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>>fghtr+(OP)
This blogpost propagates what I'd like to describe as an urban legend about baseband processors and main memory. The story originates from old times where even fancy phones allowed the baseband to write everywhere in main memory. The myth then becomes that you need the baseband physically separated from your main application processor.

But the world's moved on since those reports were made. It's FUD: https://www.reddit.com/r/CopperheadOS/comments/6wtul0/on_sen...

>>DCKing+ua
I know very little about the topic so bearing that in mind:

We're already in a world were we can't quite trust our CPUs, so why trusting baseband chips?

If it does make the design more complicated, it may also reduce the potential attack surface.

>>alex_d+8b
We can't fully trust the correctness of modern complicated CPU designs, leading to problems like <insert all speculative bypasses that have affected Intel CPUs the past 2 years>. But despite their complexity, CPUs and the CPU part of a smartphone SoC are usually extremely well understood (relatively speaking). The reason is that you actually need to run your software on these CPUs, so they need to be understood rather well. With better understanding comes better trust.

On the other hand, the baseband processor is mostly unknown, black box hardware, running unknown black box software, that completely controls the transmission of cellular data. Of course it would be horrible if there was no separation between the CPU and baseband. You shouldn't trust that setup. But as it turns out, separation does exist!

>>DCKing+3d
> But as it turns out, separation does exist!

The article you linked to says: "There can be an IOMMU with very tight restrictions providing proper isolation or a setup where the IOMMU is effectively not doing anything and permits access to all of the memory. Determining that requires real research."

So it sounds more like separation might or might not exist and you're not likely to find out if it does on your particular device.