[PATCH 0/2] arm64: permit KASLR in linear region even VArange == PArange

[Kefeng Wang]

On 2021/12/15 22:52, Ard Biesheuvel wrote:
> Kefeng reports in [0] that using PArange to size the randomized linear
> region offset leads to cases where randomization is no longer possible
> even if the actual placement of DRAM in memory would otherwise have
> permitted it.
>
> Instead of using CONFIG_MEMORY_HOTPLUG to choose at build time between
> to different behaviors in this regard, let's try addressing this by
> reducing the minimum relative aligment between VA and PA in the linear
> region, and taking advantage of the space at the base of physical memory
> below the first memblock to permit some randomization of the placement
> of physical DRAM in the virtual address map.
VArange == PArange is ok, but our case is Va=39/Pa=48, this is still not 
works :(

Could we add a way(maybe cmdline) to set max parange, then we could make

randomization works, or some other way?


> Cc: Kefeng Wang <wangkefeng.wang at huawei.com>
>
> [0] https://lore.kernel.org/linux-arm-kernel/20211104062747.55206-1-wangkefeng.wang@huawei.com/
>
> Ard Biesheuvel (2):
>    arm64: simplify rules for defining ARM64_MEMSTART_ALIGN
>    arm64: kaslr: take free space at start of DRAM into account
>
>   arch/arm64/include/asm/kernel-pgtable.h | 27 +++-----------------
>   arch/arm64/mm/init.c                    |  3 ++-
>   2 files changed, 6 insertions(+), 24 deletions(-)
>