KASLR: about the vmalloc area for randomization kernel image

Ard Biesheuvel ard.biesheuvel at linaro.org
Fri Jan 3 06:47:21 PST 2020

On Fri, 3 Jan 2020 at 07:52, Zong Li <zong.li at sifive.com> wrote:
> Hi Ard,
> I'm working on KASLR for RISC-V, and I'm interested in what is the
> consideration of choosing the vmalloc area on arm64. I was wondering
> if you could give me some advice.
> There are other architectures had implemented KASLR, such as x86,
> mips, s390 and ppc, they use the lowmem to randomize the address of
> kernel image, it seems that only arm64 move the kernel image to
> vmalloc area.
> I tried to understand the history and reason for using vmalloc area
> through some discussions at the end of mail, but I still couldn't know
> what is the reason for using vmalloc area in the beginning.
> For the randomization purpose, it seems to me that there is no
> significant difference between using lowmem and vmalloc area. Would
> you be willing to help to give some ideas about that? :)
> Sorry if I missed anything. Thank you very much.

Are we talking about 32-bit here? If not, what do you mean by lowmem?

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