From: Jeremy Linton <jeremy.linton@arm.com>
Date: Mon, 15 Apr 2019 16:21:26 -0500
Subject: arm64: add sysfs vulnerability show for spectre-v2
Git-commit: d2532e27b5638bb2e2dd52b80b7ea2ec65135377
Patch-mainline: v5.2-rc1
References: bsc#1174547
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: Mian Yousaf Kaukab <ykaukab@suse.de>
---
arch/arm64/kernel/cpu_errata.c | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -507,6 +507,10 @@ multi_entry_cap_matches(const struct arm
return false;
}
+/* Track overall mitigation state. We are only mitigated if all cores are ok */
+static bool __hardenbp_enab = true;
+static bool __spectrev2_safe = true;
+
/*
* Take appropriate action for all matching entries in the shared capability
* entry.
@@ -532,6 +536,10 @@ static const struct midr_range spectre_v
{ /* 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)
{
@@ -553,6 +561,8 @@ check_branch_predictor(const struct arm6
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;
@@ -562,11 +572,14 @@ check_branch_predictor(const struct arm6
/* 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);
}
@@ -736,3 +749,15 @@ ssize_t cpu_show_spectre_v1(struct devic
{
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");
+}