39 lines
929 B
C
39 lines
929 B
C
#include <fcntl.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <unistd.h>
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enum {
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MBR_END = 510,
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};
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int main(int argc, char *argv[]) {
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if (argc != 3) {
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fprintf(stderr, "Usage: %s mbr.bin fs.img\n", argv[0]);
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return 1;
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}
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const char *filename = argv[1];
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const char *fsimg_path = argv[2];
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int fd = open(filename, O_RDWR);
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off_t length = lseek(fd, 0, SEEK_END);
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if (length > MBR_END) {
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fprintf(stderr, "file %s is larger than %d bytes (size: %llu)\n",
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filename, MBR_END, (unsigned long long)length);
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return 1;
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}
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lseek(fd, MBR_END, SEEK_SET);
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write(fd, "\x55\xaa", 2);
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int fsimg = open(fsimg_path, O_RDONLY);
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if (fsimg < 0) {
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perror(fsimg_path);
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return 1;
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}
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char buf[1024];
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ssize_t bytes;
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while ((bytes = read(fsimg, buf, sizeof(buf))) > 0) {
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write(fd, buf, bytes);
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}
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return 0;
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}
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