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#!/usr/bin/perl
# Copyright (C) 2016 Intel Corporation.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
# Changes the Mach-O file type header to PowerPC.
#
# The header is (from mach-o/loader.h):
# struct mach_header {
# uint32_t magic; /* mach magic number identifier */
# cpu_type_t cputype; /* cpu specifier */
# cpu_subtype_t cpusubtype; /* machine specifier */
# uint32_t filetype; /* type of file */
# uint32_t ncmds; /* number of load commands */
# uint32_t sizeofcmds; /* the size of all the load commands */
# uint32_t flags; /* flags */
# };
#
# The 64-bit header is identical in the first three fields, except for a different
# magic number. We will not touch the magic number, we'll just reset the cputype
# field to the PowerPC type and the subtype field to zero.
#
# We will not change the file's endianness. That means we might create a little-endian
# PowerPC binary, which could not be run in real life.
#
# We will also not change the 64-bit ABI flag, which is found in the cputype's high
# byte. That means we'll create a PPC64 binary if fed a 64-bit input.
#
use strict;
use constant MH_MAGIC => 0xfeedface;
use constant MH_CIGAM => 0xcefaedfe;
use constant MH_MAGIC_64 => 0xfeedfacf;
use constant MH_CIGAM_64 => 0xcffaedfe;
use constant CPU_TYPE_POWERPC => 18;
use constant CPU_SUBTYPE_POWERPC_ALL => 0;
my $infile = shift @ARGV or die("Missing input filename");
my $outfile = shift @ARGV or die("Missing output filename");
open IN, "<$infile" or die("Can't open $infile for reading: $!\n");
open OUT, ">$outfile" or die("Can't open $outfile for writing: $!\n");
binmode IN;
binmode OUT;
# Read the first 12 bytes, which includes the interesting fields of the header
my $buffer;
read(IN, $buffer, 12);
my $magic = vec($buffer, 0, 32);
if ($magic == MH_MAGIC || $magic == MH_MAGIC_64) {
# Big endian
# The low byte of cputype is at offset 7
vec($buffer, 7, 8) = CPU_TYPE_POWERPC;
} elsif ($magic == MH_CIGAM || $magic == MH_CIGAM_64) {
# Little endian
# The low byte of cpytype is at offset 4
vec($buffer, 4, 8) = CPU_TYPE_POWERPC;
} else {
$magic = '';
$magic .= sprintf("%02X ", $_) for unpack("CCCC", $buffer);
die("Invalid input. Unknown magic $magic\n");
}
vec($buffer, 2, 32) = CPU_SUBTYPE_POWERPC_ALL;
print OUT $buffer;
# Copy the rest
while (!eof(IN)) {
read(IN, $buffer, 4096) and
print OUT $buffer or
die("Problem copying: $!\n");
}
close(IN);
close(OUT);
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