xref: /linux/arch/um/drivers/random.c (revision 4b132aacb0768ac1e652cf517097ea6f237214b9)
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/hw_random.h>
15 #include <linux/delay.h>
16 #include <linux/uaccess.h>
17 #include <init.h>
18 #include <irq_kern.h>
19 #include <os.h>
20 
21 /*
22  * core module information
23  */
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 struct hwrng hwrng;
32 static DECLARE_COMPLETION(have_data);
33 
34 static int rng_dev_read(struct hwrng *rng, void *buf, size_t max, bool block)
35 {
36 	int ret;
37 
38 	for (;;) {
39 		ret = os_read_file(random_fd, buf, max);
40 		if (block && ret == -EAGAIN) {
41 			add_sigio_fd(random_fd);
42 
43 			ret = wait_for_completion_killable(&have_data);
44 
45 			ignore_sigio_fd(random_fd);
46 			deactivate_fd(random_fd, RANDOM_IRQ);
47 
48 			if (ret < 0)
49 				break;
50 		} else {
51 			break;
52 		}
53 	}
54 
55 	return ret != -EAGAIN ? ret : 0;
56 }
57 
58 static irqreturn_t random_interrupt(int irq, void *data)
59 {
60 	complete(&have_data);
61 
62 	return IRQ_HANDLED;
63 }
64 
65 /*
66  * rng_init - initialize RNG module
67  */
68 static int __init rng_init (void)
69 {
70 	int err;
71 
72 	err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0);
73 	if (err < 0)
74 		goto out;
75 
76 	random_fd = err;
77 	err = um_request_irq(RANDOM_IRQ, random_fd, IRQ_READ, random_interrupt,
78 			     0, "random", NULL);
79 	if (err < 0)
80 		goto err_out_cleanup_hw;
81 
82 	sigio_broken(random_fd);
83 	hwrng.name = RNG_MODULE_NAME;
84 	hwrng.read = rng_dev_read;
85 
86 	err = hwrng_register(&hwrng);
87 	if (err) {
88 		pr_err(RNG_MODULE_NAME " registering failed (%d)\n", err);
89 		goto err_out_cleanup_hw;
90 	}
91 out:
92 	return err;
93 
94 err_out_cleanup_hw:
95 	os_close_file(random_fd);
96 	random_fd = -1;
97 	goto out;
98 }
99 
100 /*
101  * rng_cleanup - shutdown RNG module
102  */
103 
104 static void cleanup(void)
105 {
106 	free_irq_by_fd(random_fd);
107 	os_close_file(random_fd);
108 }
109 
110 static void __exit rng_cleanup(void)
111 {
112 	hwrng_unregister(&hwrng);
113 	os_close_file(random_fd);
114 }
115 
116 module_init (rng_init);
117 module_exit (rng_cleanup);
118 __uml_exitcall(cleanup);
119 
120 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
121 MODULE_LICENSE("GPL");
122