1 /*
2  * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 // Test
17 // 1) read of every file in /proc
18 // 2) readlink of every symlink in /proc
19 // 3) recursively (1) + (2) for every directory in /proc
20 // 4) write to /proc/*/clear_refs and /proc/*/task/*/clear_refs
21 // 5) write to /proc/sysrq-trigger
22 #undef NDEBUG
23 #include <assert.h>
24 #include <errno.h>
25 #include <sys/types.h>
26 #include <dirent.h>
27 #include <stdbool.h>
28 #include <stdlib.h>
29 #include <string.h>
30 #include <sys/stat.h>
31 #include <fcntl.h>
32 #include <unistd.h>
33 
34 static inline bool streq(const char *s1, const char *s2)
35 {
36 	return strcmp(s1, s2) == 0;
37 }
38 
39 static struct dirent *xreaddir(DIR *d)
40 {
41 	struct dirent *de;
42 
43 	errno = 0;
44 	de = readdir(d);
45 	if (!de && errno != 0) {
46 		exit(1);
47 	}
48 	return de;
49 }
50 
51 static void f_reg(DIR *d, const char *filename)
52 {
53 	char buf[4096];
54 	int fd;
55 	ssize_t rv;
56 
57 	/* read from /proc/kmsg can block */
58 	fd = openat(dirfd(d), filename, O_RDONLY|O_NONBLOCK);
59 	if (fd == -1)
60 		return;
61 	rv = read(fd, buf, sizeof(buf));
62 	assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
63 	close(fd);
64 }
65 
66 static void f_reg_write(DIR *d, const char *filename, const char *buf, size_t len)
67 {
68 	int fd;
69 	ssize_t rv;
70 
71 	fd = openat(dirfd(d), filename, O_WRONLY);
72 	if (fd == -1)
73 		return;
74 	rv = write(fd, buf, len);
75 	assert((0 <= rv && rv <= len) || rv == -1);
76 	close(fd);
77 }
78 
79 static void f_lnk(DIR *d, const char *filename)
80 {
81 	char buf[4096];
82 	ssize_t rv;
83 
84 	rv = readlinkat(dirfd(d), filename, buf, sizeof(buf));
85 	assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
86 }
87 
88 static void f(DIR *d, unsigned int level)
89 {
90 	struct dirent *de;
91 
92 	de = xreaddir(d);
93 	assert(de->d_type == DT_DIR);
94 	assert(streq(de->d_name, "."));
95 
96 	de = xreaddir(d);
97 	assert(de->d_type == DT_DIR);
98 	assert(streq(de->d_name, ".."));
99 
100 	while ((de = xreaddir(d))) {
101 		assert(!streq(de->d_name, "."));
102 		assert(!streq(de->d_name, ".."));
103 
104 		switch (de->d_type) {
105 			DIR *dd;
106 			int fd;
107 
108 		case DT_REG:
109 			if (level == 0 && streq(de->d_name, "sysrq-trigger")) {
110 				f_reg_write(d, de->d_name, "h", 1);
111 			} else if (level == 1 && streq(de->d_name, "clear_refs")) {
112 				f_reg_write(d, de->d_name, "1", 1);
113 			} else if (level == 3 && streq(de->d_name, "clear_refs")) {
114 				f_reg_write(d, de->d_name, "1", 1);
115 			} else {
116 				f_reg(d, de->d_name);
117 			}
118 			break;
119 		case DT_DIR:
120 			fd = openat(dirfd(d), de->d_name, O_DIRECTORY|O_RDONLY);
121 			if (fd == -1)
122 				continue;
123 			dd = fdopendir(fd);
124 			if (!dd)
125 				continue;
126 			f(dd, level + 1);
127 			closedir(dd);
128 			break;
129 		case DT_LNK:
130 			f_lnk(d, de->d_name);
131 			break;
132 		default:
133 			assert(0);
134 		}
135 	}
136 }
137 
138 int main(void)
139 {
140 	DIR *d;
141 
142 	d = opendir("/proc");
143 	if (!d)
144 		return 2;
145 	f(d, 0);
146 	return 0;
147 }
148