Where can I find the source code for _start that the bare metal version of llvm uses to initialise Morello?
The start function is in crt0.S from libgloss/newlib. You would have to check the version specific to the release that you are using.
The source for the latest release is here: git.morello-project.org/.../crt0.S
ah! thanks! - I didn't think to look in a different repo - I was searching the llvm-project!