CRUNCHGEN(1) BSD Reference Manual CRUNCHGEN(1)
crunchgen - generates build environment for a crunched binary
crunchgen [-fq] [-c c-file-name] [-D src-root] [-e exec-file-name]
[-L lib-dir] [-m makefile-name] [-O objdir-name] conf-file
A crunched binary is a program made up of many other programs linked to-
gether 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.
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 in a file named <conf-
name>.cache between runs. crunchgen uses GNU objcopy(1) to eliminate
link-time conflicts between the component programs by hiding all unneces-
sary symbols and renaming the main() function.
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
"<conf-name>.c".
-D src-root
Assume that relative source directory specifications begin with
src-root.
-E Ignored for compatibility with crunchgen version 0.x.
-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 objdir-name
Specify an object directory to use. It defaults to "obj", though
for cross building purposes it can be used to specify
"obj.${HOST}.${MACHINE}". Normally used in combination with the
make variable ${MAKEOBJDIR}.
-q Quiet operation. Status messages are suppressed.
Distinguishing between executable formats with (COFF, a.out, PE) and
without (ELF) leading underscores is no longer necessary.
crunchgen 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 specialised 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.
libdirs dirname
A list of source trees in which the source directories for sup-
plementary libraries can be found.
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 specialised 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 srcdir pathname
Set the source directory for progname. This is normally calculat-
ed 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.
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 in-
cludes "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.
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 it 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.
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
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.
crunchgen was written by James da Silva <jds@cs.umd.edu>.
Copyright (C) 1994 University of Maryland. All Rights Reserved.
Thorsten Glaser <tg@mirbsd.de> did major cleanup for MirBSD, replaced the
traditional crunchide with GNU objcopy, made the -E switch and crunched
stub objects obsolete.
While crunchgen takes care to eliminate link conflicts between the com-
ponent 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. Other build systems, like automake, suffer from the
same issues.
MirBSD #10-current July 7, 2007 2