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
 34static inline bool streq(const char *s1, const char *s2)
 35{
 36	return strcmp(s1, s2) == 0;
 37}
 38
 39static 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
 51static 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
 66static 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
 79static 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
 88static 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
138int 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}