150 lines
4.0 KiB
C
150 lines
4.0 KiB
C
/* ----------------------------------------------------------------------- *
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*
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* Copyright 2012 Intel Corporation; author H. Peter Anvin
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*
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* This file is part of the Linux kernel, and is made available
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* under the terms of the GNU General Public License version 2, as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* ----------------------------------------------------------------------- */
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/*
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* earlycpio.c
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*
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* Find a specific cpio member; must precede any compressed content.
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* This is used to locate data items in the initramfs used by the
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* kernel itself during early boot (before the main initramfs is
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* decompressed.) It is the responsibility of the initramfs creator
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* to ensure that these items are uncompressed at the head of the
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* blob. Depending on the boot loader or package tool that may be a
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* separate file or part of the same file.
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*/
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#include <linux/earlycpio.h>
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#include <linux/kernel.h>
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#include <linux/string.h>
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enum cpio_fields {
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C_MAGIC,
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C_INO,
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C_MODE,
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C_UID,
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C_GID,
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C_NLINK,
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C_MTIME,
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C_FILESIZE,
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C_MAJ,
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C_MIN,
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C_RMAJ,
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C_RMIN,
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C_NAMESIZE,
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C_CHKSUM,
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C_NFIELDS
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};
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/**
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* cpio_data find_cpio_data - Search for files in an uncompressed cpio
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* @path: The directory to search for, including a slash at the end
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* @data: Pointer to the the cpio archive or a header inside
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* @len: Remaining length of the cpio based on data pointer
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* @nextoff: When a matching file is found, this is the offset from the
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* beginning of the cpio to the beginning of the next file, not the
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* matching file itself. It can be used to iterate through the cpio
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* to find all files inside of a directory path.
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*
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* @return: struct cpio_data containing the address, length and
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* filename (with the directory path cut off) of the found file.
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* If you search for a filename and not for files in a directory,
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* pass the absolute path of the filename in the cpio and make sure
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* the match returned an empty filename string.
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*/
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struct cpio_data find_cpio_data(const char *path, void *data,
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size_t len, long *nextoff)
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{
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const size_t cpio_header_len = 8*C_NFIELDS - 2;
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struct cpio_data cd = { NULL, 0, "" };
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const char *p, *dptr, *nptr;
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unsigned int ch[C_NFIELDS], *chp, v;
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unsigned char c, x;
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size_t mypathsize = strlen(path);
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int i, j;
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p = data;
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while (len > cpio_header_len) {
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if (!*p) {
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/* All cpio headers need to be 4-byte aligned */
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p += 4;
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len -= 4;
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continue;
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}
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j = 6; /* The magic field is only 6 characters */
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chp = ch;
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for (i = C_NFIELDS; i; i--) {
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v = 0;
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while (j--) {
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v <<= 4;
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c = *p++;
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x = c - '0';
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if (x < 10) {
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v += x;
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continue;
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}
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x = (c | 0x20) - 'a';
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if (x < 6) {
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v += x + 10;
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continue;
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}
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goto quit; /* Invalid hexadecimal */
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}
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*chp++ = v;
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j = 8; /* All other fields are 8 characters */
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}
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if ((ch[C_MAGIC] - 0x070701) > 1)
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goto quit; /* Invalid magic */
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len -= cpio_header_len;
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dptr = PTR_ALIGN(p + ch[C_NAMESIZE], 4);
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nptr = PTR_ALIGN(dptr + ch[C_FILESIZE], 4);
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if (nptr > p + len || dptr < p || nptr < dptr)
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goto quit; /* Buffer overrun */
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if ((ch[C_MODE] & 0170000) == 0100000 &&
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ch[C_NAMESIZE] >= mypathsize &&
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!memcmp(p, path, mypathsize)) {
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if (nextoff)
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*nextoff = (long)nptr - (long)data;
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if (ch[C_NAMESIZE] - mypathsize >= MAX_CPIO_FILE_NAME) {
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pr_warn(
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"File %s exceeding MAX_CPIO_FILE_NAME [%d]\n",
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p, MAX_CPIO_FILE_NAME);
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}
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strlcpy(cd.name, p + mypathsize, MAX_CPIO_FILE_NAME);
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cd.data = (void *)dptr;
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cd.size = ch[C_FILESIZE];
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return cd; /* Found it! */
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}
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len -= (nptr - p);
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p = nptr;
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}
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quit:
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return cd;
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}
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