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 /* Changed at init time, in the non-modular case, and at module load 27 * time, in the module case. Presumably, the module subsystem 28 * protects against a module being loaded twice at the same time. 29 */ 30 static int random_fd = -1; 31 static DECLARE_WAIT_QUEUE_HEAD(host_read_wait); 32 33 static int rng_dev_open (struct inode *inode, struct file *filp) 34 { 35 /* enforce read-only access to this chrdev */ 36 if ((filp->f_mode & FMODE_READ) == 0) 37 return -EINVAL; 38 if ((filp->f_mode & FMODE_WRITE) != 0) 39 return -EINVAL; 40 41 return 0; 42 } 43 44 static atomic_t host_sleep_count = ATOMIC_INIT(0); 45 46 static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size, 47 loff_t *offp) 48 { 49 u32 data; 50 int n, ret = 0, have_data; 51 52 while (size) { 53 n = os_read_file(random_fd, &data, sizeof(data)); 54 if (n > 0) { 55 have_data = n; 56 while (have_data && size) { 57 if (put_user((u8) data, buf++)) { 58 ret = ret ? : -EFAULT; 59 break; 60 } 61 size--; 62 ret++; 63 have_data--; 64 data >>= 8; 65 } 66 } 67 else if (n == -EAGAIN) { 68 DECLARE_WAITQUEUE(wait, current); 69 70 if (filp->f_flags & O_NONBLOCK) 71 return ret ? : -EAGAIN; 72 73 atomic_inc(&host_sleep_count); 74 add_sigio_fd(random_fd); 75 76 add_wait_queue(&host_read_wait, &wait); 77 set_current_state(TASK_INTERRUPTIBLE); 78 79 schedule(); 80 remove_wait_queue(&host_read_wait, &wait); 81 82 if (atomic_dec_and_test(&host_sleep_count)) { 83 ignore_sigio_fd(random_fd); 84 deactivate_fd(random_fd, RANDOM_IRQ); 85 } 86 } 87 else 88 return n; 89 90 if (signal_pending (current)) 91 return ret ? : -ERESTARTSYS; 92 } 93 return ret; 94 } 95 96 static const struct file_operations rng_chrdev_ops = { 97 .owner = THIS_MODULE, 98 .open = rng_dev_open, 99 .read = rng_dev_read, 100 .llseek = noop_llseek, 101 }; 102 103 /* rng_init shouldn't be called more than once at boot time */ 104 static struct miscdevice rng_miscdev = { 105 HWRNG_MINOR, 106 RNG_MODULE_NAME, 107 &rng_chrdev_ops, 108 }; 109 110 static irqreturn_t random_interrupt(int irq, void *data) 111 { 112 wake_up(&host_read_wait); 113 114 return IRQ_HANDLED; 115 } 116 117 /* 118 * rng_init - initialize RNG module 119 */ 120 static int __init rng_init (void) 121 { 122 int err; 123 124 err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0); 125 if (err < 0) 126 goto out; 127 128 random_fd = err; 129 130 err = um_request_irq(RANDOM_IRQ, random_fd, IRQ_READ, random_interrupt, 131 0, "random", NULL); 132 if (err) 133 goto err_out_cleanup_hw; 134 135 sigio_broken(random_fd, 1); 136 137 err = misc_register (&rng_miscdev); 138 if (err) { 139 printk (KERN_ERR RNG_MODULE_NAME ": misc device register " 140 "failed\n"); 141 goto err_out_cleanup_hw; 142 } 143 out: 144 return err; 145 146 err_out_cleanup_hw: 147 os_close_file(random_fd); 148 random_fd = -1; 149 goto out; 150 } 151 152 /* 153 * rng_cleanup - shutdown RNG module 154 */ 155 156 static void cleanup(void) 157 { 158 free_irq_by_fd(random_fd); 159 os_close_file(random_fd); 160 } 161 162 static void __exit rng_cleanup(void) 163 { 164 os_close_file(random_fd); 165 misc_deregister (&rng_miscdev); 166 } 167 168 module_init (rng_init); 169 module_exit (rng_cleanup); 170 __uml_exitcall(cleanup); 171 172 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver"); 173 MODULE_LICENSE("GPL"); 174