From: Josh Poimboeuf jpoimboe@redhat.com
commit a111b7c0f20e13b54df2fa959b3dc0bdf1925ae6 upstream.
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 jpoimboe@redhat.com [will: reorder checks so KASLR implies KPTI and SSBS is affected by cmdline] Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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(-)
--- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2503,8 +2503,8 @@ 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.
@@ -2513,12 +2513,14 @@ 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_v1 [X86] - 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] mds=off [X86]
--- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -19,6 +19,7 @@ #include <linux/arm-smccc.h> #include <linux/psci.h> #include <linux/types.h> +#include <linux/cpu.h> #include <asm/cpu.h> #include <asm/cputype.h> #include <asm/cpufeature.h> @@ -355,6 +356,9 @@ static bool has_ssbd_mitigation(const st
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; @@ -600,7 +604,7 @@ check_branch_predictor(const struct arm6 }
/* 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; --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -24,6 +24,7 @@ #include <linux/stop_machine.h> #include <linux/types.h> #include <linux/mm.h> +#include <linux/cpu.h> #include <asm/cpu.h> #include <asm/cpufeature.h> #include <asm/cpu_ops.h> @@ -907,7 +908,7 @@ static bool unmap_kernel_at_el0(const st MIDR_ALL_VERSIONS(MIDR_CORTEX_A73), { /* 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); @@ -937,6 +938,11 @@ static bool unmap_kernel_at_el0(const st } }
+ 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;