#! /usr/bin/perl

use strict;
use warnings;

use POSIX qw ( SIGCONT );

my $pid = shift;

my $base = "/proc/$pid";
open(my $mem_fh, "$base/mem") || die "$base/mem: $!";
open(my $maps_fh, "$base/maps") || die "$base/maps: $!";

require 'syscall.ph';
my $result = syscall(&SYS_ptrace, 16, int($pid), 1, 0);

if ($result == -1) {
  die "Error: $!\n";
}

while (<$maps_fh>)
{
  my ($start, $end) = map {hex($_)} /^(\w+)-(\w+)/;

  dump_range_seek($mem_fh, $start, $end - $start);
}

# wake the patient back up
kill(SIGCONT(), $pid);

sub dump_range_seek
{
  my $fh = shift;
  my $start = shift;
  my $len = shift;

  my $seek = sysseek($fh, $start, 0);
  die "seek, $!" unless defined($seek);
  # warn "seek = $seek";

  my $buf;
  while ($len)
  {
    my $chunk = $len > 4096 ? 4096 : $len;
    # warn "reading $chunk\n";
    my $read = sysread($fh, $buf, $chunk);
    die "$!" unless defined($read);

    die "read 0" unless $read;
    $len -= $read;
    print $buf;
  }
}