1 /*
2  * Copyright (C) 2012 Google, Inc.
3  *
4  * This software is licensed under the terms of the GNU General Public
5  * License version 2, as published by the Free Software Foundation, and
6  * may be copied, distributed, and modified under those terms.
7  *
8  * This program is distributed in the hope that it will be useful,
9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11  * GNU General Public License for more details.
12  *
13  */
14 
15 #define pr_fmt(fmt) "persistent_ram: " fmt
16 
17 #include <linux/device.h>
18 #include <linux/err.h>
19 #include <linux/errno.h>
20 #include <linux/init.h>
21 #include <linux/io.h>
22 #include <linux/kernel.h>
23 #include <linux/list.h>
24 #include <linux/memblock.h>
25 #include <linux/pstore_ram.h>
26 #include <linux/rslib.h>
27 #include <linux/slab.h>
28 #include <linux/uaccess.h>
29 #include <linux/vmalloc.h>
30 #include <asm/page.h>
31 
32 struct persistent_ram_buffer {
33 	uint32_t    sig;
34 	atomic_t    start;
35 	atomic_t    size;
36 	uint8_t     data[0];
37 };
38 
39 #define PERSISTENT_RAM_SIG (0x43474244) /* DBGC */
40 
buffer_size(struct persistent_ram_zone * prz)41 static inline size_t buffer_size(struct persistent_ram_zone *prz)
42 {
43 	return atomic_read(&prz->buffer->size);
44 }
45 
buffer_start(struct persistent_ram_zone * prz)46 static inline size_t buffer_start(struct persistent_ram_zone *prz)
47 {
48 	return atomic_read(&prz->buffer->start);
49 }
50 
51 /* increase and wrap the start pointer, returning the old value */
buffer_start_add(struct persistent_ram_zone * prz,size_t a)52 static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a)
53 {
54 	int old;
55 	int new;
56 	unsigned long flags = 0;
57 
58 	if (!(prz->flags & PRZ_FLAG_NO_LOCK))
59 		raw_spin_lock_irqsave(&prz->buffer_lock, flags);
60 
61 	old = atomic_read(&prz->buffer->start);
62 	new = old + a;
63 	while (unlikely(new >= prz->buffer_size))
64 		new -= prz->buffer_size;
65 	atomic_set(&prz->buffer->start, new);
66 
67 	if (!(prz->flags & PRZ_FLAG_NO_LOCK))
68 		raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
69 
70 	return old;
71 }
72 
73 /* increase the size counter until it hits the max size */
buffer_size_add(struct persistent_ram_zone * prz,size_t a)74 static void buffer_size_add(struct persistent_ram_zone *prz, size_t a)
75 {
76 	size_t old;
77 	size_t new;
78 	unsigned long flags = 0;
79 
80 	if (!(prz->flags & PRZ_FLAG_NO_LOCK))
81 		raw_spin_lock_irqsave(&prz->buffer_lock, flags);
82 
83 	old = atomic_read(&prz->buffer->size);
84 	if (old == prz->buffer_size)
85 		goto exit;
86 
87 	new = old + a;
88 	if (new > prz->buffer_size)
89 		new = prz->buffer_size;
90 	atomic_set(&prz->buffer->size, new);
91 
92 exit:
93 	if (!(prz->flags & PRZ_FLAG_NO_LOCK))
94 		raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
95 }
96 
persistent_ram_encode_rs8(struct persistent_ram_zone * prz,uint8_t * data,size_t len,uint8_t * ecc)97 static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz,
98 	uint8_t *data, size_t len, uint8_t *ecc)
99 {
100 	int i;
101 
102 	/* Initialize the parity buffer */
103 	memset(prz->ecc_info.par, 0,
104 	       prz->ecc_info.ecc_size * sizeof(prz->ecc_info.par[0]));
105 	encode_rs8(prz->rs_decoder, data, len, prz->ecc_info.par, 0);
