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 */ 31static int random_fd = -1; 32static DECLARE_WAIT_QUEUE_HEAD(host_read_wait); 33 34static 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 45static atomic_t host_sleep_count = ATOMIC_INIT(0); 46 47static 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 99static const struct file_operations rng_chrdev_ops = { 100 .owner = THIS_MODULE, 101 .open = rng_dev_open, 102 .read = rng_dev_read, 103}; 104 105/* rng_init shouldn't be called more than once at boot time */ 106static struct miscdevice rng_miscdev = { 107 RNG_MISCDEV_MINOR, 108 RNG_MODULE_NAME, 109 &rng_chrdev_ops, 110}; 111 112static 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 */ 122static 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 IRQF_DISABLED | IRQF_SAMPLE_RANDOM, "random", 134 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 } 146out: 147 return err; 148 149err_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 */ 158static void __exit rng_cleanup (void) 159{ 160 os_close_file(random_fd); 161 misc_deregister (&rng_miscdev); 162} 163 164module_init (rng_init); 165module_exit (rng_cleanup); 166 167MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver"); 168MODULE_LICENSE("GPL"); 169