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/*
* Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
// Test
// 1) read of every file in /proc
// 2) readlink of every symlink in /proc
// 3) recursively (1) + (2) for every directory in /proc
// 4) write to /proc/*/clear_refs and /proc/*/task/*/clear_refs
// 5) write to /proc/sysrq-trigger
#undef NDEBUG
#include <assert.h>
#include <errno.h>
#include <sys/types.h>
#include <dirent.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
static inline bool streq(const char *s1, const char *s2)
{
return strcmp(s1, s2) == 0;
}
static struct dirent *xreaddir(DIR *d)
{
struct dirent *de;
errno = 0;
de = readdir(d);
if (!de && errno != 0) {
exit(1);
}
return de;
}
static void f_reg(DIR *d, const char *filename)
{
char buf[4096];
int fd;
ssize_t rv;
/* read from /proc/kmsg can block */
fd = openat(dirfd(d), filename, O_RDONLY|O_NONBLOCK);
if (fd == -1)
return;
rv = read(fd, buf, sizeof(buf));
assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
close(fd);
}
static void f_reg_write(DIR *d, const char *filename, const char *buf, size_t len)
{
int fd;
ssize_t rv;
fd = openat(dirfd(d), filename, O_WRONLY);
if (fd == -1)
return;
rv = write(fd, buf, len);
assert((0 <= rv && rv <= len) || rv == -1);
close(fd);
}
static void f_lnk(DIR *d, const char *filename)
{
char buf[4096];
ssize_t rv;
rv = readlinkat(dirfd(d), filename, buf, sizeof(buf));
assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
}
static void f(DIR *d, unsigned int level)
{
struct dirent *de;
de = xreaddir(d);
assert(de->d_type == DT_DIR);
assert(streq(de->d_name, "."));
de = xreaddir(d);
assert(de->d_type == DT_DIR);
assert(streq(de->d_name, ".."));
while ((de = xreaddir(d))) {
assert(!streq(de->d_name, "."));
assert(!streq(de->d_name, ".."));
switch (de->d_type) {
DIR *dd;
int fd;
case DT_REG:
if (level == 0 && streq(de->d_name, "sysrq-trigger")) {
f_reg_write(d, de->d_name, "h", 1);
} else if (level == 1 && streq(de->d_name, "clear_refs")) {
f_reg_write(d, de->d_name, "1", 1);
} else if (level == 3 && streq(de->d_name, "clear_refs")) {
f_reg_write(d, de->d_name, "1", 1);
} else {
f_reg(d, de->d_name);
}
break;
case DT_DIR:
fd = openat(dirfd(d), de->d_name, O_DIRECTORY|O_RDONLY);
if (fd == -1)
continue;
dd = fdopendir(fd);
if (!dd)
continue;
f(dd, level + 1);
closedir(dd);
break;
case DT_LNK:
f_lnk(d, de->d_name);
break;
default:
assert(0);
}
}
}
int main(void)
{
DIR *d;
d = opendir("/proc");
if (!d)
return 2;
f(d, 0);
return 0;
}
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