113 строки
2.2 KiB
C
113 строки
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
|
|
#define _GNU_SOURCE
|
|
#include <err.h>
|
|
#include <errno.h>
|
|
#include <fcntl.h>
|
|
#include <inttypes.h>
|
|
#include <limits.h>
|
|
#include <sched.h>
|
|
#include <signal.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <sys/stat.h>
|
|
#include <sys/syscall.h>
|
|
#include <sys/types.h>
|
|
#include <sys/wait.h>
|
|
#include <unistd.h>
|
|
|
|
#ifndef CLONE_PIDFD
|
|
#define CLONE_PIDFD 0x00001000
|
|
#endif
|
|
|
|
static int do_child(void *args)
|
|
{
|
|
printf("%d\n", getpid());
|
|
_exit(EXIT_SUCCESS);
|
|
}
|
|
|
|
static pid_t pidfd_clone(int flags, int *pidfd)
|
|
{
|
|
size_t stack_size = 1024;
|
|
char *stack[1024] = { 0 };
|
|
|
|
#ifdef __ia64__
|
|
return __clone2(do_child, stack, stack_size, flags | SIGCHLD, NULL, pidfd);
|
|
#else
|
|
return clone(do_child, stack + stack_size, flags | SIGCHLD, NULL, pidfd);
|
|
#endif
|
|
}
|
|
|
|
static inline int sys_pidfd_send_signal(int pidfd, int sig, siginfo_t *info,
|
|
unsigned int flags)
|
|
{
|
|
return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags);
|
|
}
|
|
|
|
static int pidfd_metadata_fd(pid_t pid, int pidfd)
|
|
{
|
|
int procfd, ret;
|
|
char path[100];
|
|
|
|
snprintf(path, sizeof(path), "/proc/%d", pid);
|
|
procfd = open(path, O_DIRECTORY | O_RDONLY | O_CLOEXEC);
|
|
if (procfd < 0) {
|
|
warn("Failed to open %s\n", path);
|
|
return -1;
|
|
}
|
|
|
|
/*
|
|
* Verify that the pid has not been recycled and our /proc/<pid> handle
|
|
* is still valid.
|
|
*/
|
|
ret = sys_pidfd_send_signal(pidfd, 0, NULL, 0);
|
|
if (ret < 0) {
|
|
switch (errno) {
|
|
case EPERM:
|
|
/* Process exists, just not allowed to signal it. */
|
|
break;
|
|
default:
|
|
warn("Failed to signal process\n");
|
|
close(procfd);
|
|
procfd = -1;
|
|
}
|
|
}
|
|
|
|
return procfd;
|
|
}
|
|
|
|
int main(int argc, char *argv[])
|
|
{
|
|
int pidfd = 0, ret = EXIT_FAILURE;
|
|
char buf[4096] = { 0 };
|
|
pid_t pid;
|
|
int procfd, statusfd;
|
|
ssize_t bytes;
|
|
|
|
pid = pidfd_clone(CLONE_PIDFD, &pidfd);
|
|
if (pid < 0)
|
|
exit(ret);
|
|
|
|
procfd = pidfd_metadata_fd(pid, pidfd);
|
|
close(pidfd);
|
|
if (procfd < 0)
|
|
goto out;
|
|
|
|
statusfd = openat(procfd, "status", O_RDONLY | O_CLOEXEC);
|
|
close(procfd);
|
|
if (statusfd < 0)
|
|
goto out;
|
|
|
|
bytes = read(statusfd, buf, sizeof(buf));
|
|
if (bytes > 0)
|
|
bytes = write(STDOUT_FILENO, buf, bytes);
|
|
close(statusfd);
|
|
ret = EXIT_SUCCESS;
|
|
|
|
out:
|
|
(void)wait(NULL);
|
|
|
|
exit(ret);
|
|
}
|