Summary on Arm macs

By: never_released (never_released.delete@this.twitter.com), June 24, 2020 11:16 am
Room: Moderated Discussions
Hello,

This is a short summary of the most important bits to me from WWDC sessions.

Page size:

- Apple went with 16KB, as they did with iOS.

MMU:

- Per thread page permissions are available for making JITs easier to write. Two threads of the same process can see the _same_ page as R-X on one and RW- on the other for example.

Pointer authentication:

- On for the kernel, experimental ABI with a knob to turn it on for user-space.

Secure Boot:

- Can be disabled via csrutil in Recovery, but not shown as an option in the GUI. (so won't be an issue to anyone in practice).

Third-party kernel extensions:

- Reduced Security mode is required to enable third-party kernel extensions. This mode also allows macOS downgrades.

Rosetta:

- The emulation is at the system call level, all the OS frameworks go through binary translation too inside x86_64 processes.

- 4KB pages work there, unknown if an hypothetical hardware support is used or if they hacked it up.
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Summary on Arm macsnever_released2020/06/24 11:16 AM
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