[PATCH v7 05/27] x86/fpu/xstate: Add XSAVES system states for shadow stack

[Yu-cheng Yu]

Intel Control-flow Enforcement Technology (CET) introduces the
following MSRs.

    MSR_IA32_U_CET (user-mode CET settings),
    MSR_IA32_PL3_SSP (user-mode shadow stack),
    MSR_IA32_PL0_SSP (kernel-mode shadow stack),
    MSR_IA32_PL1_SSP (Privilege Level 1 shadow stack),
    MSR_IA32_PL2_SSP (Privilege Level 2 shadow stack).

Introduce them into XSAVES system states.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
---
 arch/x86/include/asm/fpu/types.h            | 22 +++++++++++++++++++++
 arch/x86/include/asm/fpu/xstate.h           |  4 +++-
 arch/x86/include/uapi/asm/processor-flags.h |  2 ++
 arch/x86/kernel/fpu/xstate.c                | 10 ++++++++++
 4 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index f098f6cab94b..d7ef4d9c7ad5 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -114,6 +114,9 @@ enum xfeature {
 	XFEATURE_Hi16_ZMM,
 	XFEATURE_PT_UNIMPLEMENTED_SO_FAR,
 	XFEATURE_PKRU,
+	XFEATURE_RESERVED,
+	XFEATURE_CET_USER,
+	XFEATURE_CET_KERNEL,
 
 	XFEATURE_MAX,
 };
@@ -128,6 +131,8 @@ enum xfeature {
 #define XFEATURE_MASK_Hi16_ZMM		(1 << XFEATURE_Hi16_ZMM)
 #define XFEATURE_MASK_PT		(1 << XFEATURE_PT_UNIMPLEMENTED_SO_FAR)
 #define XFEATURE_MASK_PKRU		(1 << XFEATURE_PKRU)
+#define XFEATURE_MASK_CET_USER		(1 << XFEATURE_CET_USER)
+#define XFEATURE_MASK_CET_KERNEL	(1 << XFEATURE_CET_KERNEL)
 
 #define XFEATURE_MASK_FPSSE		(XFEATURE_MASK_FP | XFEATURE_MASK_SSE)
 #define XFEATURE_MASK_AVX512		(XFEATURE_MASK_OPMASK \
@@ -229,6 +234,23 @@ struct pkru_state {
 	u32				pad;
 } __packed;
 
+/*
+ * State component 11 is Control-flow Enforcement user states
+ */
+struct cet_user_state {
+	u64 user_cet;			/* user control-flow settings */
+	u64 user_ssp;			/* user shadow stack pointer */
+};
+
+/*
+ * State component 12 is Control-flow Enforcement kernel states
+ */
+struct cet_kernel_state {
+	u64 kernel_ssp;			/* kernel shadow stack */
+	u64 pl1_ssp;			/* privilege level 1 shadow stack */
+	u64 pl2_ssp;			/* privilege level 2 shadow stack */
+};
+
 struct xstate_header {
 	u64				xfeatures;
 	u64				xcomp_bv;
diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index 2ec19415c58e..9ac8a81e851d 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -30,7 +30,9 @@
 				  XFEATURE_MASK_Hi16_ZMM | \
 				  XFEATURE_MASK_PKRU | \
 				  XFEATURE_MASK_BNDREGS | \
-				  XFEATURE_MASK_BNDCSR)
+				  XFEATURE_MASK_BNDCSR | \
+				  XFEATURE_MASK_CET_USER | \
+				  XFEATURE_MASK_CET_KERNEL)
 
 #ifdef CONFIG_X86_64
 #define REX_PREFIX	"0x48, "
diff --git a/arch/x86/include/uapi/asm/processor-flags.h b/arch/x86/include/uapi/asm/processor-flags.h
index bcba3c643e63..a8df907e8017 100644
--- a/arch/x86/include/uapi/asm/processor-flags.h
+++ b/arch/x86/include/uapi/asm/processor-flags.h
@@ -130,6 +130,8 @@
 #define X86_CR4_SMAP		_BITUL(X86_CR4_SMAP_BIT)
 #define X86_CR4_PKE_BIT		22 /* enable Protection Keys support */
 #define X86_CR4_PKE		_BITUL(X86_CR4_PKE_BIT)
+#define X86_CR4_CET_BIT		23 /* enable Control-flow Enforcement */
+#define X86_CR4_CET		_BITUL(X86_CR4_CET_BIT)
 
 /*
  * x86-64 Task Priority Register, CR8
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 6b453455a4f0..7f99878111d7 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -36,6 +36,9 @@ static const char *xfeature_names[] =
 	"Processor Trace (unused)"	,
 	"Protection Keys User registers",
 	"unknown xstate feature"	,
+	"Control-flow User registers"	,
+	"Control-flow Kernel registers"	,
+	"unknown xstate feature"	,
 };
 
 static short xsave_cpuid_features[] __initdata = {
@@ -49,6 +52,9 @@ static short xsave_cpuid_features[] __initdata = {
 	X86_FEATURE_AVX512F,
 	X86_FEATURE_INTEL_PT,
 	X86_FEATURE_PKU,
+	0,		   /* Unused */
+	X86_FEATURE_SHSTK, /* XFEATURE_CET_USER */
+	X86_FEATURE_SHSTK, /* XFEATURE_CET_KERNEL */
 };
 
 /*
@@ -320,6 +326,8 @@ static void __init print_xstate_features(void)
 	print_xstate_feature(XFEATURE_MASK_ZMM_Hi256);
 	print_xstate_feature(XFEATURE_MASK_Hi16_ZMM);
 	print_xstate_feature(XFEATURE_MASK_PKRU);
+	print_xstate_feature(XFEATURE_MASK_CET_USER);
+	print_xstate_feature(XFEATURE_MASK_CET_KERNEL);
 }
 
 /*
@@ -566,6 +574,8 @@ static void check_xstate_against_struct(int nr)
 	XCHECK_SZ(sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state);
 	XCHECK_SZ(sz, nr, XFEATURE_Hi16_ZMM,  struct avx_512_hi16_state);
 	XCHECK_SZ(sz, nr, XFEATURE_PKRU,      struct pkru_state);
+	XCHECK_SZ(sz, nr, XFEATURE_CET_USER,   struct cet_user_state);
+	XCHECK_SZ(sz, nr, XFEATURE_CET_KERNEL, struct cet_kernel_state);
 
 	/*
 	 * Make *SURE* to add any feature numbers in below if
-- 
2.17.1