diff options
| -rw-r--r-- | arch/arm64/include/asm/mmu.h | 62 | ||||
| -rw-r--r-- | arch/arm64/kernel/cpufeature.c | 2 |
2 files changed, 46 insertions, 18 deletions
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h index f217e3292919..2a93d34cc0ca 100644 --- a/arch/arm64/include/asm/mmu.h +++ b/arch/arm64/include/asm/mmu.h @@ -35,10 +35,46 @@ static inline bool arm64_kernel_unmapped_at_el0(void) cpus_have_const_cap(ARM64_UNMAP_KERNEL_AT_EL0); } -static inline bool arm64_kernel_use_ng_mappings(void) +/* + * This check is triggered during the early boot before the cpufeature + * is initialised. Checking the status on the local CPU allows the boot + * CPU to detect the need for non-global mappings and thus avoiding a + * pagetable re-write after all the CPUs are booted. This check will be + * anyway run on individual CPUs, allowing us to get the consistent + * state once the SMP CPUs are up and thus make the switch to non-global + * mappings if required. + */ +static inline bool kaslr_requires_kpti(void) { bool tx1_bug; + if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE)) + return false; + + /* + * Systems affected by Cavium erratum 24756 are incompatible + * with KPTI. + */ + if (!IS_ENABLED(CONFIG_CAVIUM_ERRATUM_27456)) { + tx1_bug = false; +#ifndef MODULE + } else if (!static_branch_likely(&arm64_const_caps_ready)) { + extern const struct midr_range cavium_erratum_27456_cpus[]; + + tx1_bug = is_midr_in_range_list(read_cpuid_id(), + cavium_erratum_27456_cpus); +#endif + } else { + tx1_bug = __cpus_have_const_cap(ARM64_WORKAROUND_CAVIUM_27456); + } + if (tx1_bug) + return false; + + return kaslr_offset() > 0; +} + +static inline bool arm64_kernel_use_ng_mappings(void) +{ /* What's a kpti? Use global mappings if we don't know. */ if (!IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0)) return false; @@ -52,29 +88,21 @@ static inline bool arm64_kernel_use_ng_mappings(void) if (arm64_kernel_unmapped_at_el0()) return true; - if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE)) + /* + * Once we are far enough into boot for capabilities to be + * ready we will have confirmed if we are using non-global + * mappings so don't need to consider anything else here. + */ + if (static_branch_likely(&arm64_const_caps_ready)) return false; /* * KASLR is enabled so we're going to be enabling kpti on non-broken * CPUs regardless of their susceptibility to Meltdown. Rather * than force everybody to go through the G -> nG dance later on, - * just put down non-global mappings from the beginning. + * just put down non-global mappings from the beginning */ - if (!IS_ENABLED(CONFIG_CAVIUM_ERRATUM_27456)) { - tx1_bug = false; -#ifndef MODULE - } else if (!static_branch_likely(&arm64_const_caps_ready)) { - extern const struct midr_range cavium_erratum_27456_cpus[]; - - tx1_bug = is_midr_in_range_list(read_cpuid_id(), - cavium_erratum_27456_cpus); -#endif - } else { - tx1_bug = __cpus_have_const_cap(ARM64_WORKAROUND_CAVIUM_27456); - } - - return !tx1_bug && kaslr_offset() > 0; + return kaslr_requires_kpti(); } typedef void (*bp_hardening_cb_t)(void); diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 9d578e720168..88aa5ab02926 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1009,7 +1009,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, } /* Useful for KASLR robustness */ - if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_offset() > 0) { + if (kaslr_requires_kpti()) { if (!__kpti_forced) { str = "KASLR"; __kpti_forced = 1; |