From mboxrd@z Thu Jan 1 00:00:00 1970 From: mlangsdo@redhat.com (Mark Langsdorf) Date: Thu, 24 May 2018 14:09:31 -0500 Subject: [PATCH 3/4] arm64: cpufeature: add debugfs interface for KPTI In-Reply-To: <20180524190932.32118-1-mlangsdo@redhat.com> References: <20180524190932.32118-1-mlangsdo@redhat.com> Message-ID: <20180524190932.32118-4-mlangsdo@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Add a debugfs interface to check if KPTI is enabled or disabled: cat /sys/kernel/debug/arm64/pti_enabled Slightly rework unmap_kernel_at_el0 logic to simplify calculating if KPTI is enabled. Signed-off-by: Mark Langsdorf --- arch/arm64/kernel/cpufeature.c | 30 ++++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 7c5d8712..697a6ef 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -24,6 +24,7 @@ #include #include #include +#include #include #include #include @@ -860,6 +861,7 @@ static bool has_cache_dic(const struct arm64_cpu_capabilities *entry, #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ +static bool __pti_enabled; static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, int scope) @@ -884,21 +886,21 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, /* Forced? */ if (__kpti_forced) { + __pti_enabled = __kpti_forced > 0; pr_info_once("kernel page table isolation forced %s by %s\n", - __kpti_forced > 0 ? "ON" : "OFF", str); - return __kpti_forced > 0; + __pti_enabled ? "ON" : "OFF", str); } - /* Useful for KASLR robustness */ - if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) - return true; - + else if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) + __pti_enabled = true; /* Don't force KPTI for CPUs that are not vulnerable */ - if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list)) - return false; - + else if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list)) + __pti_enabled = false; /* Defer to CPU feature registers */ - return !has_cpuid_feature(entry, scope); + else + __pti_enabled = !has_cpuid_feature(entry, scope); + + return __pti_enabled; } static void @@ -947,6 +949,14 @@ static int __init force_nokpti(char *arg) return 0; } early_param("nopti", force_nokpti); + +static int __init create_kpti_enabled(void) +{ + debugfs_create_bool("pti_enabled", S_IRUSR, + arch_debugfs_dir, &__pti_enabled); + return 0; +} +late_initcall(create_kpti_enabled); #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ #ifdef CONFIG_ARM64_HW_AFDBM -- 2.9.5