* variant4 from common.c::cpu_no_spec_store_bypass
Variant 4 - Add function to 'whitelist' the hand-full of CPUs unaffected by speculative store bypass.
This would allow improved determination of variant 4 status ( #189 ) of immune CPUs while waiting for the 4.17/stable patches to be backported to distro kernels.
Source of cpu list : https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/kernel/cpu/common.c#n945)
Modeled after is_cpu_specex_free()
* amd families fix
amd families are reported by parse_cpu_details() in decimal
* remove duplicates
Only list processors which speculate and are immune to variant 4.
Avoids duplication with non-speculating CPUs listed in is_cpu_specex_free()
On linux systems which need dd, this check if the version is compatible before continuing with hardware checks.
If the install of dd is obsolete, user is warnd, and hardware checks do not continue, any other requested checks performed as normal.
(Old versions (before circa 2012) of dd do not support the iflag=skip_bytes option. They are therefore unable to read from cpuid, or msr, where read offset is used to pass the required page. To complicate matters, some versions of dd may not return an error code when this happens.)
* ibrs can't be enabled on no ibrs cpu
If the cpu is identified, and does not support SPEC_CTRL or IBRS, then ibrs can't be enabled, even if supported by the kernel.
Instead of reporting IBRS enabled and active UNKNOWN, report IBRS enabled and active NO.
This adds a check before loading the cpuid and msr modules under linux, ensuring they are not unloaded in exit_cleanup() if they were initially present.