106 	for (i = 0; i < prz->ecc_info.ecc_size; i++)
107 		ecc[i] = prz->ecc_info.par[i];
108 }
109 
persistent_ram_decode_rs8(struct persistent_ram_zone * prz,void * data,size_t len,uint8_t * ecc)110 static int persistent_ram_decode_rs8(struct persistent_ram_zone *prz,
111 	void *data, size_t len, uint8_t *ecc)
112 {
113 	int i;
114 
115 	for (i = 0; i < prz->ecc_info.ecc_size; i++)
116 		prz->ecc_info.par[i] = ecc[i];
117 	return decode_rs8(prz->rs_decoder, data, prz->ecc_info.par, len,
118 				NULL, 0, NULL, 0, NULL);
119 }
120 
persistent_ram_update_ecc(struct persistent_ram_zone * prz,unsigned int start,unsigned int count)121 static void notrace persistent_ram_update_ecc(struct persistent_ram_zone *prz,
122 	unsigned int start, unsigned int count)
123 {
124 	struct persistent_ram_buffer *buffer = prz->buffer;
125 	uint8_t *buffer_end = buffer->data + prz->buffer_size;
126 	uint8_t *block;
127 	uint8_t *par;
128 	int ecc_block_size = prz->ecc_info.block_size;
129 	int ecc_size = prz->ecc_info.ecc_size;
130 	int size = ecc_block_size;
131 
132 	if (!ecc_size)
133 		return;
134 
135 	block = buffer->data + (start & ~(ecc_block_size - 1));
136 	par = prz->par_buffer + (start / ecc_block_size) * ecc_size;
137 
138 	do {
139 		if (block + ecc_block_size > buffer_end)
140 			size = buffer_end - block;
141 		persistent_ram_encode_rs8(prz, block, size, par);
142 		block += ecc_block_size;
143 		par += ecc_size;
144 	} while (block < buffer->data + start + count);
145 }
146 
persistent_ram_update_header_ecc(struct persistent_ram_zone * prz)147 static void persistent_ram_update_header_ecc(struct persistent_ram_zone *prz)
148 {
149 	struct persistent_ram_buffer *buffer = prz->buffer;
150 
151 	if (!prz->ecc_info.ecc_size)
152 		return;
153 
154 	persistent_ram_encode_rs8(prz, (uint8_t *)buffer, sizeof(*buffer),
155 				  prz->par_header);
156 }
157 
persistent_ram_ecc_old(struct persistent_ram_zone * prz)158 static void persistent_ram_ecc_old(struct persistent_ram_zone *prz)
159 {
160 	struct persistent_ram_buffer *buffer = prz->buffer;
161 	uint8_t *block;
162 	uint8_t *par;
163 
164 	if (!prz->ecc_info.ecc_size)
165 		return;
166 
167 	block = buffer->data;
168 	par = prz->par_buffer;
169 	while (block < buffer->data + buffer_size(prz)) {
170 		int numerr;
171 		int size = prz->ecc_info.block_size;
172 		if (block + size > buffer->data + prz->buffer_size)
173 			size = buffer->data + prz->buffer_size - block;
174 		numerr = persistent_ram_decode_rs8(prz, block, size, par);
175 		if (numerr > 0) {
176 			pr_devel("error in block %p, %d\n", block, numerr);
177 			prz->corrected_bytes += numerr;
178 		} else if (numerr < 0) {
179 			pr_devel("uncorrectable error in block %p\n", block);
180 			prz->bad_blocks++;
181 		}
182 		block += prz->ecc_info.block_size;
183 		par += prz->ecc_info.ecc_size;
184 	}
185 }
186 
persistent_ram_init_ecc(struct persistent_ram_zone * prz,struct persistent_ram_ecc_info * ecc_info)187 static int persistent_ram_init_ecc(struct persistent_ram_zone *prz,
188 				   struct persistent_ram_ecc_info *ecc_info)
189 {
190 	int numerr;
191 	struct persistent_ram_buffer *buffer = prz->buffer;
192 	int ecc_blocks;
193 	size_t ecc_total;
194 
195 	if (!ecc_info || !ecc_info->ecc_size)
196 		return 0;
197 
