crunch/crunchgen/crunchgen.1

.\"	$NetBSD: crunchgen.1,v 1.32 2014/03/18 18:20:44 riastradh Exp $
.\"
.\" Copyright (c) 1994 University of Maryland
.\" All Rights Reserved.
.\"
.\" Permission to use, copy, modify, distribute, and sell this software and its
.\" documentation for any purpose is hereby granted without fee, provided that
.\" the above copyright notice appear in all copies and that both that
.\" copyright notice and this permission notice appear in supporting
.\" documentation, and that the name of U.M. not be used in advertising or
.\" publicity pertaining to distribution of the software without specific,
.\" written prior permission.  U.M. makes no representations about the
.\" suitability of this software for any purpose.  It is provided "as is"
.\" without express or implied warranty.
.\"
.\" U.M. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL U.M.
.\" BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
.\" IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.\" Author: James da Silva, Systems Design and Analysis Group
.\"			   Computer Science Department
.\"			   University of Maryland at College Park
.\"
.Dd June 10, 2013
.Dt CRUNCHGEN 1
.Os
.Sh NAME
.Nm crunchgen
.Nd generates build environment for a crunched binary
.Sh SYNOPSIS
.Nm
.Op Fl fOoq
.Op Fl c Ar c-file-name
.Op Fl D Ar src-root
.Op Fl d Ar build-options
.Op Fl e Ar exec-file-name
.Op Fl L Ar lib-dir
.Op Fl m Ar makefile-name
.Op Fl v Ar var-spec
.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
.Fn 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.
.Pp
.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 create the crunched executable
file from the component programs.
For each component program,
.Nm
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
uses the companion program
.Em crunchide
to eliminate link-time conflicts between the component programs by
hiding all unnecessary symbols.
.Pp
After
.Nm
is run, the crunched binary can be built by running
.Dq make -f Ao conf-name Ac Ns .mk .
The component programs' object files must already be built.
An
.Dq 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.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl c Ar c-file-name
Set output C file name to
.Ar c-file-name .
The default name is
.Dq Ao confname Ac Ns .c .
.It Fl D Ar src-root
Assume that relative source directory specifications begin with
.Ar src-root .
.It Fl d Ar build-options
Set the DBG variable in the generated makefile to
.Ar build-options .
The default flags are -Os.
.It Fl e Ar exec-file-name
Set crunched binary executable file name to
.Ar exec-file-name .
The default name is
.Dq Aq Mt conf-name .
.It Fl f
Flush cache.
Forces the recalculation of cached parameters.
.It Fl L Ar lib-dir
Try to obtain libraries from
.Ar lib-dir .
.It Fl m Ar makefile-name
Set output Makefile name to
.Ar makefile-name .
The default name is
.Dq Ao conf-name Ac Ns .mk .
.It Fl O
Force
.Nm
to parse the program's Makefile in determine the list of .o files.
Without this option
.Nm
expects the program's Makefile to have a program.ro target that links all
the program objects into a single relocatable.
.It Fl o
Use existing object files.
Rather than rebuilding object files via reach-over
makefiles, instead search for and use existing object files.
.It Fl q
Quiet operation.
Status messages are suppressed.
.It Fl v Ar varspec
Append a variable specification to the on-the fly generated Makefile.
.El
.Sh CRUNCHGEN CONFIGURATION FILE COMMANDS
.Nm
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
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.
.Pp
The
.Ar conf-file
commands are as follows:
.Bl -tag -width indent
.It 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
.Bx
.Dq Ao source-dir Ac Ns / Ns Ao progname Ac Ns /
convention.
Multiple
.Em srcdirs
lines can be specified.
The directories are searched in the order they are given.
.It Nm progs Ar progname ...
A list of programs that make up the crunched binary.
Multiple
.Em progs
lines can be specified.
.It Nm libs Ar libspec ...
A list of library specifications to be included in the crunched binary link.
Multiple
.Em libs
lines can be specified.
.It 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
.Pp
To handle specialized situations, such as when the source is not
available or not built via a conventional Makefile, the following
.Em special
commands can be used to set
.Nm
parameters for a component program.
.Bl -tag -width indent
.It Nm special Ar progname Nm keepsymbols Ar symbols ...
Don't hide the specified symbols for
.Ar progname .
Normally all externally visible symbols for
a program is hidden to avoid interference.
