From: Jeremy Linton jeremy.linton@arm.com
[ Upstream commit 526e065dbca6df0b5a130b84b836b8b3c9f54e21 ]
Return status based on ssbd_state and __ssb_safe. If the mitigation is disabled, or the firmware isn't responding then return the expected machine state based on a whitelist of known good cores.
Given a heterogeneous machine, the overall machine vulnerability defaults to safe but is reset to unsafe when we miss the whitelist and the firmware doesn't explicitly tell us the core is safe. In order to make that work we delay transitioning to vulnerable until we know the firmware isn't responding to avoid a case where we miss the whitelist, but the firmware goes ahead and reports the core is not vulnerable. If all the cores in the machine have SSBS, then __ssb_safe will remain true.
Tested-by: Stefan Wahren stefan.wahren@i2se.com Signed-off-by: Jeremy Linton jeremy.linton@arm.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 | 42 ++++++++++++++++++++ 1 file changed, 42 insertions(+)
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index 809a736f38a9..2898130c3156 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -225,6 +225,7 @@ static int detect_harden_bp_fw(void) DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
int ssbd_state __read_mostly = ARM64_SSBD_KERNEL; +static bool __ssb_safe = true;
static const struct ssbd_options { const char *str; @@ -328,6 +329,7 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry, struct arm_smccc_res res; bool required = true; s32 val; + bool this_cpu_safe = false;
WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
@@ -336,8 +338,14 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry, goto out_printmsg; }
+ /* 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; + if (psci_ops.smccc_version == SMCCC_VERSION_1_0) { ssbd_state = ARM64_SSBD_UNKNOWN; + if (!this_cpu_safe) + __ssb_safe = false; return false; }
@@ -354,6 +362,8 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry,
default: ssbd_state = ARM64_SSBD_UNKNOWN; + if (!this_cpu_safe) + __ssb_safe = false; return false; }
@@ -362,14 +372,18 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry, switch (val) { case SMCCC_RET_NOT_SUPPORTED: ssbd_state = ARM64_SSBD_UNKNOWN; + if (!this_cpu_safe) + __ssb_safe = false; return false;
+ /* machines with mixed mitigation requirements must not return this */ case SMCCC_RET_NOT_REQUIRED: pr_info_once("%s mitigation not required\n", entry->desc); ssbd_state = ARM64_SSBD_MITIGATED; return false;
case SMCCC_RET_SUCCESS: + __ssb_safe = false; required = true; break;
@@ -379,6 +393,8 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry,
default: WARN_ON(1); + if (!this_cpu_safe) + __ssb_safe = false; return false; }
@@ -419,6 +435,14 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry, return required; }
+/* known invulnerable cores */ +static const struct midr_range arm64_ssb_cpus[] = { + MIDR_ALL_VERSIONS(MIDR_CORTEX_A35), + MIDR_ALL_VERSIONS(MIDR_CORTEX_A53), + MIDR_ALL_VERSIONS(MIDR_CORTEX_A55), + {}, +}; + #define CAP_MIDR_RANGE(model, v_min, r_min, v_max, r_max) \ .matches = is_affected_midr_range, \ .midr_range = MIDR_RANGE(model, v_min, r_min, v_max, r_max) @@ -666,6 +690,7 @@ const struct arm64_cpu_capabilities arm64_errata[] = { .type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM, .capability = ARM64_SSBD, .matches = has_ssbd_mitigation, + .midr_range_list = arm64_ssb_cpus, }, { } @@ -688,3 +713,20 @@ ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr,
return sprintf(buf, "Vulnerable\n"); } + +ssize_t cpu_show_spec_store_bypass(struct device *dev, + struct device_attribute *attr, char *buf) +{ + if (__ssb_safe) + return sprintf(buf, "Not affected\n"); + + switch (ssbd_state) { + case ARM64_SSBD_KERNEL: + case ARM64_SSBD_FORCE_ENABLE: + if (IS_ENABLED(CONFIG_ARM64_SSBD)) + return sprintf(buf, + "Mitigation: Speculative Store Bypass disabled via prctl\n"); + } + + return sprintf(buf, "Vulnerable\n"); +}