LLVM has recently gained support for an ELF implementation of the AArch64 Pointer Authentication ABI (PAuthABI) for a Linux Musl target. This talk will cover: * An introduction to the PAuthABI and its LLVM support. * How to experiment with it on any Linux machine using qemu-aarch64 emulation. * How to adapt the Linux Musl target to a bare-metal target using LLVM libc.

The AArch64 Pointer Authentication Code instructions are currently deployed on Linux to protect the return address on hardware that has support for it. This limited use case can be deployed in an ABI neutral way and run on existing hardware. The PAuthABI, based on Apple's Arm64E, takes the hardware and software backwards compatibility gloves off, and makes use of pointer authentication for code pointers such as function pointers and vtables.

The main challenge to adapt the PAuthABI support for bare-metal is initialization of global pointers as on Linux this is done by the dynamic loader. We will need to build our own signer that operates before main.