libinstaller/advio.c

   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 "syslxrw.h"
  36 #include "syslxcom.h"
  37
  38 /*
  39  * Read the ADV from an existing instance, or initialize if invalid.
  40  * Returns -1 on fatal errors, 0 if ADV is okay, 1 if the ADV is
  41  * invalid, and 2 if the file does not exist.
  42  */
  43 int read_adv(const char *path, const char *cfg)
  44 {
  45     char *file;
  46     int fd = -1;
  47     struct stat st;
  48     int err = 0;
  49     int rv;
  50
  51     rv = asprintf(&file, "%s%s%s", path,
  52                   path[0] && path[strlen(path) - 1] == '/' ? "" : "/", cfg);
  53
  54     if (rv < 0 || !file) {
  55         perror(program);
  56         return -1;
  57     }
  58
  59     fd = open(file, O_RDONLY);
  60     if (fd < 0) {
  61         if (errno != ENOENT) {
  62             err = -1;
  63         } else {
  64             syslinux_reset_adv(syslinux_adv);
  65             err = 2;            /* Nonexistence is not a fatal error */
  66         }
  67     } else if (fstat(fd, &st)) {
  68         err = -1;
  69     } else if (st.st_size < 2 * ADV_SIZE) {
  70         /* Too small to be useful */
  71         syslinux_reset_adv(syslinux_adv);
  72         err = 0;                /* Nothing to read... */
  73     } else if (xpread(fd, syslinux_adv, 2 * ADV_SIZE,
  74                       st.st_size - 2 * ADV_SIZE) != 2 * ADV_SIZE) {
  75         err = -1;
  76     } else {
  77         /* We got it... maybe? */
  78         err = syslinux_validate_adv(syslinux_adv) ? 1 : 0;
  79     }
  80
  81     if (err < 0)
  82         perror(file);
  83
  84     if (fd >= 0)
  85         close(fd);
  86
  87     free(file);
  88
  89     return err;
  90 }
  91
  92 /*
  93  * Update the ADV in an existing installation.
  94  */
  95 int write_adv(const char *path, const char *cfg)
  96 {
  97     unsigned char advtmp[2 * ADV_SIZE];
  98     char *file;
  99     int fd = -1;
 100     struct stat st, xst;
 101     int err = 0;
 102     int rv;
 103
 104     rv = asprintf(&file, "%s%s%s", path,
 105                   path[0] && path[strlen(path) - 1] == '/' ? "" : "/", cfg);
 106
 107     if (rv < 0 || !file) {
 108         perror(program);
 109         return -1;
 110     }
 111
 112     fd = open(file, O_RDONLY);
 113     if (fd < 0) {
 114         err = -1;
 115     } else if (fstat(fd, &st)) {
 116         err = -1;
 117     } else if (st.st_size < 2 * ADV_SIZE) {
 118         /* Too small to be useful */
 119         err = -2;
 120     } else if (xpread(fd, advtmp, 2 * ADV_SIZE,
 121                       st.st_size - 2 * ADV_SIZE) != 2 * ADV_SIZE) {
 122         err = -1;
 123     } else {
 124         /* We got it... maybe? */
 125         err = syslinux_validate_adv(advtmp) ? -2 : 0;
 126         if (!err) {
 127             /* Got a good one, write our own ADV here */
 128             clear_attributes(fd);
 129
 130             /* Need to re-open read-write */
 131             close(fd);
 132             fd = open(file, O_RDWR | O_SYNC);
 133             if (fd < 0) {
 134                 fprintf(stderr, "Cannot open file '%s' in read/write mode !\nFatal error, exiting.\n", file);
 135                 return -EACCES;
 136             } else if (fstat(fd, &xst) || xst.st_ino != st.st_ino ||
 137                        xst.st_dev != st.st_dev || xst.st_size != st.st_size) {
 138                 fprintf(stderr, "%s: race condition on write\n", file);
 139                 err = -2;
 140             }
 141             /* Write our own version ... */
 142             if (xpwrite(fd, syslinux_adv, 2 * ADV_SIZE,
 143                         st.st_size - 2 * ADV_SIZE) != 2 * ADV_SIZE) {
 144                 err = -1;
 145             }
 146
 147             sync();
 148             set_attributes(fd);
 149         }
 150     }
 151
 152     if (err == -2)
 153         fprintf(stderr, "%s: cannot write auxiliary data (need --update)?\n",
 154                 file);
 155     else if (err == -1)
 156         perror(file);
 157
 158     if (fd >= 0)
 159         close(fd);
 160     if (file)
 161         free(file);
 162
 163     return err;
 164 }