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