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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pidfd-metadata.c (2389B)

      1// SPDX-License-Identifier: GPL-2.0
      2
      3#define _GNU_SOURCE
      4#include <err.h>
      5#include <errno.h>
      6#include <fcntl.h>
      7#include <inttypes.h>
      8#include <limits.h>
      9#include <sched.h>
     10#include <signal.h>
     11#include <stdio.h>
     12#include <stdlib.h>
     13#include <string.h>
     14#include <sys/stat.h>
     15#include <sys/syscall.h>
     16#include <sys/types.h>
     17#include <sys/wait.h>
     18#include <unistd.h>
     19
     20#ifndef CLONE_PIDFD
     21#define CLONE_PIDFD 0x00001000
     22#endif
     23
     24#ifndef __NR_pidfd_send_signal
     25#define __NR_pidfd_send_signal -1
     26#endif
     27
     28static int do_child(void *args)
     29{
     30	printf("%d\n", getpid());
     31	_exit(EXIT_SUCCESS);
     32}
     33
     34static pid_t pidfd_clone(int flags, int *pidfd)
     35{
     36	size_t stack_size = 1024;
     37	char *stack[1024] = { 0 };
     38
     39#ifdef __ia64__
     40	return __clone2(do_child, stack, stack_size, flags | SIGCHLD, NULL, pidfd);
     41#else
     42	return clone(do_child, stack + stack_size, flags | SIGCHLD, NULL, pidfd);
     43#endif
     44}
     45
     46static inline int sys_pidfd_send_signal(int pidfd, int sig, siginfo_t *info,
     47					unsigned int flags)
     48{
     49	return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags);
     50}
     51
     52static int pidfd_metadata_fd(pid_t pid, int pidfd)
     53{
     54	int procfd, ret;
     55	char path[100];
     56
     57	snprintf(path, sizeof(path), "/proc/%d", pid);
     58	procfd = open(path, O_DIRECTORY | O_RDONLY | O_CLOEXEC);
     59	if (procfd < 0) {
     60		warn("Failed to open %s\n", path);
     61		return -1;
     62	}
     63
     64	/*
     65	 * Verify that the pid has not been recycled and our /proc/<pid> handle
     66	 * is still valid.
     67	 */
     68	ret = sys_pidfd_send_signal(pidfd, 0, NULL, 0);
     69	if (ret < 0) {
     70		switch (errno) {
     71		case EPERM:
     72			/* Process exists, just not allowed to signal it. */
     73			break;
     74		default:
     75			warn("Failed to signal process\n");
     76			close(procfd);
     77			procfd = -1;
     78		}
     79	}
     80
     81	return procfd;
     82}
     83
     84int main(int argc, char *argv[])
     85{
     86	int pidfd = -1, ret = EXIT_FAILURE;
     87	char buf[4096] = { 0 };
     88	pid_t pid;
     89	int procfd, statusfd;
     90	ssize_t bytes;
     91
     92	pid = pidfd_clone(CLONE_PIDFD, &pidfd);
     93	if (pid < 0)
     94		err(ret, "CLONE_PIDFD");
     95	if (pidfd == -1) {
     96		warnx("CLONE_PIDFD is not supported by the kernel");
     97		goto out;
     98	}
     99
    100	procfd = pidfd_metadata_fd(pid, pidfd);
    101	close(pidfd);
    102	if (procfd < 0)
    103		goto out;
    104
    105	statusfd = openat(procfd, "status", O_RDONLY | O_CLOEXEC);
    106	close(procfd);
    107	if (statusfd < 0)
    108		goto out;
    109
    110	bytes = read(statusfd, buf, sizeof(buf));
    111	if (bytes > 0)
    112		bytes = write(STDOUT_FILENO, buf, bytes);
    113	close(statusfd);
    114	ret = EXIT_SUCCESS;
    115
    116out:
    117	(void)wait(NULL);
    118
    119	exit(ret);
    120}