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Re: [Libguestfs] [PATCH] febootstrap-supermin-helper: Replace objcopy call for embedding init binary



On Wed, Aug 24, 2011 at 05:16:51PM +0200, Hilko Bengen wrote:
> objcopy needs "output-target" and "binary-architecture" parameters
> which makes it necessary to keep a list of known architectures.
> 
> The bin2s.pl script generates input for the GNU assembler which should
> produce an object file that is equivalent to that produced by objcopy.
> 
> I have successfully tested the change on an amd64 Debian/unstable system.
> ---
>  helper/Makefile.am      |   10 ++++++++--
>  helper/bin2s.pl         |   45 +++++++++++++++++++++++++++++++++++++++++++++
>  helper/elf-default-arch |   32 --------------------------------
>  3 files changed, 53 insertions(+), 34 deletions(-)
>  create mode 100755 helper/bin2s.pl
>  delete mode 100755 helper/elf-default-arch
> 
> diff --git a/helper/Makefile.am b/helper/Makefile.am
> index 01a6af1..ab7f692 100644
> --- a/helper/Makefile.am
> +++ b/helper/Makefile.am
> @@ -45,11 +45,17 @@ init_LDFLAGS = -static
>  # http://www.doof.me.uk/2010/05/07/cute-objcopy-hack/
>  ELF_DEFAULT_ARCH = $(shell $(srcdir)/elf-default-arch | gawk '{ print $$1 }')
>  DEFAULT_ARCH = $(shell $(srcdir)/elf-default-arch | gawk '{ print $$2 }')
> -ext2init.o: init
> +
> +CLEANFILES = ext2init.S
> +
> +ext2init.o: ext2init.S
> +	$(CC) -o $@ -c $<
> +
> +ext2init.S: init
>  	strip --strip-all $<
>  	@file $< | grep -isq static || \
>  	  (echo "*** error: init is not staticly linked"; exit 1)
> -	objcopy -I binary -B $(DEFAULT_ARCH) -O $(ELF_DEFAULT_ARCH) $< $@
> +	./bin2s.pl $< $@
>  
>  man_MANS = \
>  	febootstrap-supermin-helper.8
> diff --git a/helper/bin2s.pl b/helper/bin2s.pl
> new file mode 100755
> index 0000000..2c78b5e
> --- /dev/null
> +++ b/helper/bin2s.pl
> @@ -0,0 +1,45 @@
> +#!/usr/bin/perl
> +
> +# This script creates a source file for the GNU assembler which shuold
> +# result in an object file equivalent to that of
> +#
> +# objcopy -I binary -B $(DEFAULT_ARCH) -O $(ELF_DEFAULT_ARCH) <in> <out>
> +
> +use strict;
> +use warnings;
> +
> +die "usage: $0 <in> <out>\n" if @ARGV != 2;
> +
> +my ($infile, $outfile) = @ARGV;
> +my ($buf, $i, $sz);
> +open my $ifh, '<', $infile or die "open $infile: $!";
> +open my $ofh, '>', $outfile or die "open $outfile: $!";
> +
> +print $ofh <<"EOF";
> +/* This file has been automatically generated from $infile by $0 */
> +
> +\t.globl\t_binary_${infile}_start
> +\t.globl\t_binary_${infile}_end
> +\t.globl\t_binary_${infile}_size
> +
> +\t.section\t.data
> +_binary_${infile}_start:
> +EOF
> +
> +$sz = 0;
> +while ( $i = read $ifh, $buf, 12 ) {
> +    print $ofh "\t.byte\t"
> +      . join( ',', map { sprintf '0x%02x', ord $_ } split //, $buf ) . "\n";
> +    $sz += $i;
> +}
> +die "read $infile (at offset $sz): $!\n" if not defined $i;
> +close $ifh;
> +
> +print $ofh <<"EOF";
> +
> +_binary_${infile}_end:
> +
> +\t.equ _binary_${infile}_size, $sz
> +EOF
> +
> +close $ofh;
> diff --git a/helper/elf-default-arch b/helper/elf-default-arch
> deleted file mode 100755
> index 54af14d..0000000
> --- a/helper/elf-default-arch
> +++ /dev/null
> @@ -1,32 +0,0 @@
> -#!/bin/sh -
> -# Copyright (C) 2010 Red Hat Inc.
> -#
> -# This program is free software; you can redistribute it and/or modify
> -# it under the terms of the GNU General Public License as published by
> -# the Free Software Foundation; either version 2 of the License, or
> -# (at your option) any later version.
> -#
> -# This program is distributed in the hope that it will be useful,
> -# but WITHOUT ANY WARRANTY; without even the implied warranty of
> -# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> -# GNU General Public License for more details.
> -#
> -# You should have received a copy of the GNU General Public License
> -# along with this program; if not, write to the Free Software
> -# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> -
> -# Calculate the default ELF object architecture for this format.
> -# There doesn't seem to be an easy way to derive this from binutils,
> -# so instead we hard code it.
> -
> -case $(uname -m) in
> -    i[3456]86) echo "elf32-i386 i386" ;;
> -    x86_64) echo "elf64-x86-64 i386" ;;
> -    s390) echo "elf32-s390 s390:31-bit" ;;
> -    s390x) echo "elf64-s390 s390:31-bit" ;;
> -    ppc) echo "elf32-powerpc powerpc" ;;
> -    ppc64) echo "elf64-powerpc powerpc" ;;
> -    *)
> -        echo "This architecture is not recognized.  Please update helper/elf-default-arch."
> -        exit 1
> -esac

ACK.

I pushed this with a couple of minor modifications.

Thanks for fixing this hopefully once and for all :-)

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org


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