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