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> there are so many phones with devicetree... and proprietary blobs controlling boot and running beneath ring 0 It's not the same! A bootloader, once it loads
by M95D 8mo ago
> there are so many phones with devicetree... and proprietary blobs controlling boot and running beneath ring 0
It's not the same!
A bootloader, once it loads the kernel and executes it, is overwritten in memory. No trace of it remains while the sistem is running - until the next boot. UEFI / ACPI / SMM continue to execute on the CPU after it finished booting, "under" the kernel, preempting it as they please.
- yjftsjthsd-h 8mo agoI mean, it's not uniformly literally technically identical, but yes, an Android phone running its OS in ring 0 while other OSs run in other VMs on top of the EL2 (ring -1) hypervisor under the supervision of the Secure Monitor in L3 (ring -2) is very much in the same boat. Suggested reading: * https://www.maven-silicon.com/blog/privilege-levels-in-arm-architecture/ https://www.maven-silicon.com/blog/privilege-levels-in-arm-a... * https://projectzero.google/2017/02/lifting-hyper-visor-bypassing-samsungs.html https://projectzero.google/2017/02/lifting-hyper-visor-bypas... * https://en.wikipedia.org/wiki/ARM_architecture_family#Security_extensions https://en.wikipedia.org/wiki/ARM_architecture_family#Securi... * https://docs.samsungknox.com/admin/fundamentals/whitepaper/samsung-knox-mobile-security/system-security/real-time-kernel-protection/ https://docs.samsungknox.com/admin/fundamentals/whitepaper/s... (in which Samsung uses firmware running under the kernel to protect against kernel exploits)
- M95D 8mo agoOh, I didn't know that! There goes freedom in the ARM world too.