Copyright (c) 1994 University of Maryland
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Author: James da Silva, Systems Design and Analysis Group
Computer Science Department
University of Maryland at College Park
$FreeBSD: head/usr.sbin/crunch/crunchgen/crunchgen.1 68512 2000-11-09 02:31:02Z steve $

.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 foql .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.

p .Nm 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 creates 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.

p .Nm places specific requirements on package

a Makefiles which make it unsuitable for use with non-BSD sources. In particular, the .Nm Makefile must contain the target .Ar depend , and it must define all object files in the variable .Ar OBJS . In some cases, you can use a fake

a Makefile : before looking for

a Makefile in the source directory

a foo , .Nm looks for the file

a Makefile.foo in the current directory.

p 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.

p The options are as follows: l -tag -width indent t Fl c Ar c-file-name Set output C file name to .Ar c-file-name . The default name is ``<conf-name>.c''. t Fl e Ar exec-file-name Set crunched binary executable file name to .Ar exec-file-name . The default name is ``<conf-name>''. t Fl f Flush cache. Forces the recalculation of cached parameters. t Fl l List names. Lists the names this binary will respond to. t 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. t Fl m Ar makefile-name Set output Makefile name to .Ar makefile-name . The default name is ``<conf-name>.mk''. t Fl o Add ``make obj'' rules to each program make target. t 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.

p The .Ar conf-file commands are as follows: l -tag -width indent t 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. t Nm progs Ar progname ... A list of programs that make up the crunched binary. Multiple .Nm progs lines can be specified. t Nm libs Ar libspec ... A list of library specifications to be included in the crunched binary link. Multiple .Nm libs lines can be specified. t 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. l -tag -width indent t 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 . t 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 . t 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). t 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. t 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 . t 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

p 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.

p 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 :

p

 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

p 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.

p The crunched binary ``kcopy'' can be built as follows:

p

 % 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!

p 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.

p 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.