On Sat, 26 Sep 2020 at 05:17, Kees Cook [off-list ref] wrote:

quoted

For a 3/1 split ARM kernel of the typical size, all kernel virtual
addresses start with 0xc0, and given that the kernel is located at the
start of the linear map, those addresses cannot change even if you
move the kernel around in physical memory.

I wonder if this is an Android Common kernel? I think there was %p
hashing in there before v4.15, but with a different implementation...

Hi,
Thank you all for all your reply and comments so far!
Here are some follow-up replies.

quoted

What device is this? Is it a stock kernel?

This is a Qualcomm Snapdragon Automotive board one with Linux Kernel
4.9 and one with 4.14.

quoted

Is the boot loader changing the base address? (What boot loader are you
using?)

Ohh I did not knew that the bootloader can also change the base address.
I think it uses UEFI.
How to check if bootloader is doing this ?
BTW, both 4.9 board and 4.14 board, uses same bootloader.

quoted

I wonder if this is an Android Common kernel?

It uses the below kernel for 4.14:
https://gitlab.com/quicla/kernel/msm-4.14/-/tree/LE.UM.3.4.2.r1.5  (or
similar branch).
==> The case where symbol addresses are changing.

kptr_restrict is set to 2 by default:
/ # cat /proc/sys/kernel/kptr_restrict
2

Basically, the goal is:
* To understand how addresses are changing in 4.14 Kernel (without
KASLR support)?
* Is it possible to support the same in 4.9 Kernel ?

--
Thanks,
Pintu

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