[PATCH v8 05/27] x86/fpu/xstate: Introduce CET MSR system states

Yu-cheng Yu
2019-08-13T20:52:03Z

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@intel.com>
---
arch/x86/include/asm/fpu/types.h | 22 ++++++++++++++++++
arch/x86/include/asm/fpu/xstate.h | 4 +++-
arch/x86/include/asm/msr-index.h | 18 +++++++++++++++
arch/x86/include/uapi/asm/processor-flags.h | 2 ++
arch/x86/kernel/fpu/xstate.c | 25 +++++++++++++++++++--
5 files changed, 68 insertions(+), 3 deletions(-)

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 970bbd303cfb..ebf5979b21e7 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/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 6b4fc2788078..e06c1e3fde2f 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -848,4 +848,22 @@
#define MSR_VM_IGNNE 0xc0010115
#define MSR_VM_HSAVE_PA 0xc0010117

+/* Control-flow Enforcement Technology MSRs */
+#define MSR_IA32_U_CET 0x6a0 /* user mode cet setting */
+#define MSR_IA32_S_CET 0x6a2 /* kernel mode cet setting */
+#define MSR_IA32_PL0_SSP 0x6a4 /* kernel shstk pointer */
+#define MSR_IA32_PL1_SSP 0x6a5 /* ring-1 shstk pointer */
+#define MSR_IA32_PL2_SSP 0x6a6 /* ring-2 shstk pointer */
+#define MSR_IA32_PL3_SSP 0x6a7 /* user shstk pointer */
+#define MSR_IA32_INT_SSP_TAB 0x6a8 /* exception shstk table */
+
+/* MSR_IA32_U_CET and MSR_IA32_S_CET bits */
+#define MSR_IA32_CET_SHSTK_EN 0x0000000000000001ULL
+#define MSR_IA32_CET_WRSS_EN 0x0000000000000002ULL
+#define MSR_IA32_CET_ENDBR_EN 0x0000000000000004ULL
+#define MSR_IA32_CET_LEG_IW_EN 0x0000000000000008ULL
+#define MSR_IA32_CET_NO_TRACK_EN 0x0000000000000010ULL
+#define MSR_IA32_CET_WAIT_ENDBR 0x00000000000000800UL
+#define MSR_IA32_CET_BITMAP_MASK 0xfffffffffffff000ULL
+
#endif /* _ASM_X86_MSR_INDEX_H */
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 9fbe73c546df..63374bb19066 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -38,6 +38,9 @@ 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 = {
@@ -51,6 +54,9 @@ static short xsave_cpuid_features[] __initdata = {
X86_FEATURE_AVX512F,
X86_FEATURE_INTEL_PT,
X86_FEATURE_PKU,
+ -1, /* Unused */
+ X86_FEATURE_SHSTK, /* XFEATURE_CET_USER */
+ X86_FEATURE_SHSTK, /* XFEATURE_CET_KERNEL */
};

/*
@@ -313,6 +319,8 @@ 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);
}

/*
@@ -559,6 +567,8 @@ 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
@@ -770,8 +780,19 @@ void __init fpu__init_system_xstate(void)
* Clear XSAVE features that are disabled in the normal CPUID.
*/
for (i = 0; i < ARRAY_SIZE(xsave_cpuid_features); i++) {
- if (!boot_cpu_has(xsave_cpuid_features[i]))
- xfeatures_mask_all &= ~BIT_ULL(i);
+ if (xsave_cpuid_features[i] == X86_FEATURE_SHSTK) {
+ /*
+ * X86_FEATURE_SHSTK and X86_FEATURE_IBT share
+ * same states, but can be enabled separately.
+ */
+ if (!boot_cpu_has(X86_FEATURE_SHSTK) &&
+ !boot_cpu_has(X86_FEATURE_IBT))
+ xfeatures_mask_all &= ~BIT_ULL(i);
+ } else {
+ if ((xsave_cpuid_features[i] == -1) ||
+ !boot_cpu_has(xsave_cpuid_features[i]))
+ xfeatures_mask_all &= ~BIT_ULL(i);
+ }
}

xfeatures_mask_all &= SUPPORTED_XFEATURES_MASK;
--
2.17.1