1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Author: Aleksa Sarai <cyphar@cyphar.com>
  4 * Copyright (C) 2018-2019 SUSE LLC.
  5 */
  6
  7#define _GNU_SOURCE
  8#include <errno.h>
  9#include <fcntl.h>
 10#include <stdbool.h>
 11#include <string.h>
 12#include <syscall.h>
 13#include <limits.h>
 14
 15#include "helpers.h"
 16
 17bool needs_openat2(const struct open_how *how)
 18{
 19	return how->resolve != 0;
 20}
 21
 22int raw_openat2(int dfd, const char *path, void *how, size_t size)
 23{
 24	int ret = syscall(__NR_openat2, dfd, path, how, size);
 25	return ret >= 0 ? ret : -errno;
 26}
 27
 28int sys_openat2(int dfd, const char *path, struct open_how *how)
 29{
 30	return raw_openat2(dfd, path, how, sizeof(*how));
 31}
 32
 33int sys_openat(int dfd, const char *path, struct open_how *how)
 34{
 35	int ret = openat(dfd, path, how->flags, how->mode);
 36	return ret >= 0 ? ret : -errno;
 37}
 38
 39int sys_renameat2(int olddirfd, const char *oldpath,
 40		  int newdirfd, const char *newpath, unsigned int flags)
 41{
 42	int ret = syscall(__NR_renameat2, olddirfd, oldpath,
 43					  newdirfd, newpath, flags);
 44	return ret >= 0 ? ret : -errno;
 45}
 46
 47int touchat(int dfd, const char *path)
 48{
 49	int fd = openat(dfd, path, O_CREAT, 0700);
 50	if (fd >= 0)
 51		close(fd);
 52	return fd;
 53}
 54
 55char *fdreadlink(int fd)
 56{
 57	char *target, *tmp;
 58
 59	E_asprintf(&tmp, "/proc/self/fd/%d", fd);
 60
 61	target = malloc(PATH_MAX);
 62	if (!target)
 63		ksft_exit_fail_msg("fdreadlink: malloc failed\n");
 64	memset(target, 0, PATH_MAX);
 65
 66	E_readlink(tmp, target, PATH_MAX);
 67	free(tmp);
 68	return target;
 69}
 70
 71bool fdequal(int fd, int dfd, const char *path)
 72{
 73	char *fdpath, *dfdpath, *other;
 74	bool cmp;
 75
 76	fdpath = fdreadlink(fd);
 77	dfdpath = fdreadlink(dfd);
 78
 79	if (!path)
 80		E_asprintf(&other, "%s", dfdpath);
 81	else if (*path == '/')
 82		E_asprintf(&other, "%s", path);
 83	else
 84		E_asprintf(&other, "%s/%s", dfdpath, path);
 85
 86	cmp = !strcmp(fdpath, other);
 87
 88	free(fdpath);
 89	free(dfdpath);
 90	free(other);
 91	return cmp;
 92}
 93
 94bool openat2_supported = false;
 95
 96void __attribute__((constructor)) init(void)
 97{
 98	struct open_how how = {};
 99	int fd;
100
101	BUILD_BUG_ON(sizeof(struct open_how) != OPEN_HOW_SIZE_VER0);
102
103	/* Check openat2(2) support. */
104	fd = sys_openat2(AT_FDCWD, ".", &how);
105	openat2_supported = (fd >= 0);
106
107	if (fd >= 0)
108		close(fd);
109}