summaryrefslogtreecommitdiffstats
path: root/drivers/char/hw_random.c
blob: 3480535a09c5f113af1ca110bb0fa37ae58c2206 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
/*
 	Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
	(c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
 
 	derived from
 
        Hardware driver for the AMD 768 Random Number Generator (RNG)
        (c) Copyright 2001 Red Hat Inc <alan@redhat.com>

 	derived from
 
	Hardware driver for Intel i810 Random Number Generator (RNG)
	Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
	Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>

	Please read Documentation/hw_random.txt for details on use.

	----------------------------------------------------------
	This software may be used and distributed according to the terms
        of the GNU General Public License, incorporated herein by reference.

 */


#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/random.h>
#include <linux/miscdevice.h>
#include <linux/smp_lock.h>
#include <linux/mm.h>
#include <linux/delay.h>

#ifdef __i386__
#include <asm/msr.h>
#include <asm/cpufeature.h>
#endif

#include <asm/io.h>
#include <asm/uaccess.h>


/*
 * core module and version information
 */
#define RNG_VERSION "1.0.0"
#define RNG_MODULE_NAME "hw_random"
#define RNG_DRIVER_NAME   RNG_MODULE_NAME " hardware driver " RNG_VERSION
#define PFX RNG_MODULE_NAME ": "


/*
 * debugging macros
 */

/* pr_debug() collapses to a no-op if DEBUG is not defined */
#define DPRINTK(fmt, args...) pr_debug(PFX "%s: " fmt, __FUNCTION__ , ## args)


#undef RNG_NDEBUG        /* define to enable lightweight runtime checks */
#ifdef RNG_NDEBUG
#define assert(expr)							\
		if(!(expr)) {						\
		printk(KERN_DEBUG PFX "Assertion failed! %s,%s,%s,"	\
		"line=%d\n", #expr, __FILE__, __FUNCTION__, __LINE__);	\
		}
#else
#define assert(expr)
#endif

#define RNG_MISCDEV_MINOR		183 /* official */

static int rng_dev_open (struct inode *inode, struct file *filp);
static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
				loff_t * offp);

static int __init intel_init (struct pci_dev *dev);
static void intel_cleanup(void);
static unsigned int intel_data_present (void);
static u32 intel_data_read (void);

static int __init amd_init (struct pci_dev *dev);
static void amd_cleanup(void);
static unsigned int amd_data_present (void);
static u32 amd_data_read (void);

#ifdef __i386__
static int __init via_init(struct pci_dev *dev);
static void via_cleanup(void);
static unsigned int via_data_present (void);
static u32 via_data_read (void);
#endif

struct rng_operations {
	int (*init) (struct pci_dev *dev);
	void (*cleanup) (void);
	unsigned int (*data_present) (void);
	u32 (*data_read) (void);
	unsigned int n_bytes; /* number of bytes per ->data_read */
};
static struct rng_operations *rng_ops;

static struct file_operations rng_chrdev_ops = {
	.owner		= THIS_MODULE,
	.open		= rng_dev_open,
	.read		= rng_dev_read,
};


static struct miscdevice rng_miscdev = {
	RNG_MISCDEV_MINOR,
	RNG_MODULE_NAME,
	&rng_chrdev_ops,
};

enum {
	rng_hw_none,
	rng_hw_intel,
	rng_hw_amd,
	rng_hw_via,
};

static struct rng_operations rng_vendor_ops[] = {
	/* rng_hw_none */
	{ },

	/* rng_hw_intel */
	{ intel_init, intel_cleanup, intel_data_present,
	  intel_data_read, 1 },

	/* rng_hw_amd */
	{ amd_init, amd_cleanup, amd_data_present, amd_data_read, 4 },

#ifdef __i386__
	/* rng_hw_via */
	{ via_init, via_cleanup, via_data_present, via_data_read, 1 },
#endif
};

/*
 * Data for PCI driver interface
 *
 * This data only exists for exporting the supported
 * PCI ids via MODULE_DEVICE_TABLE.  We do not actually
 * register a pci_driver, because someone else might one day
 * want to register another driver on the same PCI id.
 */
static struct pci_device_id rng_pci_tbl[] = {
	{ 0x1022, 0x7443, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_amd },
	{ 0x1022, 0x746b, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_amd },

	{ 0x8086, 0x2418, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
	{ 0x8086, 0x2428, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
	{ 0x8086, 0x2448, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
	{ 0x8086, 0x244e, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
	{ 0x8086, 0x245e, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },

