freebsd-dev/usr.sbin/crunch/crunchgen/crunchgen.1

.\"
.\" Copyright (c) 1994 University of Maryland
.\" All Rights Reserved.
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.\" documentation for any purpose is hereby granted without fee, provided that
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.\" suitability of this software for any purpose.  It is provided "as is"
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.\" U.M. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL U.M.
.\" BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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.\" IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.\" Author: James da Silva, Systems Design and Analysis Group
.\"			   Computer Science Department
.\"			   University of Maryland at College Park
.\" $FreeBSD$
.\"
.Dd September 29, 1997
.Dt CRUNCHGEN 1
.Os BSD 4
.Sh NAME
.Nm \&crunchgen
.Nd generates build environment for a crunched binary
.Sh SYNOPSIS
.Nm \&crunchgen
.Op Fl fql
.Op Fl h Ar makefile-header-name
.Op Fl m Ar makefile-name
.Op Fl c Ar c-file-name
.Op Fl e Ar exec-file-name
.Op Ar conf-file
.Sh DESCRIPTION

A crunched binary is a program made up of many other programs linked
together into a single executable.  The crunched binary main()
function determines which component program to run by the contents of
argv[0].  The main reason to crunch programs together is for fitting
as many programs as possible onto an installation or system recovery
floppy.

.Pp
.Nm Crunchgen
reads in the specifications in
.Ar conf-file
for a crunched binary, and generates a Makefile and accompanying
top-level C source file that when built create the crunched executable
file from the component programs.  For each component program, 
.Nm crunchgen
can optionally attempt to determine the object (.o) files that make up
the program from its source directory Makefile.  This information is
cached between runs.
.Nm Crunchgen
uses the companion program
.Nm crunchide
to eliminate link-time conflicts between the component programs by
hiding all unnecessary symbols.

.Pp
After
.Nm
is run, the crunched binary can be built by running ``make -f
<conf-name>.mk''.  The component programs' object files must already
be built.  A ``objs'' target, included in the output makefile, will
run make in each component program's source dir to build the object
files for the user.  This is not done automatically since in release
engineering circumstances it is generally not desirable to be
modifying objects in other directories.

.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl c Ar c-file-name
Set output C file name to
.Ar c-file-name .
The default name is ``<conf-name>.c''.
.It Fl e Ar exec-file-name
Set crunched binary executable file name to
.Ar exec-file-name .
The default name is ``<conf-name>''.
.It Fl f
Flush cache.  Forces the recalculation of cached parameters.
.It Fl l
List names.  Lists the names this binary will respond to.
.It Fl h Ar makefile-header-name
Set the name of a file to be included at the beginning of the
Makefiles generated by
.Nm crunchgen .
This is useful to define some make variables such as
.Ar RELEASE_CRUNCH
or similar, which might affect the behaviour of make and
are annoying to pass through environment variables.
.It Fl m Ar makefile-name
Set output Makefile name to
.Ar makefile-name .
The default name is ``<conf-name>.mk''.
.It Fl q
Quiet operation.  Status messages are suppressed.
.El
.Sh CRUNCHGEN CONFIGURATION FILE COMMANDS

.Nm Crunchgen
reads specifications from the 
.Ar conf-file
that describe the components of the crunched binary.  In its simplest
use, the component program names are merely listed along with the
top-level source directories in which their sources can be found.
.Nm Crunchgen
then calculates (via the source makefiles) and caches the
list of object files and their locations.  For more specialized
situations, the user can specify by hand all the parameters that 
.Nm
needs.
.Pp
The
.Ar conf-file
commands are as follows:
.Bl -tag -width indent
.It Nm srcdirs Ar dirname ...
A list of source trees in which the source directories of the
component programs can be found.  These dirs are searched using the
BSD ``<source-dir>/<progname>/'' convention.  Multiple 
.Nm srcdirs
lines can be specified.  The directories are searched in the order
they are given.
.It Nm progs Ar progname ...
A list of programs that make up the crunched binary.  Multiple
.Nm progs
lines can be specified.
.It Nm libs Ar libspec ...
A list of library specifications to be included in the crunched binary link.
Multiple
.Nm libs
lines can be specified.
.It Nm ln Ar progname linkname
Causes the crunched binary to invoke
.Ar progname
whenever
.Ar linkname
appears in argv[0].  This allows programs that change their behavior when
run under different names to operate correctly. 
.El

