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