userabi)This directory contains the kernel-side support for the Zircon user-space ABI:
libzircon.so): Located in vdso/, providing the system call entry points and fast-path time/ticks routines mapped into user-space processes.userboot bootstrap: userabi.rs (along with elf.rs, resource.rs, and vdso.rs) loads the first user-space process (userboot) from the kernel package and sends it the two bootstrap channel messages (the process capability message followed by the system capability message).The canonical documentation for the kernel-to-userboot bootstrap protocol and the userboot startup support library lives in //src/bringup/lib/userboot/README.md. The userboot binary implementation itself lives in //src/bringup/bin/userboot/.