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#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include "syscall.h"
int renameat(int oldfd, const char *old, int newfd, const char *new)
{
char old_copy[PATH_MAX+1], new_copy[PATH_MAX+1];
char *base;
size_t old_size, new_size;
struct stat statbuf;
if ((old_size = strlen(old)) > PATH_MAX || \
(new_size = strlen(new)) > PATH_MAX) {
errno = ENAMETOOLONG;
return -1;
}
if (strlen(old) == 0 || strlen(new) == 0) {
errno = ENOENT;
return -1;
}
strcpy(old_copy, old);
strcpy(new_copy, new);
base = basename(old_copy);
strncpy(old_copy, base, sizeof(old_copy));
base = basename(new_copy);
strncpy(new_copy, base, sizeof(new_copy));
if (strcmp(old_copy, ".") == 0 || strcmp(old_copy, "..") == 0 ||
strcmp(new_copy, ".") == 0 || strcmp(new_copy, "..") == 0) {
errno = EINVAL;
return -1;
}
/* The Linux kernel will fail when attempting to rename a symlink of a
directory with a trailing slash. We therefore have to handle this
case ourselves. */
if (old[old_size - 1] == '/') {
/* Calling stat(2) on a symlink to a dir with the trailing
slash causes stat(2) to return the actual directory instead
of the symlink itself. */
strcpy(old_copy, old);
old_copy[old_size - 1] = '\0';
if (fstatat(oldfd, old_copy, &statbuf, AT_SYMLINK_NOFOLLOW) == -1) {
return -1;
}
if (S_ISLNK(statbuf.st_mode)) {
if (fstatat(oldfd, old, &statbuf, 0) == -1) {
return -1;
}
if (S_ISDIR(statbuf.st_mode)) {
old = old_copy;
} else {
/* may as well not waste the syscall */
errno = ENOTDIR;
return -1;
}
}
}
return syscall(SYS_renameat, oldfd, old, newfd, new);
}
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