2 * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
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.
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.
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
25 #include <sys/types.h>
36 static void f_reg(DIR *d, const char *filename)
42 /* read from /proc/kmsg can block */
43 fd = openat(dirfd(d), filename, O_RDONLY|O_NONBLOCK);
46 rv = read(fd, buf, sizeof(buf));
47 assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
51 static void f_reg_write(DIR *d, const char *filename, const char *buf, size_t len)
56 fd = openat(dirfd(d), filename, O_WRONLY);
59 rv = write(fd, buf, len);
60 assert((0 <= rv && rv <= len) || rv == -1);
64 static void f_lnk(DIR *d, const char *filename)
69 rv = readlinkat(dirfd(d), filename, buf, sizeof(buf));
70 assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
73 static void f(DIR *d, unsigned int level)
78 assert(de->d_type == DT_DIR);
79 assert(streq(de->d_name, "."));
82 assert(de->d_type == DT_DIR);
83 assert(streq(de->d_name, ".."));
85 while ((de = xreaddir(d))) {
86 assert(!streq(de->d_name, "."));
87 assert(!streq(de->d_name, ".."));
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);
101 f_reg(d, de->d_name);
105 fd = openat(dirfd(d), de->d_name, O_DIRECTORY|O_RDONLY);
115 f_lnk(d, de->d_name);
127 d = opendir("/proc");