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Message-Id: <20230110055204.3227669-3-yian.chen@intel.com>
Date: Mon, 9 Jan 2023 21:51:59 -0800
From: Yian Chen <yian.chen@...el.com>
To: linux-kernel@...r.kernel.org, x86@...nel.org,
Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Ravi Shankar <ravi.v.shankar@...el.com>,
Tony Luck <tony.luck@...el.com>,
Sohil Mehta <sohil.mehta@...el.com>,
Paul Lai <paul.c.lai@...el.com>,
Yian Chen <yian.chen@...el.com>
Subject: [PATCH 2/7] x86: Add CONFIG option X86_LASS
LASS is an Intel x86-64 only feature. Add CONFIG
option X86_LASS and flag DISABLE_LASS to choose
opt-in/out the feature from kernel binary.
CONFIG_X86_LASS is enabled by default because it
is a security feature which should have little
to no overhead or side effects. If any issues are
found with specific use cases, the CONFIG option
makes it easy to disable.
Signed-off-by: Yian Chen <yian.chen@...el.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
---
arch/x86/Kconfig | 10 ++++++++++
arch/x86/include/asm/disabled-features.h | 8 +++++++-
tools/arch/x86/include/asm/disabled-features.h | 8 +++++++-
3 files changed, 24 insertions(+), 2 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 3604074a878b..38b1497afd75 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1826,6 +1826,16 @@ config ARCH_USES_PG_UNCACHED
def_bool y
depends on X86_PAT
+config X86_LASS
+ def_bool y
+ prompt "Linear Address Space Separation"
+ depends on X86_64 && CPU_SUP_INTEL
+ help
+ Linear Address Space Separation (LASS) is a processor
+ feature that mitigates address space layout probes.
+
+ if unsure, say Y.
+
config X86_UMIP
def_bool y
prompt "User Mode Instruction Prevention" if EXPERT
diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index c44b56f7ffba..0cad37d59e0f 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -16,6 +16,12 @@
# define DISABLE_UMIP (1<<(X86_FEATURE_UMIP & 31))
#endif
+#ifdef CONFIG_X86_LASS
+# define DISABLE_LASS 0
+#else
+# define DISABLE_LASS (1<<(X86_FEATURE_LASS & 31))
+#endif
+
#ifdef CONFIG_X86_64
# define DISABLE_VME (1<<(X86_FEATURE_VME & 31))
# define DISABLE_K6_MTRR (1<<(X86_FEATURE_K6_MTRR & 31))
@@ -115,7 +121,7 @@
#define DISABLED_MASK10 0
#define DISABLED_MASK11 (DISABLE_RETPOLINE|DISABLE_RETHUNK|DISABLE_UNRET| \
DISABLE_CALL_DEPTH_TRACKING)
-#define DISABLED_MASK12 0
+#define DISABLED_MASK12 (DISABLE_LASS)
#define DISABLED_MASK13 0
#define DISABLED_MASK14 0
#define DISABLED_MASK15 0
diff --git a/tools/arch/x86/include/asm/disabled-features.h b/tools/arch/x86/include/asm/disabled-features.h
index c44b56f7ffba..0cad37d59e0f 100644
--- a/tools/arch/x86/include/asm/disabled-features.h
+++ b/tools/arch/x86/include/asm/disabled-features.h
@@ -16,6 +16,12 @@
# define DISABLE_UMIP (1<<(X86_FEATURE_UMIP & 31))
#endif
+#ifdef CONFIG_X86_LASS
+# define DISABLE_LASS 0
+#else
+# define DISABLE_LASS (1<<(X86_FEATURE_LASS & 31))
+#endif
+
#ifdef CONFIG_X86_64
# define DISABLE_VME (1<<(X86_FEATURE_VME & 31))
# define DISABLE_K6_MTRR (1<<(X86_FEATURE_K6_MTRR & 31))
@@ -115,7 +121,7 @@
#define DISABLED_MASK10 0
#define DISABLED_MASK11 (DISABLE_RETPOLINE|DISABLE_RETHUNK|DISABLE_UNRET| \
DISABLE_CALL_DEPTH_TRACKING)
-#define DISABLED_MASK12 0
+#define DISABLED_MASK12 (DISABLE_LASS)
#define DISABLED_MASK13 0
#define DISABLED_MASK14 0
#define DISABLED_MASK15 0
--
2.34.1
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