Re: [PATCH] Linux: Add tables with system call numbers

[Zack Weinberg <zackw at panix dot com>]

On Tue, May 28, 2019 at 6:10 PM Florian Weimer <fweimer@redhat.com> wrote:
...
> The goal is to use these architecture-specific tables to ensure
> that system call wrappers are available irrespective of the version
> of the installed kernel headers.
>
> The tables are formatted in the form of C header files so that they
> can be used directly in an #include directive, without external
> preprocessing.  (External preprocessing of a plain table file
> would introduce cross-subdirectory dependency issues.)  However,
> the intent is that they can still be treated as tables and processed
> by simple tools.

Is there any reason why, instead of inventing a new name
"arch-syscall.h", these tables could not be checked in as
bits/syscall.h for each architecture, allowing us to eliminate the
process of generating bits/syscall.h at build time, and decoupling our
sys/syscall.h altogether from the installed kernel headers?  They
would need a little boilerplate at top and bottom, which shouldn't be
a big deal, and they would have to define the SYS_ names rather than
the __NR_ names, but my old-fashioned heart is inclined to say that
that's a win anyway, the __NR_ names were never part of *our* official
API, include <asm/unistd.h> yourself if you want them.

Relatedly, I think gen-syscall-h.awk could be recycled as the
script Joseph wants (perhaps rewritten in Python).

A couple of small notes on the patch (this is not a full review):

> +++ b/sysdeps/unix/sysv/linux/glibcsyscalls.py
> @@ -0,0 +1,141 @@
> +#!/usr/bin/python3
> +# Helpers for glibc system call list processing.
> +# Copyright (C) 2018-2019 Free Software Foundation, Inc.
> +# This file is part of the GNU C Library.

This appears _not_ to be the script Joseph was asking for.  Could you
please make it clearer in the file what it does do?

> diff --git a/sysdeps/unix/sysv/linux/syscall-names.list b/sysdeps/unix/sysv/linux/syscall-names.list
> index 2d0354b8b3..9a51b46cbb 100644
> --- a/sysdeps/unix/sysv/linux/syscall-names.list
> +++ b/sysdeps/unix/sysv/linux/syscall-names.list
> @@ -499,6 +499,7 @@ set_mempolicy
>  set_robust_list
>  set_thread_area
>  set_tid_address
> +set_tls
>  setdomainname
>  setfsgid
>  setfsgid32

This should probably happen as a separate patch.

> diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/arch-syscall.h b/sysdeps/unix/sysv/linux/x86_64/x32/arch-syscall.h
> new file mode 100644
> index 0000000000..ef4ec281ef
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/x86_64/x32/arch-syscall.h
> @@ -0,0 +1,324 @@
> +#define __NR_accept 1073741867

Would it be possible to make this come out as (0x40000000 | 43), and
similarly for the others?

zw