Re: [PATCH v5 2/7] powerpc/vmlinux.lds: Align __init_begin to 16M

On Thu, Jun 29, 2017 at 9:29 PM, David Laight [off-list ref] wrote:

From: Balbir Singh

quoted

Sent: 28 June 2017 18:04
For CONFIG_STRICT_KERNEL_RWX align __init_begin to 16M.
We use 16M since its the larger of 2M on radix and 16M
on hash for our linear mapping. The plan is to have
.text, .rodata and everything upto __init_begin marked
as RX. Note we still have executable read only data.
We could further align rodata to another 16M boundary.
I've used keeping text plus rodata as read-only-executable
as a trade-off to doing read-only-executable for text and
read-only for rodata.

...

Doesn't this go against 'address space randomisation'?
(Yes I realise a PIC kernel is probably non-trivial to compile
and load.)

I presume you mean Kernel ASLR. I am not sure why you think
it goes against KASLR, it's just aligning the _stext and __init_begin,
they can be anywhere in memory. I've tested with a relocatable kernel

Balbir Singh.