blob: db283ba4d2c1fb5041180fe712781c3138b7ae9a
1 | /* ----------------------------------------------------------------------- * |
2 | * |
3 | * Copyright 2012 Intel Corporation; author H. Peter Anvin |
4 | * |
5 | * This file is part of the Linux kernel, and is made available |
6 | * under the terms of the GNU General Public License version 2, as |
7 | * published by the Free Software Foundation. |
8 | * |
9 | * This program is distributed in the hope it will be useful, but |
10 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
12 | * General Public License for more details. |
13 | * |
14 | * ----------------------------------------------------------------------- */ |
15 | |
16 | /* |
17 | * earlycpio.c |
18 | * |
19 | * Find a specific cpio member; must precede any compressed content. |
20 | * This is used to locate data items in the initramfs used by the |
21 | * kernel itself during early boot (before the main initramfs is |
22 | * decompressed.) It is the responsibility of the initramfs creator |
23 | * to ensure that these items are uncompressed at the head of the |
24 | * blob. Depending on the boot loader or package tool that may be a |
25 | * separate file or part of the same file. |
26 | */ |
27 | |
28 | #include <linux/earlycpio.h> |
29 | #include <linux/kernel.h> |
30 | #include <linux/string.h> |
31 | |
32 | enum cpio_fields { |
33 | C_MAGIC, |
34 | C_INO, |
35 | C_MODE, |
36 | C_UID, |
37 | C_GID, |
38 | C_NLINK, |
39 | C_MTIME, |
40 | C_FILESIZE, |
41 | C_MAJ, |
42 | C_MIN, |
43 | C_RMAJ, |
44 | C_RMIN, |
45 | C_NAMESIZE, |
46 | C_CHKSUM, |
47 | C_NFIELDS |
48 | }; |
49 | |
50 | /** |
51 | * cpio_data find_cpio_data - Search for files in an uncompressed cpio |
52 | * @path: The directory to search for, including a slash at the end |
53 | * @data: Pointer to the the cpio archive or a header inside |
54 | * @len: Remaining length of the cpio based on data pointer |
55 | * @nextoff: When a matching file is found, this is the offset from the |
56 | * beginning of the cpio to the beginning of the next file, not the |
57 | * matching file itself. It can be used to iterate through the cpio |
58 | * to find all files inside of a directory path. |
59 | * |
60 | * @return: struct cpio_data containing the address, length and |
61 | * filename (with the directory path cut off) of the found file. |
62 | * If you search for a filename and not for files in a directory, |
63 | * pass the absolute path of the filename in the cpio and make sure |
64 | * the match returned an empty filename string. |
65 | */ |
66 | |
67 | struct cpio_data find_cpio_data(const char *path, void *data, |
68 | size_t len, long *nextoff) |
69 | { |
70 | const size_t cpio_header_len = 8*C_NFIELDS - 2; |
71 | struct cpio_data cd = { NULL, 0, "" }; |
72 | const char *p, *dptr, *nptr; |
73 | unsigned int ch[C_NFIELDS], *chp, v; |
74 | unsigned char c, x; |
75 | size_t mypathsize = strlen(path); |
76 | int i, j; |
77 | |
78 | p = data; |
79 | |
80 | while (len > cpio_header_len) { |
81 | if (!*p) { |
82 | /* All cpio headers need to be 4-byte aligned */ |
83 | p += 4; |
84 | len -= 4; |
85 | continue; |
86 | } |
87 | |
88 | j = 6; /* The magic field is only 6 characters */ |
89 | chp = ch; |
90 | for (i = C_NFIELDS; i; i--) { |
91 | v = 0; |
92 | while (j--) { |
93 | v <<= 4; |
94 | c = *p++; |
95 | |
96 | x = c - '0'; |
97 | if (x < 10) { |
98 | v += x; |
99 | continue; |
100 | } |
101 | |
102 | x = (c | 0x20) - 'a'; |
103 | if (x < 6) { |
104 | v += x + 10; |
105 | continue; |
106 | } |
107 | |
108 | goto quit; /* Invalid hexadecimal */ |
109 | } |
110 | *chp++ = v; |
111 | j = 8; /* All other fields are 8 characters */ |
112 | } |
113 | |
114 | if ((ch[C_MAGIC] - 0x070701) > 1) |
115 | goto quit; /* Invalid magic */ |
116 | |
117 | len -= cpio_header_len; |
118 | |
119 | dptr = PTR_ALIGN(p + ch[C_NAMESIZE], 4); |
120 | nptr = PTR_ALIGN(dptr + ch[C_FILESIZE], 4); |
121 | |
122 | if (nptr > p + len || dptr < p || nptr < dptr) |
123 | goto quit; /* Buffer overrun */ |
124 | |
125 | if ((ch[C_MODE] & 0170000) == 0100000 && |
126 | ch[C_NAMESIZE] >= mypathsize && |
127 | !memcmp(p, path, mypathsize)) { |
128 | |
129 | if (nextoff) |
130 | *nextoff = (long)nptr - (long)data; |
131 | |
132 | if (ch[C_NAMESIZE] - mypathsize >= MAX_CPIO_FILE_NAME) { |
133 | pr_warn( |
134 | "File %s exceeding MAX_CPIO_FILE_NAME [%d]\n", |
135 | p, MAX_CPIO_FILE_NAME); |
136 | } |
137 | strlcpy(cd.name, p + mypathsize, MAX_CPIO_FILE_NAME); |
138 | |
139 | cd.data = (void *)dptr; |
140 | cd.size = ch[C_FILESIZE]; |
141 | return cd; /* Found it! */ |
142 | } |
143 | len -= (nptr - p); |
144 | p = nptr; |
145 | } |
146 | |
147 | quit: |
148 | return cd; |
149 | } |
150 |