1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Code for looking up block devices in the early boot code before mounting the
4 * root file system.
5 */
6#include <linux/blkdev.h>
7#include <linux/ctype.h>
8
9struct uuidcmp {
10 const char *uuid;
11 int len;
12};
13
14/**
15 * match_dev_by_uuid - callback for finding a partition using its uuid
16 * @dev: device passed in by the caller
17 * @data: opaque pointer to the desired struct uuidcmp to match
18 *
19 * Returns 1 if the device matches, and 0 otherwise.
20 */
21static int __init match_dev_by_uuid(struct device *dev, const void *data)
22{
23 struct block_device *bdev = dev_to_bdev(dev);
24 const struct uuidcmp *cmp = data;
25
26 if (!bdev->bd_meta_info ||
27 strncasecmp(s1: cmp->uuid, s2: bdev->bd_meta_info->uuid, n: cmp->len))
28 return 0;
29 return 1;
30}
31
32/**
33 * devt_from_partuuid - looks up the dev_t of a partition by its UUID
34 * @uuid_str: char array containing ascii UUID
35 * @devt: dev_t result
36 *
37 * The function will return the first partition which contains a matching
38 * UUID value in its partition_meta_info struct. This does not search
39 * by filesystem UUIDs.
40 *
41 * If @uuid_str is followed by a "/PARTNROFF=%d", then the number will be
42 * extracted and used as an offset from the partition identified by the UUID.
43 *
44 * Returns 0 on success or a negative error code on failure.
45 */
46static int __init devt_from_partuuid(const char *uuid_str, dev_t *devt)
47{
48 struct uuidcmp cmp;
49 struct device *dev = NULL;
50 int offset = 0;
51 char *slash;
52
53 cmp.uuid = uuid_str;
54
55 slash = strchr(uuid_str, '/');
56 /* Check for optional partition number offset attributes. */
57 if (slash) {
58 char c = 0;
59
60 /* Explicitly fail on poor PARTUUID syntax. */
61 if (sscanf(slash + 1, "PARTNROFF=%d%c", &offset, &c) != 1)
62 goto out_invalid;
63 cmp.len = slash - uuid_str;
64 } else {
65 cmp.len = strlen(uuid_str);
66 }
67
68 if (!cmp.len)
69 goto out_invalid;
70
71 dev = class_find_device(class: &block_class, NULL, data: &cmp, match: &match_dev_by_uuid);
72 if (!dev)
73 return -ENODEV;
74
75 if (offset) {
76 /*
77 * Attempt to find the requested partition by adding an offset
78 * to the partition number found by UUID.
79 */
80 *devt = part_devt(dev_to_disk(dev),
81 dev_to_bdev(dev)->bd_partno + offset);
82 } else {
83 *devt = dev->devt;
84 }
85
86 put_device(dev);
87 return 0;
88
89out_invalid:
90 pr_err("VFS: PARTUUID= is invalid.\n"
91 "Expected PARTUUID=<valid-uuid-id>[/PARTNROFF=%%d]\n");
92 return -EINVAL;
93}
94
95/**
96 * match_dev_by_label - callback for finding a partition using its label
97 * @dev: device passed in by the caller
98 * @data: opaque pointer to the label to match
99 *
100 * Returns 1 if the device matches, and 0 otherwise.
101 */
102static int __init match_dev_by_label(struct device *dev, const void *data)
103{
104 struct block_device *bdev = dev_to_bdev(dev);
105 const char *label = data;
106
107 if (!bdev->bd_meta_info || strcmp(label, bdev->bd_meta_info->volname))
108 return 0;
109 return 1;
110}
111
112static int __init devt_from_partlabel(const char *label, dev_t *devt)
113{
114 struct device *dev;
115
116 dev = class_find_device(class: &block_class, NULL, data: label, match: &match_dev_by_label);
117 if (!dev)
118 return -ENODEV;
119 *devt = dev->devt;
120 put_device(dev);
121 return 0;
122}
123
124static dev_t __init blk_lookup_devt(const char *name, int partno)
125{
126 dev_t devt = MKDEV(0, 0);
127 struct class_dev_iter iter;
128 struct device *dev;
129
130 class_dev_iter_init(iter: &iter, class: &block_class, NULL, type: &disk_type);
131 while ((dev = class_dev_iter_next(iter: &iter))) {
132 struct gendisk *disk = dev_to_disk(dev);
133
134 if (strcmp(dev_name(dev), name))
135 continue;
136
137 if (partno < disk->minors) {
138 /* We need to return the right devno, even
139 * if the partition doesn't exist yet.
140 */
141 devt = MKDEV(MAJOR(dev->devt),
142 MINOR(dev->devt) + partno);
143 } else {
144 devt = part_devt(disk, partno);
145 if (devt)
146 break;
147 }
148 }
149 class_dev_iter_exit(iter: &iter);
150 return devt;
151}
152
153static int __init devt_from_devname(const char *name, dev_t *devt)
154{
155 int part;
156 char s[32];
157 char *p;
158
159 if (strlen(name) > 31)
160 return -EINVAL;
161 strcpy(p: s, q: name);
162 for (p = s; *p; p++) {
163 if (*p == '/')
164 *p = '!';
165 }
166
167 *devt = blk_lookup_devt(name: s, partno: 0);
168 if (*devt)
169 return 0;
170
171 /*
172 * Try non-existent, but valid partition, which may only exist after
173 * opening the device, like partitioned md devices.
