On implementing vnop_mmap, vnop_strategy and other related VNOPs as suggested in https://developer.apple.com/forums/thread/756358 my vnop_strategy routine ends up zero-extending files. I don't understand why my filesystem behaves as described above. Perusing the source code of both the relevant parts of Darwin/XNU and SMBClient did not clarify things for me. A nudge in the right direction would be greatly appreciated. The technical details of the issue are given in the plain text file attached, as some text was found to be sensitive. Unsure what exactly it was. apple-dts-issue-desc.txt

I'm having trouble opening files residing on a custom filesystem implemented as a kext via sandboxed apps. Preview.app is one such example. The app launches, but it won't display file contents. In system log files I'm seeing entries related to com.apple.foundation.filecoordination:claims with no error messages to indicate a possible reason why file contents aren't being displayed. Non-sandboxed apps, such as GoogleChrome.app do not exhibit such behaviour. The kext is unsigned and running in an environment with SIP disabled and Security Mode reduced to Permissive. What is required for a 3rd party filesystem kext to integrate with sandboxed apps? Any pointers and/or assistance would be greatly appreciated.

I am able to dtrace my custom kext on 12.5.1 running on Apple Silicon, but not on the subsequent releases of macOS. Is that by design? Thanks.