Re: [RFC] new SYSCALL_DEFINE/COMPAT_SYSCALL_DEFINE wrappers

Adam Borowski
2018-03-30T15:54:51Z

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On Fri, Mar 30, 2018 at 12:58:02PM +0200, Ingo Molnar wrote:
> * John Paul Adrian Glaubitz <glaubitz@physik.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@physik.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.

> Here's the direct download link:
> $ wget https://people.debian.org/~glaubitz/chroots/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?

Instead of mucking with fakechroot which would require installing its :x32
part inside the guest, or running the test as root, what about using any
random static binary? For example, a shell like sash or bash-static would
have a decentish syscall coverage even by itself.

I've extracted sash from
http://ftp.ports.debian.org/debian-ports//pool-x32/main/s/sash/sash_3.8-4_x32.deb
and placed at https://angband.pl/tmp/sash.x32

$ sha256sum sash.x32
de24097c859b313fa422af742b648c9d731de6b33b98cb995658d1da16398456 sash.x32

Obviously, you can compile a static binary that uses whatever syscalls you
want. Without a native chroot, you can "gcc -mx32" although you'd need some
kind of libc unless your program is stand-alone.

It might be worth mentioning my "arch-test:
https://github.com/kilobyte/arch-test
Because of many toolchain pieces it needs, you want a prebuilt copy:
https://github.com/kilobyte/arch-test/releases/download/v0.10/arch-test_prebuilt_0.10.tar.xz
https://github.com/kilobyte/arch-test/releases/download/v0.10/arch-test_prebuilt_0.10.tar.xz.asc
-- while it has _extremely_ small coverage of syscalls (just write() and
_exit(), enough to check endianness and pointer width), concentrating on
instruction set inadequacies (broken SWP on arm, POWER7 vs POWER8, powerpc
vs powerpcspe, etc), it provides minimal test binaries for a wide range of
architectures.

Meow!
--
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