CRUNCHGEN(8) OpenBSD System Manager's Manual CRUNCHGEN(8)NAMEcrunchgen - generates build environment for a crunched binary
SYNOPSIScrunchgen [-EfMq] [-c c-file-name] [-D src-root] [-e exec-file-name]
[-L lib-dir] [-m makefile-name] [-O objdir-name] conf-file
crunchgen-h [-f keep-list-file] [-k keep-symbol] object-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 in a file named
<conf-name>.cache between runs.
crunchgen is later run again with the -h flag to eliminate link-time
conflicts between the component programs by hiding all unnecessary
symbols. Some symbols may be left visible via the -k keep-symbol and -f
keep-list-file options. The keep-list-file must contain a list of
symbols to keep visible, one symbol per line. Note that the C compiler
prepends an underscore in front of symbols, so to keep the C function
``foo'' visible, the option ``-k _foo'' must be used.
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:
-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 Don't prepend stub names with an underscore. Used for
architectures that don't have underscore prepended to symbol
names, such as ELF architectures.
-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.
-h Hide all unnecessary symbols. Note that this is done on some ELF
architectures by marking the symbol local, while the -M option
causes it to mangle the symbol name to hide the symbol. It is
therefore not advisable to try to run nm(1) on a crunched object
file. This is due to the nature of the ELF symbol table and how
some architectures use the symbol attributes for their GOT build.
-L lib-dir
Try to obtain libraries from lib-dir.
-M On ELF architectures mangle the symbol instead of marking it
global; necessary for some architectures due to GOT usage.
-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 with the make variable
${MAKEOBJDIR}.
-q Quiet operation. Status messages are suppressed.
CRUNCHGEN CONFIGURATION FILE COMMANDScrunchgen 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:
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
supplementary 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 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. 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
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.
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
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
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.
AUTHORScrunchgen was written by James da Silva <jds@cs.umd.edu>.
Copyright (c) 1994 University of Maryland. All Rights Reserved.
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'' target must then be used to get those object files built, or some
other arrangements made.
OpenBSD 4.9 August 8, 2010 OpenBSD 4.9