198 	prz->ecc_info.block_size = ecc_info->block_size ?: 128;
199 	prz->ecc_info.ecc_size = ecc_info->ecc_size ?: 16;
200 	prz->ecc_info.symsize = ecc_info->symsize ?: 8;
201 	prz->ecc_info.poly = ecc_info->poly ?: 0x11d;
202 
203 	ecc_blocks = DIV_ROUND_UP(prz->buffer_size - prz->ecc_info.ecc_size,
204 				  prz->ecc_info.block_size +
205 				  prz->ecc_info.ecc_size);
206 	ecc_total = (ecc_blocks + 1) * prz->ecc_info.ecc_size;
207 	if (ecc_total >= prz->buffer_size) {
208 		pr_err("%s: invalid ecc_size %u (total %zu, buffer size %zu)\n",
209 		       __func__, prz->ecc_info.ecc_size,
210 		       ecc_total, prz->buffer_size);
211 		return -EINVAL;
212 	}
213 
214 	prz->buffer_size -= ecc_total;
215 	prz->par_buffer = buffer->data + prz->buffer_size;
216 	prz->par_header = prz->par_buffer +
217 			  ecc_blocks * prz->ecc_info.ecc_size;
218 
219 	/*
220 	 * first consecutive root is 0
221 	 * primitive element to generate roots = 1
222 	 */
223 	prz->rs_decoder = init_rs(prz->ecc_info.symsize, prz->ecc_info.poly,
224 				  0, 1, prz->ecc_info.ecc_size);
225 	if (prz->rs_decoder == NULL) {
226 		pr_info("init_rs failed\n");
227 		return -EINVAL;
228 	}
229 
230 	/* allocate workspace instead of using stack VLA */
231 	prz->ecc_info.par = kmalloc_array(prz->ecc_info.ecc_size,
232 					  sizeof(*prz->ecc_info.par),
233 					  GFP_KERNEL);
234 	if (!prz->ecc_info.par) {
235 		pr_err("cannot allocate ECC parity workspace\n");
236 		return -ENOMEM;
237 	}
238 
239 	prz->corrected_bytes = 0;
240 	prz->bad_blocks = 0;
241 
242 	numerr = persistent_ram_decode_rs8(prz, buffer, sizeof(*buffer),
243 					   prz->par_header);
244 	if (numerr > 0) {
245 		pr_info("error in header, %d\n", numerr);
246 		prz->corrected_bytes += numerr;
247 	} else if (numerr < 0) {
248 		pr_info("uncorrectable error in header\n");
249 		prz->bad_blocks++;
250 	}
251 
252 	return 0;
253 }
254 
persistent_ram_ecc_string(struct persistent_ram_zone * prz,char * str,size_t len)255 ssize_t persistent_ram_ecc_string(struct persistent_ram_zone *prz,
256 	char *str, size_t len)
257 {
258 	ssize_t ret;
259 
260 	if (!prz->ecc_info.ecc_size)
261 		return 0;
262 
263 	if (prz->corrected_bytes || prz->bad_blocks)
264 		ret = snprintf(str, len, ""
265 			"\n%d Corrected bytes, %d unrecoverable blocks\n",
266 			prz->corrected_bytes, prz->bad_blocks);
267 	else
268 		ret = snprintf(str, len, "\nNo errors detected\n");
269 
270 	return ret;
271 }
272 
persistent_ram_update(struct persistent_ram_zone * prz,const void * s,unsigned int start,unsigned int count)273 static void notrace persistent_ram_update(struct persistent_ram_zone *prz,
274 	const void *s, unsigned int start, unsigned int count)
275 {
276 	struct persistent_ram_buffer *buffer = prz->buffer;
277 	memcpy_toio(buffer->data + start, s, count);
278 	persistent_ram_update_ecc(prz, start, count);
279 }
280 
persistent_ram_update_user(struct persistent_ram_zone * prz,const void __user * s,unsigned int start,unsigned int count)281 static int notrace persistent_ram_update_user(struct persistent_ram_zone *prz,
282 	const void __user *s, unsigned int start, unsigned int count)
283 {
284 	struct persistent_ram_buffer *buffer = prz->buffer;
285 	int ret = unlikely(__copy_from_user(buffer->data + start, s, count)) ?
