1 /*
2 loadramdisk.c
3 
4 Copy a device or file specified as argument to /dev/ram
5 */
6 
7 #include <errno.h>
8 #include <fcntl.h>
9 #include <stdio.h>
10 #include <stdlib.h>
11 #include <string.h>
12 #include <unistd.h>
13 #include <sys/ioctl.h>
14 
15 #define RAM	"/dev/ram"
16 
17 char buf[10240];
18 
19 static unsigned long size_device(int fd);
20 
21 int main(int argc, char *argv[])
22 {
23 	unsigned long off, size;
24 	int r, s, fd, ramfd;
25 	char *src;
26 
27 	if (argc != 2)
28 	{
29 		fprintf(stderr, "Usage: loadramdisk <file>\n");
30 		exit(1);
31 	}
32 	src= argv[1];
33 	fd= open(src, O_RDONLY);
34 	if (fd < 0)
35 	{
36 		fprintf(stderr, "Unable to open '%s': %s\n",
37 			src, strerror(errno));
38 		exit(1);
39 	}
40 
41 	/* Get the size of the device */
42 	errno= 0;
43 	size= size_device(fd);
44 	if (errno != 0)
45 	{
46 		fprintf(stderr, "Lseek(end) failed on '%s': %s\n",
47 			src, strerror(errno));
48 		exit(1);
49 	}
50 	if (lseek(fd, 0, SEEK_SET) != 0)
51 	{
52 		fprintf(stderr, "Lseek(0) failed on '%s': %s\n",
53 			src, strerror(errno));
54 		exit(1);
55 	}
56 
57 	ramfd= open(RAM, O_RDWR);
58 	if (ramfd < 0)
59 	{
60 		fprintf(stderr, "Unable to open '%s': %s\n",
61 			RAM, strerror(errno));
62 		exit(1);
63 	}
64 	r= ioctl(ramfd, MIOCRAMSIZE, &size);
65 	if (r != 0)
66 	{
67 		fprintf(stderr, "MIOCRAMSIZE %lu failed on '%s': %s\n",
68 			size, RAM, strerror(errno));
69 		exit(1);
70 	}
71 
72 	off= 0;
73 	while (off < size)
74 	{
75 		r= read(fd, buf, sizeof(buf));
76 		if (r <= 0)
77 		{
78 			fprintf(stderr, "error reading '%s': %s\n",
79 				src, r == 0 ? "unexpected EOF" :
80 				strerror(errno));
81 			exit(1);
82 		}
83 		s= write(ramfd, buf, r);
84 		if (s != r)
85 		{
86 			fprintf(stderr, "error writing to '%s': %s\n", RAM,
87 				s >= 0 ? "short write" : strerror(errno));
88 			exit(1);
89 		}
90 		off += r;
91 	}
92 	exit(0);
93 }
94 
95 static unsigned long size_device(int fd)
96 {
97 	char b;
98 	int r;
99 	unsigned long low, mid, high;
100 
101 	/* Try to find the size of a device using binary search */
102 	low= 0;
103 	high= -1;
104 
105 	while (mid= low+(high-low)/2, mid > low)
106 	{
107 		if (lseek(fd, mid, SEEK_SET) != mid)
108 		{
109 			fprintf(stderr, "lseek to %lu failed: %s\n",
110 				mid, strerror(errno));
111 			exit(1);
112 		}
113 		r= read(fd, &b, 1);
114 		if (r < 0)
115 		{
116 			fprintf(stderr, "read failed at position %lu: %s\n",
117 				mid, strerror(errno));
118 			exit(1);
119 		}
120 		if (r > 0)
121 			low= mid;
122 		else
123 			high= mid;
124 	}
125 	return high;
126 }
127