1 /* 2 3 /usr/src/ext2ed/disk.c 4 5 A part of the extended file system 2 disk editor. 6 7 ------------------------------------------------- 8 The filesystem's disk activity pass through here. 9 ------------------------------------------------- 10 11 This file is acting as a filter - Before we pass an actual read or write request to the operating system, we 12 double check the various permissions and possible errors here. 13 14 The major update which needs to be done here is switching to the use of the llseek system call, so that we will 15 be able to support ext2 filesystems up to 4 TB. Currently, due to the standard fseek usage, we can't handle 16 filesystems bigger than 4 GB. The limit is actually 2 GB because I used long rather than unsigned long long at too 17 many places in the program. To conclude - This upgrade needs to be done carefuly; There are many places to change. 18 19 First written on: April 9 1995 20 21 Copyright (C) 1995 Gadi Oxman 22 23 */ 24 25 #include "config.h" 26 #include <stdio.h> 27 #include <stdlib.h> 28 #include <string.h> 29 #include <time.h> 30 31 #include "ext2ed.h" 32 33 int write_access; 34 35 int low_read (unsigned char *buffer,unsigned long length,unsigned long offset) 36 37 /* 38 39 This function is used when we need to read something from the filesystem. 40 41 */ 42 43 { 44 45 #ifdef DEBUG 46 47 char temp [80]; 48 49 if (device_handle==NULL) { /* Check that a device is indeed open */ 50 internal_error ("No device opened yet read requested","disk","low_read"); 51 return (0); 52 } 53 if (offset > file_system_info.file_system_size) { /* Check that the offset is within limits */ 54 sprintf (temp,"Seek offset %ld is out of range",offset); 55 internal_error (temp,"disk","low_read"); 56 return (0); 57 } 58 59 #endif 60 61 if ( (fseek (device_handle,offset,SEEK_SET))==-1) { /* Seek to the required offset */ 62 wprintw (command_win,"Error - Failed to seek to offset %ld in device %s\n",offset,device_name); 63 refresh_command_win (); 64 return (0); 65 }; 66 67 if ( (fread (buffer,1,length,device_handle))==-1) { /* And do the actual reading */ 68 wprintw (command_win,"Error - Failed to read from offset %ld in device %s\n",offset,device_name); 69 refresh_command_win ();return (0); 70 }; 71 72 return (1); 73 } 74 75 int low_write (unsigned char *buffer,unsigned long length,unsigned long offset) 76 77 /* 78 79 This is used to change something in the filesystem. 80 write_access is checked to see if we are allowed to do the actual writing. 81 As a double safety measure, AllowChanges is rechecked here. 82 If logging is enabled, we log the change before writing it to the device. 83 84 */ 85 { 86 char temp [80]; 87 88 if (!write_access) { 89 wprintw (command_win,"Error - Write access not aviable (use enablewrite)\n"); 90 return (0); 91 } 92 93 #ifdef DEBUG 94 95 if (!AllowChanges) { 96 internal_error ("AllowChanges=0 yet enablewrite succeeded","disk","low_write"); 97 return (0); 98 } 99 100 if (device_handle==NULL) { 101 internal_error ("No device opened yet read requested","disk","low_write"); 102 return (0); 103 } 104 105 if (offset > file_system_info.file_system_size) { 106 sprintf (temp,"Seek offset %ld is out of range",offset); 107 internal_error (temp,"disk","low_write"); 108 return (0); 109 } 110 111 #endif 112 113 if (LogChanges) 114 if (!log_changes (buffer,length,offset)) 115 return (0); 116 117 if ( (fseek (device_handle,offset,SEEK_SET))==-1) { 118 wprintw (command_win,"Error - Failed to seek to offset %ld in device %s\n",offset,device_name); 119 refresh_command_win ();return (0); 120 }; 121 122 123 if ( (fwrite (buffer,1,length,device_handle))==-1) { 124 wprintw (command_win,"Error - Failed to write to offset %ld in device %s\n",offset,device_name); 125 refresh_command_win ();return (0); 126 }; 127 128 wprintw (command_win,"Data written");refresh_command_win (); 129 return (1); 130 } 131 132 int log_changes (unsigned char *buffer,unsigned long length,unsigned long offset) 133 134 /* 135 136 Log the change in a primitive form - An hex dump of the data before the change and after the change. 137 The hex bytes are converted to text, so that they will be readable with a standard text editor. 138 139 */ 140 141 { 142 unsigned char *original; 143 144 int i; 145 time_t current_time; 146 FILE *fp; 147 148 if ((fp=fopen (LogFile,"a+"))==NULL) { 149 wprintw (command_win,"Error - Unable to open log file %s\n",LogFile); 150 refresh_command_win ();return (0); 151 }; 152 153 current_time=time (NULL); 154 155 fprintf (fp,"\n----- EXT2ED log begin -----\n\n"); 156 fprintf (fp,"Time: %s\nDevice: %s\n",ctime ((time_t *) ¤t_time),device_name); 157 fprintf (fp,"Offset: %lu\nLength: %lu\n",offset,length); 158 159 original=(unsigned char *) malloc (length*sizeof (unsigned char)); 160 161 if (original==NULL) { 162 wprintw (command_win,"Fatal error - Can\'t allocate %lu bytes!"); 163 refresh_command_win ();fclose (fp);return (0); 164 } 165 166 if (!low_read (original,length,offset)) { 167 fclose (fp);return (0); 168 } 169 170 fprintf (fp,"\nOriginal data:\n\n"); 171 172 for (i=0;i<length;i++) { 173 if (i%16==0 && i!=0) fprintf (fp,"\n"); 174 fprintf (fp,"%02x ",original [i]); 175 } 176 177 fprintf (fp,"\n\nNew data:\n\n"); 178 179 for (i=0;i<length;i++) { 180 if (i%16==0 && i!=0) fprintf (fp,"\n"); 181 fprintf (fp,"%02x ",buffer [i]); 182 } 183 184 fprintf (fp,"\n----- EXT2ED log end -----\n"); 185 186 fclose (fp); 187 return (1); 188 } 189 190 int load_type_data (void) 191 192 /* 193 194 Just read from the current position into type data. 195 196 */ 197 198 { 199 if (device_handle==NULL) { 200 printf ("Error - No device opened\n"); 201 return (0); 202 } 203 204 if (device_offset==-1) { 205 printf ("Error - No offset set\n"); 206 return (0); 207 } 208 209 if (low_read (type_data.u.buffer,EXT2_MAX_BLOCK_SIZE,device_offset)==0) 210 return (0); 211 212 if (current_type!=NULL) 213 if (strcmp (current_type->name,"ext2_dir_entry")==0) 214 current_type->length=type_data.u.t_ext2_dir_entry.rec_len; 215 216 return (1); 217 } 218 219 int write_type_data (void) 220 221 { 222 if (device_handle==NULL) { 223 wprintw (command_win,"Error - No device opened\n"); 224 refresh_command_win (); 225 return (0); 226 } 227 228 if (device_offset==-1) { 229 wprintw (command_win,"Error - No offset set\n"); 230 refresh_command_win (); 231 return (0); 232 } 233 234 if (low_write (type_data.u.buffer,file_system_info.block_size,device_offset)==0) 235 return (0); 236 237 return (1); 238 } 239 240