	{ 0, },	/* terminate list */
};
MODULE_DEVICE_TABLE (pci, rng_pci_tbl);


/***********************************************************************
 *
 * Intel RNG operations
 *
 */

/*
 * RNG registers (offsets from rng_mem)
 */
#define INTEL_RNG_HW_STATUS			0
#define         INTEL_RNG_PRESENT		0x40
#define         INTEL_RNG_ENABLED		0x01
#define INTEL_RNG_STATUS			1
#define         INTEL_RNG_DATA_PRESENT		0x01
#define INTEL_RNG_DATA				2

/*
 * Magic address at which Intel PCI bridges locate the RNG
 */
#define INTEL_RNG_ADDR				0xFFBC015F
#define INTEL_RNG_ADDR_LEN			3

/* token to our ioremap'd RNG register area */
static void __iomem *rng_mem;

static inline u8 intel_hwstatus (void)
{
	assert (rng_mem != NULL);
	return readb (rng_mem + INTEL_RNG_HW_STATUS);
}

static inline u8 intel_hwstatus_set (u8 hw_status)
{
	assert (rng_mem != NULL);
	writeb (hw_status, rng_mem + INTEL_RNG_HW_STATUS);
	return intel_hwstatus ();
}

static unsigned int intel_data_present(void)
{
	assert (rng_mem != NULL);

	return (readb (rng_mem + INTEL_RNG_STATUS) & INTEL_RNG_DATA_PRESENT) ?
		1 : 0;
}

static u32 intel_data_read(void)
{
	assert (rng_mem != NULL);

	return readb (rng_mem + INTEL_RNG_DATA);
}

static int __init intel_init (struct pci_dev *dev)
{
	int rc;
	u8 hw_status;

	DPRINTK ("ENTER\n");

	rng_mem = ioremap (INTEL_RNG_ADDR, INTEL_RNG_ADDR_LEN);
	if (rng_mem == NULL) {
		printk (KERN_ERR PFX "cannot ioremap RNG Memory\n");
		rc = -EBUSY;
		goto err_out;
	}

	/* Check for Intel 82802 */
	hw_status = intel_hwstatus ();
	if ((hw_status & INTEL_RNG_PRESENT) == 0) {
		printk (KERN_ERR PFX "RNG not detected\n");
		rc = -ENODEV;
		goto err_out_free_map;
	}

	/* turn RNG h/w on, if it's off */
	if ((hw_status & INTEL_RNG_ENABLED) == 0)
		hw_status = intel_hwstatus_set (hw_status | INTEL_RNG_ENABLED);
	if ((hw_status & INTEL_RNG_ENABLED) == 0) {
		printk (KERN_ERR PFX "cannot enable RNG, aborting\n");
		rc = -EIO;
		goto err_out_free_map;
	}

	DPRINTK ("EXIT, returning 0\n");
	return 0;

err_out_free_map:
	iounmap (rng_mem);
	rng_mem = NULL;
err_out:
	DPRINTK ("EXIT, returning %d\n", rc);
	return rc;
}

static void intel_cleanup(void)
{
	u8 hw_status;

	hw_status = intel_hwstatus ();
	if (hw_status & INTEL_RNG_ENABLED)
		intel_hwstatus_set (hw_status & ~INTEL_RNG_ENABLED);
	else
		printk(KERN_WARNING PFX "unusual: RNG already disabled\n");
	iounmap(rng_mem);
	rng_mem = NULL;
}

/***********************************************************************
 *
 * AMD RNG operations
 *
 */

static u32 pmbase;			/* PMxx I/O base */
static struct pci_dev *amd_dev;

static unsigned int amd_data_present (void)
{
      	return inl(pmbase + 0xF4) & 1;
}


static u32 amd_data_read (void)
{
	return inl(pmbase + 0xF0);
}

static int __init amd_init (struct pci_dev *dev)
{
	int rc;
	u8 rnen;

	DPRINTK ("ENTER\n");

	pci_read_config_dword(dev, 0x58, &pmbase);

	pmbase &= 0x0000FF00;

	if (pmbase == 0)
	{
		printk (KERN_ERR PFX "power management base not set\n");
		rc = -EIO;
		goto err_out;
	}

	pci_read_config_byte(dev, 0x40, &rnen);
	rnen |= (1 << 7);	/* RNG on */
	pci_write_config_byte(dev, 0x40, rnen);

	pci_read_config_byte(dev, 0x41, &rnen);
	rnen |= (1 << 7);	/* PMIO enable */
	pci_write_config_byte(dev, 0x41, rnen);

	pr_info( PFX "AMD768 system management I/O registers at 0x%X.\n",
			pmbase);

	amd_dev = dev;

