1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* ----------------------------------------------------------------------- * |
3 | * |
4 | * Copyright 2012 Intel Corporation; author H. Peter Anvin |
5 | * |
6 | * ----------------------------------------------------------------------- */ |
7 | |
8 | /* |
9 | * earlycpio.c |
10 | * |
11 | * Find a specific cpio member; must precede any compressed content. |
12 | * This is used to locate data items in the initramfs used by the |
13 | * kernel itself during early boot (before the main initramfs is |
14 | * decompressed.) It is the responsibility of the initramfs creator |
15 | * to ensure that these items are uncompressed at the head of the |
16 | * blob. Depending on the boot loader or package tool that may be a |
17 | * separate file or part of the same file. |
18 | */ |
19 | |
20 | #include <linux/earlycpio.h> |
21 | #include <linux/kernel.h> |
22 | #include <linux/string.h> |
23 | |
24 | enum cpio_fields { |
25 | C_MAGIC, |
26 | C_INO, |
27 | C_MODE, |
28 | C_UID, |
29 | C_GID, |
30 | C_NLINK, |
31 | C_MTIME, |
32 | C_FILESIZE, |
33 | C_MAJ, |
34 | C_MIN, |
35 | C_RMAJ, |
36 | C_RMIN, |
37 | C_NAMESIZE, |
38 | C_CHKSUM, |
39 | C_NFIELDS |
40 | }; |
41 | |
42 | /** |
43 | * find_cpio_data - Search for files in an uncompressed cpio |
44 | * @path: The directory to search for, including a slash at the end |
45 | * @data: Pointer to the cpio archive or a header inside |
46 | * @len: Remaining length of the cpio based on data pointer |
47 | * @nextoff: When a matching file is found, this is the offset from the |
48 | * beginning of the cpio to the beginning of the next file, not the |
49 | * matching file itself. It can be used to iterate through the cpio |
50 | * to find all files inside of a directory path. |
51 | * |
52 | * Return: &struct cpio_data containing the address, length and |
53 | * filename (with the directory path cut off) of the found file. |
54 | * If you search for a filename and not for files in a directory, |
55 | * pass the absolute path of the filename in the cpio and make sure |
56 | * the match returned an empty filename string. |
57 | */ |
58 | |
59 | struct cpio_data find_cpio_data(const char *path, void *data, |
60 | size_t len, long *nextoff) |
61 | { |
62 | const size_t = 8*C_NFIELDS - 2; |
63 | struct cpio_data cd = { NULL, 0, "" }; |
64 | const char *p, *dptr, *nptr; |
65 | unsigned int ch[C_NFIELDS], *chp, v; |
66 | unsigned char c, x; |
67 | size_t mypathsize = strlen(path); |
68 | int i, j; |
69 | |
70 | p = data; |
71 | |
72 | while (len > cpio_header_len) { |
73 | if (!*p) { |
74 | /* All cpio headers need to be 4-byte aligned */ |
75 | p += 4; |
76 | len -= 4; |
77 | continue; |
78 | } |
79 | |
80 | j = 6; /* The magic field is only 6 characters */ |
81 | chp = ch; |
82 | for (i = C_NFIELDS; i; i--) { |
83 | v = 0; |
84 | while (j--) { |
85 | v <<= 4; |
86 | c = *p++; |
87 | |
88 | x = c - '0'; |
89 | if (x < 10) { |
90 | v += x; |
91 | continue; |
92 | } |
93 | |
94 | x = (c | 0x20) - 'a'; |
95 | if (x < 6) { |
96 | v += x + 10; |
97 | continue; |
98 | } |
99 | |
100 | goto quit; /* Invalid hexadecimal */ |
101 | } |
102 | *chp++ = v; |
103 | j = 8; /* All other fields are 8 characters */ |
104 | } |
105 | |
106 | if ((ch[C_MAGIC] - 0x070701) > 1) |
107 | goto quit; /* Invalid magic */ |
108 | |
109 | len -= cpio_header_len; |
110 | |
111 | dptr = PTR_ALIGN(p + ch[C_NAMESIZE], 4); |
112 | nptr = PTR_ALIGN(dptr + ch[C_FILESIZE], 4); |
113 | |
114 | if (nptr > p + len || dptr < p || nptr < dptr) |
115 | goto quit; /* Buffer overrun */ |
116 | |
117 | if ((ch[C_MODE] & 0170000) == 0100000 && |
118 | ch[C_NAMESIZE] >= mypathsize && |
119 | !memcmp(p, q: path, size: mypathsize)) { |
120 | |
121 | if (nextoff) |
122 | *nextoff = (long)nptr - (long)data; |
123 | |
124 | if (ch[C_NAMESIZE] - mypathsize >= MAX_CPIO_FILE_NAME) { |
125 | pr_warn( |
126 | "File %s exceeding MAX_CPIO_FILE_NAME [%d]\n" , |
127 | p, MAX_CPIO_FILE_NAME); |
128 | } |
129 | strscpy(p: cd.name, q: p + mypathsize, MAX_CPIO_FILE_NAME); |
130 | |
131 | cd.data = (void *)dptr; |
132 | cd.size = ch[C_FILESIZE]; |
133 | return cd; /* Found it! */ |
134 | } |
135 | len -= (nptr - p); |
136 | p = nptr; |
137 | } |
138 | |
139 | quit: |
140 | return cd; |
141 | } |
142 | |