linux-kernel - Re: Official Linux system wrapper library?

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Date:   Sun, 11 Nov 2018 07:55:30 +0100
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Daniel Colascione <dancol@...gle.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Cc:     mtk.manpages@...il.com, Joel Fernandes <joelaf@...gle.com>,
        Linux API <linux-api@...r.kernel.org>,
        Willy Tarreau <w@....eu>, Vlastimil Babka <vbabka@...e.cz>,
        Florian Weimer <fweimer@...hat.com>,
        Carlos O'Donell <carlos@...hat.com>,
        "libc-alpha@...rceware.org" <libc-alpha@...rceware.org>
Subject: Re: Official Linux system wrapper library?

[adding in glibc folk for comment]

On 11/10/18 7:52 PM, Daniel Colascione wrote:
> Now that glibc is basically not adding any new system call wrappers,
> how about publishing an "official" system call glue library as part of
> the kernel distribution, along with the uapi headers? I don't think
> it's reasonable to expect people to keep using syscall(__NR_XXX) for
> all new functionality, especially as the system grows increasingly
> sophisticated capabilities (like the new mount API, and hopefully the
> new process API) outside the strictures of the POSIX process.

As a quick glance at the glibc NEWS file shows, the above is not
quite true:

[[
Version 2.28
* The renameat2 function has been added...
* The statx function has been added...

Version 2.27
* Support for memory protection keys was added.  The <sys/mman.h> header now
  declares the functions pkey_alloc, pkey_free, pkey_mprotect...
* The copy_file_range function was added.

Version 2.26
* New wrappers for the Linux-specific system calls preadv2 and pwritev2.

Version 2.25
* The getrandom [function] have been added.
]]

I make that 11 system call wrappers added in the last 2 years.

That said, of course, there are many system calls that lack wrappers [1],
and the use of syscall() is undesirable.

The glibc folk do have their reasons for being conservative around
adding system calls (https://lwn.net/Articles/655028/). However, at
this point, I think one of the limiting factors is developer time
on the glibc project. Quite possibly, they just need some help to
add more (properly designed) wrappers faster.

Cheers,

Michael

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=6399 is a
    longstanding example.

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/