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