CRUNCHGEN(1) FreeBSD General Commands Manual CRUNCHGEN(1)
NAME
crunchgen - generates build environment for a crunched binary
SYNOPSIS
crunchgen [-foql] [-h makefile-header-name] [-m makefile-name]
[-p obj-prefix] [-c c-file-name] [-e exec-file-name] conf-file
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.
The crunchgen utility reads in the specifications in conf-file for a
crunched binary, and generates a Makefile and accompanying top-level C
source file that when built creates the crunched executable file from the
component programs. For each component program, 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.
The crunchgen utility uses the companion program crunchide(1) to
eliminate link-time conflicts between the component programs by hiding
all unnecessary symbols.
The crunchgen utility places specific requirements on package Makefiles
which make it unsuitable for use with non-BSD sources. In particular,
the Makefile must contain the target depend, and it must define all
object files in the variable OBJS. In some cases, you can use a fake
Makefile: before looking for Makefile in the source directory foo,
crunchgen looks for the file Makefile.foo in the current directory.
After crunchgen is run, the crunched binary can be built by running "make
-f <conf-name>.mk". The component programs' object files must already be
built. An objs target, included in the output makefile, will run make(1)
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.
The options are as follows:
-c c-file-name
Set output C file name to c-file-name. The default name is
<conf-name>.c.
-e exec-file-name
Set crunched binary executable file name to exec-file-name. The
default name is <conf-name>.
-f Flush cache. Forces the recalculation of cached parameters.
-l List names. Lists the names this binary will respond to.
-h makefile-header-name
Set the name of a file to be included at the beginning of the
Makefiles generated by crunchgen. This is useful to define some
make variables which might affect the behavior of make(1) and are
annoying to pass through environment variables.
-m makefile-name
Set output Makefile name to makefile-name. The default name is
<conf-name>.mk.
-o Add "make obj" rules to each program make target.
-p obj-prefix
Set the pathname to be prepended to the srcdir when computing the
objdir. If this option is not present, then the prefix used is
the content of the MAKEOBJDIRPREFIX environment variable, or
/usr/obj.
-q Quiet operation. Status messages are suppressed.
CRUNCHGEN CONFIGURATION FILE COMMANDS
The crunchgen utility reads specifications from the 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. The crunchgen utility
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 crunchgen needs.
The conf-file commands are as follows:
srcdirs 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 srcdirs
lines can be specified. The directories are searched in the
order they are given.
progs progname ...
A list of programs that make up the crunched binary. Multiple
progs lines can be specified.
libs libspec ...
A list of library specifications to be included in the crunched
binary link. Multiple libs lines can be specified.
libs_so libspec ...
A list of library specifications to be dynamically linked in the
crunched binary. These libraries will need to be made available
via the run-time link-editor rtld(1) when the component program
that requires them is executed from the crunched binary.
Multiple libs_so lines can be specified. The libs_so directive
overrides a library specified gratuitously on a libs line.
buildopts buildopts ...
A list of build options to be added to every make target.
ln progname linkname
Causes the crunched binary to invoke progname whenever linkname
appears in argv[0]. This allows programs that change their
behavior when run under different names to operate correctly.
To handle specialized situations, such as when the source is not
available or not built via a conventional Makefile, the following special
commands can be used to set crunchgen parameters for a component program.
special progname srcdir pathname
Set the source directory for progname. This is normally
calculated by searching the specified srcdirs for a directory
named progname.
special progname objdir pathname
Set the obj directory for progname. The obj directory is
normally calculated by looking for a directory whose name is that
of the source directory prepended by one of the following
components, in order of priority: the -p argument passed to the
command line; or, the value of the MAKEOBJDIRPREFIX environment
variable, or /usr/obj. If the directory is not found, the srcdir
itself becomes the objdir.
special progname buildopts buildopts
Define a set of build options that should be added to make(1)
targets in addition to those specified using buildopts when
processing progname.
special progname objs object-file-name ...
Set the list of object files for program progname. This is
normally calculated by constructing a temporary makefile that
includes "srcdir/Makefile" and outputs the value of $(OBJS).
special progname objpaths full-pathname-to-object-file ...
Sets the pathnames of the object files for program progname.
This is normally calculated by prepending the objdir pathname to
each file in the objs list.
special progname objvar variable_name
Sets the name of the make(1) variable which holds the list of
object files for program progname. This is normally OBJS but
some Makefiles might like to use other conventions or prepend the
program's name to the variable, e.g., SSHD_OBJS.
special progname lib library-name ...
Specifies libraries to be linked with object files to produce
progname.lo. This can be useful with libraries which redefine
routines in the standard libraries, or poorly written libraries
which reference symbols in the object files.
special progname keep symbol-name ...
Add specified list of symbols to the keep list for program
progname. An underscore (`_') is prepended to each symbol and it
becomes the argument to a -k option for the 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.
special progname ident identifier
Set the Makefile/C identifier for progname. This is normally
generated from a progname, mapping `-' to `_' and ignoring all
other non-identifier characters. This leads to programs named
"foo.bar" and "foobar" to map to the same identifier.
Only the objpaths parameter is actually needed by crunchgen, but it is
calculated from objdir and objs, which are in turn calculated from
srcdir, so is sometimes convenient to specify the earlier parameters and
let crunchgen calculate forward from there if it can.
The makefile produced by crunchgen contains an optional objs target that
will build the object files for each component program by running make(1)
inside that program's source directory. For this to work the srcdir and
objs parameters must also be valid. If they are not valid for a
particular program, that program is skipped in the objs target.
EXAMPLES
Here is an example crunchgen input conf file, named "kcopy.conf":
srcdirs /usr/src/bin /usr/src/sbin
progs test cp echo sh fsck halt init mount umount myinstall
progs anotherprog
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
special anotherprog -DNO_FOO WITHOUT_BAR=YES
libs -lutil -lcrypt
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 special line.
Additionally when "anotherprog" is built the arguments
-DNO_FOO WITHOUT_BAR=YES
are added to all build targets.
The crunched binary "kcopy" can be built as follows:
% 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!
At this point the binary "kcopy" can be copied onto an install floppy and
hard-linked to the names of the component programs.
Note that if the libs_so command had been used, copies of the libraries
so named would also need to be copied to the install floppy.
SEE ALSO
crunchide(1), make(1), rtld(1)
AUTHORS
The crunchgen utility was written by James da Silva <jds@cs.umd.edu>.
Copyright (c) 1994 University of Maryland. All Rights Reserved.
The libs_so keyword was added in 2005 by Adrian Steinmann <ast@marabu.ch>
and Ceri Davies <ceri@FreeBSD.org>.
CAVEATS
While crunchgen 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.
Some versions of the BSD build environment do not by default build the
intermediate object file for single-source file programs. The "make
objs" must then be used to get those object files built, or some other
arrangements made.
FreeBSD 13.1-RELEASE-p6 January 6, 2017 FreeBSD 13.1-RELEASE-p6
man2web Home...