NetBSD/sys/rump/README.compileopts

	$NetBSD: README.compileopts,v 1.13 2015/06/17 11:48:06 pooka Exp $

This file describes compile-time options for rump kernels.  Additionally,
NetBSD build options will have an effect.  See src/share/mk/bsd.README
for a desciption of NetBSD build options.

Note: after changing an option, do a clean build.

Global options:


    RUMP_DIAGNOSTIC

values:	yes|no
defval:	yes
effect:	Iff "yes", build with -DDIAGNOSTIC.


    RUMP_DEBUG

values:	<defined> / <undefined>
defval:	<undefined>
effect:	Iff defined, build with -DDEBUG.


    RUMP_LOCKDEBUG

values:	<defined> / <undefined>
defval:	<undefined>
effect:	Iff defined, build with -DLOCKDEBUG.


    RUMP_KTRACE

values:	yes|no
defval:	yes
effect:	Iff "yes", build with -DKTRACE.


    RUMP_LOCKS_UP

values: yes|no
defval:	no
effect: If "yes", build rump kernel with uniprocess-optimized locking.
	An implication of this is that RUMP_NCPU==1 is required at
	runtime.  If "no", build with multiprocessor-capable locking.


    RUMP_VIRTIF

values:	yes|no
defval:	yes
effect:	Iff "yes", build the virt(4) network interface.  Turning this
	off may be necessary on systems that lack the necessary headers,
	e.g. musl libc based Linux.


    RUMP_CURLWP

values: hypercall/__thread/register or <undefined>
defval: <undefined>
effect: Control how curlwp is obtained in a rump kernel.  This is
	a very frequently accessed thread-local variable, and optimizing
	access has a significant performance impact.  Note that all
	options are not available on hosts/machine architectures.
	<undefined> - use default implementation (currently "hypercall")
	hypercall   - use a hypercall to fetch the value
	__thread    - use the __thread feature to fetch value via TLS
	register    - use a dedicated register (implies -ffixed)


    RUMP_NBCOMPAT

values: comma-separated list of releases; e.g. "60,70";
	or "all" or "default" or "none".  Currently default == all (but
	might not be so in the future)
defval:	all
effect:	Builds NetBSD COMPAT_nn code for each of the elements in the list.
	This option is useful only when building rump kernels for
	NetBSD userspace, and an empty value may be supplied elsewhere.


================================================================================

Rumpuser options:

    RUMPUSER_THREADS

values: pthread/none/fiber or <undefined>
defval: <undefined>
effect: Define the way threading is implemented in the rumpuser hypercall
	implmentation.
	<undefined> - use default implementation (currently "pthread")
	pthread     - use pthreads to implement threading
	none        - do not support kernel threads at all
	fiber       - user a fiber interface, cooperatively scheduled contexts


================================================================================

Per-component options:

    RUMP_SYM_NORENAME

values: regexp matching symbol names
defval: <undefined>
effect: Causes matching symbols from the component to not be renamed
	into the rump kernel symbol namespace (rumpns_).  This option
	can only be used in embedded environments where there is full
	control over the platform's namespace.	Conversely, this option
	cannot be used in kernel components which are not meant to be
	tied to a specific platform.  Note: the value is processed by
	make and must be appropriately escaped.  example:
	RUMP_SYM_NORENAME=HYPERVISOR_|block$$
	will not rename "^HYPERVISOR_" or "^block$"


================================================================================


The rest of the options described in this file are not intended to be
set by users, but by the package building rump kernels.


    RUMP_KERNEL_IS_LIBC

values:	defined / not defined
effect: Iff defined, export normal system call symbols from libc.
	For example, without this option rump_sys_open() is exported.
	With this option, both open() and rump_sys_open() are exported.
	This option is meant for building systems where a rump kernel
	is the only operating system like component.


    RUMP_LDSCRIPT

values: no/GNU/sun/ctor
defval: GNU
effect: Select the linker script to be used for linking rump kernel shared
	library components.
	no	- do not use a linker script
	GNU	- use a linker script for GNU ld 2.18 and later
	sun	- use a linker script for the Solaris linker
	ctor	- do not use a linker script, make the code
		  generate __attribute__((constructor))