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