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 
low_read(unsigned char * buffer,unsigned long length,unsigned long offset)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 
low_write(unsigned char * buffer,unsigned long length,unsigned long offset)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 
log_changes(unsigned char * buffer,unsigned long length,unsigned long offset)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 *) &current_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 
load_type_data(void)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 
write_type_data(void)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