1 /*
2 * Simple program to compare two mmap'd areas.
3 *
4 * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
5 * Copyright (C) 2001 O'Reilly & Associates
6 *
7 * The source code in this file can be freely used, adapted,
8 * and redistributed in source or binary form, so long as an
9 * acknowledgment appears in derived source files. The citation
10 * should list that the code comes from the book "Linux Device
11 * Drivers" by Alessandro Rubini and Jonathan Corbet, published
12 * by O'Reilly & Associates. No warranty is attached;
13 * we cannot take responsibility for errors or fitness for use.
14 *
15 * $Id: mapcmp.c,v 1.2 2004/03/05 17:35:41 corbet Exp $
16 */
17
18 #include <stdio.h>
19 #include <stdlib.h>
20 #include <unistd.h>
21 #include <sys/mman.h>
22 #include <sys/errno.h>
23 #include <fcntl.h>
24
25 static char *mapdev (const char *, unsigned long, unsigned long);
26 #define PAGE_SIZE 4096
27
28 /*
29 * memcmp dev1 dev2 offset pages
30 */
31 int main (int argc, char **argv)
32 {
33 unsigned long offset, size, i;
34 char *addr1, *addr2;
35 /*
36 * Sanity check.
37 */
38 if (argc != 5)
39 {
40 fprintf (stderr, "Usage: mapcmp dev1 dev2 offset pages\n");
41 exit (1);
42 }
43 /*
44 * Map the two devices.
45 */
46 offset = strtoul (argv[3], NULL, 16);
47 size = atoi (argv[4])*PAGE_SIZE;
48 printf ("Offset is 0x%lx\n", offset);
49 addr1 = mapdev (argv[1], offset, size);
50 addr2 = mapdev (argv[2], offset, size);
51 /*
52 * Do the comparison.
53 */
54 printf ("Comparing...");
55 fflush (stdout);
56 for (i = 0; i < size; i++)
57 if (*addr1++ != *addr2++)
58 {
59 printf ("areas differ at byte %ld\n", i);
60 exit (0);
61 }
62 printf ("areas are identical.\n");
63 exit (0);
64 }
65
66
67
68 static char *mapdev (const char *dev, unsigned long offset,
69 unsigned long size)
70 {
71 char *addr;
72 int fd = open (dev, O_RDONLY);
73
74 if (fd < 0)
75 {
76 perror (dev);
77 exit (1);
78 }
79 addr = mmap (0, size, PROT_READ, MAP_PRIVATE, fd, offset);
80 if (addr == MAP_FAILED)
81 {
82 perror (dev);
83 exit (1);
84 }
85 printf ("Mapped %s (%lu @ %lx) at %p\n", dev, size, offset, addr);
86 return (addr);
87 }
88
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