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  
needs_openat2(const struct open_how * how)17  bool needs_openat2(const struct open_how *how)
18  {
19  	return how->resolve != 0;
20  }
21  
raw_openat2(int dfd,const char * path,void * how,size_t size)22  int 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  
sys_openat2(int dfd,const char * path,struct open_how * how)28  int sys_openat2(int dfd, const char *path, struct open_how *how)
29  {
30  	return raw_openat2(dfd, path, how, sizeof(*how));
31  }
32  
sys_openat(int dfd,const char * path,struct open_how * how)33  int 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  
sys_renameat2(int olddirfd,const char * oldpath,int newdirfd,const char * newpath,unsigned int flags)39  int 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  
touchat(int dfd,const char * path)47  int 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  
fdreadlink(int fd)55  char *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  
fdequal(int fd,int dfd,const char * path)71  bool 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  
94  bool openat2_supported = false;
95  
init(void)96  void __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