Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Yu-cheng Yu <yu-cheng.yu@intel.com>
To:     x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@amacapital.net>,
        Balbir Singh <bsingharora@gmail.com>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Florian Weimer <fweimer@redhat.com>,
        "H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Kees Cook <keescook@chromium.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>
Cc:     Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: [RFC PATCH v4 1/9] x86/cet/ibt: Add Kconfig option for user-mode Indirect Branch Tracking
Date:   Fri, 21 Sep 2018 08:05:45 -0700
Message-Id: <20180921150553.21016-2-yu-cheng.yu@intel.com>
In-Reply-To: <20180921150553.21016-1-yu-cheng.yu@intel.com>
References: <20180921150553.21016-1-yu-cheng.yu@intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The user-mode indirect branch tracking support is done mostly by
GCC to insert ENDBR64/ENDBR32 instructions at branch targets.
The kernel provides CPUID enumeration, feature MSR setup and
the allocation of legacy bitmap.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
 arch/x86/Kconfig  | 12 ++++++++++++
 arch/x86/Makefile |  7 +++++++
 2 files changed, 19 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6377125543cc..2a0ff538a229 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1941,6 +1941,18 @@ config X86_INTEL_SHADOW_STACK_USER
 
 	  If unsure, say y.
 
+config X86_INTEL_BRANCH_TRACKING_USER
+	prompt "Intel Indirect Branch Tracking for user-mode"
+	def_bool n
+	depends on CPU_SUP_INTEL && X86_64
+	select X86_INTEL_CET
+	select ARCH_HAS_PROGRAM_PROPERTIES
+	---help---
+	  Indirect Branch Tracking provides hardware protection against return-/jmp-
+	  oriented programming attacks.
+
+	  If unsure, say y
+
 config EFI
 	bool "EFI runtime service support"
 	depends on ACPI
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index b28842b80295..ff652bba849f 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -159,6 +159,13 @@ ifdef CONFIG_X86_INTEL_SHADOW_STACK_USER
   endif
 endif
 
+# Check compiler ibt support
+ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER
+  ifeq ($(call cc-option-yn, -fcf-protection=branch), n)
+      $(error CONFIG_X86_INTEL_BRANCH_TRACKING_USER not supported by compiler)
+  endif
+endif
+
 #
 # If the function graph tracer is used with mcount instead of fentry,
 # '-maccumulate-outgoing-args' is needed to prevent a GCC bug
-- 
2.17.1