[PATCHv16 03/17] x86: CPUID and CR3/CR4 flags for Linear Address Masking

[Kirill A. Shutemov]

Enumerate Linear Address Masking and provide defines for CR3 and CR4
flags.

The new CONFIG_ADDRESS_MASKING option enables the feature support in
kernel.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Alexander Potapenko <glider@xxxxxxxxxx>
---
 arch/x86/Kconfig                            | 11 +++++++++++
 arch/x86/include/asm/cpufeatures.h          |  1 +
 arch/x86/include/asm/processor-flags.h      |  2 ++
 arch/x86/include/uapi/asm/processor-flags.h |  6 ++++++
 4 files changed, 20 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a825bf031f49..aa9f73f5d670 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2290,6 +2290,17 @@ config RANDOMIZE_MEMORY_PHYSICAL_PADDING
 
 	  If unsure, leave at the default value.
 
+config ADDRESS_MASKING
+	bool "Linear Address Masking support"
+	depends on X86_64
+	help
+	  Linear Address Masking (LAM) modifies the checking that is applied
+	  to 64-bit linear addresses, allowing software to use of the
+	  untranslated address bits for metadata.
+
+	  The capability can be used for efficient address sanitizers (ASAN)
+	  implementation and for optimizations in JITs.
+
 config HOTPLUG_CPU
 	def_bool y
 	depends on SMP
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 73c9672c123b..353b054812de 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -321,6 +321,7 @@
 #define X86_FEATURE_LKGS		(12*32+18) /* "" Load "kernel" (userspace) GS */
 #define X86_FEATURE_AMX_FP16		(12*32+21) /* "" AMX fp16 Support */
 #define X86_FEATURE_AVX_IFMA            (12*32+23) /* "" Support for VPMADD52[H,L]UQ */
+#define X86_FEATURE_LAM			(12*32+26) /* Linear Address Masking */
 
 /* AMD-defined CPU features, CPUID level 0x80000008 (EBX), word 13 */
 #define X86_FEATURE_CLZERO		(13*32+ 0) /* CLZERO instruction */
diff --git a/arch/x86/include/asm/processor-flags.h b/arch/x86/include/asm/processor-flags.h
index a7f3d9100adb..d8cccadc83a6 100644
--- a/arch/x86/include/asm/processor-flags.h
+++ b/arch/x86/include/asm/processor-flags.h
@@ -28,6 +28,8 @@
  * On systems with SME, one bit (in a variable position!) is stolen to indicate
  * that the top-level paging structure is encrypted.
  *
+ * On systemms with LAM, bits 61 and 62 are used to indicate LAM mode.
+ *
  * All of the remaining bits indicate the physical address of the top-level
  * paging structure.
  *
diff --git a/arch/x86/include/uapi/asm/processor-flags.h b/arch/x86/include/uapi/asm/processor-flags.h
index c47cc7f2feeb..d898432947ff 100644
--- a/arch/x86/include/uapi/asm/processor-flags.h
+++ b/arch/x86/include/uapi/asm/processor-flags.h
@@ -82,6 +82,10 @@
 #define X86_CR3_PCID_BITS	12
 #define X86_CR3_PCID_MASK	(_AC((1UL << X86_CR3_PCID_BITS) - 1, UL))
 
+#define X86_CR3_LAM_U57_BIT	61 /* Activate LAM for userspace, 62:57 bits masked */
+#define X86_CR3_LAM_U57		_BITULL(X86_CR3_LAM_U57_BIT)
+#define X86_CR3_LAM_U48_BIT	62 /* Activate LAM for userspace, 62:48 bits masked */
+#define X86_CR3_LAM_U48		_BITULL(X86_CR3_LAM_U48_BIT)
 #define X86_CR3_PCID_NOFLUSH_BIT 63 /* Preserve old PCID */
 #define X86_CR3_PCID_NOFLUSH    _BITULL(X86_CR3_PCID_NOFLUSH_BIT)
 
@@ -132,6 +136,8 @@
 #define X86_CR4_PKE		_BITUL(X86_CR4_PKE_BIT)
 #define X86_CR4_CET_BIT		23 /* enable Control-flow Enforcement Technology */
 #define X86_CR4_CET		_BITUL(X86_CR4_CET_BIT)
+#define X86_CR4_LAM_SUP_BIT	28 /* LAM for supervisor pointers */
+#define X86_CR4_LAM_SUP		_BITUL(X86_CR4_LAM_SUP_BIT)
 
 /*
  * x86-64 Task Priority Register, CR8
-- 
2.39.2