On Mon, Aug 27, 2018 at 04:33:06PM +0200, Mian Yousaf Kaukab wrote:
> Checking CSV3 support directly in case CONFIG_UNMAP_KERNEL_AT_EL0
> is not enabled.
>
> Signed-off-by: Mian Yousaf Kaukab <ykau...@suse.de>
> ---
> arch/arm64/kernel/cpu_errata.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index dec10898d688..996edb4e18ad 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -22,6 +22,7 @@
> #include <asm/cpu.h>
> #include <asm/cputype.h>
> #include <asm/cpufeature.h>
> +#include <asm/mmu.h>
>
> static bool __maybe_unused
> is_affected_midr_range(const struct arm64_cpu_capabilities *entry, int scope)
> @@ -683,3 +684,26 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
> {
> }
> };
> +
> +#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
> +
> +ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr,
> + char *buf)
> +{
> + u64 pfr0;
> + u32 csv3;
> +
> + if (arm64_kernel_unmapped_at_el0())
> + return sprintf(buf, "Mitigation: KPTI\n");
> +
> + pfr0 = read_cpuid(ID_AA64PFR0_EL1);
> + csv3 = cpuid_feature_extract_unsigned_field(pfr0,
> + ID_AA64PFR0_CSV3_SHIFT);
> +
> + if (csv3 || is_cpu_meltdown_safe())
> + return sprintf(buf, "Not affected\n");
> +
> + return sprintf(buf, "Vulnerable\n");
This should say something like "Unknown", since we don't actually have a
reliable way to determine that a CPU is vulnerable. That's also a large
part of the reason why we haven't bothered implementing the sysfs interface
so far.
Will
