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KERNEL MAKEFILE STRUCTURE
-------------------------

The advent of dynamic loading of kernel modules has obsoleted the
4.x kernel configuration scheme which was centered around a derived
Makefile and a collection of derived header files generated by the
config(8) program. This file describes the structure of the replacement
"static" set of Makefiles.

Some additional secondary goals were associated with the generation
of these Makefiles.  It should be noted that the ability to properly
deal with derived Makefiles is an explicit non-goal of the ongoing
NSE enhancements, so this project is a necessary consequence of that
decision.

All project goals are enumerated below:

1]  To provide a set of static Makefiles to support kernel build
    and installation.

2]  To provide a set of static Makefiles which conform to the
    "Makefiles Guidelines".  (This document is currently available
    on-line as "terminator:/usr/integration/doc/make.std")

3]  To completely eliminate the config(8) program.

4]  To provide a framework for linting the kernel (so that "lint free"
    can be made an integration criterion, in addition to being general
    good hygiene).

5]  To eliminate the need for the small headers generated by config(8).
    In the ddi/dki world this need is completely eliminated as drivers
    will be expected to dynamically configure themselves. Interim support
    for existing drivers will be provided.

6]  To be able to "acquire" only the files needed to build a specific
    module, if that is all that is needed.

7]  To provide a framework suitable for the production of "implementation
    architecture" independent modules.

8]  To restructure the assembly language files to support the generation
    of "lint-libraries" from them.

9]  To provide support for the incidental Makefile targets many developers
    are accustomed to (such as cscope and tags). These can be added to the
    Makefiles asd required. (cscope is currently supported.)


GENERAL STRUCTURE
-----------------

The source code layout is not generally effected by the Makefiles. However,
the location of the generated files has changed dramatically.

"Implementation architecture" independent modules are produced in
individual directories (one per module) under the "instruction-set
architecture" directory (i.e.: sparc). Similarly, "implementation
architecture" dependent modules are produced in individual directories
under the "implementation architecture" directory (i.e.: sun4, sun4c).
It should be noted that currently (4/14/91) no implementation architecture
modules exist. This situation is expected to change shortly.

The driving Makefile for any module is located in the leaf directory
where the module (and associated objects) are built. After a 'make
clobber' operation, the Makefile is the only file remaining in that
directory. Common definitions and rules are contained in suffixed
Makefiles in non-leaf directories which are included in the leaf
Makefiles. Non-suffixed Makefiles in non-leaf directories generally
invoke lower level Makefiles to perform the actual tasks.

uts/Makefile
uts/sparc/Makefile
uts/sun4c/Makefile
uts/sun4c/svvs/Makefile
	These Makefiles generally are cognizant of the components
	made in subdirectories and invoke Makefiles in those sub-
	directories to perform the actual build. Some targets (or
	pseudo-targets) may be directly built at this level (such
	as the cscope databases).

uts/Makefile.uts
	Contains common definitions for all possible architectures.

uts/Makefile.targ
	Contains common targets for all possible architectures.

uts/common/Makefile.files
uts/sun/Makefile.files
uts/sparc/Makefile.files
uts/sun4c/Makefile.files
uts/sun4/Makefile.files
	These Makefiles are divided into two sections. The first
	section can be viewed as the equivalent of the "files" (sparc
	and sun4c) and "files.cmn" (common and sun) files. These
	define the object lists which define each module. The second
	section defines the appropriate header search paths and other
	machine specific global build parameters.

uts/common/Makefile.rules
uts/sun/Makefile.rules
uts/sparc/Makefile.rules
uts/sun4c/Makefile.rules
uts/sun4/Makefile.rules
	The files provide build rules (targets) which allow make to function
	in a multiple directory environment. Each source tree below the
	directory containing the Makefile has a build rule in the file.

uts/sun4c/Makefile.sun4c
uts/sun4/Makefile.sun4
	These Makefile contains the definitions specific (defaults) to
	the obvious "implementation architecture". These rules can be
	overridden in specific leaf node Makefiles if necessary.

uts/sun4c/unix/Makefile
	Main driving Makefile for building /unix.

uts/sun4c/MODULE/Makefile (for MODULE in arp, aoutexec, ...)
	Main driving Makefile for building MODULE.kmod.

uts/sun4c/unix.static/Makefile
	Main driving Makefile for building a static unix (for development
	work only). This Makefile is known to NSE, but its targets are
	not. This makefile may be copied to additional parallel directories
	to build multiple configurations. This configuration is roughly
	equivalent to the GENERIC kernel of SunOS 4.x.

The Makefiles are verbosely commented. It is desired that they should
stay this way.


USE
---

Issuing the command 'make' in the uts directory will cause all supported,
modularized kernels and modules to be built.

Issuing the command 'make' in a uts/ARCHITECTURE directory (i.e.: uts/sparc)
will cause all supported, "implementation architecture" independent modules
for ARCHITECTURE to be built.

Issuing the command 'make' in a uts/MACHINE directory (i.e.: uts/sun4c)
will cause that kernel and all supported, "implementation architecture"
dependent modules for MACHINE to be built.

