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 "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 }