[v23,04/28] x86/cpufeatures: Introduce X86_FEATURE_CET and setup functions

Commit Message

Yu-cheng Yu March 16, 2021, 3:10 p.m. UTC

Introduce a software-defined X86_FEATURE_CET, which indicates either Shadow
Stack or Indirect Branch Tracking (or both) is present.  Also introduce
related cpu init/setup functions.

Signed-off-by: Yu-cheng Yu <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
---
 arch/x86/include/asm/cpufeatures.h          |  2 +-
 arch/x86/include/asm/disabled-features.h    |  5 ++++-
 arch/x86/include/uapi/asm/processor-flags.h |  2 ++
 arch/x86/kernel/cpu/common.c                | 14 ++++++++++++++
 arch/x86/kernel/cpu/intel.c                 |  3 +++
 5 files changed, 24 insertions(+), 2 deletions(-)

Patch

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index bf861fc89fef..d771e62677de 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -108,7 +108,7 @@ 
 #define X86_FEATURE_EXTD_APICID		( 3*32+26) /* Extended APICID (8 bits) */
 #define X86_FEATURE_AMD_DCM		( 3*32+27) /* AMD multi-node processor */
 #define X86_FEATURE_APERFMPERF		( 3*32+28) /* P-State hardware coordination feedback capability (APERF/MPERF MSRs) */
-/* free					( 3*32+29) */
+#define X86_FEATURE_CET			( 3*32+29) /* Control-flow enforcement */
 #define X86_FEATURE_NONSTOP_TSC_S3	( 3*32+30) /* TSC doesn't stop in S3 state */
 #define X86_FEATURE_TSC_KNOWN_FREQ	( 3*32+31) /* TSC has known frequency */
 
diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index 914b353fe75c..b9a73b882cf9 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -71,9 +71,11 @@ 
 #ifdef CONFIG_X86_CET
 #define DISABLE_SHSTK	0
 #define DISABLE_IBT	0
+#define DISABLE_CET	0
 #else
 #define DISABLE_SHSTK	(1 << (X86_FEATURE_SHSTK & 31))
 #define DISABLE_IBT	(1 << (X86_FEATURE_IBT & 31))
+#define DISABLE_CET	(1 << (X86_FEATURE_CET & 31))
 #endif
 
 /*
@@ -82,7 +84,8 @@ 
 #define DISABLED_MASK0	(DISABLE_VME)
 #define DISABLED_MASK1	0
 #define DISABLED_MASK2	0
-#define DISABLED_MASK3	(DISABLE_CYRIX_ARR|DISABLE_CENTAUR_MCR|DISABLE_K6_MTRR)
+#define DISABLED_MASK3	(DISABLE_CYRIX_ARR|DISABLE_CENTAUR_MCR|DISABLE_K6_MTRR| \
+			 DISABLE_CET)
 #define DISABLED_MASK4	(DISABLE_PCID)
 #define DISABLED_MASK5	0
 #define DISABLED_MASK6	0
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/cpu/common.c b/arch/x86/kernel/cpu/common.c
index ab640abe26b6..6bd07727089e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -510,6 +510,14 @@  static __init int setup_disable_pku(char *arg)
 __setup("nopku", setup_disable_pku);
 #endif /* CONFIG_X86_64 */
 
+static __always_inline void setup_cet(struct cpuinfo_x86 *c)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_CET))
+		return;
+
+	cr4_set_bits(X86_CR4_CET);
+}
+
 /*
  * Some CPU features depend on higher CPUID levels, which may not always
  * be available due to CPUID level capping or broken virtualization
@@ -1255,6 +1263,11 @@  static void __init cpu_parse_early_param(void)
 	if (cmdline_find_option_bool(boot_command_line, "noxsaves"))
 		setup_clear_cpu_cap(X86_FEATURE_XSAVES);
 
+	if (cmdline_find_option_bool(boot_command_line, "no_user_shstk"))
+		setup_clear_cpu_cap(X86_FEATURE_SHSTK);
+	if (cmdline_find_option_bool(boot_command_line, "no_user_ibt"))
+		setup_clear_cpu_cap(X86_FEATURE_IBT);
+
 	arglen = cmdline_find_option(boot_command_line, "clearcpuid", arg, sizeof(arg));
 	if (arglen <= 0)
 		return;
@@ -1594,6 +1607,7 @@  static void identify_cpu(struct cpuinfo_x86 *c)
 
 	x86_init_rdrand(c);
 	setup_pku(c);
+	setup_cet(c);
 
 	/*
 	 * Clear/Set all flags overridden by options, need do it
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 0e422a544835..2e11d9555e9b 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -334,6 +334,9 @@  static void early_init_intel(struct cpuinfo_x86 *c)
 
 static void bsp_init_intel(struct cpuinfo_x86 *c)
 {
+	if (cpu_has(c, X86_FEATURE_SHSTK) || cpu_has(c, X86_FEATURE_IBT))
+		setup_force_cpu_cap(X86_FEATURE_CET);
+
 	resctrl_cpu_detect(c);
 }