#!/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 this is that each object file will have a
  # section called __mcount_loc that will hold the list of pointers to mcount
  # callers. After final linking, the vmlinux will have within .init.data the
  # list of all callers to mcount between __start_mcount_loc and __stop_mcount_loc.
  # 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.
  #

  # When parse this object file using 'objdump', the references to the call
  # sites are offsets from the section 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.
  #
  # But where this section will reside finally in vmlinx is undetermined at
  # this point. So we can't use this kind of offsets to record the final
  # address of this call site.
  #
  # The trick is to change the call offset referring the start of a section to
  # referring a function symbol in this section. During the link step, 'ld' will
  # compute the final address according to the information we record.

  #

  # e.g.
  #

  #  .section ".sched.text", "ax"

  #        [...]

  #  func1:
  #        [...]
  #        call mcount  (offset: 0x10)
  #        [...]
  #        ret
  #  .globl fun2
  #  func2:             (offset: 0x20)
  #        [...]

  #        [...]
  #        ret

  #  func3:

  #        [...]

  #        call mcount (offset: 0x30)

  #        [...]
  #
  # Both relocation offsets for the mcounts in the above example will be

  # offset from .sched.text. If we choose global symbol func2 as a reference and
  # make another file called tmp.s with the new offsets:

  #
  #  .section __mcount_loc

  #  .quad  func2 - 0x10
  #  .quad  func2 + 0x10

  #

  # We can then compile this tmp.s into tmp.o, and link it back to the original

  # object.
  #

  # In our algorithm, we will choose the first global function we meet in this
  # section as the reference. But this gets hard if there is no global functions
  # in this section. In such a case we have to select a local one. E.g. func1:

  #

  #  .section ".sched.text", "ax"

  #  func1:

  #        [...]

  #        call mcount  (offset: 0x10)

  #        [...]
  #        ret

  #  func2:

  #        [...]

  #        call mcount (offset: 0x20)

  #        [...]

  #  .section "other.section"

  #
  # 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 func1:

  # one local, one global.  After final compile, we will end up with

  # an undefined reference to func1 or a wrong reference to another global
  # func1 in other files.

  #
  # 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 func1

  # into a global symbol before linking tmp.o. Then after we link tmp.o

  # we will only have a single symbol for func1 that is global.
  # We can convert func1 back into a local symbol and we are done.

  #
  # Here are the steps we take:
  #

  # 1) Record all the local and weak 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.

  # 8) Link the object with the list object.
  # 9) Move the result back to the original object.

  #
  
  use strict;
  
  my $P = $0;
  $P =~ s@.*/@@g;
  
  my $V = '0.1';

  if ($#ARGV != 11) {
  	print "usage: $P arch endian bits objdump objcopy cc ld nm rm mv is_module inputfile
  ";

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

  my ($arch, $endian, $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 ($inputfile =~ m,kernel/trace/ftrace\.o$,) {

      exit(0);
  }

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

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

       ".irqentry.text" => 1,

       ".text.unlikely" => 1,

  );

  # Note: we are nice to C-programmers here, thus we skip the '||='-idiom.
  $objdump = 'objdump' if (!$objdump);
  $objcopy = 'objcopy' if (!$objcopy);
  $cc = 'gcc' if (!$cc);
  $ld = 'ld' if (!$ld);
  $nm = 'nm' if (!$nm);
  $rm = 'rm' if (!$rm);
  $mv = 'mv' if (!$mv);

  
  #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 $local_regex;	# Match a local function (return function)
  my $weak_regex; 	# Match a weak function (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

  my $can_use_local = 0; 	# If we can use local function references

  # Shut up recordmcount if user has older objcopy
  my $quiet_recordmcount = ".tmp_quiet_recordmcount";
  my $print_warning = 1;
  $print_warning = 0 if ( -f $quiet_recordmcount);

  ##
  # check_objcopy - whether objcopy supports --globalize-symbols
  #
  #  --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.
  sub check_objcopy
  {
      open (IN, "$objcopy --version |") or die "error running $objcopy";
      while (<IN>) {
  	if (/objcopy.*\s(\d+)\.(\d+)/) {
  	    $can_use_local = 1 if ($1 > 2 || ($1 == 2 && $2 >= 17));
  	    last;
  	}
      }
      close (IN);

      if (!$can_use_local && $print_warning) {

  	print STDERR "WARNING: could not find objcopy version or version " .
  	    "is less than 2.17.
  " .

