Adding a 3rd party KEXT to a prelinkedkernel with safe boot and T2

Question

slavaim OP

Created May ’19

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Hi,

Can somebody confirm that it is not possible to add a 3rd party KEXT to a prelinked kernel on systems with the T2 chip and active safeboot mode?

I need an IOKit object being probed against a device nub as early as possible. This requires a KEXT to be added to a prelinked kernel hosted at /System/Library/PrelinkedKernel . I noticed that the system uses /System/Library/PrelinkedKernel/immutablekernel instead of /System/Library/PrelinkedKernel/prelinkedkernel if safeboot is active and the system has the T2 chip . The immutablekernel file is protected by the UEFI boot module which checks a prelinked kernel signature saved at the Preboot volume so there is no way to modify it with the kextcache command.

The existing procedure when a 3rd party KEXT is being loaded by the kextd process after the system has been initialized might not be the best solution in my case.

Is there a procedure for a 3rd party KEXT to be linked with immutablekernel or change the system behavior to load /System/Library/PrelinkedKernel/prelinkedkernel in safeboot mode?

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Answer 1

jeff_f OP

Jan ’21

I am having this same problem when trying to get a third party kext to load during the boot process. Instead of loading my kext, macOS loads a builtin (native) kext that also matches my device. I am running macOS 10.15.7 (19H114) on a MacBook Pro (16-inch, 2019). Did you ever receive guidance from Apple about this problem?

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