1 /* ----------------------------------------------------------------------- * 2 * 3 * Copyright 2007-2008 H. Peter Anvin - All Rights Reserved 4 * Copyright 2010 Intel Corporation; author: H. Peter Anvin 5 * 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. 11 * 12 * ----------------------------------------------------------------------- */ 13 14 /* 15 * advio.c 16 * 17 * Linux ADV I/O 18 * 19 * Return 0 on success, -1 on error, and set errno. 20 * 21 */ 22 #define _GNU_SOURCE 23 24 #include <stdio.h> 25 #include <stdlib.h> 26 #include <stddef.h> 27 #include <stdint.h> 28 #include <string.h> 29 #include <unistd.h> 30 #include <errno.h> 31 #include <fcntl.h> 32 #include <sys/stat.h> 33 #include <sys/types.h> 34 #include "syslxint.h" 35 #include "syslxcom.h" 36 37 /* 38 * Read the ADV from an existing instance, or initialize if invalid. 39 * Returns -1 on fatal errors, 0 if ADV is okay, 1 if the ADV is 40 * invalid, and 2 if the file does not exist. 41 */ 42 int read_adv(const char *path, const char *cfg) 43 { 44 char *file; 45 int fd = -1; 46 struct stat st; 47 int err = 0; 48 int rv; 49 50 rv = asprintf(&file, "%s%s%s", path, 51 path[0] && path[strlen(path) - 1] == '/' ? "" : "/", cfg); 52 53 if (rv < 0 || !file) { 54 perror(program); 55 return -1; 56 } 57 58 fd = open(file, O_RDONLY); 59 if (fd < 0) { 60 if (errno != ENOENT) { 61 err = -1; 62 } else { 63 syslinux_reset_adv(syslinux_adv); 64 err = 2; /* Nonexistence is not a fatal error */ 65 } 66 } else if (fstat(fd, &st)) { 67 err = -1; 68 } else if (st.st_size < 2 * ADV_SIZE) { 69 /* Too small to be useful */ 70 syslinux_reset_adv(syslinux_adv); 71 err = 0; /* Nothing to read... */ 72 } else if (xpread(fd, syslinux_adv, 2 * ADV_SIZE, 73 st.st_size - 2 * ADV_SIZE) != 2 * ADV_SIZE) { 74 err = -1; 75 } else { 76 /* We got it... maybe? */ 77 err = syslinux_validate_adv(syslinux_adv) ? 1 : 0; 78 } 79 80 if (err < 0) 81 perror(file); 82 83 if (fd >= 0) 84 close(fd); 85 86 free(file); 87 88 return err; 89 } 90 91 /* 92 * Update the ADV in an existing installation. 93 */ 94 int write_adv(const char *path, const char *cfg) 95 { 96 unsigned char advtmp[2 * ADV_SIZE]; 97 char *file; 98 int fd = -1; 99 struct stat st, xst; 100 int err = 0; 101 int rv; 102 103 rv = asprintf(&file, "%s%s%s", path, 104 path[0] && path[strlen(path) - 1] == '/' ? "" : "/", cfg); 105 106 if (rv < 0 || !file) { 107 perror(program); 108 return -1; 109 } 110 111 fd = open(file, O_RDONLY); 112 if (fd < 0) { 113 err = -1; 114 } else if (fstat(fd, &st)) { 115 err = -1; 116 } else if (st.st_size < 2 * ADV_SIZE) { 117 /* Too small to be useful */ 118 err = -2; 119 } else if (xpread(fd, advtmp, 2 * ADV_SIZE, 120 st.st_size - 2 * ADV_SIZE) != 2 * ADV_SIZE) { 121 err = -1; 122 } else { 123 /* We got it... maybe? */ 124 err = syslinux_validate_adv(advtmp) ? -2 : 0; 125 if (!err) { 126 /* Got a good one, write our own ADV here */ 127 clear_attributes(fd); 128 129 /* Need to re-open read-write */ 130 close(fd); 131 fd = open(file, O_RDWR | O_SYNC); 132 if (fd < 0) { 133 err = -1; 134 } else if (fstat(fd, &xst) || xst.st_ino != st.st_ino || 135 xst.st_dev != st.st_dev || xst.st_size != st.st_size) { 136 fprintf(stderr, "%s: race condition on write\n", file); 137 err = -2; 138 } 139 /* Write our own version ... */ 140 if (xpwrite(fd, syslinux_adv, 2 * ADV_SIZE, 141 st.st_size - 2 * ADV_SIZE) != 2 * ADV_SIZE) { 142 err = -1; 143 } 144 145 sync(); 146 set_attributes(fd); 147 } 148 } 149 150 if (err == -2) 151 fprintf(stderr, "%s: cannot write auxilliary data (need --update)?\n", 152 file); 153 else if (err == -1) 154 perror(file); 155 156 if (fd >= 0) 157 close(fd); 158 if (file) 159 free(file); 160 161 return err; 162 } 163
