On Thu, 21 Mar 2019 18:05:50 -0500 Jeremy Linton <[email protected]> wrote:
Hi, > Display the system vulnerability status. This means that > while its possible to have the mitigation enabled, the > sysfs entry won't indicate that status. This is because > the core ABI doesn't express the concept of mitigation > when the system isn't vulnerable. > > Signed-off-by: Jeremy Linton <[email protected]> > Reviewed-by: Suzuki K Poulose <[email protected]> > Tested-by: Stefan Wahren <[email protected]> Thanks for the changes, look good to me now for all the cases I tried on the logic. Reviewed-by: Andre Przywara <[email protected]> Cheers, Andre. > --- > arch/arm64/kernel/cpufeature.c | 58 ++++++++++++++++++++++++++-------- > 1 file changed, 44 insertions(+), 14 deletions(-) > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 4061de10cea6..6b7e1556460a 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -947,7 +947,7 @@ has_useable_cnp(const struct arm64_cpu_capabilities > *entry, int scope) > return has_cpuid_feature(entry, scope); > } > > -#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 > +static bool __meltdown_safe = true; > static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ > > static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > @@ -967,6 +967,16 @@ static bool unmap_kernel_at_el0(const struct > arm64_cpu_capabilities *entry, > { /* sentinel */ } > }; > char const *str = "command line option"; > + bool meltdown_safe; > + > + meltdown_safe = is_midr_in_range_list(read_cpuid_id(), kpti_safe_list); > + > + /* Defer to CPU feature registers */ > + if (has_cpuid_feature(entry, scope)) > + meltdown_safe = true; > + > + if (!meltdown_safe) > + __meltdown_safe = false; > > /* > * For reasons that aren't entirely clear, enabling KPTI on Cavium > @@ -978,6 +988,19 @@ static bool unmap_kernel_at_el0(const struct > arm64_cpu_capabilities *entry, > __kpti_forced = -1; > } > > + /* Useful for KASLR robustness */ > + if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_offset() > 0) { > + if (!__kpti_forced) { > + str = "KASLR"; > + __kpti_forced = 1; > + } > + } > + > + if (!IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0)) { > + pr_info_once("kernel page table isolation disabled by > CONFIG\n"); > + return false; > + } > + > /* Forced? */ > if (__kpti_forced) { > pr_info_once("kernel page table isolation forced %s by %s\n", > @@ -985,18 +1008,10 @@ static bool unmap_kernel_at_el0(const struct > arm64_cpu_capabilities *entry, > return __kpti_forced > 0; > } > > - /* Useful for KASLR robustness */ > - if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) > - return kaslr_offset() > 0; > - > - /* Don't force KPTI for CPUs that are not vulnerable */ > - if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list)) > - return false; > - > - /* Defer to CPU feature registers */ > - return !has_cpuid_feature(entry, scope); > + return !meltdown_safe; > } > > +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 > static void > kpti_install_ng_mappings(const struct arm64_cpu_capabilities *__unused) > { > @@ -1026,6 +1041,12 @@ kpti_install_ng_mappings(const struct > arm64_cpu_capabilities *__unused) > > return; > } > +#else > +static void > +kpti_install_ng_mappings(const struct arm64_cpu_capabilities *__unused) > +{ > +} > +#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ > > static int __init parse_kpti(char *str) > { > @@ -1039,7 +1060,6 @@ static int __init parse_kpti(char *str) > return 0; > } > early_param("kpti", parse_kpti); > -#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ > > #ifdef CONFIG_ARM64_HW_AFDBM > static inline void __cpu_enable_hw_dbm(void) > @@ -1306,7 +1326,6 @@ static const struct arm64_cpu_capabilities > arm64_features[] = { > .field_pos = ID_AA64PFR0_EL0_SHIFT, > .min_field_value = ID_AA64PFR0_EL0_32BIT_64BIT, > }, > -#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 > { > .desc = "Kernel page table isolation (KPTI)", > .capability = ARM64_UNMAP_KERNEL_AT_EL0, > @@ -1322,7 +1341,6 @@ static const struct arm64_cpu_capabilities > arm64_features[] = { > .matches = unmap_kernel_at_el0, > .cpu_enable = kpti_install_ng_mappings, > }, > -#endif > { > /* FP/SIMD is not implemented */ > .capability = ARM64_HAS_NO_FPSIMD, > @@ -2101,3 +2119,15 @@ static int __init enable_mrs_emulation(void) > } > > core_initcall(enable_mrs_emulation); > + > +ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, > + char *buf) > +{ > + if (__meltdown_safe) > + return sprintf(buf, "Not affected\n"); > + > + if (arm64_kernel_unmapped_at_el0()) > + return sprintf(buf, "Mitigation: KPTI\n"); > + > + return sprintf(buf, "Vulnerable\n"); > +}