286 		-EFAULT : 0;
287 	persistent_ram_update_ecc(prz, start, count);
288 	return ret;
289 }
290 
persistent_ram_save_old(struct persistent_ram_zone * prz)291 void persistent_ram_save_old(struct persistent_ram_zone *prz)
292 {
293 	struct persistent_ram_buffer *buffer = prz->buffer;
294 	size_t size = buffer_size(prz);
295 	size_t start = buffer_start(prz);
296 
297 	if (!size)
298 		return;
299 
300 	if (!prz->old_log) {
301 		persistent_ram_ecc_old(prz);
302 		prz->old_log = kmalloc(size, GFP_KERNEL);
303 	}
304 	if (!prz->old_log) {
305 		pr_err("failed to allocate buffer\n");
306 		return;
307 	}
308 
309 	prz->old_log_size = size;
310 	memcpy_fromio(prz->old_log, &buffer->data[start], size - start);
311 	memcpy_fromio(prz->old_log + size - start, &buffer->data[0], start);
312 }
313 
persistent_ram_write(struct persistent_ram_zone * prz,const void * s,unsigned int count)314 int notrace persistent_ram_write(struct persistent_ram_zone *prz,
315 	const void *s, unsigned int count)
316 {
317 	int rem;
318 	int c = count;
319 	size_t start;
320 
321 	if (unlikely(c > prz->buffer_size)) {
322 		s += c - prz->buffer_size;
323 		c = prz->buffer_size;
324 	}
325 
326 	buffer_size_add(prz, c);
327 
328 	start = buffer_start_add(prz, c);
329 
330 	rem = prz->buffer_size - start;
331 	if (unlikely(rem < c)) {
332 		persistent_ram_update(prz, s, start, rem);
333 		s += rem;
334 		c -= rem;
335 		start = 0;
336 	}
337 	persistent_ram_update(prz, s, start, c);
338 
339 	persistent_ram_update_header_ecc(prz);
340 
341 	return count;
342 }
343 
persistent_ram_write_user(struct persistent_ram_zone * prz,const void __user * s,unsigned int count)344 int notrace persistent_ram_write_user(struct persistent_ram_zone *prz,
345 	const void __user *s, unsigned int count)
346 {
347 	int rem, ret = 0, c = count;
348 	size_t start;
349 
350 	if (unlikely(!access_ok(VERIFY_READ, s, count)))
351 		return -EFAULT;
352 	if (unlikely(c > prz->buffer_size)) {
353 		s += c - prz->buffer_size;
354 		c = prz->buffer_size;
355 	}
356 
357 	buffer_size_add(prz, c);
358 
359 	start = buffer_start_add(prz, c);
360 
361 	rem = prz->buffer_size - start;
362 	if (unlikely(rem < c)) {
363 		ret = persistent_ram_update_user(prz, s, start, rem);
364 		s += rem;
365 		c -= rem;
366 		start = 0;
367 	}
368 	if (likely(!ret))
369 		ret = persistent_ram_update_user(prz, s, start, c);
370 
371 	persistent_ram_update_header_ecc(prz);
372 
373 	return unlikely(ret) ? ret : count;
374 }
375 
persistent_ram_old_size(struct persistent_ram_zone * prz)376 size_t persistent_ram_old_size(struct persistent_ram_zone *prz)
377 {
378 	return prz->old_log_size;
379 }
380 
persistent_ram_old(struct persistent_ram_zone * prz)381 void *persistent_ram_old(struct persistent_ram_zone *prz)
