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