Some CPUs report "illegal instruction" error for the crc test because
they do not support the relevant optional feature . This can be fixed by
introducing CPU feature detection for AArch64 .
The difference with the x86 implementation is the dispatcher . It is based
on the glibc function `getauxval(AT_HWCAP)` and `getauxval(AT_HWCAP2)` , not
registers or instructions .
On a heterogeneous system (big.LITTLE) , it is dangerous to detect CPU
features using identification registers . And while it is possible to use
architectural feature registers from userspace on recent kernels, this
won't necessarily work with older platforms . Thus we use the HW_CAPs
exported from the kernel (and visible in getauxval) as the solution.
- According to kernel suggestion , getauxval should be used for this purpose .
- [CPU Feature detection](https://github.com/torvalds/linux/blob/master/Documentation/arm64/cpu-feature-registers.rst)
- According to AAPCS result/paramter registers should be saved/restore for function call
- [AAPCS](http://infocenter.arm.com/help/topic/com.arm.doc.ihi0055b/IHI0055B_aapcs64.pdf)
- [GLibc](https://sourceware.org/git/gitweb.cgi?p=glibc.git;a=blob;f=sysdeps/aarch64/dl-trampoline.S)
Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
Change-Id: Ic9abe0d2268ac95537e1abf10acc642fc58a5054
