#!/usr/bin/perl -w
  # (c) 2008, Steven Rostedt <srostedt@redhat.com>
  # Licensed under the terms of the GNU GPL License version 2
  #
  # recordmcount.pl - makes a section called __mcount_loc that holds
  #                   all the offsets to the calls to mcount.
  #
  #
  # What we want to end up with is a section in vmlinux called
  # __mcount_loc that contains a list of pointers to all the
  # call sites in the kernel that call mcount. Later on boot up, the kernel
  # will read this list, save the locations and turn them into nops.
  # When tracing or profiling is later enabled, these locations will then
  # be converted back to pointers to some function.
  #
  # This is no easy feat. This script is called just after the original
  # object is compiled and before it is linked.
  #
  # The references to the call sites are offsets from the section of text
  # that the call site is in. Hence, all functions in a section that
  # has a call site to mcount, will have the offset from the beginning of
  # the section and not the beginning of the function.
  #
  # The trick is to find a way to record the beginning of the section.
  # The way we do this is to look at the first function in the section
  # which will also be the location of that section after final link.
  # e.g.
  #
  #  .section ".text.sched"
  #  .globl my_func
  #  my_func:
  #        [...]
  #        call mcount  (offset: 0x5)
  #        [...]
  #        ret
  #  other_func:
  #        [...]
  #        call mcount (offset: 0x1b)
  #        [...]
  #
  # Both relocation offsets for the mcounts in the above example will be
  # offset from .text.sched. If we make another file called tmp.s with:
  #
  #  .section __mcount_loc
  #  .quad  my_func + 0x5
  #  .quad  my_func + 0x1b
  #
  # We can then compile this tmp.s into tmp.o, and link it to the original
  # object.
  #
  # But this gets hard if my_func is not globl (a static function).
  # In such a case we have:
  #
  #  .section ".text.sched"
  #  my_func:
  #        [...]
  #        call mcount  (offset: 0x5)
  #        [...]
  #        ret
  #  .globl my_func
  #  other_func:
  #        [...]
  #        call mcount (offset: 0x1b)
  #        [...]
  #
  # If we make the tmp.s the same as above, when we link together with
  # the original object, we will end up with two symbols for my_func:
  # one local, one global.  After final compile, we will end up with
  # an undefined reference to my_func.
  #
  # Since local objects can reference local variables, we need to find
  # a way to make tmp.o reference the local objects of the original object
  # file after it is linked together. To do this, we convert the my_func
  # into a global symbol before linking tmp.o. Then after we link tmp.o
  # we will only have a single symbol for my_func that is global.
  # We can convert my_func back into a local symbol and we are done.
  #
  # Here are the steps we take:
  #
  # 1) Record all the local symbols by using 'nm'
  # 2) Use objdump to find all the call site offsets and sections for
  #    mcount.
  # 3) Compile the list into its own object.
  # 4) Do we have to deal with local functions? If not, go to step 8.
  # 5) Make an object that converts these local functions to global symbols
  #    with objcopy.
  # 6) Link together this new object with the list object.
  # 7) Convert the local functions back to local symbols and rename
  #    the result as the original object.
  #    End.
  # 8) Link the object with the list object.
  # 9) Move the result back to the original object.
  #    End.
  #
  
  use strict;
  
  my $P = $0;
  $P =~ s@.*/@@g;
  
  my $V = '0.1';

  if ($#ARGV < 7) {

  	print "usage: $P arch bits objdump objcopy cc ld nm rm mv is_module inputfile
  ";

  	print "version: $V
  ";
  	exit(1);
  }

  my ($arch, $bits, $objdump, $objcopy, $cc,

      $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;

  # This file refers to mcount and shouldn't be ftraced, so lets' ignore it
  if ($inputfile eq "kernel/trace/ftrace.o") {
      exit(0);
  }

  # Acceptable sections to record.
  my %text_sections = (
       ".text" => 1,

       ".sched.text" => 1,
       ".spinlock.text" => 1,

       ".irqentry.text" => 1,

  );

  $objdump = "objdump" if ((length $objdump) == 0);
  $objcopy = "objcopy" if ((length $objcopy) == 0);
  $cc = "gcc" if ((length $cc) == 0);
  $ld = "ld" if ((length $ld) == 0);
  $nm = "nm" if ((length $nm) == 0);
  $rm = "rm" if ((length $rm) == 0);
  $mv = "mv" if ((length $mv) == 0);
  
