1// SPDX-License-Identifier: GPL-2.0-only
  2/* ----------------------------------------------------------------------- *
  3 *
  4 *   Copyright 2012 Intel Corporation; author H. Peter Anvin
  5 *
  6 * ----------------------------------------------------------------------- */
  7
  8/*
  9 * earlycpio.c
 10 *
 11 * Find a specific cpio member; must precede any compressed content.
 12 * This is used to locate data items in the initramfs used by the
 13 * kernel itself during early boot (before the main initramfs is
 14 * decompressed.)  It is the responsibility of the initramfs creator
 15 * to ensure that these items are uncompressed at the head of the
 16 * blob.  Depending on the boot loader or package tool that may be a
 17 * separate file or part of the same file.
 18 */
 19
 20#include <linux/earlycpio.h>
 21#include <linux/kernel.h>
 22#include <linux/string.h>
 23
 24enum cpio_fields {
 25	C_MAGIC,
 26	C_INO,
 27	C_MODE,
 28	C_UID,
 29	C_GID,
 30	C_NLINK,
 31	C_MTIME,
 32	C_FILESIZE,
 33	C_MAJ,
 34	C_MIN,
 35	C_RMAJ,
 36	C_RMIN,
 37	C_NAMESIZE,
 38	C_CHKSUM,
 39	C_NFIELDS
 40};
 41
 42/**
 43 * find_cpio_data - Search for files in an uncompressed cpio
 44 * @path:       The directory to search for, including a slash at the end
 45 * @data:       Pointer to the cpio archive or a header inside
 46 * @len:        Remaining length of the cpio based on data pointer
 47 * @nextoff:    When a matching file is found, this is the offset from the
 48 *              beginning of the cpio to the beginning of the next file, not the
 49 *              matching file itself. It can be used to iterate through the cpio
 50 *              to find all files inside of a directory path.
 51 *
 52 * Return:      &struct cpio_data containing the address, length and
 53 *              filename (with the directory path cut off) of the found file.
 54 *              If you search for a filename and not for files in a directory,
 55 *              pass the absolute path of the filename in the cpio and make sure
 56 *              the match returned an empty filename string.
 57 */
 58
 59struct cpio_data find_cpio_data(const char *path, void *data,
 60				size_t len,  long *nextoff)
 61{
 62	const size_t cpio_header_len = 8*C_NFIELDS - 2;
 63	struct cpio_data cd = { NULL, 0, "" };
 64	const char *p, *dptr, *nptr;
 65	unsigned int ch[C_NFIELDS], *chp, v;
 66	unsigned char c, x;
 67	size_t mypathsize = strlen(path);
 68	int i, j;
 69
 70	p = data;
 71
 72	while (len > cpio_header_len) {
 73		if (!*p) {
 74			/* All cpio headers need to be 4-byte aligned */
 75			p += 4;
 76			len -= 4;
 77			continue;
 78		}
 79
 80		j = 6;		/* The magic field is only 6 characters */
 81		chp = ch;
 82		for (i = C_NFIELDS; i; i--) {
 83			v = 0;
 84			while (j--) {
 85				v <<= 4;
 86				c = *p++;
 87
 88				x = c - '0';
 89				if (x < 10) {
 90					v += x;
 91					continue;
 92				}
 93
 94				x = (c | 0x20) - 'a';
 95				if (x < 6) {
 96					v += x + 10;
 97					continue;
 98				}
 99
100				goto quit; /* Invalid hexadecimal */
101			}
102			*chp++ = v;
103			j = 8;	/* All other fields are 8 characters */
104		}
105
106		if ((ch[C_MAGIC] - 0x070701) > 1)
107			goto quit; /* Invalid magic */
108
109		len -= cpio_header_len;
110
111		dptr = PTR_ALIGN(p + ch[C_NAMESIZE], 4);
112		nptr = PTR_ALIGN(dptr + ch[C_FILESIZE], 4);
113
114		if (nptr > p + len || dptr < p || nptr < dptr)
115			goto quit; /* Buffer overrun */
116
117		if ((ch[C_MODE] & 0170000) == 0100000 &&
118		    ch[C_NAMESIZE] >= mypathsize &&
119		    !memcmp(p, path, mypathsize)) {
120
121			if (nextoff)
122				*nextoff = (long)nptr - (long)data;
123
124			if (ch[C_NAMESIZE] - mypathsize >= MAX_CPIO_FILE_NAME) {
125				pr_warn(
126				"File %s exceeding MAX_CPIO_FILE_NAME [%d]\n",
127				p, MAX_CPIO_FILE_NAME);
128			}
129			strlcpy(cd.name, p + mypathsize, MAX_CPIO_FILE_NAME);
130
131			cd.data = (void *)dptr;
132			cd.size = ch[C_FILESIZE];
133			return cd; /* Found it! */
134		}
135		len -= (nptr - p);
136		p = nptr;
137	}
138
139quit:
140	return cd;
141}