CRUNCHGEN(1)

CRUNCHGEN(1) | General Commands Manual | CRUNCHGEN(1)

# NAME

`crunchgen` —
generates build environment for a crunched binary

# SYNOPSIS

`crunchgen` | [`-fOopqSs`] [`-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:

`-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 program'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.
`-p`
  Produce static pie (position independent executables).
`-q`
  Quiet operation. Status messages are suppressed.
`-S`
  Enable sanitization with a sanitizer in libc.
`-s`
  Enable sanitization.
`-v` varspec
  Append a variable specification to the on-the fly generated Makefile.

# 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:

`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 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 `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 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.

  `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 normally 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 specified 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 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:

`.eh_frame`
  Unwinding tables for exceptions and backtraces.
`.eh_frame_hdr`
  Index of the `.eh_frame` section.
`.note`
  Optional data for the kernel and/or runtime linker.
`.comment`
  Comments in the binary.
`.ident`
  Embedded source revisions used by ident(1).
`.copyright`
  Embedded copyright notes.

# 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 ALSO

crunchide(1), make(1)

# AUTHORS

`crunchgen` 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 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.

June 21, 2018 | NetBSD 9.0