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Linux/arch/um/drivers/random.c

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  1 /* Copyright (C) 2005 - 2008 Jeff Dike <jdike@{linux.intel,addtoit}.com> */
  2 
  3 /* Much of this ripped from drivers/char/hw_random.c, see there for other
  4  * copyright.
  5  *
  6  * This software may be used and distributed according to the terms
  7  * of the GNU General Public License, incorporated herein by reference.
  8  */
  9 #include <linux/sched/signal.h>
 10 #include <linux/module.h>
 11 #include <linux/fs.h>
 12 #include <linux/interrupt.h>
 13 #include <linux/miscdevice.h>
 14 #include <linux/delay.h>
 15 #include <linux/uaccess.h>
 16 #include <init.h>
 17 #include <irq_kern.h>
 18 #include <os.h>
 19 
 20 /*
 21  * core module and version information
 22  */
 23 #define RNG_VERSION "1.0.0"
 24 #define RNG_MODULE_NAME "hw_random"
 25 
 26 #define RNG_MISCDEV_MINOR               183 /* official */
 27 
 28 /* Changed at init time, in the non-modular case, and at module load
 29  * time, in the module case.  Presumably, the module subsystem
 30  * protects against a module being loaded twice at the same time.
 31  */
 32 static int random_fd = -1;
 33 static DECLARE_WAIT_QUEUE_HEAD(host_read_wait);
 34 
 35 static int rng_dev_open (struct inode *inode, struct file *filp)
 36 {
 37         /* enforce read-only access to this chrdev */
 38         if ((filp->f_mode & FMODE_READ) == 0)
 39                 return -EINVAL;
 40         if ((filp->f_mode & FMODE_WRITE) != 0)
 41                 return -EINVAL;
 42 
 43         return 0;
 44 }
 45 
 46 static atomic_t host_sleep_count = ATOMIC_INIT(0);
 47 
 48 static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
 49                              loff_t *offp)
 50 {
 51         u32 data;
 52         int n, ret = 0, have_data;
 53 
 54         while (size) {
 55                 n = os_read_file(random_fd, &data, sizeof(data));
 56                 if (n > 0) {
 57                         have_data = n;
 58                         while (have_data && size) {
 59                                 if (put_user((u8) data, buf++)) {
 60                                         ret = ret ? : -EFAULT;
 61                                         break;
 62                                 }
 63                                 size--;
 64                                 ret++;
 65                                 have_data--;
 66                                 data >>= 8;
 67                         }
 68                 }
 69                 else if (n == -EAGAIN) {
 70                         DECLARE_WAITQUEUE(wait, current);
 71 
 72                         if (filp->f_flags & O_NONBLOCK)
 73                                 return ret ? : -EAGAIN;
 74 
 75                         atomic_inc(&host_sleep_count);
 76                         reactivate_fd(random_fd, RANDOM_IRQ);
 77                         add_sigio_fd(random_fd);
 78 
 79                         add_wait_queue(&host_read_wait, &wait);
 80                         set_current_state(TASK_INTERRUPTIBLE);
 81 
 82                         schedule();
 83                         remove_wait_queue(&host_read_wait, &wait);
 84 
 85                         if (atomic_dec_and_test(&host_sleep_count)) {
 86                                 ignore_sigio_fd(random_fd);
 87                                 deactivate_fd(random_fd, RANDOM_IRQ);
 88                         }
 89                 }
 90                 else
 91                         return n;
 92 
 93                 if (signal_pending (current))
 94                         return ret ? : -ERESTARTSYS;
 95         }
 96         return ret;
 97 }
 98 
 99 static const struct file_operations rng_chrdev_ops = {
100         .owner          = THIS_MODULE,
101         .open           = rng_dev_open,
102         .read           = rng_dev_read,
103         .llseek         = noop_llseek,
104 };
105 
106 /* rng_init shouldn't be called more than once at boot time */
107 static struct miscdevice rng_miscdev = {
108         RNG_MISCDEV_MINOR,
109         RNG_MODULE_NAME,
110         &rng_chrdev_ops,
111 };
112 
113 static irqreturn_t random_interrupt(int irq, void *data)
114 {
115         wake_up(&host_read_wait);
116 
117         return IRQ_HANDLED;
118 }
119 
120 /*
121  * rng_init - initialize RNG module
122  */
123 static int __init rng_init (void)
124 {
125         int err;
126 
127         err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0);
128         if (err < 0)
129                 goto out;
130 
131         random_fd = err;
132 
133         err = um_request_irq(RANDOM_IRQ, random_fd, IRQ_READ, random_interrupt,
134                              0, "random", NULL);
135         if (err)
136                 goto err_out_cleanup_hw;
137 
138         sigio_broken(random_fd, 1);
139 
140         err = misc_register (&rng_miscdev);
141         if (err) {
142                 printk (KERN_ERR RNG_MODULE_NAME ": misc device register "
143                         "failed\n");
144                 goto err_out_cleanup_hw;
145         }
146 out:
147         return err;
148 
149 err_out_cleanup_hw:
150         os_close_file(random_fd);
151         random_fd = -1;
152         goto out;
153 }
154 
155 /*
156  * rng_cleanup - shutdown RNG module
157  */
158 
159 static void cleanup(void)
160 {
161         free_irq_by_fd(random_fd);
162         os_close_file(random_fd);
163 }
164 
165 static void __exit rng_cleanup(void)
166 {
167         os_close_file(random_fd);
168         misc_deregister (&rng_miscdev);
169 }
170 
171 module_init (rng_init);
172 module_exit (rng_cleanup);
173 __uml_exitcall(cleanup);
174 
175 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
176 MODULE_LICENSE("GPL");
177 

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