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

[Denis 'GNUtoo' Carikli]

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...

Denis.