To handle specialized situations, such as when the source is not
available or not built via a conventional Makefile, the following
.Nm special
commands can be used to set 
.Nm
parameters for a component program.
.Bl -tag -width indent
.It Nm special Ar progname Nm srcdir Ar pathname
Set the source directory for
.Ar progname .
This is normally calculated by searching the specified
.Nm srcdirs
for a directory named
.Ar progname .
.It Nm special Ar progname Nm objdir Ar pathname
Set the obj directory for
.Ar progname .
This is normally calculated by looking for a directory named
.Dq Pa obj
under the
.Ar srcdir ,
and if that is not found, the 
.Ar srcdir
itself becomes the
.Ar objdir .
.It Nm special Ar progname Nm objs Ar object-file-name ...
Set the list of object files for program
.Ar progname .
This is normally calculated by constructing a temporary makefile that includes
.Dq Nm srcdir / Pa Makefile 
and outputs the value of $(OBJS).
.It Nm special Ar progname Nm objpaths Ar full-pathname-to-object-file ...
Sets the pathnames of the object files for program
.Ar progname .
This is normally calculated by prepending the
.Nm objdir
pathname to each file in the
.Nm objs
list.
.It Nm special Ar progname Nm objvar Ar variable_name
Sets the name of the Make variable which holds the list of
object files for program
.Ar progname .
This is normally
.Nm OBJS
but some Makefiles might like to use other conventions or
prepend the program's name to the variable, e.g.
.Nm SSHD_OBJS .
.It Nm special Ar progname Nm keep Ar symbol-name ...
Add specified list of symbols to the keep list for program
.Ar progname .
An underscore is prepended to each symbol and it becomes the argument to a
.Fl k
option for the
.Xr crunchide 1
phase.
This option is to be used as a last resort as its use can cause a
symbol conflict, however in certain instances it may be the only way to
have a symbol resolve.
.El

.Pp
Only the 
.Nm objpaths
parameter is actually needed by
.Nm crunchgen ,
but it is calculated from
.Nm objdir
and
.Nm objs ,
which are in turn calculated from
.Nm srcdir ,
so is sometimes convenient to specify the earlier parameters and let 
.Nm
calculate forward from there if it can.

.Pp
The makefile produced by
.Nm
contains an optional
.Ar objs
target that will build the object files for each component program by
running make inside that program's source directory.  For this to work the
.Nm srcdir
and
.Nm objs
parameters must also be valid.  If they are not valid for a particular program, that
program is skipped in the 
.Ar objs
target.
.Sh EXAMPLE
Here is an example
.Nm
input conf file, named
.Dq Pa kcopy.conf :
.Pp
.nf
	srcdirs /usr/src/bin /usr/src/sbin

	progs test cp echo sh fsck halt init mount umount myinstall
	ln test [       # test can be invoked via [
	ln sh -sh       # init invokes the shell with "-sh" in argv[0]

	special myprog objpaths /homes/leroy/src/myinstall.o # no sources

	libs -lutil -lcrypt
.fi
.Pp
This conf file specifies a small crunched binary consisting of some
basic system utilities plus a homegrown install program ``myinstall'',
for which no source directory is specified, but its object file is
specified directly with the
.Nm special
line.
.Pp
The crunched binary ``kcopy'' can be built as follows:
.Pp
.nf
	% crunchgen -m Makefile kcopy.conf    # gen Makefile and kcopy.c
	% make objs             # build the component programs' .o files
	% make                  # build the crunched binary kcopy
	% kcopy sh              # test that this invokes a sh shell
	$			# it works!
.fi
.Pp
At this point the binary ``kcopy'' can be copied onto an install floppy
and hard-linked to the names of the component programs.
.Sh SEE ALSO
.Xr crunchide 1
.Sh CAVEATS
While
.Nm crunch
takes care to eliminate link conflicts between the component programs
of a crunched binary, conflicts are still possible between the
libraries that are linked in.  Some shuffling in the order of
libraries may be required, and in some rare cases two libraries may
have an unresolvable conflict and thus cannot be crunched together.
.Pp
Some versions of the BSD build environment do not by default build the
intermediate object file for single-source file programs.  The ``make
objs'' target must then be used to get those object files built, or
some other arrangements made.
.Sh AUTHORS
.Nm Crunch
was written by
.An James da Silva Aq jds@cs.umd.edu .
Copyright (c) 1994 University of Maryland.  All Rights Reserved.