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 <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_current_state(TASK_INTERRUPTIBLE); 80 81 schedule(); 82 remove_wait_queue(&host_read_wait, &wait); 83 84 if (atomic_dec_and_test(&host_sleep_count)) { 85 ignore_sigio_fd(random_fd); 86 deactivate_fd(random_fd, RANDOM_IRQ); 87 } 88 } 89 else 90 return n; 91 92 if (signal_pending (current)) 93 return ret ? : -ERESTARTSYS; 94 } 95 return ret; 96 } 97 98 static const struct file_operations rng_chrdev_ops = { 99 .owner = THIS_MODULE, 100 .open = rng_dev_open, 101 .read = rng_dev_read, 102 .llseek = noop_llseek, 103 }; 104 105 /* rng_init shouldn't be called more than once at boot time */ 106 static struct miscdevice rng_miscdev = { 107 RNG_MISCDEV_MINOR, 108 RNG_MODULE_NAME, 109 &rng_chrdev_ops, 110 }; 111 112 static irqreturn_t random_interrupt(int irq, void *data) 113 { 114 wake_up(&host_read_wait); 115 116 return IRQ_HANDLED; 117 } 118 119 /* 120 * rng_init - initialize RNG module 121 */ 122 static int __init rng_init (void) 123 { 124 int err; 125 126 err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0); 127 if (err < 0) 128 goto out; 129 130 random_fd = err; 131 132 err = um_request_irq(RANDOM_IRQ, random_fd, IRQ_READ, random_interrupt, 133 0, "random", NULL); 134 if (err) 135 goto err_out_cleanup_hw; 136 137 sigio_broken(random_fd, 1); 138 139 err = misc_register (&rng_miscdev); 140 if (err) { 141 printk (KERN_ERR RNG_MODULE_NAME ": misc device register " 142 "failed\n"); 143 goto err_out_cleanup_hw; 144 } 145 out: 146 return err; 147 148 err_out_cleanup_hw: 149 os_close_file(random_fd); 150 random_fd = -1; 151 goto out; 152 } 153 154 /* 155 * rng_cleanup - shutdown RNG module 156 */ 157 static void __exit rng_cleanup (void) 158 { 159 os_close_file(random_fd); 160 misc_deregister (&rng_miscdev); 161 } 162 163 module_init (rng_init); 164 module_exit (rng_cleanup); 165 166 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver"); 167 MODULE_LICENSE("GPL"); 168