174 */
175 while (p > s && isdigit(c: p[-1]))
176 p--;
177 if (p == s || !*p || *p == '0')
178 return -ENODEV;
179
180 /* try disk name without <part number> */
181 part = simple_strtoul(p, NULL, 10);
182 *p = '\0';
183 *devt = blk_lookup_devt(name: s, partno: part);
184 if (*devt)
185 return 0;
186
187 /* try disk name without p<part number> */
188 if (p < s + 2 || !isdigit(c: p[-2]) || p[-1] != 'p')
189 return -ENODEV;
190 p[-1] = '\0';
191 *devt = blk_lookup_devt(name: s, partno: part);
192 if (*devt)
193 return 0;
194 return -ENODEV;
195}
196
197static int __init devt_from_devnum(const char *name, dev_t *devt)
198{
199 unsigned maj, min, offset;
200 char *p, dummy;
201
202 if (sscanf(name, "%u:%u%c", &maj, &min, &dummy) == 2 ||
203 sscanf(name, "%u:%u:%u:%c", &maj, &min, &offset, &dummy) == 3) {
204 *devt = MKDEV(maj, min);
205 if (maj != MAJOR(*devt) || min != MINOR(*devt))
206 return -EINVAL;
207 } else {
208 *devt = new_decode_dev(dev: simple_strtoul(name, &p, 16));
209 if (*p)
210 return -EINVAL;
211 }
212
213 return 0;
214}
215
216/*
217 * Convert a name into device number. We accept the following variants:
218 *
219 * 1) <hex_major><hex_minor> device number in hexadecimal represents itself
220 * no leading 0x, for example b302.
221 * 3) /dev/<disk_name> represents the device number of disk
222 * 4) /dev/<disk_name><decimal> represents the device number
223 * of partition - device number of disk plus the partition number
224 * 5) /dev/<disk_name>p<decimal> - same as the above, that form is
225 * used when disk name of partitioned disk ends on a digit.
226 * 6) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
227 * unique id of a partition if the partition table provides it.
228 * The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
229 * partition using the format SSSSSSSS-PP, where SSSSSSSS is a zero-
230 * filled hex representation of the 32-bit "NT disk signature", and PP
231 * is a zero-filled hex representation of the 1-based partition number.
232 * 7) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation to
233 * a partition with a known unique id.
234 * 8) <major>:<minor> major and minor number of the device separated by
235 * a colon.
236 * 9) PARTLABEL=<name> with name being the GPT partition label.
237 * MSDOS partitions do not support labels!
238 *
239 * If name doesn't have fall into the categories above, we return (0,0).
240 * block_class is used to check if something is a disk name. If the disk
241 * name contains slashes, the device name has them replaced with
242 * bangs.
243 */
244int __init early_lookup_bdev(const char *name, dev_t *devt)
245{
246 if (strncmp(name, "PARTUUID=", 9) == 0)
247 return devt_from_partuuid(uuid_str: name + 9, devt);
248 if (strncmp(name, "PARTLABEL=", 10) == 0)
249 return devt_from_partlabel(label: name + 10, devt);
250 if (strncmp(name, "/dev/", 5) == 0)
251 return devt_from_devname(name: name + 5, devt);
252 return devt_from_devnum(name, devt);
253}
254
255static char __init *bdevt_str(dev_t devt, char *buf)
256{
257 if (MAJOR(devt) <= 0xff && MINOR(devt) <= 0xff) {
258 char tbuf[BDEVT_SIZE];
259 snprintf(buf: tbuf, BDEVT_SIZE, fmt: "%02x%02x", MAJOR(devt), MINOR(devt));
260 snprintf(buf, BDEVT_SIZE, fmt: "%-9s", tbuf);
261 } else
262 snprintf(buf, BDEVT_SIZE, fmt: "%03x:%05x", MAJOR(devt), MINOR(devt));
263
264 return buf;
265}
266
267/*
268 * print a full list of all partitions - intended for places where the root
269 * filesystem can't be mounted and thus to give the victim some idea of what
270 * went wrong
271 */
272void __init printk_all_partitions(void)
273{
274 struct class_dev_iter iter;
275 struct device *dev;
276
277 class_dev_iter_init(iter: &iter, class: &block_class, NULL, type: &disk_type);
278 while ((dev = class_dev_iter_next(iter: &iter))) {
279 struct gendisk *disk = dev_to_disk(dev);
280 struct block_device *part;
281 char devt_buf[BDEVT_SIZE];
282 unsigned long idx;
283
284 /*
285 * Don't show empty devices or things that have been
286 * suppressed
287 */
288 if (get_capacity(disk) == 0 || (disk->flags & GENHD_FL_HIDDEN))
289 continue;
290
291 /*
292 * Note, unlike /proc/partitions, I am showing the numbers in
293 * hex - the same format as the root= option takes.
294 */
295 rcu_read_lock();
296 xa_for_each(&disk->part_tbl, idx, part) {
297 if (!bdev_nr_sectors(bdev: part))
298 continue;
299 printk("%s%s %10llu %pg %s",
300 bdev_is_partition(part) ? " " : "",
301 bdevt_str(part->bd_dev, devt_buf),
302 bdev_nr_sectors(part) >> 1, part,
303 part->bd_meta_info ?
304 part->bd_meta_info->uuid : "");
305 if (bdev_is_partition(bdev: part))
306 printk("\n");
307 else if (dev->parent && dev->parent->driver)
308 printk(" driver: %s\n",
309 dev->parent->driver->name);
310 else
311 printk(" (driver?)\n");
312 }
313 rcu_read_unlock();
314 }
315 class_dev_iter_exit(iter: &iter);
316}
317

source code of linux/block/early-lookup.c