CRUNCHGEN(1) BSD General Commands Manual CRUNCHGEN(1)NAMEcrunchgen — generates build environment for a crunched binary
SYNOPSIScrunchgen [-fOoq] [-c c-file-name] [-D src-root] [-d build-options]
[-e exec-file-name] [-L lib-dir] [-m makefile-name]
[-v var-spec] 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 pro‐
grams as possible onto an installation or system recovery floppy.
crunchgen 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 create the crunched executable file from the component pro‐
grams. 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. crunchgen
uses the companion program crunchide to eliminate link-time conflicts
between the component programs by hiding all unnecessary symbols.
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
in each component program's source dir to build the object files for the
user. This is not done automatically since in release engineering cir‐
cumstances 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
“⟨confname⟩.c”.
-D src-root
Assume that relative source directory specifications begin with
src-root.
-d build-options
Set the DBG variable in the generated makefile to build-options.
The default flags are -Os.
-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 lib-dir
Try to obtain libraries from lib-dir.
-m makefile-name
Set output Makefile name to makefile-name. The default name is
“⟨conf-name⟩.mk”.
-O Force crunchgen to parse the program's Makefile in determine the
list of .o files. Without this option crunchgen expects the pro‐
gram's Makefile to have a program.ro target that links all the
program objects into a single relocatable.
-o Use existing object files. Rather than rebuilding object files
via reach-over makefiles, instead search for and use existing
object files.
-q Quiet operation. Status messages are suppressed.
-v varspec
Append a variable specification to the on-the fly generated Make‐
file.
CRUNCHGEN CONFIGURATION FILE COMMANDScrunchgen reads specifications from the conf-file that describe the com‐
ponents of the crunched binary. In its simplest use, the component pro‐
gram names are merely listed along with the top-level source directories
in which their sources can be found. crunchgen then calculates (via the
source makefiles) and caches the list of object files and their loca‐
tions. 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.
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 avail‐
able or not built via a conventional Makefile, the following special com‐
mands can be used to set crunchgen parameters for a component program.
special progname keepsymbols symbols ...
Don't hide the specified symbols for progname. Normally all
externally visible symbols for a program is hidden to avoid
interference. Multiple keepsymbols lines can be specified for
given progname.
special progname srcdir pathname
Set the source directory for progname. This is normally calcu‐
lated by searching the specified srcdirs for a directory named
progname.
special progname objdir pathname
Set the obj directory for progname. This is normally calculated
by looking for a directory named “obj” under the srcdir, and if
that is not found, the srcdir itself becomes the objdir.
Note: This option only takes effect if the -o option to use
existing object files is also specified.
special progname objs object-file-name ...
Set the list of object files for program progname. This is nor‐
mally calculated by constructing a temporary makefile that
includes “srcdir / Makefile” and outputs the value of $(OBJS).
Multiple objs lines can be specified for given progname.
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. Multiple objpaths lines can be spec‐
ified for given progname.
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
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 particu‐
lar program, that program is skipped in the objs target.
ENVIRONMENT
MAKEOBJDIRPREFIX If the environment variable MAKEOBJDIRPREFIX is set,
the object directory will be prefixed with the path
contained in this environment variable.
Note: This variable is only used if the -o option to
use existing object files is also specified.
MACHINE If the environment variable MACHINE is set, it is used
as the name of the machine type, when accessing object
directories of the form obj.MACHINE. If it is not set,
it defaults to the machine type returned by uname(3).
Note: This option is only used if the -o option to use
existing object files is also specified.
MAKE If the environment variable MAKE is set, it is used as
the name of the make(1) executable to be called. If
this environment variable is not set, crunchgen
defaults to “make”.
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
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
This conf file specifies a small crunched binary consisting of some basic
system utilities plus a home-grown install program “myinstall”, for which
no source directory is specified, but its object file is specified
directly with the special line.
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.
SEE ALSOcrunchide(1), make(1)AUTHORScrunchgen was written by James da Silva ⟨jds@cs.umd.edu⟩.
Copyright (c) 1994 University of Maryland. All Rights Reserved.
BUGS
While crunchgen takes care to eliminate link conflicts between the compo‐
nent 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” target must then be used to get those object files built, or some
other arrangements made.
If a program directory being searched for is found, but contains no
objects, other directories are not searched. This causes the following
directive to fail:
srcdirs /usr/src/usr.bin /usr/src/usr.bin/less
progs less gzip
as the /usr/src/usr.bin/less directory will be found with the
/usr/src/usr.bin srcdirs entry, and as it does not contain the require
objects, crunchgen fails to find objects for the less program. To avoid
this problem, list specific srcdirs first, and the more general ones
later, for e.g.:
srcdirs /usr/src/usr.bin/less /usr/src/usr.bin
progs less gzip
will not have the above problem.
BSD October 18, 2006 BSD
