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