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
32enum 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
67struct 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			*nextoff = (long)nptr - (long)data;
129			if (ch[C_NAMESIZE] - mypathsize >= MAX_CPIO_FILE_NAME) {
130				pr_warn(
131				"File %s exceeding MAX_CPIO_FILE_NAME [%d]\n",
132				p, MAX_CPIO_FILE_NAME);
133			}
134			strlcpy(cd.name, p + mypathsize, MAX_CPIO_FILE_NAME);
135
136			cd.data = (void *)dptr;
137			cd.size = ch[C_FILESIZE];
138			return cd; /* Found it! */
139		}
140		len -= (nptr - p);
141		p = nptr;
142	}
143
144quit:
145	return cd;
146}
147