XNU does embed BSD (and so POSIX) semantics into the kernel—some of which are their own efficient primitives, since there's no way to efficiently implement them in terms of Mach. But whatever BSD syscalls can be implemented kernel-side in terms of Mach primitives, are.
Re:Fuchsia is not Linux
by monocasa on Wednesday April 11, 2018 @08:06PM
(#16816942)
It has both. Mach system calls are negative, BSD system calls are positive. The BSD side has system calls for stuff like fork() that would otherwise be pretty clearly in Mach's domain.
XNU does embed BSD (and so POSIX) semantics into the kernel—some of which are their own efficient primitives, since there's no way to efficiently implement them in terms of Mach. But whatever BSD syscalls can be implemented kernel-side in terms of Mach primitives, are.