On Mon, Aug 27, 2018 at 04:33:08PM +0200, Mian Yousaf Kaukab wrote:
> Only report mitigation present if hardening callback has been
> successfully installed.
>
> Signed-off-by: Mian Yousaf Kaukab <ykau...@suse.de>
> ---
> 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
