[PATCH 3/6] shm: add memfd_create() syscall

[Konstantin Khlebnikov]

On Wed, Mar 19, 2014 at 11:06 PM, David Herrmann <dh.herrmann at gmail.com> wrote:
> memfd_create() is similar to mmap(MAP_ANON), but returns a file-descriptor
> that you can pass to mmap(). It explicitly allows sealing and
> avoids any connection to user-visible mount-points. Thus, it's not
> subject to quotas on mounted file-systems, but can be used like
> malloc()'ed memory, but with a file-descriptor to it.
>
> memfd_create() does not create a front-FD, but instead returns the raw
> shmem file, so calls like ftruncate() can be used. Also calls like fstat()
> will return proper information and mark the file as regular file. Sealing
> is explicitly supported on memfds.
>
> Compared to O_TMPFILE, it does not require a tmpfs mount-point and is not
> subject to quotas and alike.

Instead of adding new syscall we can extend existing openat() a little
bit more:

openat(AT_FDSHM, "name", O_TMPFILE | O_RDWR, 0666)