NAME

crunchgen — generates build environment for a crunched binary

SYNOPSIS

crunchgen

[-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 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 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. 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 circumstances it is generally not desirable to be modifying objects in other directories.

The options are as follows:

CRUNCHGEN CONFIGURATION FILE COMMANDS

crunchgen 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. 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 crunchgen needs.

The conf-file commands are as follows:

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.

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 particular program, that program is skipped in the objs target.

The makefile produced by crunchgen strips certain sections from the final binary to reduce its size. This includes:

ENVIRONMENT

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.

AUTHORS

crunchgen was written by James da Silva <jds@cs.umd.edu>.

BUGS

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” 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.

Manual browser: crunchgen(1)