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 */
read_adv(const char * path,const char * cfg)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 */
write_adv(const char * path,const char * cfg)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