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 and lseek on 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 <stdio.h>
30 #include <string.h>
31 #include <sys/stat.h>
32 #include <sys/vfs.h>
33 #include <fcntl.h>
34 #include <unistd.h>
35 
36 #include "proc.h"
37 
f_reg(DIR * d,const char * filename)38 static void f_reg(DIR *d, const char *filename)
39 {
40 	char buf[4096];
41 	int fd;
42 	ssize_t rv;
43 
44 	/* read from /proc/kmsg can block */
45 	fd = openat(dirfd(d), filename, O_RDONLY|O_NONBLOCK);
46 	if (fd == -1)
47 		return;
48 	/* struct proc_ops::proc_lseek is mandatory if file is seekable. */
49 	(void)lseek(fd, 0, SEEK_SET);
50 	rv = read(fd, buf, sizeof(buf));
51 	assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
52 	close(fd);
53 }
54 
f_reg_write(DIR * d,const char * filename,const char * buf,size_t len)55 static void f_reg_write(DIR *d, const char *filename, const char *buf, size_t len)
56 {
57 	int fd;
58 	ssize_t rv;
59 
60 	fd = openat(dirfd(d), filename, O_WRONLY);
61 	if (fd == -1)
62 		return;
63 	rv = write(fd, buf, len);
64 	assert((0 <= rv && rv <= len) || rv == -1);
65 	close(fd);
66 }
67 
f_lnk(DIR * d,const char * filename)68 static void f_lnk(DIR *d, const char *filename)
69 {
70 	char buf[4096];
71 	ssize_t rv;
72 
73 	rv = readlinkat(dirfd(d), filename, buf, sizeof(buf));
74 	assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
75 }
76 
f(DIR * d,unsigned int level)77 static void f(DIR *d, unsigned int level)
78 {
79 	struct dirent *de;
80 
81 	de = xreaddir(d);
82 	assert(de->d_type == DT_DIR);
83 	assert(streq(de->d_name, "."));
84 
85 	de = xreaddir(d);
86 	assert(de->d_type == DT_DIR);
87 	assert(streq(de->d_name, ".."));
88 
89 	while ((de = xreaddir(d))) {
90 		assert(!streq(de->d_name, "."));
91 		assert(!streq(de->d_name, ".."));
92 
93 		switch (de->d_type) {
94 			DIR *dd;
95 			int fd;
96 
97 		case DT_REG:
98 			if (level == 0 && streq(de->d_name, "sysrq-trigger")) {
99 				f_reg_write(d, de->d_name, "h", 1);
100 			} else if (level == 1 && streq(de->d_name, "clear_refs")) {
101 				f_reg_write(d, de->d_name, "1", 1);
102 			} else if (level == 3 && streq(de->d_name, "clear_refs")) {
103 				f_reg_write(d, de->d_name, "1", 1);
104 			} else {
105 				f_reg(d, de->d_name);
106 			}
107 			break;
108 		case DT_DIR:
109 			fd = openat(dirfd(d), de->d_name, O_DIRECTORY|O_RDONLY);
110 			if (fd == -1)
111 				continue;
112 			dd = fdopendir(fd);
113 			if (!dd)
114 				continue;
115 			f(dd, level + 1);
116 			closedir(dd);
117 			break;
118 		case DT_LNK:
119 			f_lnk(d, de->d_name);
120 			break;
121 		default:
122 			assert(0);
123 		}
124 	}
125 }
126 
main(void)127 int main(void)
128 {
129 	DIR *d;
130 	struct statfs sfs;
131 
132 	d = opendir("/proc");
133 	if (!d)
134 		return 4;
135 
136 	/* Ensure /proc is proc. */
137 	if (fstatfs(dirfd(d), &sfs) == -1) {
138 		return 1;
139 	}
140 	if (sfs.f_type != 0x9fa0) {
141 		fprintf(stderr, "error: unexpected f_type %lx\n", (long)sfs.f_type);
142 		return 2;
143 	}
144 
145 	f(d, 0);
146 
147 	return 0;
148 }
149