TrustZone OS is started during SBL2 (secureboot level 2), running in hypervisor mode, while you're looking at the Android OS started during SBL3 (secureboot level 3). You cannot see hypervisor processes & apps from your vantage point (the android kernel).
The trustzone OS is usually located in TZ partition, and it uses some additional partitions for custom TZ apps and data persistence.
The hypervisor has independent access to the internet, the wifi card (for indoor location), and more.
Qualcom boot process, showing SBL1, SBL2 and SBL3 stages:
TrustZone OS is started during SBL2 (secureboot level 2), running in hypervisor mode, while you're looking at the Android OS started during SBL3 (secureboot level 3). You cannot see hypervisor processes & apps from your vantage point (the android kernel).
The trustzone OS is usually located in TZ partition, and it uses some additional partitions for custom TZ apps and data persistence.
The hypervisor has independent access to the internet, the wifi card (for indoor location), and more.
Qualcom boot process, showing SBL1, SBL2 and SBL3 stages:
https://forum.xda-developers.com/showthread.php?t=1769411&pa...
It goes without saying that without TrustZone OS, the phone won't boot to Android OS (won't proceed to SBL3).