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 *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 } 143 144 quit: 145 return cd; 146 } 147