Re: [RFC PATCH] xen/arm: try to get stack in any case

[Julien Grall <julien.grall@linaro.org>]

Hi Frediano,

On 10/17/2014 04:22 PM, Frediano Ziglio wrote:
> Well,
>   this is more an experiment than a patch but in my case was really
> useful. Basically I was trying to get dom0 raw stack hitting '0' key
> on Xen console. The problem is that when you hit such key you are Xen
> domain, not domain 0 (code is called from Xen console). While Xen is
> handling '0' command (dump dom0 state) show_guest_stack (in
> xen/arch/arm/traps.c) try to get page from stack pointer failing as is
> not current domain. In my case I had only domain0 so EL1 TTBR0/TTBR1
> was domain0 and this patch work but obviously this can lead on real
> cases to dump pages not from the wanted domain.

I guess you see "Failed to convert stack to physical address"?

> Possible solution is to get manually TTBR0/TTBR1 from the proper
> domain and manually parse page tables. Now some question
> - did somebody else have same issue?
> - is there any helper function to get the proper page?

The function get_page is used in many different place to get a reference
to the page and check if the page belongs to the domain.

This patch would lead to a security issue on most of the hypercalls that
deal with memory.

The proper solution would be to switch temporally on the p2m of the v we
want to dump (see an example with flush_tlb_domain());

Regards,

-- 
Julien Grall