382 {
383 	return prz->old_log;
384 }
385 
persistent_ram_free_old(struct persistent_ram_zone * prz)386 void persistent_ram_free_old(struct persistent_ram_zone *prz)
387 {
388 	kfree(prz->old_log);
389 	prz->old_log = NULL;
390 	prz->old_log_size = 0;
391 }
392 
persistent_ram_zap(struct persistent_ram_zone * prz)393 void persistent_ram_zap(struct persistent_ram_zone *prz)
394 {
395 	atomic_set(&prz->buffer->start, 0);
396 	atomic_set(&prz->buffer->size, 0);
397 	persistent_ram_update_header_ecc(prz);
398 }
399 
persistent_ram_vmap(phys_addr_t start,size_t size,unsigned int memtype)400 static void *persistent_ram_vmap(phys_addr_t start, size_t size,
401 		unsigned int memtype)
402 {
403 	struct page **pages;
404 	phys_addr_t page_start;
405 	unsigned int page_count;
406 	pgprot_t prot;
407 	unsigned int i;
408 	void *vaddr;
409 
410 	page_start = start - offset_in_page(start);
411 	page_count = DIV_ROUND_UP(size + offset_in_page(start), PAGE_SIZE);
412 
413 	if (memtype)
414 		prot = pgprot_noncached(PAGE_KERNEL);
415 	else
416 		prot = pgprot_writecombine(PAGE_KERNEL);
417 
418 	pages = kmalloc_array(page_count, sizeof(struct page *), GFP_KERNEL);
419 	if (!pages) {
420 		pr_err("%s: Failed to allocate array for %u pages\n",
421 		       __func__, page_count);
422 		return NULL;
423 	}
424 
425 	for (i = 0; i < page_count; i++) {
426 		phys_addr_t addr = page_start + i * PAGE_SIZE;
427 		pages[i] = pfn_to_page(addr >> PAGE_SHIFT);
428 	}
429 	/*
430 	 * VM_IOREMAP used here to bypass this region during vread()
431 	 * and kmap_atomic() (i.e. kcore) to avoid __va() failures.
432 	 */
433 	vaddr = vmap(pages, page_count, VM_MAP | VM_IOREMAP, prot);
434 	kfree(pages);
435 
436 	/*
437 	 * Since vmap() uses page granularity, we must add the offset
438 	 * into the page here, to get the byte granularity address
439 	 * into the mapping to represent the actual "start" location.
440 	 */
441 	return vaddr + offset_in_page(start);
442 }
443 
persistent_ram_iomap(phys_addr_t start,size_t size,unsigned int memtype)444 static void *persistent_ram_iomap(phys_addr_t start, size_t size,
445 		unsigned int memtype)
446 {
447 	void *va;
448 
449 	if (!request_mem_region(start, size, "persistent_ram")) {
450 		pr_err("request mem region (0x%llx@0x%llx) failed\n",
451 			(unsigned long long)size, (unsigned long long)start);
452 		return NULL;
453 	}
454 
455 	if (memtype)
456 		va = ioremap(start, size);
457 	else
458 		va = ioremap_wc(start, size);
459 
460 	/*
461 	 * Since request_mem_region() and ioremap() are byte-granularity
462 	 * there is no need handle anything special like we do when the
463 	 * vmap() case in persistent_ram_vmap() above.
