получить дубликат файлового дескриптора другого процесса (obtain a duplicate of another process's file descriptor)
Имя (Name)
pidfd_getfd - obtain a duplicate of another process's file
descriptor
Синопсис (Synopsis)
#include <sys/syscall.h> /* Definition of SYS_* constants */
#include <unistd.h>
int syscall(SYS_pidfd_getfd, int pidfd, int targetfd,
unsigned int flags);
Note: glibc provides no wrapper for pidfd_getfd(), necessitating
the use of syscall(2).
Описание (Description)
The pidfd_getfd() system call allocates a new file descriptor in
the calling process. This new file descriptor is a duplicate of
an existing file descriptor, targetfd, in the process referred to
by the PID file descriptor pidfd.
The duplicate file descriptor refers to the same open file
description (see open(2)) as the original file descriptor in the
process referred to by pidfd. The two file descriptors thus
share file status flags and file offset. Furthermore, operations
on the underlying file object (for example, assigning an address
to a socket object using bind(2)) can equally be performed via
the duplicate file descriptor.
The close-on-exec flag (FD_CLOEXEC; see fcntl(2)) is set on the
file descriptor returned by pidfd_getfd().
The flags argument is reserved for future use. Currently, it
must be specified as 0.
Permission to duplicate another process's file descriptor is
governed by a ptrace access mode PTRACE_MODE_ATTACH_REALCREDS
check (see ptrace(2)).
Возвращаемое значение (Return value)
On success, pidfd_getfd() returns a file descriptor (a
nonnegative integer). On error, -1 is returned and errno is set
to indicate the error.
Ошибки (Error)
EBADF pidfd is not a valid PID file descriptor.
EBADF targetfd is not an open file descriptor in the process
referred to by pidfd.
EINVAL flags is not 0.
EMFILE The per-process limit on the number of open file
descriptors has been reached (see the description of
RLIMIT_NOFILE in getrlimit(2)).
ENFILE The system-wide limit on the total number of open files
has been reached.
EPERM The calling process did not have
PTRACE_MODE_ATTACH_REALCREDS permissions (see ptrace(2))
over the process referred to by pidfd.
ESRCH The process referred to by pidfd does not exist (i.e., it
has terminated and been waited on).
Версии (Versions)
pidfd_getfd() first appeared in Linux 5.6.
Стандарты (Conforming to)
pidfd_getfd() is Linux specific.
Примечание (Note)
For a description of PID file descriptors, see pidfd_open(2).
The effect of pidfd_getfd() is similar to the use of SCM_RIGHTS
messages described in unix(7), but differs in the following
respects:
• In order to pass a file descriptor using an SCM_RIGHTS message,
the two processes must first establish a UNIX domain socket
connection.
• The use of SCM_RIGHTS requires cooperation on the part of the
process whose file descriptor is being copied. By contrast, no
such cooperation is necessary when using pidfd_getfd().
• The ability to use pidfd_getfd() is restricted by a
PTRACE_MODE_ATTACH_REALCREDS ptrace access mode check.
Смотри также (See also)
clone3(2), dup(2), kcmp(2), pidfd_open(2)