  #print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
  #    "'$nm' '$rm' '$mv' '$inputfile'
  ";

  my %locals;		# List of local (static) functions
  my %weak;		# List of weak functions
  my %convert;		# List of local functions used that needs conversion

  
  my $type;

  my $nm_regex;		# Find the local functions (return function)

  my $section_regex;	# Find the start of a section

  my $function_regex;	# Find the name of a function
  			#    (return offset and func name)

  my $mcount_regex;	# Find the call site to mcount (return offset)

  my $alignment;		# The .align value to use for $mcount_section

  my $section_type;	# Section header plus possible alignment command

  if ($arch eq "x86") {
      if ($bits == 64) {
  	$arch = "x86_64";
      } else {
  	$arch = "i386";
      }
  }

  #
  # We base the defaults off of i386, the other archs may
  # feel free to change them in the below if statements.
  #
  $nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
  $section_regex = "Disassembly of section\\s+(\\S+):";
  $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
  $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";

  $section_type = '@progbits';

  $type = ".long";

  if ($arch eq "x86_64") {

      $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
      $type = ".quad";

      $alignment = 8;

  
      # force flags for this arch
      $ld .= " -m elf_x86_64";
      $objdump .= " -M x86-64";
      $objcopy .= " -O elf64-x86-64";
      $cc .= " -m64";

  } elsif ($arch eq "i386") {

      $alignment = 4;

  
      # force flags for this arch
      $ld .= " -m elf_i386";
      $objdump .= " -M i386";
      $objcopy .= " -O elf32-i386";
      $cc .= " -m32";

  } elsif ($arch eq "sh") {

      $alignment = 2;

  
      # force flags for this arch
      $ld .= " -m shlelf_linux";
      $objcopy .= " -O elf32-sh-linux";
      $cc .= " -m32";

  } elsif ($arch eq "powerpc") {
      $nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";

      $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:";
      $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";

      if ($bits == 64) {
  	$type = ".quad";

      }

  } elsif ($arch eq "arm") {
      $alignment = 2;
      $section_type = '%progbits';

  } elsif ($arch eq "ia64") {
      $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
      $type = "data8";
  
      if ($is_module eq "0") {
          $cc .= " -mconstant-gp";
      }

  } else {
      die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
  }
  
  my $text_found = 0;
  my $read_function = 0;
  my $opened = 0;

  my $mcount_section = "__mcount_loc";
  
  my $dirname;
  my $filename;
  my $prefix;
  my $ext;
  
  if ($inputfile =~ m,^(.*)/([^/]*)$,) {
      $dirname = $1;
      $filename = $2;
  } else {
      $dirname = ".";
      $filename = $inputfile;
  }
  
  if ($filename =~ m,^(.*)(\.\S),) {
      $prefix = $1;
      $ext = $2;
  } else {
      $prefix = $filename;
      $ext = "";
  }
  
  my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
  my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
  
  #

  # --globalize-symbols came out in 2.17, we must test the version
  # of objcopy, and if it is less than 2.17, then we can not
  # record local functions.
  my $use_locals = 01;
  my $local_warn_once = 0;
  my $found_version = 0;
  
  open (IN, "$objcopy --version |") || die "error running $objcopy";
  while (<IN>) {
      if (/objcopy.*\s(\d+)\.(\d+)/) {
  	my $major = $1;
  	my $minor = $2;
  
  	$found_version = 1;
  	if ($major < 2 ||
  	    ($major == 2 && $minor < 17)) {
  	    $use_locals = 0;
  	}
  	last;
      }
  }
  close (IN);
  
  if (!$found_version) {
      print STDERR "WARNING: could not find objcopy version.
  " .
  	"\tDisabling local function references.
  ";
  }

  #

  # Step 1: find all the local (static functions) and weak symbols.
  #        't' is local, 'w/W' is weak (we never use a weak function)

  #
  open (IN, "$nm $inputfile|") || die "error running $nm";
  while (<IN>) {

      if (/$nm_regex/) {

  	$locals{$1} = 1;

      } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) {
  	$weak{$2} = $1;

      }
  }
  close(IN);

  my @offsets;		# Array of offsets of mcount callers
  my $ref_func;		# reference function to use for offsets
  my $offset = 0;		# offset of ref_func to section beginning
  
  ##
  # update_funcs - print out the current mcount callers
  #
  #  Go through the list of offsets to callers and write them to
  #  the output file in a format that can be read by an assembler.
  #
  sub update_funcs
  {
      return if ($#offsets < 0);
  
      defined($ref_func) || die "No function to reference";
  
      # A section only had a weak function, to represent it.
      # Unfortunately, a weak function may be overwritten by another
      # function of the same name, making all these offsets incorrect.
      # To be safe, we simply print a warning and bail.
      if (defined $weak{$ref_func}) {
  	print STDERR
  	    "$inputfile: WARNING: referencing weak function" .
  	    " $ref_func for mcount
  ";
  	return;
      }
  
