summaryrefslogtreecommitdiff
path: root/src/drivers/smmstore/store.c
blob: e0bfa10e0bd1cd6832a6558c619a7e0e809e95c7 (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
/*
 * This file is part of the coreboot project.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <boot_device.h>
#include <cbfs.h>
#include <fmap.h>
#include <commonlib/helpers.h>
#include <commonlib/region.h>
#include <console/console.h>
#include <smmstore.h>
#include <types.h>

/*
 * The region format is still not finalized, but so far it looks like this:
 *   (
 *    uint32le_t key_sz
 *    uint32le_t value_sz
 *    uint8_t key[key_sz]
 *    uint8_t value[value_sz]
 *    uint8_t active
 *    align to 4 bytes
 *  )*
 *   uint32le_t endmarker = 0xffffffff
 *
 * active needs to be set to 0x00 for the entry to be valid. This satisfies
 * the constraint that entries are either complete or will be ignored, as long
 * as flash is written sequentially and into a fully erased block.
 *
 * Future additions to the format will split the region in half with an active
 * block marker to allow safe compaction (ie. write the new data in the unused
 * region, mark it active after the write completed). Otherwise a well-timed
 * crash/reboot could clear out all variables.
 */

static enum cb_err lookup_store_region(struct region *region)
{
	if (CONFIG(SMMSTORE_IN_CBFS)) {
		struct cbfsf file;
		if (cbfs_locate_file_in_region(&file,
					       CONFIG_SMMSTORE_REGION,
					       CONFIG_SMMSTORE_FILENAME, NULL) < 0) {
			printk(BIOS_WARNING,
			       "smm store: Unable to find SMM store file in region '%s'\n",
			       CONFIG_SMMSTORE_REGION);
			return CB_ERR;
		}
		struct region_device rdev;
		cbfs_file_data(&rdev, &file);
		*region = *region_device_region(&rdev);
	} else {
		if (fmap_locate_area(CONFIG_SMMSTORE_REGION, region)) {
			printk(BIOS_WARNING,
			       "smm store: Unable to find SMM store FMAP region '%s'\n",
			       CONFIG_SMMSTORE_REGION);
			return CB_ERR;
		}
	}

	return CB_SUCCESS;
}

/*
 * Return a region device that points into the store file.
 *
 * It's the image builder's responsibility to make it block aligned so that
 * erase works without destroying other data.
 *
 * It doesn't cache the location to cope with flash changing underneath (eg
 * due to an update)
 *
 * returns 0 on success, -1 on failure
 * outputs the valid store rdev in rstore
 */
static int lookup_store(struct region_device *rstore)
{
	static struct region_device read_rdev, write_rdev;
	static struct incoherent_rdev store_irdev;
	struct region region;
	const struct region_device *rdev;

	if (lookup_store_region(&region) != CB_SUCCESS)
		return -1;

	if (boot_device_ro_subregion(&region, &read_rdev) < 0)
		return -1;

	if (boot_device_rw_subregion(&region, &write_rdev) < 0)
		return -1;

	rdev = incoherent_rdev_init(&store_irdev, &region, &read_rdev, &write_rdev);

	if (rdev == NULL)
		return -1;

	return rdev_chain(rstore, rdev, 0, region_device_sz(rdev));
}

/*
 * Read entire store into user provided buffer
 *
 * returns 0 on success, -1 on failure
 * writes up to `*bufsize` bytes into `buf` and updates `*bufsize`
 */
int smmstore_read_region(void *buf, ssize_t *bufsize)
{
	struct region_device store;

	if (bufsize == NULL)
		return -1;

	if (lookup_store(&store) < 0) {
		printk(BIOS_WARNING, "reading region failed\n");
		return -1;
	}

	ssize_t tx = MIN(*bufsize, region_device_sz(&store));
	*bufsize = rdev_readat(&store, buf, 0, tx);

	if (*bufsize < 0)
		return -1;

	return 0;
}

static enum cb_err scan_end(struct region_device *store)
{
	/* scan for end */
	ssize_t end = 0;
	uint32_t k_sz, v_sz;
	const ssize_t data_sz = region_device_sz(store);
	while (end < data_sz) {
		/* make odd corner cases identifiable, eg. invalid v_sz */
		k_sz = 0;

		if (rdev_readat(store, &k_sz, end, sizeof(k_sz)) < 0) {
			printk(BIOS_WARNING, "failed reading key size\n");
			return CB_ERR;
		}

