#!/usr/sbin/perl
#
# Usage example:   
#              findoff.perl 0x400000 a.out
#
# Given an elf file, and a virtual address, find the
# offset in the elf file corresponding to that address
# Using elfdump -o (or elfdump -h if it must) 
# to find virtual addresses
# and file offsets.
#
# Stops as soon as it sees a program header with the right virtual
# address.
#
# If the file has no program headers (a .o has none ) this
# looks for all matches and also prints the section info so
# you can decide if you really want this section as the one.
# Prints all section header matches.
#
# elfdump -o output format example:
#  Type        Offset      Vaddr              Paddr
#  Filesz      Memsz       Flags              Align
#
#  LOAD        0xf000      0x1000f000         0x1000f000        
#  0x1000      0x1000      rw-                0x1000            


$_ = $ARGV[0];
shift;
sub getvalue 
{
  my $vin = $_[0];
  my $v = 0;
  $v = oct($vin);
  return $v;
}
$y = $_;
$v = getvalue($y,"2");
$file =  $ARGV[0];
if ( ! -e $file )  {die "$file does not exist";}
$waspt = 0;
open MYF, "elfdump -o $file |" or die "elfdump  on $file failed: $!";
while(<MYF>) {
  if(/PT_.*/) {
	@lin1 = split(" ",$_);
	$waspt = 1;
	next;
  }
  if($waspt == 1 ) {
	@lin2 = split(" ",$_);
	$waspt = 0;
	$lo = getvalue($lin1[2]);
        $high = $lo + getvalue($lin2[0]);
        $offbase = getvalue($lin1[1]);

	if(($v >= $lo) && ($v  < $high)) {
	    $off = $offbase + ($v - $lo);
	    printf "0x%lx ( %ld decimal) in %s\n",
			$off,
			$off,
			$file;
	    exit(0);
        }

  }
  next;
}
close MYF or die "bad elfdump completion on $file: $! $?";
#
#  We found nothing
# so lets try -h
#          **** SECTION  HEADER  TABLE ****
#[No]   Type                  Addr       Offset     Size        Name
#       Link       Info       Adralgn    Entsize    Flags
#
#[1]    SHT_SYMTAB            0          0x34       0xd0        .symtab
#       3          0x5        0x4        0x10       
#
$waspt = 0;
$linec = 1;
$lineh1 = "\n";
$lineh2 = "\n";
open MYF, "elfdump -h $file |" or die "elfdump  on $file failed: $!";
while(<MYF>) {
  if($linec == 5) {
	$lineh1 = $_;
  }
  if($linec == 6) {
	$lineh2 = $_;
  }
  $linec = $linec + 1;
  if(/SHT.*/) {
        @lin1 = split(" ",$_);
        $waspt = 1;
	$line1entire = $_;
        next;
  }
  if($waspt == 1 ) {
        @lin2 = split(" ",$_);
	$line2entire = $_;
        $waspt = 0;
        $lo = getvalue($lin1[2]);
        $high = $lo + getvalue($lin2[3]);

        $offbase = getvalue($lin1[3]);
        if(($v >= $lo) && ($v  < $high)) {
            $off = $offbase + ($v - $lo);
            printf "0x%lx ( %ld decimal) in %s section %s\n",
                        $off,
                        $off,
                        $file,
			$lin1[5];
	   print  $lineh1;
	   print  $lineh2;
	   print  $line1entire;
	   print  $line2entire;
	   printf "\n";
        }

  }
  next;
}
close MYF or die "bad elfdump completion on $file: $! $?";

exit(0);