Issuing the command 'make' in the uts/MACHINE/unix directory will cause the
kernel for MACHINE to be built (and unix.o).

Issuing the command 'make' in a uts/MACHINE/MODULE or a uts/ARCHITECTURE/MODULE
directory will cause MODULE.kmod to be built.


LINT
----

Linting is fairly similar to the builds, but it has an additional complication.
In order to get meaningful output from lint pass2, all the modules must be
linted together. This is accomplished by each module being responsible to
produce its own pass1 output (file.ln, one per .c/.s file). It is also
responsible for placing the a lint-library (llib-lMODULE) in the
uts/MACHINE/lint-libs directory. The final full lint is accomplished by the
Makefile in the uts/MACHINE directory by linting all the lint-libraries
against each other.

Note that there is no equivalent to Locore.c in the current source base.
The C prototypes are in the .s files. As example:

	#if defined(lint)
	int
	blort(int, int)
	{ return 0 }
	#else	/* lint */

		ENTRY(blort)
		ld	[%i0],....
		....
		SET_SIZE(blort)

	#endif	/* lint */


COMPONENT HIERARCHY
------------------

The component hierarchy has been restructured to allow the acquisition of
more finely grained objects; specificly a kernel module. The basic component
structure is:

	:src:uts.all --+--> :sparc --+--> :MODULES... (none currently)
		       |
		       +--> :sun4c --+--> :unix
		       |             |
		       |             +--> :MODULES...
		       |             |
		       |             +--> :unix.static
		       |
		       +--> :sun4 ---+--> :unix
		       |             |
		       |             +--> :MODULES...
		       |             |
		       |             +--> :unix.static
		       ...

The above diagram does not reflect the full component tree. The full component
tree may be displayed with the "nsecomp list -r :src:uts.all" command.


COMMON OPERATIONS
-----------------

Adding a New Kernel Module
--------------------------

    0]  Create the source files (and directories) as usual.

    1]  Edit uts/*/Makefile.files to define the set of objects. By convention
	the symbolic name of this set is of the form MODULE_OBJS, where
	MODULE is the module name (i.e.: namefs). The files in each subtree
	should be defined in the Makefile.files in the root directory of that
	subtree. Note that they are defined using the += operator, so that
	the set can be built across multiple files. As example:

		NAMEFS_OBJS +=	namevfs.o namevno.o

	Each source file needs a build rule in the corresponding Makefile.rules
	file (compilation and lint). A typical pair of entries would be:

		$(OBJS_DIR)/mem.o:		$(UTSBASE)/sun4c/io/mem.c
			$(COMPILE.c) -o $@ $(UTSBASE)/sun4c/io/mem.c

		$(LINTS_DIR)/mem.ln:		$(UTSBASE)/sun4c/io/mem.c
			@($(LHEAD) $(LINT.c) $(UTSBASE)/sun4c/io/mem.c $(LTAIL))

    2]	Create build directories in the appropriate places. If the module
	can be built in a machine independent way, this would be in the
	"instruction set architecture" directory (i.e.: sparc). If not, these
	directories would be created for all appropriate "implementation
	architecture" dependent directories (i.e.: sun4, sun4c).

    3]  In each build directory, create a Makefile. This can usually be
	accomplished by copying a Makefile from a parallel directory and
	editing the following lines (in addition to comments).

		MODULE		= namefs
			- replace with module name
		OBJECTS		= $(NAMEFS_OBJS:%=$(OBJS_DIR)/%)
		LINTS		= $(NAMEFS_OBJS:%.o=$(LINTS_DIR)/%.ln)
			- replace with MODULE_OBJS
		ROOTMODULE	= $(ROOT_FS_DIR)/$(MODULE).kmod
			- replace directory part with the appropriate
			  installation directory name (see Makefile.uts)

	If a custom version of modstubs.o is needed to check the undefines
	for this routine, the following lines need to appear in the
	Makefile (after the inclusion of Makefile.mach (i.e.: Makefile.sun4c)).

		MODSTUBS_DIR	 = $(OBJS_DIR)
		$(MODSTUBS_O)	:= AS_CPPFLAGS += -DNAMEFS_MODULE
			- replace "-DNAMEFS_MODULE" with the appropriate flag
			  for the modstubs.o assembly.
		CLEANFILES	+= $(MODSTUBS_O)

    4]  Edit the parent Makefile.mach (i.e.: Makefile.sun4c) to know about
	the new module:

		FS_KMODS	+= fd fifo namefs nfs proc spec ufs
					   ------
Any additional questions can be easily answered by looking at the many
existing examples.


Moving a Module to the "Implementation Architecture" Independent Build
----------------------------------------------------------------------

    1]  Create the build directory under the appropriate "instruction
	set architecture" build directory (i.e.: sparc/MODULE).

    2]  Move the Makefile from the "implementation architecture" build
	directory (i.e.: sun4c/MODULE) to the directory created above.
	Edit this Makefile to reflect the change of parent (trivial:
	comments, paths and includes).

    3]  Edit the "implementation architecture" directory Makefile (i.e.:
	Makefile.sun4c) to *not* know about this module and edit the
	"instruction set architecture" directory Makefile (i.e.:
	Makefile.sparc) to know about it.