cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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cgroup_event_listener.c (1858B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * cgroup_event_listener.c - Simple listener of cgroup events
      4 *
      5 * Copyright (C) Kirill A. Shutemov <kirill@shutemov.name>
      6 */
      7
      8#include <assert.h>
      9#include <err.h>
     10#include <errno.h>
     11#include <fcntl.h>
     12#include <libgen.h>
     13#include <limits.h>
     14#include <stdio.h>
     15#include <string.h>
     16#include <unistd.h>
     17
     18#include <sys/eventfd.h>
     19
     20#define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>"
     21
     22int main(int argc, char **argv)
     23{
     24	int efd = -1;
     25	int cfd = -1;
     26	int event_control = -1;
     27	char event_control_path[PATH_MAX];
     28	char line[LINE_MAX];
     29	int ret;
     30
     31	if (argc != 3)
     32		errx(1, "%s", USAGE_STR);
     33
     34	cfd = open(argv[1], O_RDONLY);
     35	if (cfd == -1)
     36		err(1, "Cannot open %s", argv[1]);
     37
     38	ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control",
     39			dirname(argv[1]));
     40	if (ret >= PATH_MAX)
     41		errx(1, "Path to cgroup.event_control is too long");
     42
     43	event_control = open(event_control_path, O_WRONLY);
     44	if (event_control == -1)
     45		err(1, "Cannot open %s", event_control_path);
     46
     47	efd = eventfd(0, 0);
     48	if (efd == -1)
     49		err(1, "eventfd() failed");
     50
     51	ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);
     52	if (ret >= LINE_MAX)
     53		errx(1, "Arguments string is too long");
     54
     55	ret = write(event_control, line, strlen(line) + 1);
     56	if (ret == -1)
     57		err(1, "Cannot write to cgroup.event_control");
     58
     59	while (1) {
     60		uint64_t result;
     61
     62		ret = read(efd, &result, sizeof(result));
     63		if (ret == -1) {
     64			if (errno == EINTR)
     65				continue;
     66			err(1, "Cannot read from eventfd");
     67		}
     68		assert(ret == sizeof(result));
     69
     70		ret = access(event_control_path, W_OK);
     71		if ((ret == -1) && (errno == ENOENT)) {
     72			puts("The cgroup seems to have removed.");
     73			break;
     74		}
     75
     76		if (ret == -1)
     77			err(1, "cgroup.event_control is not accessible any more");
     78
     79		printf("%s %s: crossed\n", argv[1], argv[2]);
     80	}
     81
     82	return 0;
     83}