	DPRINTK ("EXIT, returning 0\n");
	return 0;

err_out:
	DPRINTK ("EXIT, returning %d\n", rc);
	return rc;
}

static void amd_cleanup(void)
{
	u8 rnen;

	pci_read_config_byte(amd_dev, 0x40, &rnen);
	rnen &= ~(1 << 7);	/* RNG off */
	pci_write_config_byte(amd_dev, 0x40, rnen);

	/* FIXME: twiddle pmio, also? */
}

#ifdef __i386__
/***********************************************************************
 *
 * VIA RNG operations
 *
 */

enum {
	VIA_STRFILT_CNT_SHIFT	= 16,
	VIA_STRFILT_FAIL	= (1 << 15),
	VIA_STRFILT_ENABLE	= (1 << 14),
	VIA_RAWBITS_ENABLE	= (1 << 13),
	VIA_RNG_ENABLE		= (1 << 6),
	VIA_XSTORE_CNT_MASK	= 0x0F,

	VIA_RNG_CHUNK_8		= 0x00,	/* 64 rand bits, 64 stored bits */
	VIA_RNG_CHUNK_4		= 0x01,	/* 32 rand bits, 32 stored bits */
	VIA_RNG_CHUNK_4_MASK	= 0xFFFFFFFF,
	VIA_RNG_CHUNK_2		= 0x02,	/* 16 rand bits, 32 stored bits */
	VIA_RNG_CHUNK_2_MASK	= 0xFFFF,
	VIA_RNG_CHUNK_1		= 0x03,	/* 8 rand bits, 32 stored bits */
	VIA_RNG_CHUNK_1_MASK	= 0xFF,
};

static u32 via_rng_datum;

/*
 * Investigate using the 'rep' prefix to obtain 32 bits of random data
 * in one insn.  The upside is potentially better performance.  The
 * downside is that the instruction becomes no longer atomic.  Due to
 * this, just like familiar issues with /dev/random itself, the worst
 * case of a 'rep xstore' could potentially pause a cpu for an
 * unreasonably long time.  In practice, this condition would likely
 * only occur when the hardware is failing.  (or so we hope :))
 *
 * Another possible performance boost may come from simply buffering
 * until we have 4 bytes, thus returning a u32 at a time,
 * instead of the current u8-at-a-time.
 */

static inline u32 xstore(u32 *addr, u32 edx_in)
{
	u32 eax_out;

	asm(".byte 0x0F,0xA7,0xC0 /* xstore %%edi (addr=%0) */"
		:"=m"(*addr), "=a"(eax_out)
		:"D"(addr), "d"(edx_in));

	return eax_out;
}

static unsigned int via_data_present(void)
{
	u32 bytes_out;

	/* We choose the recommended 1-byte-per-instruction RNG rate,
	 * for greater randomness at the expense of speed.  Larger
	 * values 2, 4, or 8 bytes-per-instruction yield greater
	 * speed at lesser randomness.
	 *
	 * If you change this to another VIA_CHUNK_n, you must also
	 * change the ->n_bytes values in rng_vendor_ops[] tables.
	 * VIA_CHUNK_8 requires further code changes.
	 *
	 * A copy of MSR_VIA_RNG is placed in eax_out when xstore
	 * completes.
	 */
	via_rng_datum = 0; /* paranoia, not really necessary */
	bytes_out = xstore(&via_rng_datum, VIA_RNG_CHUNK_1) & VIA_XSTORE_CNT_MASK;
	if (bytes_out == 0)
		return 0;

	return 1;
}

static u32 via_data_read(void)
{
	return via_rng_datum;
}

static int __init via_init(struct pci_dev *dev)
{
	u32 lo, hi, old_lo;

	/* Control the RNG via MSR.  Tread lightly and pay very close
	 * close attention to values written, as the reserved fields
	 * are documented to be "undefined and unpredictable"; but it
	 * does not say to write them as zero, so I make a guess that
	 * we restore the values we find in the register.
	 */
	rdmsr(MSR_VIA_RNG, lo, hi);

	old_lo = lo;
	lo &= ~(0x7f << VIA_STRFILT_CNT_SHIFT);
	lo &= ~VIA_XSTORE_CNT_MASK;
	lo &= ~(VIA_STRFILT_ENABLE | VIA_STRFILT_FAIL | VIA_RAWBITS_ENABLE);
	lo |= VIA_RNG_ENABLE;

	if (lo != old_lo)
		wrmsr(MSR_VIA_RNG, lo, hi);

