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client-ip=162.221.158.21; receiver=esa1.hc3370-68.iphmx.com; envelope-from="Andrew.Cooper3@citrix.com"; x-sender="postmaster@mail.citrix.com"; x-conformance=sidf_compatible Authentication-Results: esa1.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none; spf=None smtp.pra=andrew.cooper3@citrix.com; spf=Pass smtp.mailfrom=Andrew.Cooper3@citrix.com; spf=None smtp.helo=postmaster@mail.citrix.com; dmarc=pass (p=none dis=none) d=citrix.com IronPort-SDR: PBwiuavzafFtcce7TY/uOXgN1tTXnJ+s1m+WMDEnJTkyadmsH7TPFfUwRDQDuQmV67huSJee6e /G4x1e/Igmwppwy/Nt1vKUIE90uZP+K59wXFR32m/yrPVyrKP3RcfuTLgRATacAcWvRqJdWmdC f447dNQL5Gw2m32E1Tq3re8yrcrqM6pG4w32pbHR+UbRRuMLz2ZzJBCk6h7AFtp55pN1ONzEU6 VK/Q/586PvfBzNP+bDcTCI7QwoujHHGXhH3DKEviXZPl7hM0doEuxxqciXYC1xike67kCeT0UD zNM= X-SBRS: 2.7 X-MesageID: 17620682 X-Ironport-Server: esa1.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.73,384,1583211600"; d="scan'208";a="17620682" From: Andrew Cooper To: Xen-devel Subject: [PATCH] x86/build: Unilaterally disable -fcf-protection Date: Tue, 12 May 2020 20:11:16 +0100 Message-ID: <20200512191116.6851-1-andrew.cooper3@citrix.com> X-Mailer: git-send-email 2.11.0 MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Wei Liu , Jason Andryuk , Andrew Cooper , Stefan Bader , Jan Beulich , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" See comment for details. Works around a GCC-9 bug which breaks the build on Ubuntu. Reported-by: Jason Andryuk Signed-off-by: Andrew Cooper --- CC: Jan Beulich CC: Wei Liu CC: Roger Pau Monné CC: Jason Andryuk CC: Stefan Bader Sorry for messing you around with how to fix this. I'd neglected to consider the CONFIG_LIVEPATCH interaction. With that extra observation, there is no point having the extra complexity given that the result with CET-IBT and Retpoline still isn't usable. --- xen/arch/x86/arch.mk | 9 +++++++++ xen/arch/x86/boot/build32.mk | 1 + 2 files changed, 10 insertions(+) diff --git a/xen/arch/x86/arch.mk b/xen/arch/x86/arch.mk index 2a51553edb..93e30e4bea 100644 --- a/xen/arch/x86/arch.mk +++ b/xen/arch/x86/arch.mk @@ -67,6 +67,15 @@ CFLAGS-$(CONFIG_INDIRECT_THUNK) += -mindirect-branch=thunk-extern CFLAGS-$(CONFIG_INDIRECT_THUNK) += -mindirect-branch-register CFLAGS-$(CONFIG_INDIRECT_THUNK) += -fno-jump-tables +# Xen doesn't support CET-IBT yet. At a minimum, logic is required to +# enable it for supervisor use, but the Livepatch functionality needs +# to learn not to overwrite ENDBR64 instructions. +# +# Furthermore, Ubuntu enables -fcf-protection by default, along with a +# buggy version of GCC-9 which objects to it in combination with +# -mindirect-branch=thunk-extern (Fixed in GCC 10, 9.4). +$(call cc-option-add,CFLAGS,CC,-fcf-protection=none) + # If supported by the compiler, reduce stack alignment to 8 bytes. But allow # this to be overridden elsewhere. $(call cc-option-add,CFLAGS-stack-boundary,CC,-mpreferred-stack-boundary=3) diff --git a/xen/arch/x86/boot/build32.mk b/xen/arch/x86/boot/build32.mk index 48c7407c00..5a00755512 100644 --- a/xen/arch/x86/boot/build32.mk +++ b/xen/arch/x86/boot/build32.mk @@ -3,6 +3,7 @@ CFLAGS = include $(XEN_ROOT)/Config.mk $(call cc-options-add,CFLAGS,CC,$(EMBEDDED_EXTRA_CFLAGS)) +$(call cc-option-add,CFLAGS,CC,-fcf-protection=none) CFLAGS += -Werror -fno-asynchronous-unwind-tables -fno-builtin -g0 -msoft-float CFLAGS += -I$(XEN_ROOT)/xen/include -- 2.11.0