		/* found the end */
		if (k_sz == 0xffffffff)
			break;

		/* something is fishy here:
		 * Avoid wrapping (since data_size < MAX_UINT32_T / 2) while
		 * other problems are covered by the loop condition
		 */
		if (k_sz > data_sz) {
			printk(BIOS_WARNING, "key size out of bounds\n");
			return CB_ERR;
		}

		if (rdev_readat(store, &v_sz, end + sizeof(k_sz), sizeof(v_sz)) < 0) {
			printk(BIOS_WARNING, "failed reading value size\n");
			return CB_ERR;
		}

		if (v_sz > data_sz) {
			printk(BIOS_WARNING, "value size out of bounds\n");
			return CB_ERR;
		}

		end += sizeof(k_sz) + sizeof(v_sz) + k_sz + v_sz + 1;
		end = ALIGN_UP(end, sizeof(uint32_t));
	}

	printk(BIOS_DEBUG, "used smm store size might be 0x%zx bytes\n", end);

	if (k_sz != 0xffffffff) {
		printk(BIOS_WARNING,
			"eof of data marker looks invalid: 0x%x\n", k_sz);
		return CB_ERR;
	}

	if (rdev_chain(store, store, end, data_sz - end))
		return CB_ERR;

	return CB_SUCCESS;

}
/*
 * Append data to region
 *
 * Returns 0 on success, -1 on failure
 */
int smmstore_append_data(void *key, uint32_t key_sz, void *value,
			 uint32_t value_sz)
{
	struct region_device store;

	if (lookup_store(&store) < 0) {
		printk(BIOS_WARNING, "reading region failed\n");
		return -1;
	}

	ssize_t offset = 0;
	ssize_t size;
	uint8_t nul = 0;
	if (scan_end(&store) != CB_SUCCESS)
		return -1;

	printk(BIOS_DEBUG, "used size looks legit\n");

	printk(BIOS_DEBUG, "open (%zx, %zx) for writing\n",
		region_device_offset(&store), region_device_sz(&store));

	size = sizeof(key_sz) + sizeof(value_sz) + key_sz + value_sz
		+ sizeof(nul);
	if (rdev_chain(&store, &store, 0, size)) {
		printk(BIOS_WARNING, "not enough space for new data\n");
		return -1;
	}

	if (rdev_writeat(&store, &key_sz, offset, sizeof(key_sz))
	    != sizeof(key_sz)) {
		printk(BIOS_WARNING, "failed writing key size\n");
		return -1;
	}
	offset += sizeof(key_sz);
	if (rdev_writeat(&store, &value_sz, offset, sizeof(value_sz))
	    != sizeof(value_sz)) {
		printk(BIOS_WARNING, "failed writing value size\n");
		return -1;
	}
	offset += sizeof(value_sz);
	if (rdev_writeat(&store, key, offset, key_sz) != key_sz) {
		printk(BIOS_WARNING, "failed writing key data\n");
		return -1;
	}
	offset += key_sz;
	if (rdev_writeat(&store, value, offset, value_sz) != value_sz) {
		printk(BIOS_WARNING, "failed writing value data\n");
		return -1;
	}
	offset += value_sz;
	if (rdev_writeat(&store, &nul, offset, sizeof(nul)) != sizeof(nul)) {
		printk(BIOS_WARNING, "failed writing termination\n");
		return -1;
	}

	return 0;
}

/*
 * Clear region
 *
 * Returns 0 on success, -1 on failure, including partial erase
 */
int smmstore_clear_region(void)
{
	struct region_device store;

	if (lookup_store(&store) < 0) {
		printk(BIOS_WARNING, "smm store: reading region failed\n");
		return -1;
	}

	ssize_t res = rdev_eraseat(&store, 0, region_device_sz(&store));
	if (res != region_device_sz(&store)) {
		printk(BIOS_WARNING, "smm store: erasing region failed\n");
		return -1;
	}

	return 0;
}