127 lines
2.1 KiB
C
127 lines
2.1 KiB
C
/*
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loadramdisk.c
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Copy a device or file specified as argument to /dev/ram
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*/
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/ioctl.h>
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#define RAM "/dev/ram"
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char buf[10240];
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static unsigned long size_device(int fd);
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int main(int argc, char *argv[])
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{
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unsigned long off, size;
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int r, s, fd, ramfd;
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char *src;
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if (argc != 2)
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{
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fprintf(stderr, "Usage: loadramdisk <file>\n");
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exit(1);
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}
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src= argv[1];
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fd= open(src, O_RDONLY);
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if (fd < 0)
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{
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fprintf(stderr, "Unable to open '%s': %s\n",
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src, strerror(errno));
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exit(1);
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}
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/* Get the size of the device */
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errno= 0;
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size= size_device(fd);
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if (errno != 0)
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{
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fprintf(stderr, "Lseek(end) failed on '%s': %s\n",
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src, strerror(errno));
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exit(1);
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}
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if (lseek(fd, 0, SEEK_SET) != 0)
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{
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fprintf(stderr, "Lseek(0) failed on '%s': %s\n",
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src, strerror(errno));
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exit(1);
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}
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ramfd= open(RAM, O_RDWR);
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if (ramfd < 0)
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{
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fprintf(stderr, "Unable to open '%s': %s\n",
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RAM, strerror(errno));
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exit(1);
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}
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r= ioctl(ramfd, MIOCRAMSIZE, &size);
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if (r != 0)
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{
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fprintf(stderr, "MIOCRAMSIZE %lu failed on '%s': %s\n",
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size, RAM, strerror(errno));
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exit(1);
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}
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off= 0;
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while (off < size)
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{
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r= read(fd, buf, sizeof(buf));
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if (r <= 0)
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{
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fprintf(stderr, "error reading '%s': %s\n",
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src, r == 0 ? "unexpected EOF" :
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strerror(errno));
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exit(1);
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}
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s= write(ramfd, buf, r);
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if (s != r)
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{
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fprintf(stderr, "error writing to '%s': %s\n",
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s >= 0 ? "short write" : strerror(errno));
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exit(1);
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}
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off += r;
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}
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exit(0);
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}
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static unsigned long size_device(int fd)
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{
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char b;
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int r;
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unsigned long low, mid, high;
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/* Try to find the size of a device using binary search */
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low= 0;
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high= -1;
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while (mid= low+(high-low)/2, mid > low)
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{
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if (lseek(fd, mid, SEEK_SET) != mid)
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{
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fprintf(stderr, "lseek to %lu failed: %s\n",
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mid, strerror(errno));
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exit(1);
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}
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r= read(fd, &b, 1);
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if (r < 0)
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{
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fprintf(stderr, "read failed at position %lu: %s\n",
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mid, strerror(errno));
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exit(1);
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}
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if (r > 0)
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low= mid;
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else
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high= mid;
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}
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return high;
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}
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