
  				error = -EFAULT;
  				break;
  			}
  
  			/*
  			 * User space encodes device types as two-byte values,
  			 * so we need to recode them
  			 */
  			swdev = new_decode_dev(swap_area.dev);
  			if (swdev) {
  				offset = swap_area.offset;
  				data->swap = swap_type_of(swdev, offset, NULL);
  				if (data->swap < 0)
  					error = -ENODEV;
  			} else {
  				data->swap = -1;
  				error = -EINVAL;
  			}
  		}
  		break;
  
  	default:
  		error = -ENOTTY;
  
  	}
  
  	unlock_device_hotplug();
  	mutex_unlock(&pm_mutex);
  
  	return error;
  }
  
  #ifdef CONFIG_COMPAT
  
  struct compat_resume_swap_area {
  	compat_loff_t offset;
  	u32 dev;
  } __packed;
  
  static long
  snapshot_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  {
  	BUILD_BUG_ON(sizeof(loff_t) != sizeof(compat_loff_t));
  
  	switch (cmd) {
  	case SNAPSHOT_GET_IMAGE_SIZE:
  	case SNAPSHOT_AVAIL_SWAP_SIZE:
  	case SNAPSHOT_ALLOC_SWAP_PAGE: {
  		compat_loff_t __user *uoffset = compat_ptr(arg);
  		loff_t offset;
  		mm_segment_t old_fs;
  		int err;
  
  		old_fs = get_fs();
  		set_fs(KERNEL_DS);
  		err = snapshot_ioctl(file, cmd, (unsigned long) &offset);
  		set_fs(old_fs);
  		if (!err && put_user(offset, uoffset))
  			err = -EFAULT;
  		return err;
  	}
  
  	case SNAPSHOT_CREATE_IMAGE:
  		return snapshot_ioctl(file, cmd,
  				      (unsigned long) compat_ptr(arg));
  
  	case SNAPSHOT_SET_SWAP_AREA: {
  		struct compat_resume_swap_area __user *u_swap_area =
  			compat_ptr(arg);
  		struct resume_swap_area swap_area;
  		mm_segment_t old_fs;
  		int err;
  
  		err = get_user(swap_area.offset, &u_swap_area->offset);
  		err |= get_user(swap_area.dev, &u_swap_area->dev);
  		if (err)
  			return -EFAULT;
  		old_fs = get_fs();
  		set_fs(KERNEL_DS);
  		err = snapshot_ioctl(file, SNAPSHOT_SET_SWAP_AREA,
  				     (unsigned long) &swap_area);
  		set_fs(old_fs);
  		return err;
  	}
  
  	default:
  		return snapshot_ioctl(file, cmd, arg);
  	}
  }
  
  #endif /* CONFIG_COMPAT */
  
  static const struct file_operations snapshot_fops = {
  	.open = snapshot_open,
  	.release = snapshot_release,
  	.read = snapshot_read,
  	.write = snapshot_write,
  	.llseek = no_llseek,
  	.unlocked_ioctl = snapshot_ioctl,
  #ifdef CONFIG_COMPAT
  	.compat_ioctl = snapshot_compat_ioctl,
  #endif
  };
  
  static struct miscdevice snapshot_device = {
  	.minor = SNAPSHOT_MINOR,
  	.name = "snapshot",
  	.fops = &snapshot_fops,
  };
  
  static int __init snapshot_device_init(void)
  {
  	return misc_register(&snapshot_device);
  };
  
  device_initcall(snapshot_device_init);
  