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Script to extract EFI el torito image (e.g. needed to get ISO9660 efi driver from vmware media)

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git-svn-id: https://svn.code.sf.net/p/xcat/code/xcat-core/trunk@10747 8638fb3e-16cb-4fca-ae20-7b5d299a9bcd
This commit is contained in:
jbjohnso
2011-10-11 19:10:08 +00:00
parent b4290393bb
commit bd3ae47ba7
1 changed files with 96 additions and 0 deletions
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96
xCAT-server/share/xcat/scripts/extractefiboot.pl Executable file
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#!/usr/bin/env perl
#This is a utility to scrape out the EFI boot image from an el torito enabled disk
use strict;
use Fcntl qw/SEEK_SET/;
my $iso;
my $outfile;
GetOptions("out=s" => \$outfile,
"iso=s" => \$iso);
my $emul;
my $blksize=2048;
my $istream;
use Getopt::Long;
sub grabimage {
my $bootcat = shift;
my $image;
my @recdata = unpack("C2vC2vV",$bootcat);
unless ($recdata[0] == 0x88) { printf "Error: EFI torito record not bootable\n"; exit; }
$emul=$recdata[1];
#for now, ignore load segment, system type
seek($istream,$recdata[6]*$blksize,SEEK_SET);
my $size=$recdata[5];
if ($size==0) { $size = 1; } #if 0/1, it's auto-detect time
my $readbytes=read($istream,$image,$size*512);
if ($size == 1) { #we have to interpret the FAT header to get the real size
seek($istream,$recdata[6]*$blksize,SEEK_SET); # go back to beginning
my @fatheader = unpack("C11vCvC3vC11V",$image);
my $secsize=$fatheader[11];
if ($fatheader[17]) {
$size=$secsize*($fatheader[17]);
} else {
die "Unsupported FAT header, requires test of commented code segment";
}
# } elsif ($fatheader[-1]) {
# $size=$secsize*$fatheader[-1];
# }
$readbytes=read($istream,$image,$size);
}
my $outh;
open($outh,">",$outfile);
print $outh $image;
close($outh);
}
if (! -r $iso) {
printf "Error, $iso does not seem to exist or is not readable";
exit 1;
}
open($istream,"<",$iso) || die "Error opening $iso";
my $bootsect;
seek($istream,17*$blksize,SEEK_SET);
my $readbytes = read($istream,$bootsect,0x4b);
unless ($readbytes == 0x4b) {
printf "Error reading boot record volume from $iso\n";
exit 1;
}
my @recdata;
@recdata = unpack("CA5CA32C32V",$bootsect); #it would have been nice if the el torito actually said little endian on it..
unless ($recdata[0] == 0 and $recdata[1] eq 'CD001'
and $recdata[2] == 1 and $recdata[3] eq "EL TORITO SPECIFICATION") {
printf "Error: Boot record volume format invalid\n";
exit 1;
}
my $bootcatidx=$recdata[-1];
my $bootcat;
seek($istream,$bootcatidx*$blksize,SEEK_SET);
$readbytes = read($istream,$bootcat,0x20);
unless ($readbytes == 0x20) { printf "Error reading boot catalog at $bootcatidx\n"; exit 1; }
@recdata = unpack("C*",$bootcat);
unless ($recdata[0] == 1 and $recdata[0x1e] == 0x55 and $recdata[0x1f] == 0xaa) {
printf "Boot catalog has invalid header\n"; exit 1;
}
$readbytes = read($istream,$bootcat,0x20);
my $image;
unless ($readbytes == 0x20) { printf "Error reading default El torito record\n"; exit; }
if ($recdata[1] == 0xef) { #wow, the efi record came first, actually interpret that first record
grabimage($bootcat);
} else { # keep looking for an *EFI* record
#read in first header
read($istream,$bootcat,0x20);
@recdata = unpack("CCv",$bootcat);
while ($recdata[0] == 0x90 and $recdata[1] != 0xef) {
my $additionalrecords=$recdata[2];
while ($additionalrecords) {
read($istream,$bootcat,0x20); #throw away irrelevant sectors
$additionalrecords -= 1;
}
read($istream,$bootcat,0x20); #throw away irrelevant sectors
@recdata = unpack("CCv",$bootcat);
}
if ($recdata[1] != 0xef) {
printf "No EFI boot image found\n";
exit 1;
}
$readbytes=read($istream,$bootcat,0x20);
grabimage($bootcat);
}