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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sun, 25 Mar 2018 20:20:52 -1000
Message-ID: <CA+55aFy974z4PQMzSKbvcz02BeyRQTbXxyjw_GgjrXSeAf3wwQ@mail.gmail.com>
Subject: Re: [RFC] new SYSCALL_DEFINE/COMPAT_SYSCALL_DEFINE wrappers
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Ingo Molnar <mingo@kernel.org>,
        Dominik Brodowski <linux@dominikbrodowski.net>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        linux-arch <linux-arch@vger.kernel.org>,
        Ralf Baechle <ralf@linux-mips.org>,
        James Hogan <jhogan@kernel.org>,
        linux-mips <linux-mips@linux-mips.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        ppc-dev <linuxppc-dev@lists.ozlabs.org>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        linux-s390 <linux-s390@vger.kernel.org>,
        "David S . Miller" <davem@davemloft.net>,
        sparclinux@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
        Jiri Slaby <jslaby@suse.com>,
        "the arch/x86 maintainers" <x86@kernel.org>
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On Sun, Mar 25, 2018 at 8:15 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> HOWEVER.
>
> I didn't actually test any of the compat or x32 ones, and the way I
> did it there also was no type-checking or other automated catching of
> getting it wrong. So it's almost certainly completely buggy, but the
> _intent_ is there and there is a remote possibility that it might even
> work.

Note: the commit message is "broken, but working, ptregs system call
conversion for x86-64".

The "but working" is not because it would be right, but because it
booted a real 64-bit distribution successfully, and I actually used
that kernel.

But that only tests the native 64-bit case, it in no way tests the
compat or x32 cases what-so-ever. That part was literally a "it
compiles - it must be perfect" with absolutely zero testing of even
the most trivial kind.

And it really would have been most trivial to just do a "Hello world"
and build it with "-m32". I didn't do even that, and if I had, I would
have been honestly surprised had it worked.

But there was a _theoretical_ chance that it could have worked. Maybe.

      Linus