linux-kernel - Re: [RFC] new SYSCALL_DEFINE/COMPAT_SYSCALL

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Date:   Fri, 30 Mar 2018 12:58:02 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        linux-arch <linux-arch@...r.kernel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>,
        linux-mips <linux-mips@...ux-mips.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        ppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        linux-s390 <linux-s390@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        sparclinux@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Jiri Slaby <jslaby@...e.com>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [RFC] new SYSCALL_DEFINE/COMPAT_SYSCALL_DEFINE wrappers


* John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de> wrote:

> On 03/27/2018 12:40 PM, Linus Torvalds wrote:
> > On Mon, Mar 26, 2018 at 4:37 PM, John Paul Adrian Glaubitz
> > <glaubitz@...sik.fu-berlin.de> wrote:
> >>
> >> What about a tarball with a minimal Debian x32 chroot? Then you can
> >> install interesting packages you would like to test yourself.
> > 
> > That probably works fine.
> 
> I just created a fresh Debian x32 unstable chroot using this command:
> 
> $ debootstrap --no-check-gpg --variant=minbase --arch=x32 unstable debian-x32-unstable http://ftp.ports.debian.org/debian-ports
> 
> It can be downloaded from my Debian webspace along checksum files for
> verification:
> 
> > https://people.debian.org/~glaubitz/chroots/
> 
> Let me know if you run into any issues.

Here's the direct download link:

  $ wget https://people.debian.org/~glaubitz/chroots/debian-x32-unstable.tar.gz

Checksum should be:

  $ sha256sum debian-x32-unstable.tar.gz
  010844bcc76bd1a3b7a20fe47f7067ed8e429a84fa60030a2868626e8fa7ec3b  debian-x32-unstable.tar.gz

Seems to work fine here (on a distro kernel) even if I extract all the files as a 
non-root user and do:

  ~/s/debian-x32-unstable> fakechroot /usr/sbin/chroot . /usr/bin/dpkg -l  | tail -2

  ERROR: ld.so: object 'libfakechroot.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored.
  ii  util-linux:x32         2.31.1-0.5           x32          miscellaneous system utilities
  ii  zlib1g:x32             1:1.2.8.dfsg-5       x32          compression library - runtime

So that 'dpkg' instance appears to be running inside the chroot environment and is 
listing x32 installed packages.

Although I did get this warning:

  ERROR: ld.so: object 'libfakechroot.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored.

Even with that warning, is still still a sufficiently complex test of x32 syscall 
code paths?

BTW., "fakechroot /usr/sbin/chroot ." crashes instead of giving me a bash shell.

Thanks,

	Ingo