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 <yu-cheng.yu@xxxxxxxxx>
---
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 | 40 ++++++++++++++++++++-
4 files changed, 46 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index c9f6d62da463..16d445e6fa6b 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 b22ba3db6b25..e4d5ca2ba5c6 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -65,9 +65,11 @@
#ifdef CONFIG_X86_CET_USER
#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
/*
@@ -76,7 +78,8 @@
#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 35ad8480c464..03c367f79adc 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
@@ -895,6 +903,12 @@ static void init_speculation_control(struct cpuinfo_x86 *c)
}
}
+static void init_cet_features(struct cpuinfo_x86 *c)
+{
+ if (cpu_has(c, X86_FEATURE_SHSTK) || cpu_has(c, X86_FEATURE_IBT))
+ set_cpu_cap(c, X86_FEATURE_CET);
+}
+
void get_cpu_cap(struct cpuinfo_x86 *c)
{
u32 eax, ebx, ecx, edx;
@@ -960,6 +974,7 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
if (c->extended_cpuid_level >= 0x8000000a)
c->x86_capability[CPUID_8000_000A_EDX] = cpuid_edx(0x8000000a);
+ init_cet_features(c);
init_scattered_cpuid_features(c);
init_speculation_control(c);
@@ -1221,6 +1236,15 @@ static void detect_nopl(void)
#endif
}
+static void adjust_combined_cpu_features(void)
+{
+#ifdef CONFIG_X86_CET_USER
+ if (test_bit(X86_FEATURE_SHSTK, (unsigned long *)cpu_caps_cleared) &&
+ test_bit(X86_FEATURE_IBT, (unsigned long *)cpu_caps_cleared))
+ setup_clear_cpu_cap(X86_FEATURE_CET);
+#endif
+}
+
/*
* We parse cpu parameters early because fpu__init_system() is executed
* before parse_early_param().
@@ -1252,9 +1276,19 @@ static void __init cpu_parse_early_param(void)
if (cmdline_find_option_bool(boot_command_line, "noxsaves"))
setup_clear_cpu_cap(X86_FEATURE_XSAVES);
+ /*
+ * CET states are XSAVES states and options must be parsed early.
+ */
+#ifdef CONFIG_X86_CET_USER
+ 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);
+#endif
+
arglen = cmdline_find_option(boot_command_line, "clearcpuid", arg, sizeof(arg));
if (arglen <= 0)
- return;
+ goto done;
pr_info("Clearing CPUID bits:");
do {
@@ -1272,6 +1306,9 @@ static void __init cpu_parse_early_param(void)
}
} while (res == 2);
pr_cont("\n");
+
+done:
+ adjust_combined_cpu_features();
}
/*
@@ -1591,6 +1628,7 @@ 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
--
2.21.0
