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- /* ----------------------------------------------------------------------- *
- *
- * Copyright 2007-2008 H. Peter Anvin - All Rights Reserved
- * Copyright 2010 Intel Corporation; author: H. Peter Anvin
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, Inc., 53 Temple Place Ste 330,
- * Boston MA 02111-1307, USA; either version 2 of the License, or
- * (at your option) any later version; incorporated herein by reference.
- *
- * ----------------------------------------------------------------------- */
- /*
- * setadv.c
- *
- * (Over)write a data item in the auxilliary data vector. To
- * delete an item, set its length to zero.
- *
- * Return 0 on success, -1 on error, and set errno.
- *
- */
- #define _GNU_SOURCE
- #include <stdio.h>
- #include <stdlib.h>
- #include <stddef.h>
- #include <stdint.h>
- #include <string.h>
- #include <errno.h>
- #include "syslxint.h"
- #include "syslxcom.h"
- #include "syslxfs.h"
- unsigned char syslinux_adv[2 * ADV_SIZE];
- #define ADV_MAGIC1 0x5a2d2fa5 /* Head signature */
- #define ADV_MAGIC2 0xa3041767 /* Total checksum */
- #define ADV_MAGIC3 0xdd28bf64 /* Tail signature */
- static void cleanup_adv(unsigned char *advbuf)
- {
- int i;
- uint32_t csum;
- /* Make sure both copies agree, and update the checksum */
- set_32((uint32_t *) advbuf, ADV_MAGIC1);
- csum = ADV_MAGIC2;
- for (i = 8; i < ADV_SIZE - 4; i += 4)
- csum -= get_32((uint32_t *) (advbuf + i));
- set_32((uint32_t *) (advbuf + 4), csum);
- set_32((uint32_t *) (advbuf + ADV_SIZE - 4), ADV_MAGIC3);
- memcpy(advbuf + ADV_SIZE, advbuf, ADV_SIZE);
- }
- int syslinux_setadv(int tag, size_t size, const void *data)
- {
- uint8_t *p;
- size_t left;
- uint8_t advtmp[ADV_SIZE];
- if ((unsigned)tag - 1 > 254) {
- errno = EINVAL;
- return -1; /* Impossible tag value */
- }
- if (size > 255) {
- errno = ENOSPC; /* Max 255 bytes for a data item */
- return -1;
- }
- left = ADV_LEN;
- p = advtmp;
- memcpy(p, syslinux_adv + 2 * 4, left); /* Make working copy */
- while (left >= 2) {
- uint8_t ptag = p[0];
- size_t plen = p[1] + 2;
- if (ptag == ADV_END)
- break;
- if (ptag == tag) {
- /* Found our tag. Delete it. */
- if (plen >= left) {
- /* Entire remainder is our tag */
- break;
- }
- memmove(p, p + plen, left - plen);
- } else {
- /* Not our tag */
- if (plen > left)
- break; /* Corrupt tag (overrun) - overwrite it */
- left -= plen;
- p += plen;
- }
- }
- /* Now (p, left) reflects the position to write in and how much space
- we have for our data. */
- if (size) {
- if (left < size + 2) {
- errno = ENOSPC; /* Not enough space for data */
- return -1;
- }
- *p++ = tag;
- *p++ = size;
- memcpy(p, data, size);
- p += size;
- left -= size + 2;
- }
- memset(p, 0, left);
- /* If we got here, everything went OK, commit the write */
- memcpy(syslinux_adv + 2 * 4, advtmp, ADV_LEN);
- cleanup_adv(syslinux_adv);
- return 0;
- }
- void syslinux_reset_adv(unsigned char *advbuf)
- {
- /* Create an all-zero ADV */
- memset(advbuf + 2 * 4, 0, ADV_LEN);
- cleanup_adv(advbuf);
- }
- static int adv_consistent(const unsigned char *p)
- {
- int i;
- uint32_t csum;
- if (get_32((uint32_t *) p) != ADV_MAGIC1 ||
- get_32((uint32_t *) (p + ADV_SIZE - 4)) != ADV_MAGIC3)
- return 0;
- csum = 0;
- for (i = 4; i < ADV_SIZE - 4; i += 4)
- csum += get_32((uint32_t *) (p + i));
- return csum == ADV_MAGIC2;
- }
- /*
- * Verify that an in-memory ADV is consistent, making the copies consistent.
- * If neither copy is OK, return -1 and call syslinux_reset_adv().
- */
- int syslinux_validate_adv(unsigned char *advbuf)
- {
- if (adv_consistent(advbuf + 0 * ADV_SIZE)) {
- memcpy(advbuf + ADV_SIZE, advbuf, ADV_SIZE);
- return 0;
- } else if (adv_consistent(advbuf + 1 * ADV_SIZE)) {
- memcpy(advbuf, advbuf + ADV_SIZE, ADV_SIZE);
- return 0;
- } else {
- syslinux_reset_adv(advbuf);
- return -1;
- }
- }
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