1 /* ----------------------------------------------------------------------- *
3 * Copyright 2007-2008 H. Peter Anvin - All Rights Reserved
4 * Copyright 2010 Intel Corporation; author: H. Peter Anvin
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, Inc., 53 Temple Place Ste 330,
9 * Boston MA 02111-1307, USA; either version 2 of the License, or
10 * (at your option) any later version; incorporated herein by reference.
12 * ----------------------------------------------------------------------- */
17 * (Over)write a data item in the auxilliary data vector. To
18 * delete an item, set its length to zero.
20 * Return 0 on success, -1 on error, and set errno.
35 unsigned char syslinux_adv[2 * ADV_SIZE];
37 #define ADV_MAGIC1 0x5a2d2fa5 /* Head signature */
38 #define ADV_MAGIC2 0xa3041767 /* Total checksum */
39 #define ADV_MAGIC3 0xdd28bf64 /* Tail signature */
41 static void cleanup_adv(unsigned char *advbuf)
46 /* Make sure both copies agree, and update the checksum */
47 set_32((uint32_t *) advbuf, ADV_MAGIC1);
50 for (i = 8; i < ADV_SIZE - 4; i += 4)
51 csum -= get_32((uint32_t *) (advbuf + i));
53 set_32((uint32_t *) (advbuf + 4), csum);
54 set_32((uint32_t *) (advbuf + ADV_SIZE - 4), ADV_MAGIC3);
56 memcpy(advbuf + ADV_SIZE, advbuf, ADV_SIZE);
59 int syslinux_setadv(int tag, size_t size, const void *data)
63 uint8_t advtmp[ADV_SIZE];
65 if ((unsigned)tag - 1 > 254) {
67 return -1; /* Impossible tag value */
71 errno = ENOSPC; /* Max 255 bytes for a data item */
77 memcpy(p, syslinux_adv + 2 * 4, left); /* Make working copy */
81 size_t plen = p[1] + 2;
87 /* Found our tag. Delete it. */
90 /* Entire remainder is our tag */
93 memmove(p, p + plen, left - plen);
97 break; /* Corrupt tag (overrun) - overwrite it */
104 /* Now (p, left) reflects the position to write in and how much space
105 we have for our data. */
108 if (left < size + 2) {
109 errno = ENOSPC; /* Not enough space for data */
115 memcpy(p, data, size);
122 /* If we got here, everything went OK, commit the write */
123 memcpy(syslinux_adv + 2 * 4, advtmp, ADV_LEN);
124 cleanup_adv(syslinux_adv);
129 void syslinux_reset_adv(unsigned char *advbuf)
131 /* Create an all-zero ADV */
132 memset(advbuf + 2 * 4, 0, ADV_LEN);
136 static int adv_consistent(const unsigned char *p)
141 if (get_32((uint32_t *) p) != ADV_MAGIC1 ||
142 get_32((uint32_t *) (p + ADV_SIZE - 4)) != ADV_MAGIC3)
146 for (i = 4; i < ADV_SIZE - 4; i += 4)
147 csum += get_32((uint32_t *) (p + i));
149 return csum == ADV_MAGIC2;
153 * Verify that an in-memory ADV is consistent, making the copies consistent.
154 * If neither copy is OK, return -1 and call syslinux_reset_adv().
156 int syslinux_validate_adv(unsigned char *advbuf)
158 if (adv_consistent(advbuf + 0 * ADV_SIZE)) {
159 memcpy(advbuf + ADV_SIZE, advbuf, ADV_SIZE);
161 } else if (adv_consistent(advbuf + 1 * ADV_SIZE)) {
162 memcpy(advbuf, advbuf + ADV_SIZE, ADV_SIZE);
165 syslinux_reset_adv(advbuf);