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 #include "proc.h"
35 
36 static void f_reg(DIR *d, const char *filename)
37 {
38 	char buf[4096];
39 	int fd;
40 	ssize_t rv;
41 
42 	/* read from /proc/kmsg can block */
43 	fd = openat(dirfd(d), filename, O_RDONLY|O_NONBLOCK);
44 	if (fd == -1)
45 		return;
46 	rv = read(fd, buf, sizeof(buf));
47 	assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
48 	close(fd);
49 }
50 
51 static void f_reg_write(DIR *d, const char *filename, const char *buf, size_t len)
52 {
53 	int fd;
54 	ssize_t rv;
55 
56 	fd = openat(dirfd(d), filename, O_WRONLY);
57 	if (fd == -1)
58 		return;
59 	rv = write(fd, buf, len);
60 	assert((0 <= rv && rv <= len) || rv == -1);
61 	close(fd);
62 }
63 
64 static void f_lnk(DIR *d, const char *filename)
65 {
66 	char buf[4096];
67 	ssize_t rv;
68 
69 	rv = readlinkat(dirfd(d), filename, buf, sizeof(buf));
70 	assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
71 }
72 
73 static void f(DIR *d, unsigned int level)
74 {
75 	struct dirent *de;
76 
77 	de = xreaddir(d);
78 	assert(de->d_type == DT_DIR);
79 	assert(streq(de->d_name, "."));
80 
81 	de = xreaddir(d);
82 	assert(de->d_type == DT_DIR);
83 	assert(streq(de->d_name, ".."));
84 
85 	while ((de = xreaddir(d))) {
86 		assert(!streq(de->d_name, "."));
87 		assert(!streq(de->d_name, ".."));
88 
89 		switch (de->d_type) {
90 			DIR *dd;
91 			int fd;
92 
93 		case DT_REG:
94 			if (level == 0 && streq(de->d_name, "sysrq-trigger")) {
95 				f_reg_write(d, de->d_name, "h", 1);
96 			} else if (level == 1 && streq(de->d_name, "clear_refs")) {
97 				f_reg_write(d, de->d_name, "1", 1);
98 			} else if (level == 3 && streq(de->d_name, "clear_refs")) {
99 				f_reg_write(d, de->d_name, "1", 1);
100 			} else {
101 				f_reg(d, de->d_name);
102 			}
103 			break;
104 		case DT_DIR:
105 			fd = openat(dirfd(d), de->d_name, O_DIRECTORY|O_RDONLY);
106 			if (fd == -1)
107 				continue;
108 			dd = fdopendir(fd);
109 			if (!dd)
110 				continue;
111 			f(dd, level + 1);
112 			closedir(dd);
113 			break;
114 		case DT_LNK:
115 			f_lnk(d, de->d_name);
116 			break;
117 		default:
118 			assert(0);
119 		}
120 	}
121 }
122 
123 int main(void)
124 {
125 	DIR *d;
126 
127 	d = opendir("/proc");
128 	if (!d)
129 		return 2;
130 	f(d, 0);
131 	return 0;
132 }
133