ARM: decompressor: add KASLR support

maillist inclusion
commit b152e5c5054c3937211a541be50d8a7c98a59974
category: feature
feature: ARM kaslr support
bugzilla: 47952
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/commit/?h=arm-kaslr-latest&id=b152e5c5054c3937211a541be50d8a7c98a59974



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Add support to the decompressor to load the kernel at a randomized
offset, and invoke the kernel proper while passing on the information
about the offset at which the kernel was loaded.

This implementation will extract some pseudo-randomness from the low
bits of the generic timer (if available), and use CRC-16 to combine
it with the build ID string and the device tree binary (which ideally
has a /chosen/kaslr-seed property, but may also have other properties
that differ between boots). This seed is used to select one of the
candidate offsets in the lowmem region that don't overlap the zImage
itself, the DTB, the initrd and /memreserve/s and/or /reserved-memory
nodes that should be left alone.

When booting via the UEFI stub, it is left up to the firmware to supply
a suitable seed and select an offset.

Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Cui GaoSheng <cuigaosheng1@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>