From: Jeremy Linton jeremy.linton@arm.com
[ Upstream commit d2532e27b5638bb2e2dd52b80b7ea2ec65135377 ]
Track whether all the cores in the machine are vulnerable to Spectre-v2, and whether all the vulnerable cores have been mitigated. We then expose this information to userspace via sysfs.
Signed-off-by: Jeremy Linton jeremy.linton@arm.com Reviewed-by: Andre Przywara andre.przywara@arm.com Reviewed-by: Catalin Marinas catalin.marinas@arm.com Tested-by: Stefan Wahren stefan.wahren@i2se.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org --- arch/arm64/kernel/cpu_errata.c | 27 +++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index 96b0319dd0d6..b29d0b3b18b2 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -480,6 +480,10 @@ has_cortex_a76_erratum_1463225(const struct arm64_cpu_capabilities *entry, .type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM, \ CAP_MIDR_RANGE_LIST(midr_list)
+/* Track overall mitigation state. We are only mitigated if all cores are ok */ +static bool __hardenbp_enab = true; +static bool __spectrev2_safe = true; + /* * Generic helper for handling capabilties with multiple (match,enable) pairs * of call backs, sharing the same capability bit. @@ -522,6 +526,10 @@ static const struct midr_range spectre_v2_safe_list[] = { { /* sentinel */ } };
+/* + * Track overall bp hardening for all heterogeneous cores in the machine. + * We are only considered "safe" if all booted cores are known safe. + */ static bool __maybe_unused check_branch_predictor(const struct arm64_cpu_capabilities *entry, int scope) { @@ -543,6 +551,8 @@ check_branch_predictor(const struct arm64_cpu_capabilities *entry, int scope) if (!need_wa) return false;
+ __spectrev2_safe = false; + if (!IS_ENABLED(CONFIG_HARDEN_BRANCH_PREDICTOR)) { pr_warn_once("spectrev2 mitigation disabled by kernel configuration\n"); __hardenbp_enab = false; @@ -552,11 +562,14 @@ check_branch_predictor(const struct arm64_cpu_capabilities *entry, int scope) /* forced off */ if (__nospectre_v2) { pr_info_once("spectrev2 mitigation disabled by command line option\n"); + __hardenbp_enab = false; return false; }
- if (need_wa < 0) + if (need_wa < 0) { pr_warn_once("ARM_SMCCC_ARCH_WORKAROUND_1 missing from firmware\n"); + __hardenbp_enab = false; + }
return (need_wa > 0); } @@ -753,3 +766,15 @@ ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, { return sprintf(buf, "Mitigation: __user pointer sanitization\n"); } + +ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, + char *buf) +{ + if (__spectrev2_safe) + return sprintf(buf, "Not affected\n"); + + if (__hardenbp_enab) + return sprintf(buf, "Mitigation: Branch predictor hardening\n"); + + return sprintf(buf, "Vulnerable\n"); +}