Re: [Adeos-main] [PATCH] I-pipe tracer for ARM

[Jan Kiszka <jan.kiszka@domain.hid>]

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Sebastian Smolorz wrote:
> Gilles Chanteperdrix wrote:
>> Jan Kiszka wrote:
>>> Gilles Chanteperdrix wrote:
>>>> Jan Kiszka wrote:
>>>>> Sebastian Smolorz wrote:
>>>>>> Jan Kiszka wrote:
>>>>>>> Are you tracing into vmalloc'ed memory?
>>>>>> Yes, without CONFIG_IPIPE_TRACE_VMALLOC the system does not boot.
>>>>> Hmm, makes me wonder of some laziness of the page mapping or a missing
>>>>> lock-against-swapping causes this. Could you have a closer look at the
>>>>> tracer code if we are lacking some magic for the vmalloc trace buffer
>>>>> (compare to the xnheap code, e.g.)?
>>>> This is a known issue, the ARM architecture lacks the set_pgdir
>>>> function, needed in mm/vmalloc.c to workaround the lazy page mapping of
>>>> vmalloced areas.
>>> Would vmalloc+memset help to be safe for the remaining system runtime?
>> Probably not, the vmalloced area is added only to the page table of the
>> process that calls vmalloc, it is added to other processes table page
>> only once they use it.
> 
> Are there any alternatives? Or do we have to live with this restriction?
> 

Try if smaller CONFIG_IPIPE_TRACE_SHIFT makes it boot without
CONFIG_IPIPE_TRACE_VMALLOC.

On the longer term: Gilles, what does "lacks the set_pgdir" means? Is
this fixable?

Jan


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