[PATCH RFC] Add support for linux memfd_create syscall

[David Herrmann]

Hi

On Fri, Nov 21, 2014 at 7:12 PM, Carlos O'Donell <carlos@redhat.com> wrote:
> On 10/17/2014 05:21 AM, David Herrmann wrote:
>> The memfd_create() syscall was released with linux-3.17. It's a linux-only
>> syscall and returns a shmem file-descriptor backed by anonymous memory
>> in a kernel-internal shmem mount.
>
> In general I'm trying hard to make this kind of patch easy to accept.
>
> See the WIP consensus here:
> https://sourceware.org/glibc/wiki/Consensus#WIP:_Kernel_syscalls_wrappers
>
> In order to get your patch accepted you have answer some implicit
> questions like "How do users use it?" "Why do users need it?"

Sure, will add that in v2.

> From a high-level perspective your patch is missing:
>
> - A test case if possible with non-root privs, or an xcheck test if root
>   is required.
>   e.g. ./sysdeps/unix/sysv/linux/tst-memfd_create.c

I already wrote extensive tests which are included in the kernel. I
will try to extract a sensible part and put it into glibc.

> - Documentation for the manual covering the use of the function.
>   e.g. ./manual/llio.texi, new section under low-level IO, and specify
>   that it is Linux specific. Feel free to submit your own text to the
>   linux-kernel man pages to get a new man page created.

My kernel patches already had man-pages included. I'm currently
talking with Michael Kerrisk to get them upstream. I will try to
include something for llio.texi in v2.

> Lastly you'll want to review:
> https://sourceware.org/glibc/wiki/Contribution%20checklist
>
> The present patch is mechanical in nature and doesn't require copyright
> assignment, but adding the test case, and manual entry brings you into
> legally significant territory. Do you have a copyright assignment with
> the FSF for glibc?

I remember someone telling me RedHat had a copyright agreement with
the FSF, but the link explicitly states you need it from the _author_.
I will send v2 as 2 patches, if you consider either a non-mechanical
contribution, we will have to delay it until my copyright agreement
with the FSF is done.

Thanks
David