How much protection does an add-on GSM modem give me vs. built into phone ?

Peter Zotov whitequark at whitequark.org
Thu Oct 4 11:10:39 UTC 2012


Denis 'GNUtoo' Carikli писал 04.10.2012 14:26:
> On Thu, 4 Oct 2012 00:32:48 +0200
> Peter Stuge <peter at stuge.se> wrote:
>
>> John Case wrote:
>> > the real trick I am interested is isolating (or at least
>> > controlling) the interaction between the baseband processor and 
>> the
>> > application processor.  Using a computer with a USB dongle gives 
>> me
>> > that control ... would I have that same level of control if we had
>> > free software running on the baseband processor, or is there still
>> > additional bleeding possible simpy by virtue of being built into
>> > the computer ?
>>
>> In a smartphone it's almost not possible to distinguish the
>> "computer" from the "GSM modem" anymore, because of how the
>> hardware is constructed, so yes.
> In some yes, in some no... it depend on how the smartphone was
> designed:
>
> On one end some smartphones (openmoko GTA02,golden delicious GTA04), 
> the
> baseband is isolated(tough on GTA04 it has access to a GPS with no
> antenna(so it can't work)) . And on the other end there are 
> smartphones
> with qualcomm System on a chip...where the modem and the CPU are in a
> single chip:
> The modem part has the audio DSP connected to it, the GPS.
> And the baseband uses shared RAM memory and shared NAND(if I remember
> well)...
> And I'm not sure but maybe the baseband is even needed for booting 
> the
> main CPU...
>
> There are also systems in between like the galaxy S/Neuxs S that uses
> shared memory but do not have other problems...

In addition to the above, there are some phones where baseband is 
completely
submissive to the AP, namely Galaxy SII. Basically it's exactly the 
same
as the USB dongle situation, but the dongle is integrated on the 
phone's
PCB.

>
> Denis.

-- 
   WBR, Peter Zotov.




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