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