[PATCH RESEND 4/6] arm64: add sysfs vulnerability show for spectre v2
From: Will Deacon <hidden>
Date: 2018-09-17 13:30:25
Also in:
lkml
On Mon, Aug 27, 2018 at 04:33:08PM +0200, Mian Yousaf Kaukab wrote:
quoted hunk ↗ jump to hunk
Only report mitigation present if hardening callback has been successfully installed. Signed-off-by: Mian Yousaf Kaukab <redacted> --- arch/arm64/kernel/cpu_errata.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-)diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index 92616431ae4e..8469d3be7b15 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c@@ -481,7 +481,8 @@ multi_entry_cap_cpu_enable(const struct arm64_cpu_capabilities *entry) caps->cpu_enable(caps); } -#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR +#if defined(CONFIG_HARDEN_BRANCH_PREDICTOR) || \ + defined(CONFIG_GENERIC_CPU_VULNERABILITIES) /* * List of CPUs where we need to issue a psci call to@@ -712,4 +713,35 @@ 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) +{ + u64 pfr0; + struct bp_hardening_data *data; + + pfr0 = read_cpuid(ID_AA64PFR0_EL1); + if (cpuid_feature_extract_unsigned_field(pfr0, ID_AA64PFR0_CSV2_SHIFT)) + return sprintf(buf, "Not affected\n");
This strikes me as a pretty terrible interface, as it means that the file can return different contents depending on which CPU it was read from on a big/little machine. I think we need to either expose this per-cpu, or expose the value of the system (e.g. if one CPU is vulnerable, we always say vulnerable).
+
+ if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR)) {
+ /*
+ * Hardware is vulnerable. Lets check if bp hardening callback
+ * has been successfully installed
+ */
+ data = arm64_get_bp_hardening_data();Related to the above, but this is accessing per-cpu stuff. Will