From a111b7c0f20e13b54df2fa959b3dc0bdf1925ae6 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 12 Apr 2019 15:39:32 -0500 Subject: [PATCH] arm64/speculation: Support 'mitigations=' cmdline option Configure arm64 runtime CPU speculation bug mitigations in accordance with the 'mitigations=' cmdline option. This affects Meltdown, Spectre v2, and Speculative Store Bypass. The default behavior is unchanged. Signed-off-by: Josh Poimboeuf [will: reorder checks so KASLR implies KPTI and SSBS is affected by cmdline] Signed-off-by: Will Deacon --- Documentation/admin-guide/kernel-parameters.txt | 8 +++++--- arch/arm64/kernel/cpu_errata.c | 6 +++++- arch/arm64/kernel/cpufeature.c | 8 +++++++- 3 files changed, 17 insertions(+), 5 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 6a929258fa..ce226f7 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2545,8 +2545,8 @@ http://repo.or.cz/w/linux-2.6/mini2440.git mitigations= - [X86,PPC,S390] Control optional mitigations for CPU - vulnerabilities. This is a set of curated, + [X86,PPC,S390,ARM64] Control optional mitigations for + CPU vulnerabilities. This is a set of curated, arch-independent options, each of which is an aggregation of existing arch-specific options. @@ -2555,11 +2555,13 @@ improves system performance, but it may also expose users to several CPU vulnerabilities. Equivalent to: nopti [X86,PPC] + kpti=0 [ARM64] nospectre_v1 [PPC] nobp=0 [S390] - nospectre_v2 [X86,PPC,S390] + nospectre_v2 [X86,PPC,S390,ARM64] spectre_v2_user=off [X86] spec_store_bypass_disable=off [X86,PPC] + ssbd=force-off [ARM64] l1tf=off [X86] auto (default) diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index 44ef98b..1b9ce0f 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -386,6 +387,9 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry, WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible()); + if (cpu_mitigations_off()) + ssbd_state = ARM64_SSBD_FORCE_DISABLE; + /* delay setting __ssb_safe until we get a firmware response */ if (is_midr_in_range_list(read_cpuid_id(), entry->midr_range_list)) this_cpu_safe = true; @@ -589,7 +593,7 @@ check_branch_predictor(const struct arm64_cpu_capabilities *entry, int scope) } /* forced off */ - if (__nospectre_v2) { + if (__nospectre_v2 || cpu_mitigations_off()) { pr_info_once("spectrev2 mitigation disabled by command line option\n"); __hardenbp_enab = false; return false; diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 703ee85..f3b32d8 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #include #include @@ -966,7 +967,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, MIDR_ALL_VERSIONS(MIDR_HISI_TSV110), { /* sentinel */ } }; - char const *str = "command line option"; + char const *str = "kpti command line option"; bool meltdown_safe; meltdown_safe = is_midr_in_range_list(read_cpuid_id(), kpti_safe_list); @@ -996,6 +997,11 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, } } + if (cpu_mitigations_off() && !__kpti_forced) { + str = "mitigations=off"; + __kpti_forced = -1; + } + if (!IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0)) { pr_info_once("kernel page table isolation disabled by kernel configuration\n"); return false; -- 2.7.4