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 * @offset: When a matching file is found, this is the offset to the 56 * beginning of the cpio. It can be used to iterate through 57 * the cpio to find all files inside of a directory path 58 * 59 * @return: struct cpio_data containing the address, length and 60 * filename (with the directory path cut off) of the found file. 61 * If you search for a filename and not for files in a directory, 62 * pass the absolute path of the filename in the cpio and make sure 63 * the match returned an empty filename string. 64 */ 65 66 struct cpio_data __cpuinit find_cpio_data(const char *path, void *data, 67 size_t len, long *offset) 68 { 69 const size_t cpio_header_len = 8*C_NFIELDS - 2; 70 struct cpio_data cd = { NULL, 0, "" }; 71 const char *p, *dptr, *nptr; 72 unsigned int ch[C_NFIELDS], *chp, v; 73 unsigned char c, x; 74 size_t mypathsize = strlen(path); 75 int i, j; 76 77 p = data; 78 79 while (len > cpio_header_len) { 80 if (!*p) { 81 /* All cpio headers need to be 4-byte aligned */ 82 p += 4; 83 len -= 4; 84 continue; 85 } 86 87 j = 6; /* The magic field is only 6 characters */ 88 chp = ch; 89 for (i = C_NFIELDS; i; i--) { 90 v = 0; 91 while (j--) { 92 v <<= 4; 93 c = *p++; 94 95 x = c - '0'; 96 if (x < 10) { 97 v += x; 98 continue; 99 } 100 101 x = (c | 0x20) - 'a'; 102 if (x < 6) { 103 v += x + 10; 104 continue; 105 } 106 107 goto quit; /* Invalid hexadecimal */ 108 } 109 *chp++ = v; 110 j = 8; /* All other fields are 8 characters */ 111 } 112 113 if ((ch[C_MAGIC] - 0x070701) > 1) 114 goto quit; /* Invalid magic */ 115 116 len -= cpio_header_len; 117 118 dptr = PTR_ALIGN(p + ch[C_NAMESIZE], 4); 119 nptr = PTR_ALIGN(dptr + ch[C_FILESIZE], 4); 120 121 if (nptr > p + len || dptr < p || nptr < dptr) 122 goto quit; /* Buffer overrun */ 123 124 if ((ch[C_MODE] & 0170000) == 0100000 && 125 ch[C_NAMESIZE] >= mypathsize && 126 !memcmp(p, path, mypathsize)) { 127 *offset = (long)nptr - (long)data; 128 if (ch[C_NAMESIZE] - mypathsize >= MAX_CPIO_FILE_NAME) { 129 pr_warn( 130 "File %s exceeding MAX_CPIO_FILE_NAME [%d]\n", 131 p, MAX_CPIO_FILE_NAME); 132 } 133 strlcpy(cd.name, p + mypathsize, MAX_CPIO_FILE_NAME); 134 135 cd.data = (void *)dptr; 136 cd.size = ch[C_FILESIZE]; 137 return cd; /* Found it! */ 138 } 139 len -= (nptr - p); 140 p = nptr; 141 } 142 143 quit: 144 return cd; 145 } 146