464 	 */
465 	return va;
466 }
467 
persistent_ram_buffer_map(phys_addr_t start,phys_addr_t size,struct persistent_ram_zone * prz,int memtype)468 static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size,
469 		struct persistent_ram_zone *prz, int memtype)
470 {
471 	prz->paddr = start;
472 	prz->size = size;
473 
474 	if (pfn_valid(start >> PAGE_SHIFT))
475 		prz->vaddr = persistent_ram_vmap(start, size, memtype);
476 	else
477 		prz->vaddr = persistent_ram_iomap(start, size, memtype);
478 
479 	if (!prz->vaddr) {
480 		pr_err("%s: Failed to map 0x%llx pages at 0x%llx\n", __func__,
481 			(unsigned long long)size, (unsigned long long)start);
482 		return -ENOMEM;
483 	}
484 
485 	prz->buffer = prz->vaddr;
486 	prz->buffer_size = size - sizeof(struct persistent_ram_buffer);
487 
488 	return 0;
489 }
490 
persistent_ram_post_init(struct persistent_ram_zone * prz,u32 sig,struct persistent_ram_ecc_info * ecc_info)491 static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
492 				    struct persistent_ram_ecc_info *ecc_info)
493 {
494 	int ret;
495 
496 	ret = persistent_ram_init_ecc(prz, ecc_info);
497 	if (ret)
498 		return ret;
499 
500 	sig ^= PERSISTENT_RAM_SIG;
501 
502 	if (prz->buffer->sig == sig) {
503 		if (buffer_size(prz) == 0 && buffer_start(prz) == 0) {
504 			pr_debug("found existing empty buffer\n");
505 			return 0;
506 		}
507 
508 		if (buffer_size(prz) > prz->buffer_size ||
509 		    buffer_start(prz) > buffer_size(prz))
510 			pr_info("found existing invalid buffer, size %zu, start %zu\n",
511 				buffer_size(prz), buffer_start(prz));
512 		else {
513 			pr_debug("found existing buffer, size %zu, start %zu\n",
514 				 buffer_size(prz), buffer_start(prz));
515 			persistent_ram_save_old(prz);
516 			return 0;
517 		}
518 	} else {
519 		pr_debug("no valid data in buffer (sig = 0x%08x)\n",
520 			 prz->buffer->sig);
521 	}
522 
523 	/* Rewind missing or invalid memory area. */
524 	prz->buffer->sig = sig;
525 	persistent_ram_zap(prz);
526 
527 	return 0;
528 }
529 
persistent_ram_free(struct persistent_ram_zone * prz)530 void persistent_ram_free(struct persistent_ram_zone *prz)
531 {
532 	if (!prz)
533 		return;
534 
535 	if (prz->vaddr) {
536 		if (pfn_valid(prz->paddr >> PAGE_SHIFT)) {
537 			/* We must vunmap() at page-granularity. */
538 			vunmap(prz->vaddr - offset_in_page(prz->paddr));
539 		} else {
540 			iounmap(prz->vaddr);
541 			release_mem_region(prz->paddr, prz->size);
542 		}
543 		prz->vaddr = NULL;
544 	}
545 	if (prz->rs_decoder) {
546 		free_rs(prz->rs_decoder);
547 		prz->rs_decoder = NULL;
548 	}
549 	kfree(prz->ecc_info.par);
550 	prz->ecc_info.par = NULL;
551 
552 	persistent_ram_free_old(prz);
553 	kfree(prz);
554 }
555 
persistent_ram_new(phys_addr_t start,size_t size,u32 sig,struct persistent_ram_ecc_info * ecc_info,unsigned int memtype,u32 flags)556 struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
557 			u32 sig, struct persistent_ram_ecc_info *ecc_info,
558 			unsigned int memtype, u32 flags)
559 {
560 	struct persistent_ram_zone *prz;
561 	int ret = -ENOMEM;
562 
563 	prz = kzalloc(sizeof(struct persistent_ram_zone), GFP_KERNEL);
564 	if (!prz) {
565 		pr_err("failed to allocate persistent ram zone\n");
566 		goto err;
567 	}
568 
569 	/* Initialize general buffer state. */
570 	raw_spin_lock_init(&prz->buffer_lock);
571 	prz->flags = flags;
572 
573 	ret = persistent_ram_buffer_map(start, size, prz, memtype);
574 	if (ret)
575 		goto err;
576 
577 	ret = persistent_ram_post_init(prz, sig, ecc_info);
578 	if (ret)
579 		goto err;
580 
581 	return prz;
582 err:
583 	persistent_ram_free(prz);
584 	return ERR_PTR(ret);
585 }
586