ARM: kernel: implement randomization of the kernel load address

maillist inclusion
commit c11744cd7b351b0fbc5233c04c32822544c96fc1
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=c11744cd7b351b0fbc5233c04c32822544c96fc1



Update the Kconfig RANDOMIZE_BASE depends on !JUMP_LABEL to resolve
compilation conflicts between fpic and JUMP_LABEL.

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This implements randomization of the placement of the kernel image
inside the lowmem region. It is intended to work together with the
decompressor to place the kernel at an offset in physical memory
that is a multiple of 2 MB, and to take the same offset into account
when creating the virtual mapping.

This uses runtime relocation of the kernel built as a PIE binary, to
fix up all absolute symbol references to refer to their runtime virtual
address. The physical-to-virtual mapping remains unchanged.

In order to allow the decompressor to hand over to the core kernel
without making assumptions that are not guaranteed to hold when
invoking the core kernel directly using bootloaders that are not
KASLR aware, the KASLR offset is expected to be placed in r3 when
entering the kernel 4 bytes past the entry point, skipping the first
instruction.

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>