Multiple
.Em keepsymbols
lines can be specified for given
.Ar progname .
.It Nm special Ar progname Nm srcdir Ar pathname
Set the source directory for
.Ar progname .
This is normally calculated by searching the specified
.Em srcdirs
for a directory named
.Ar progname .
.It 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 .
.Pp
.Nm Note :
This option only takes effect if the -o option to use existing object files is also
specified.
.It 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).
Multiple
.Em objs
lines can be specified for given
.Ar progname .
.It 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
.Em objdir
pathname to each file in the
.Nm objs
list.
Multiple
.Em objpaths
lines can be specified for given
.Ar progname .
.El
.Pp
Only the
.Em objpaths
parameter is actually needed by
.Nm
but it is calculated from
.Em objdir
and
.Em objs ,
which are in turn calculated from
.Em srcdir ,
so is sometimes convenient to specify the earlier parameters and let
.Nm
calculate forward from there if it can.
.Pp
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
.Em srcdir
and
.Em objs
parameters must also be valid.
If they are not valid for a particular program, that
program is skipped in the
.Ar objs
target.
.Pp
The makefile produced by
.Nm
strips certain sections from the final binary to reduce its size.
This includes:
.Bl -tag -width ".Li .eh_frame_hdr"
.It Li .eh_frame
Unwinding tables for exceptions and backtraces.
.It Li .eh_frame_hdr
Index of the
.Li .eh_frame
section.
.It Li .note
Optional data for the kernel and/or runtime linker.
.It Li .comment
Comments in the binary.
.It Li .ident
Embedded source revisions used by
.Xr ident 1 .
.It Li .copyright
Embedded copyright notes.
.El
.Sh ENVIRONMENT
.Bl -tag -width MAKEOBJDIRPREFIX
.It Ev MAKEOBJDIRPREFIX
If the environment variable
.Ev MAKEOBJDIRPREFIX
is set, the object directory will be prefixed with the path contained in this
environment variable.
.Pp
.Nm Note :
This variable is only used if the -o option to use existing object files is also
specified.
.It Ev MACHINE
If the environment variable
.Ev 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
.Xr uname 3 .
.Pp
.Nm Note :
This option is only used if the -o option to use existing object files is also
specified.
.It Ev MAKE
If the environment variable
.Ev MAKE
is set, it is used as the name of the
.Xr make 1
executable to be called.
If this environment variable is not set,
.Nm
defaults to
.Dq make .
.El
.Sh EXAMPLES
Here is an example
.Em crunchgen
input conf file, named
.Dq Pa kcopy.conf :
.Pp
.Bd -literal -offset indent
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
.Ed
.Pp
This conf file specifies a small crunched binary consisting of some
basic system utilities plus a home-grown install program
.Dq myinstall ,
for which no source directory is specified, but its object file is
specified directly with the
.Em special
line.
.Pp
The crunched binary
.Dq kcopy
can be built as follows:
.Pp
.Bd -literal -offset indent
% 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!
.Ed
.Pp
At this point the binary
.Dq kcopy
can be copied onto an install floppy
and hard-linked to the names of the component programs.
.Sh SEE ALSO
.Xr crunchide 1 ,
.Xr make 1
.Sh AUTHORS
.Nm
was written by
.An James da Silva Aq Mt jds@cs.umd.edu .
.Pp
Copyright (c) 1994 University of Maryland.  All Rights Reserved.
.Sh BUGS
While
.Nm
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.
.Pp
Some versions of the
.Bx
build environment do not by default build the
intermediate object file for single-source file programs.
The
.Dq make objs
target must then be used to get those object files built, or
some other arrangements made.
.Pp
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:
.Pp
.Bd -literal -offset indent
srcdirs /usr/src/usr.bin /usr/src/usr.bin/less
progs less gzip
.Ed
.Pp
as the
.Pa /usr/src/usr.bin/less
directory will be found with the
.Pa /usr/src/usr.bin
.Em srcdirs
entry, and as it does not contain the require objects,
.Nm
fails to find objects for the
.Em less
program.
To avoid this problem, list specific srcdirs first, and
the more general ones later, for e.g.:
.Pp
.Bd -literal -offset indent
srcdirs /usr/src/usr.bin/less /usr/src/usr.bin
progs less gzip
.Ed
.Pp
will not have the above problem.