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#include <stdio.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
int fd = 0;
char *ptr = NULL, *orig_ptr = NULL;
struct stat st;
if (argc != 3) {
printf("Usage: %s <file> <subst>\n", *argv);
exit(1);
}
if (strlen(argv[2]) >= strlen("init_module")) {
printf("Can't only substitute symbols by strings with at most"
"%u characters.\n", strlen("init_module"));
exit(2);
}
if ((fd = open(argv[1], O_RDWR)) < 0) {
perror("open");
exit(errno);
}
if (fstat(fd, &st) < 0) {
perror("fstat");
exit(errno);
}
ptr = mmap(NULL, st.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
orig_ptr = ptr;
if (!ptr) {
perror("mmap");
exit(errno);
}
for (; ptr < orig_ptr + st.st_size; ++ptr) {
if (strncmp(ptr, "init_module", strlen("init_module")) == 0 ||
strncmp(ptr, "cleanup_module", strlen("cleanup_module")) == 0) {
memcpy(ptr, argv[2], strlen(argv[2]));
ptr += strlen(argv[2]);
}
}
munmap(ptr, st.st_size);
return 0;
}
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