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Message-ID: <1517225725.6624.136.camel@infradead.org>
Subject: Re: Requirements for retpoline in Linux 4.15 (was: Re: Linux 4.15)
From:   David Woodhouse <dwmw2@infradead.org>
To:     Martin Steigerwald <martin@lichtvoll.de>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
In-Reply-To: <5520835.tArHHOCcxE@merkaba>
References: <CA+55aFzARtx-nA=d1j7vLOLf4FHMJLyRiQ-PKkoexJuTUHogdw@mail.gmail.com>
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Date:   Mon, 29 Jan 2018 11:35:25 +0000
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On Mon, 2018-01-29 at 12:19 +0100, Martin Steigerwald wrote:
>=20
> The whole thing works:
>=20
> % grep . /sys/devices/system/cpu/vulnerabilities/*=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0
> /sys/devices/system/cpu/vulnerabilities/meltdown:Mitigation: PTI
> /sys/devices/system/cpu/vulnerabilities/spectre_v1:Vulnerable
> /sys/devices/system/cpu/vulnerabilities/spectre_v2:Mitigation: Full gener=
ic=C2=A0
> retpoline
>=20
> I bet the virtualbox modules compiled by virtualbox-dkms will taint the=
=C2=A0
> support, but I bet sooner or later they will support retpoline as well.=
=C2=A0
> (Another reason to switch to KVM one day.)

As long as those are actually compiled, it should be fine. Any C code
will be built with the correct CFLAGS.

If they have explicit asm which has indirect jumps, that would still be
a problem. We just need to port objtool into the kernel and do it at
module load time, to check for that... :)
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