From: Kristina Martsenko <kristina.martsenko@arm.com> The Arm v8.8 extension adds a new control FEAT_TIDCP1 that allows the kernel to disable all implementation-defined system registers and instructions in userspace. This can improve robustness against covert channels between processes, for example in cases where the firmware or hardware didn't disable that functionality by default. The kernel does not currently support any implementation-defined features, as there are no hwcaps for any such features, so disable all imp-def features unconditionally. Any use of imp-def instructions will result in a SIGILL being delivered to the process (same as for undefined instructions). Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com> Link: https://lore.kernel.org/r/20220622115424.683520-1-kristina.martsenko@arm.com Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Qi Xi <xiqi2@huawei.com> --- arch/arm64/include/asm/sysreg.h | 4 ++++ arch/arm64/kernel/cpufeature.c | 18 ++++++++++++++++++ arch/arm64/tools/cpucaps | 1 + 3 files changed, 23 insertions(+) diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h index 3cafd4ef0c74..b8d00be796cf 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -907,6 +907,7 @@ /* id_aa64mmfr1 */ #define ID_AA64MMFR1_ECBHB_SHIFT 60 +#define ID_AA64MMFR1_TIDCP1_SHIFT 52 #define ID_AA64MMFR1_AFP_SHIFT 44 #define ID_AA64MMFR1_ETS_SHIFT 36 #define ID_AA64MMFR1_TWED_SHIFT 32 @@ -922,6 +923,9 @@ #define ID_AA64MMFR1_VMIDBITS_8 0 #define ID_AA64MMFR1_VMIDBITS_16 2 +#define ID_AA64MMFR1_TIDCP1_NI 0 +#define ID_AA64MMFR1_TIDCP1_IMP 1 + /* id_aa64mmfr2 */ #define ID_AA64MMFR2_E0PD_SHIFT 60 #define ID_AA64MMFR2_EVT_SHIFT 56 diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 433f95c7bb94..e0b79f932a5f 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -337,6 +337,7 @@ static const struct arm64_ftr_bits ftr_id_aa64mmfr0[] = { }; static const struct arm64_ftr_bits ftr_id_aa64mmfr1[] = { + ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_TIDCP1_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_AFP_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_ETS_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_TWED_SHIFT, 4, 0), @@ -1943,6 +1944,11 @@ static bool is_kvm_protected_mode(const struct arm64_cpu_capabilities *entry, in } #endif /* CONFIG_KVM */ +static void cpu_trap_el0_impdef(const struct arm64_cpu_capabilities *__unused) +{ + sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_TIDCP); +} + /* Internal helper functions to match cpu capability type */ static bool cpucap_late_cpu_optional(const struct arm64_cpu_capabilities *cap) @@ -2385,6 +2391,18 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .matches = has_cpuid_feature, .min_field_value = 1, }, + { + .desc = "Trap EL0 IMPLEMENTATION DEFINED functionality", + .capability = ARM64_HAS_TIDCP1, + .type = ARM64_CPUCAP_SYSTEM_FEATURE, + .sys_reg = SYS_ID_AA64MMFR1_EL1, + .sign = FTR_UNSIGNED, + .field_pos = ID_AA64MMFR1_TIDCP1_SHIFT, + .field_width = 4, + .min_field_value = ID_AA64MMFR1_TIDCP1_IMP, + .matches = has_cpuid_feature, + .cpu_enable = cpu_trap_el0_impdef, + }, {}, }; diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps index a590cabe890c..c44cd3b076e9 100644 --- a/arch/arm64/tools/cpucaps +++ b/arch/arm64/tools/cpucaps @@ -34,6 +34,7 @@ HAS_RNG HAS_SB HAS_STAGE2_FWB HAS_SYSREG_GIC_CPUIF +HAS_TIDCP1 HAS_TLB_RANGE HAS_VIRT_HOST_EXTN HW_DBM -- 2.33.0