	/* perhaps-unnecessary sanity check; remove after testing if
	   unneeded */
	rdmsr(MSR_VIA_RNG, lo, hi);
	if ((lo & VIA_RNG_ENABLE) == 0) {
		printk(KERN_ERR PFX "cannot enable VIA C3 RNG, aborting\n");
		return -ENODEV;
	}

	return 0;
}

static void via_cleanup(void)
{
	/* do nothing */
}
#endif


/***********************************************************************
 *
 * /dev/hwrandom character device handling (major 10, minor 183)
 *
 */

static int rng_dev_open (struct inode *inode, struct file *filp)
{
	/* enforce read-only access to this chrdev */
	if ((filp->f_mode & FMODE_READ) == 0)
		return -EINVAL;
	if (filp->f_mode & FMODE_WRITE)
		return -EINVAL;

	return 0;
}


static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
				loff_t * offp)
{
	static DEFINE_SPINLOCK(rng_lock);
	unsigned int have_data;
	u32 data = 0;
	ssize_t ret = 0;

	while (size) {
		spin_lock(&rng_lock);

		have_data = 0;
		if (rng_ops->data_present()) {
			data = rng_ops->data_read();
			have_data = rng_ops->n_bytes;
		}

		spin_unlock (&rng_lock);

		while (have_data && size) {
			if (put_user((u8)data, buf++)) {
				ret = ret ? : -EFAULT;
				break;
			}
			size--;
			ret++;
			have_data--;
			data>>=8;
		}

		if (filp->f_flags & O_NONBLOCK)
			return ret ? : -EAGAIN;

		if(need_resched())
		{
			current->state = TASK_INTERRUPTIBLE;
			schedule_timeout(1);
		}
		else
			udelay(200);	/* FIXME: We could poll for 250uS ?? */

		if (signal_pending (current))
			return ret ? : -ERESTARTSYS;
	}
	return ret;
}



/*
 * rng_init_one - look for and attempt to init a single RNG
 */
static int __init rng_init_one (struct pci_dev *dev)
{
	int rc;

	DPRINTK ("ENTER\n");

	assert(rng_ops != NULL);

	rc = rng_ops->init(dev);
	if (rc)
		goto err_out;

	rc = misc_register (&rng_miscdev);
	if (rc) {
		printk (KERN_ERR PFX "misc device register failed\n");
		goto err_out_cleanup_hw;
	}

	DPRINTK ("EXIT, returning 0\n");
	return 0;

err_out_cleanup_hw:
	rng_ops->cleanup();
err_out:
	DPRINTK ("EXIT, returning %d\n", rc);
	return rc;
}



MODULE_AUTHOR("The Linux Kernel team");
MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
MODULE_LICENSE("GPL");


/*
 * rng_init - initialize RNG module
 */
static int __init rng_init (void)
{
	int rc;
	struct pci_dev *pdev = NULL;
	const struct pci_device_id *ent;

	DPRINTK ("ENTER\n");

	/* Probe for Intel, AMD RNGs */
	for_each_pci_dev(pdev) {
		ent = pci_match_id(rng_pci_tbl, pdev);
		if (ent) {
			rng_ops = &rng_vendor_ops[ent->driver_data];
			goto match;
		}
	}

#ifdef __i386__
	/* Probe for VIA RNG */
	if (cpu_has_xstore) {
		rng_ops = &rng_vendor_ops[rng_hw_via];
		pdev = NULL;
		goto match;
	}
#endif

	DPRINTK ("EXIT, returning -ENODEV\n");
	return -ENODEV;

match:
	rc = rng_init_one (pdev);
	if (rc)
		return rc;

	pr_info( RNG_DRIVER_NAME " loaded\n");

	DPRINTK ("EXIT, returning 0\n");
	return 0;
}


/*
 * rng_init - shutdown RNG module
 */
static void __exit rng_cleanup (void)
{
	DPRINTK ("ENTER\n");

	misc_deregister (&rng_miscdev);

	if (rng_ops->cleanup)
		rng_ops->cleanup();

	DPRINTK ("EXIT\n");
}


module_init (rng_init);
module_exit (rng_cleanup);