      # is this function static? If so, note this fact.
      if (defined $locals{$ref_func}) {

  
  	# only use locals if objcopy supports globalize-symbols
  	if (!$use_locals) {

  	    return;
  	}

  	$convert{$ref_func} = 1;
      }
  
      # Loop through all the mcount caller offsets and print a reference
      # to the caller based from the ref_func.
      for (my $i=0; $i <= $#offsets; $i++) {
  	if (!$opened) {
  	    open(FILE, ">$mcount_s") || die "can't create $mcount_s
  ";
  	    $opened = 1;

  	    print FILE "\t.section $mcount_section,\"a\",$section_type
  ";

  	    print FILE "\t.align $alignment
  " if (defined($alignment));

  	}
  	printf FILE "\t%s %s + %d
  ", $type, $ref_func, $offsets[$i] - $offset;
      }
  }

  #
  # Step 2: find the sections and mcount call sites
  #

  open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump";

  my $text;

  my $read_headers = 1;

  while (<IN>) {
      # is it a section?
      if (/$section_regex/) {

  	$read_headers = 0;

  
  	# Only record text sections that we know are safe
  	if (defined($text_sections{$1})) {
  	    $read_function = 1;
  	} else {
  	    $read_function = 0;
  	}

  	# print out any recorded offsets
  	update_funcs() if ($text_found);
  
  	# reset all markers and arrays

  	$text_found = 0;

  	undef($ref_func);
  	undef(@offsets);

      # section found, now is this a start of a function?
      } elsif ($read_function && /$function_regex/) {

  	$text_found = 1;

  	$offset = hex $1;
  	$text = $2;
  
  	# if this is either a local function or a weak function
  	# keep looking for functions that are global that
  	# we can use safely.
  	if (!defined($locals{$text}) && !defined($weak{$text})) {
  	    $ref_func = $text;
  	    $read_function = 0;
  	} else {
  	    # if we already have a function, and this is weak, skip it
  	    if (!defined($ref_func) || !defined($weak{$text})) {
  		$ref_func = $text;
  	    }

  	}

      } elsif ($read_headers && /$mcount_section/) {
  	#
  	# Somehow the make process can execute this script on an
  	# object twice. If it does, we would duplicate the mcount
  	# section and it will cause the function tracer self test
  	# to fail. Check if the mcount section exists, and if it does,
  	# warn and exit.
  	#
  	print STDERR "ERROR: $mcount_section already in $inputfile
  " .
  	    "\tThis may be an indication that your build is corrupted.
  " .
  	    "\tDelete $inputfile and try again. If the same object file
  " .
  	    "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.
  ";
  	exit(-1);

      }
  
      # is this a call site to mcount? If so, record it to print later
      if ($text_found && /$mcount_regex/) {
  	$offsets[$#offsets + 1] = hex $1;

      }
  }

  # dump out anymore offsets that may have been found
  update_funcs() if ($text_found);

  # If we did not find any mcount callers, we are done (do nothing).
  if (!$opened) {
      exit(0);
  }
  
  close(FILE);
  
  #
  # Step 3: Compile the file that holds the list of call sites to mcount.
  #
  `$cc -o $mcount_o -c $mcount_s`;
  
  my @converts = keys %convert;
  
  #
  # Step 4: Do we have sections that started with local functions?
  #
  if ($#converts >= 0) {
      my $globallist = "";
      my $locallist = "";
  
      foreach my $con (@converts) {
  	$globallist .= " --globalize-symbol $con";
  	$locallist .= " --localize-symbol $con";
      }
  
      my $globalobj = $dirname . "/.tmp_gl_" . $filename;
      my $globalmix = $dirname . "/.tmp_mx_" . $filename;
  
      #
      # Step 5: set up each local function as a global
      #
      `$objcopy $globallist $inputfile $globalobj`;
  
      #
      # Step 6: Link the global version to our list.
      #
      `$ld -r $globalobj $mcount_o -o $globalmix`;
  
      #
      # Step 7: Convert the local functions back into local symbols
      #
      `$objcopy $locallist $globalmix $inputfile`;
  
      # Remove the temp files
      `$rm $globalobj $globalmix`;
  
  } else {
  
      my $mix = $dirname . "/.tmp_mx_" . $filename;
  
      #
      # Step 8: Link the object with our list of call sites object.
      #
      `$ld -r $inputfile $mcount_o -o $mix`;
  
      #
      # Step 9: Move the result back to the original object.
      #
      `$mv $mix $inputfile`;
  }
  
  # Clean up the temp files
  `$rm $mcount_o $mcount_s`;
  
  exit(0);