nativelibc/link.c

/*	A part of the Native C Library for Windows NT
	Copyright 2007-2015 PC GO Ld.
	Copyright 2026 Rivoreo

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or (at
	your option) any later version.

	This program is distributed in the hope that it will be useful, but
	WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
	General Public License for more details.
*/

#include <windows.h>
#include <nt.h>
#include <errno.h>
#include <pathname.h>
#include <fcntl.h>
#include <ntstatus.h>

int linkat(int old_dir_fd, const char *oldpath, int new_dir_fd, const char *newpath, int flags) {
	if(old_dir_fd == -1 || new_dir_fd == -1) {
		errno = EBADF;
		return -1;
	}
	if(!oldpath || !newpath) {
		errno = EFAULT;
		return -1;
	}
	if(flags & ~AT_SYMLINK_FOLLOW) {
		errno = EINVAL;
		return -1;
	}

	void *handle;
	IO_STATUS_BLOCK io_status;
	unsigned long int file_access = GENERIC_READ | GENERIC_WRITE | SYNCHRONIZE;
	unsigned long int file_share = FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE;
	unsigned long int options = FILE_NON_DIRECTORY_FILE | FILE_OPEN_REPARSE_POINT | FILE_SYNCHRONOUS_IO_NONALERT | FILE_OPEN_FOR_BACKUP_INTENT;
	UNICODE_STRING old_path;
	UNICODE_STRING new_path;
	RtlCreateUnicodeStringFromAsciiz(&old_path, oldpath);
	RtlCreateUnicodeStringFromAsciiz(&new_path, newpath);
	PATHNAME_UNIX2NT_UTF16_STRUCT(old_path);
	PATHNAME_UNIX2NT_UTF16_STRUCT(new_path);
	OBJECT_ATTRIBUTES obj_attr = { .Length = sizeof(OBJECT_ATTRIBUTES), .ObjectName = &old_path };
	if(*oldpath != '/') {
		if(old_dir_fd == AT_FDCWD) {
			RtlFreeUnicodeString(&old_path);
			errno = EPERM;
			return -1;
		}
		obj_attr.RootDirectory = (void *)old_dir_fd;
	}
	if(!(flags & AT_SYMLINK_FOLLOW)) {
		long int status = NtOpenSymbolicLinkObject(&handle, 0, &obj_attr);
		if(status != STATUS_OBJECT_TYPE_MISMATCH) {
			if(status >= 0) {
				NtClose(handle);
				errno = EOPNOTSUPP;
			} else {
				__set_errno_from_ntstatus(status);
			}
			return -1;
		}
	}
	long int status = NtOpenFile(&handle, file_access, &obj_attr, &io_status, file_share, options);
	RtlFreeUnicodeString(&old_path);
	if(__set_errno_from_ntstatus(status)) goto failed;

	FILE_LINK_INFORMATION *new_link = malloc(sizeof(FILE_LINK_INFORMATION) + new_path.MaximumLength);
	if(!new_link) {
		NtClose(handle);
		errno = ENOMEM;
		//return -1;
		goto failed;
	}
	memcpy(new_link->FileName, new_path.Buffer, new_path.MaximumLength);
	new_link->ReplaceIfExists = 0;
	new_link->RootDirectory = *newpath == '/' && new_dir_fd != AT_FDCWD ? NULL : (void *)new_dir_fd;
	new_link->FileNameLength = new_path.Length;
	status = NtSetInformationFile(handle, &io_status, new_link, sizeof(FILE_LINK_INFORMATION) + new_path.MaximumLength, FileLinkInformation);
	//printf("nativelibc debug: status = 0x%lx\n", status);
	RtlFreeUnicodeString(&new_path);
	free(new_link);
	NtClose(handle);
	return __set_errno_from_ntstatus(status) ? -1 : 0;

failed:
	RtlFreeUnicodeString(&new_path);
	return -1;
}

int link(const char *oldpath, const char *newpath) {
	return linkat(AT_FDCWD, oldpath, AT_FDCWD, newpath, AT_SYMLINK_FOLLOW);
}