#!/usr/bin/perl
# Zero-pads the stage2 bootloader binary out to a fixed size (STAGE2_SECTORS
# * 512 bytes), so the kernel's on-disk starting sector is predictable
# regardless of stage2's actual compiled size. Errors out if stage2 has
# grown past that budget instead of silently truncating it.

my $size = $ARGV[1] || die "usage: padstage2.pl <file> <size-in-bytes>\n";

open(F, $ARGV[0]) || die "open $ARGV[0]: $!";
my $n = sysread(F, my $buf, $size + 1);
close(F);

if ($n > $size) {
  print STDERR "stage2 too large: $n bytes (max $size)\n";
  exit 1;
}

print STDERR "stage2 is $n bytes (max $size)\n";

$buf .= "\0" x ($size - $n);

open(F, ">$ARGV[0]") || die "open >$ARGV[0]: $!";
print F $buf;
close(F);