1/* ----------------------------------------------------------------------- *
2 *
3 *   Copyright 2007-2008 H. Peter Anvin - All Rights Reserved
4 *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
5 *
6 *   Permission is hereby granted, free of charge, to any person
7 *   obtaining a copy of this software and associated documentation
8 *   files (the "Software"), to deal in the Software without
9 *   restriction, including without limitation the rights to use,
10 *   copy, modify, merge, publish, distribute, sublicense, and/or
11 *   sell copies of the Software, and to permit persons to whom
12 *   the Software is furnished to do so, subject to the following
13 *   conditions:
14 *
15 *   The above copyright notice and this permission notice shall
16 *   be included in all copies or substantial portions of the Software.
17 *
18 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
19 *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
20 *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
21 *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
22 *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
23 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
24 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
25 *   OTHER DEALINGS IN THE SOFTWARE.
26 *
27 * ----------------------------------------------------------------------- */
28
29/*
30 * syslinux/setadv.c
31 *
32 * (Over)write a data item in the auxilliary data vector.  To
33 * delete an item, set its length to zero.
34 *
35 * Return 0 on success, -1 on error, and set errno.
36 *
37 * NOTE: Data is not written to disk unless
38 * syslinux_adv_write() is called.
39 */
40
41#include <syslinux/adv.h>
42#include <klibc/compiler.h>
43#include <inttypes.h>
44#include <string.h>
45#include <errno.h>
46#include <alloca.h>
47
48__export int syslinux_setadv(int tag, size_t size, const void *data)
49{
50    uint8_t *p, *advtmp;
51    size_t rleft, left;
52
53    if ((unsigned)tag - 1 > 254) {
54	errno = EINVAL;
55	return -1;		/* Impossible tag value */
56    }
57
58    if (size > 255) {
59	errno = ENOSPC;		/* Max 255 bytes for a data item */
60	return -1;
61    }
62
63    rleft = left = syslinux_adv_size();
64    p = advtmp = alloca(left);
65    memcpy(p, syslinux_adv_ptr(), left);	/* Make working copy */
66
67    while (rleft >= 2) {
68	uint8_t ptag = p[0];
69	size_t plen = p[1] + 2;
70
71	if (ptag == ADV_END)
72	    break;
73
74	if (ptag == tag) {
75	    /* Found our tag.  Delete it. */
76
77	    if (plen >= rleft) {
78		/* Entire remainder is our tag */
79		break;
80	    }
81	    memmove(p, p + plen, rleft - plen);
82	    rleft -= plen;	/* Fewer bytes to read, but not to write */
83	} else {
84	    /* Not our tag */
85	    if (plen > rleft)
86		break;		/* Corrupt tag (overrun) - overwrite it */
87
88	    left -= plen;
89	    rleft -= plen;
90	    p += plen;
91	}
92    }
93
94    /* Now (p, left) reflects the position to write in and how much space
95       we have for our data. */
96
97    if (size) {
98	if (left < size + 2) {
99	    errno = ENOSPC;	/* Not enough space for data */
100	    return -1;
101	}
102
103	*p++ = tag;
104	*p++ = size;
105	memcpy(p, data, size);
106	p += size;
107	left -= size + 2;
108    }
109
110    memset(p, 0, left);
111
112    /* If we got here, everything went OK, commit the write to low memory */
113    memcpy(syslinux_adv_ptr(), advtmp, syslinux_adv_size());
114
115    return 0;
116}
117