The memfd_create() syscall creates anonymous files similar to O_TMPFILE but does not require an active mount-point.
Signed-off-by: David Herrmann dh.herrmann@gmail.com --- man2/memfd_create.2 | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 110 insertions(+) create mode 100644 man2/memfd_create.2
diff --git a/man2/memfd_create.2 b/man2/memfd_create.2 new file mode 100644 index 0000000..3e362e0 --- /dev/null +++ b/man2/memfd_create.2 @@ -0,0 +1,110 @@ +." Copyright (C) 2014 David Herrmann dh.herrmann@gmail.com +." starting from a version by Michael Kerrisk mtk.manpages@gmail.com +." +." %%%LICENSE_START(GPLv2+_SW_3_PARA) +." This program is free software; you can redistribute it and/or modify +." it under the terms of the GNU General Public License as published by +." the Free Software Foundation; either version 2 of the License, or +." (at your option) any later version. +." +." This program is distributed in the hope that it will be useful, +." but WITHOUT ANY WARRANTY; without even the implied warranty of +." MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +." GNU General Public License for more details. +." +." You should have received a copy of the GNU General Public +." License along with this manual; if not, see +." http://www.gnu.org/licenses/. +." %%%LICENSE_END +." +.TH MEMFD_CREATE 2 2014-03-18 Linux "Linux Programmer's Manual" +.SH NAME +memfd_create - create an anonymous file +.SH SYNOPSIS +.B #include <sys/memfd.h> +.sp +.BI "int memfd_create(const char *" name ", u64 " size ", u64 " flags ");" +.SH DESCRIPTION +.BR memfd_create () +creates an anonymous file and returns a file-descriptor to it. The file behaves +like regular files, thus can be modified, truncated, memory-mapped and more. +However, unlike regular files it lives in main memory and has no non-volatile +backing storage. Once all references to the file are dropped, it is +automatically released. Like all shmem-based files, memfd files support +.BR SHMEM +sealing parameters. See +.BR SHMEM_SET_SEALS " with " fcntl (2) +for more information. + +The initial size of the file is set to +.IR size ". " name +is used as internal file-name and will occur as such in +.IR /proc/self/fd/ . +The name is always prefixed with +.BR memfd: +and serves only debugging purposes. + +The following values may be bitwise ORed in +.IR flags +to change the behaviour of +.BR memfd_create (): +.TP +.BR MFD_CLOEXEC +Set the close-on-exec +.RB ( FD_CLOEXEC ) +flag on the new file descriptor. +See the description of the +.B O_CLOEXEC +flag in +.BR open (2) +for reasons why this may be useful. +.PP +Unused bits must be cleared to 0. + +As its return value, +.BR memfd_create () +returns a new file descriptor that can be used to refer to the file. +A copy of the file descriptor created by +.BR memfd_create () +is inherited by the child produced by +.BR fork (2). +The duplicate file descriptor is associated with the same file. +File descriptors created by +.BR memfd_create () +are preserved across +.BR execve (2), +unless the close-on-exec flag has been set. +.SH RETURN VALUE +On success, +.BR memfd_create () +returns a new file descriptor. +On error, -1 is returned and +.I errno +is set to indicate the error. +.SH ERRORS +.TP +.B EINVAL +An unsupported value was specified in one of the arguments. +.TP +.B EMFILE +The per-process limit on open file descriptors has been reached. +.TP +.B ENFILE +The system-wide limit on the total number of open files has been +reached. +.TP +.B EFAULT +The name given in +.IR name +points to invalid memory. +.TP +.B ENOMEM +There was insufficient memory to create a new anonymous file. +.SH VERSIONS +to-be-defined +.SH CONFORMING TO +.BR memfd_create () +is Linux-specific. +.SH SEE ALSO +.BR shmget (2), +.BR fcntl (2),