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.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 <asm/uaccess.h> 16 #include "irq_kern.h" 17 #include "os.h" 18 19 /* 20 * core module and version information 21 */ 22 #define RNG_VERSION "1.0.0" 23 #define RNG_MODULE_NAME "hw_random" 24 25 #define RNG_MISCDEV_MINOR 183 /* official */ 26 27 /* Changed at init time, in the non-modular case, and at module load 28 * time, in the module case. Presumably, the module subsystem 29 * protects against a module being loaded twice at the same time. 30 */ 31 static int random_fd = -1; 32 static DECLARE_WAIT_QUEUE_HEAD(host_read_wait); 33 34 static int rng_dev_open (struct inode *inode, struct file *filp) 35 { 36 /* enforce read-only access to this chrdev */ 37 if ((filp->f_mode & FMODE_READ) == 0) 38 return -EINVAL; 39 if ((filp->f_mode & FMODE_WRITE) != 0) 40 return -EINVAL; 41 42 return 0; 43 } 44 45 static atomic_t host_sleep_count = ATOMIC_INIT(0); 46 47 static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size, 48 loff_t *offp) 49 { 50 u32 data; 51 int n, ret = 0, have_data; 52 53 while (size) { 54 n = os_read_file(random_fd, &data, sizeof(data)); 55 if (n > 0) { 56 have_data = n; 57 while (have_data && size) { 58 if (put_user((u8) data, buf++)) { 59 ret = ret ? : -EFAULT; 60 break; 61 } 62 size--; 63 ret++; 64 have_data--; 65 data >>= 8; 66 } 67 } 68 else if (n == -EAGAIN) { 69 DECLARE_WAITQUEUE(wait, current); 70 71 if (filp->f_flags & O_NONBLOCK) 72 return ret ? : -EAGAIN; 73 74 atomic_inc(&host_sleep_count); 75 reactivate_fd(random_fd, RANDOM_IRQ); 76 add_sigio_fd(random_fd); 77 78 add_wait_queue(&host_read_wait, &wait); 79 set_task_state(current, TASK_INTERRUPTIBLE); 80 81 schedule(); 82 set_task_state(current, TASK_RUNNING); 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 IRQF_DISABLED | IRQF_SAMPLE_RANDOM, "random", 135 NULL); 136 if (err) 137 goto err_out_cleanup_hw; 138 139 sigio_broken(random_fd, 1); 140 141 err = misc_register (&rng_miscdev); 142 if (err) { 143 printk (KERN_ERR RNG_MODULE_NAME ": misc device register " 144 "failed\n"); 145 goto err_out_cleanup_hw; 146 } 147 out: 148 return err; 149 150 err_out_cleanup_hw: 151 os_close_file(random_fd); 152 random_fd = -1; 153 goto out; 154 } 155 156 /* 157 * rng_cleanup - shutdown RNG module 158 */ 159 static void __exit rng_cleanup (void) 160 { 161 os_close_file(random_fd); 162 misc_deregister (&rng_miscdev); 163 } 164 165 module_init (rng_init); 166 module_exit (rng_cleanup); 167 168 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver"); 169 MODULE_LICENSE("GPL"); 170