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}
110