Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 | // 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 #ifndef __NR_pidfd_send_signal #define __NR_pidfd_send_signal -1 #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 = -1, 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) err(ret, "CLONE_PIDFD"); if (pidfd == -1) { warnx("CLONE_PIDFD is not supported by the kernel"); goto out; } 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); } |