linux-kernel - [PATCH v28 01/10] x86/cet/ibt: Add Kconfig option for Indirect Branch Tracking

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Date:   Thu, 22 Jul 2021 13:57:14 -0700
From:   Yu-cheng Yu <yu-cheng.yu@...el.com>
To:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Haitao Huang <haitao.huang@...el.com>,
        Rick P Edgecombe <rick.p.edgecombe@...el.com>
Cc:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: [PATCH v28 01/10] x86/cet/ibt: Add Kconfig option for Indirect Branch Tracking

Indirect Branch Tracking (IBT) provides protection against CALL-/JMP-
oriented programming attacks.  It is active when the kernel has this
feature enabled, and the processor and the application support it.
When this feature is enabled, legacy non-IBT applications continue to
work, but without IBT protection.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
---
 arch/x86/Kconfig                         | 19 +++++++++++++++++++
 arch/x86/include/asm/disabled-features.h |  8 +++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7a2991457497..8f0bba206206 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1933,6 +1933,25 @@ config X86_SHADOW_STACK
 
 	  If unsure, say N.
 
+config X86_IBT
+	prompt "Intel Indirect Branch Tracking"
+	def_bool n
+	depends on X86_SHADOW_STACK
+	depends on $(cc-option,-fcf-protection)
+	help
+	  Indirect Branch Tracking (IBT) provides protection against
+	  CALL-/JMP-oriented programming attacks.  It is active when
+	  the kernel has this feature enabled, and the processor and
+	  the application support it.  When this feature is enabled,
+	  legacy non-IBT applications continue to work, but without
+	  IBT protection.
+	  Support for this feature is present on Tiger Lake family of
+	  processors released in 2020 or later.  Enabling this feature
+	  increases kernel text size by 3.7 KB.
+	  See Documentation/x86/intel_cet.rst for more information.
+
+	  If unsure, say N.
+
 config EFI
 	bool "EFI runtime service support"
 	depends on ACPI
diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index b7728f7afb2b..e3a08fcd72f4 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -71,6 +71,12 @@
 #define DISABLE_SHSTK	(1 << (X86_FEATURE_SHSTK & 31))
 #endif
 
+#ifdef CONFIG_X86_IBT
+#define DISABLE_IBT	0
+#else
+#define DISABLE_IBT	(1 << (X86_FEATURE_IBT & 31))
+#endif
+
 /*
  * Make sure to add features to the correct mask
  */
@@ -93,7 +99,7 @@
 #define DISABLED_MASK16	(DISABLE_PKU|DISABLE_OSPKE|DISABLE_LA57|DISABLE_UMIP| \
 			 DISABLE_ENQCMD|DISABLE_SHSTK)
 #define DISABLED_MASK17	0
-#define DISABLED_MASK18	0
+#define DISABLED_MASK18	(DISABLE_IBT)
 #define DISABLED_MASK19	0
 #define DISABLED_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != 20)
 
-- 
2.21.0