Linked by Thom Holwerda on Tue 12th Nov 2013 23:06 UTC
PDAs, Cellphones, Wireless

I've always known this, and I'm sure most of you do too, but we never really talk about it. Every smartphone or other device with mobile communications capability (e.g. 3G or LTE) actually runs not one, but two operating systems. Aside from the operating system that we as end-users see (Android, iOS, PalmOS), it also runs a small operating system that manages everything related to radio. Since this functionality is highly timing-dependent, a real-time operating system is required.

This operating system is stored in firmware, and runs on the baseband processor. As far as I know, this baseband RTOS is always entirely proprietary. For instance, the RTOS inside Qualcomm baseband processors (in this specific case, the MSM6280) is called AMSS, built upon their own proprietary REX kernel, and is made up of 69 concurrent tasks, handling everything from USB to GPS. It runs on an ARMv5 processor.

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Comment by shmerl
by shmerl on Wed 13th Nov 2013 01:23 UTC
shmerl
Member since:
2010-06-08

Aren't there 3 operating systems on many phones then? SIM card contains kind of an OS too.

Edited 2013-11-13 01:24 UTC

Reply Score: 3

RE: Comment by shmerl
by Lobotomik on Wed 13th Nov 2013 09:02 in reply to "Comment by shmerl"
Lobotomik Member since:
2006-01-03

And Bluetooth, Wifi, GPS and touch chips have an internal processor too, running their internal software, which can be quite complex. They tend to use small ARM cores (M3, M0), and generally use an RTOS.

There are tons of RTOS for these applications, from tiny to titanic and from free to very expensive (and these axes are orthogonal): ThreadX, Nucleus, RTXC, pSOS, eCOS, RTMS...

So yes, in your cellphone there are a lot more than three operating systems running at the same time.

Reply Parent Score: 6

RE[2]: Comment by shmerl
by pashar on Wed 13th Nov 2013 09:21 in reply to "RE: Comment by shmerl"
pashar Member since:
2006-07-12

Add to that storage, which runs its own firmware, usually with an RTOS. And, if smartphone has an SD card slot, SD card runs its own firmware, too.

Reply Parent Score: 2

RE: Comment by shmerl
by Tractor on Wed 13th Nov 2013 11:14 in reply to "Comment by shmerl"
Tractor Member since:
2006-08-18

Indeed, SIM Card have their own OS too.
But they are more secure by design.

SIM Card don't accept "anything that comes from the air". Data must be properly encrypted, using industry standard algorithms (3DES or AES). Just this simple protection makes it immensely more secure than baseband OS.

Now, beyond that protection, these OS are software rubbish. They are safe mostly because they are extremely limited. Someone able to crack (or pass) the encryption layer protection would have no problem crashing the SIM card OS.
But stealing data from it ? nah, that's the hardest part. This is probably the only thing which has been properly designed in these OS.

Reply Parent Score: 2

RE[2]: Comment by shmerl
by fuckregistration on Wed 13th Nov 2013 23:26 in reply to "RE: Comment by shmerl"
fuckregistration Member since:
2013-11-13

Indeed, SIM Card have their own OS too.
But they are more secure by design.


Oh yes? You might want to watch the talk of Karsten Nohl at OHM2013.

Reply Parent Score: 2

RE: Comment by shmerl
by Carewolf on Wed 13th Nov 2013 16:52 in reply to "Comment by shmerl"
Carewolf Member since:
2005-09-08

Beyond all those that run on their own chips for specific components there is also a low power operating system in most phones that run when the phone is powered off. Its main job is to react to power button key events.

edit: typos

Edited 2013-11-13 16:53 UTC

Reply Parent Score: 3