  	    "\tLocal function references are disabled.
  ";
  	open (QUIET, ">$quiet_recordmcount");
  	printf QUIET "Disables the warning from recordmcount.pl
  ";
  	close QUIET;

      }
  }

  if ($arch =~ /(x86(_64)?)|(i386)/) {

      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.
  #

  $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
  $weak_regex = "^[0-9a-fA-F]+\\s+([wW])\\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 "s390" && $bits == 32) {
      $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_32\\s+_mcount\$";
      $alignment = 4;
      $ld .= " -m elf_s390";
      $cc .= " -m31";
  
  } elsif ($arch eq "s390" && $bits == 64) {
      $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
      $alignment = 8;
      $type = ".quad";
      $ld .= " -m elf64_s390";
      $cc .= " -m64";

  } 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") {

      $local_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";
      }

  } elsif ($arch eq "sparc64") {
      # In the objdump output there are giblets like:
      # 0000000000000000 <igmp_net_exit-0x18>:
      # As there's some data blobs that get emitted into the
      # text section before the first instructions and the first
      # real symbols.  We don't want to match that, so to combat
      # this we use '\w' so we'll match just plain symbol names,
      # and not those that also include hex offsets inside of the
      # '<>' brackets.  Actually the generic function_regex setting
      # could safely use this too.
      $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:";
  
      # Sparc64 calls '_mcount' instead of plain 'mcount'.
      $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
  
      $alignment = 8;
      $type = ".xword";
      $ld .= " -m elf64_sparc";
      $cc .= " -m64";
      $objcopy .= " -O elf64-sparc";

  } elsif ($arch eq "mips") {
      # To enable module support, we need to enable the -mlong-calls option
      # of gcc for module, after using this option, we can not get the real
      # offset of the calling to _mcount, but the offset of the lui
      # instruction or the addiu one. herein, we record the address of the
      # first one, and then we can replace this instruction by a branch
      # instruction to jump over the profiling function to filter the
      # indicated functions, or swith back to the lui instruction to trace
      # them, which means dynamic tracing.
      #
      #       c:	3c030000 	lui	v1,0x0
      #			c: R_MIPS_HI16	_mcount
      #			c: R_MIPS_NONE	*ABS*
      #			c: R_MIPS_NONE	*ABS*
      #      10:	64630000 	daddiu	v1,v1,0
      #			10: R_MIPS_LO16	_mcount
      #			10: R_MIPS_NONE	*ABS*
      #			10: R_MIPS_NONE	*ABS*
      #      14:	03e0082d 	move	at,ra
      #      18:	0060f809 	jalr	v1
      #
      # for the kernel:
      #
      #     10:   03e0082d        move    at,ra
      #	  14:   0c000000        jal     0 <loongson_halt>
      #                    14: R_MIPS_26   _mcount
      #                    14: R_MIPS_NONE *ABS*
      #                    14: R_MIPS_NONE *ABS*
      #	 18:   00020021        nop
      if ($is_module eq "0") {
  	    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
      } else {
  	    $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";
      }
      $objdump .= " -Melf-trad".$endian."mips ";
  
      if ($endian eq "big") {
  	    $endian = " -EB ";
  	    $ld .= " -melf".$bits."btsmip";
      } else {
  	    $endian = " -EL ";
  	    $ld .= " -melf".$bits."ltsmip";
      }
  
      $cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian;
      $ld .= $endian;
  
      if ($bits == 64) {
  	    $function_regex =
  		"^([0-9a-fA-F]+)\\s+<(.|[^\$]L.*?|\$[^L].*?|[^\$][^L].*?)>:";
  	    $type = ".dword";
      }

  } elsif ($arch eq "microblaze") {
      # Microblaze calls '_mcount' instead of plain 'mcount'.
      $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";

  } 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";

  check_objcopy();

  #

  # Step 1: find all the local (static functions) and weak symbols.

  #         't' is local, 'w/W' is weak

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

      if (/$local_regex/) {

  	$locals{$1} = 1;

      } elsif (/$weak_regex/) {

  	$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 unless ($ref_func and @offsets);

      # Sanity check on weak function. A weak function may be overwritten by
      # another function of the same name, making all these offsets incorrect.

      if (defined $weak{$ref_func}) {

  	die "$inputfile: ERROR: referencing weak function" .

  	    " $ref_func for mcount
  ";

      }
  
      # is this function static? If so, note this fact.
      if (defined $locals{$ref_func}) {

  
  	# only use locals if objcopy supports globalize-symbols

  	if (!$can_use_local) {

  	    return;
  	}

  	$convert{$ref_func} = 1;
      }
  
      # Loop through all the mcount caller offsets and print a reference
      # to the caller based from the ref_func.

      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));
      }
      foreach my $cur_offset (@offsets) {
  	printf FILE "\t%s %s + %d
  ", $type, $ref_func, $cur_offset - $offset;

      }
  }

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

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

  my $text;

  
  # read headers first

  my $read_headers = 1;

  while (<IN>) {

  
      if ($read_headers && /$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 it a section?
      if (/$section_regex/) {

  	$read_headers = 0;

  
  	# Only record text sections that we know are safe

  	$read_function = defined($text_sections{$1});

  	# print out any recorded offsets

  	update_funcs();

  
  	# 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;

  	$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;

  	    $offset = hex $1;

  	} else {
  	    # if we already have a function, and this is weak, skip it

  	    if (!defined($ref_func) && !defined($weak{$text}) &&
  		 # PPC64 can have symbols that start with .L and
  		 # gcc considers these special. Don't use them!
  		 $text !~ /^\.L/) {

  		$ref_func = $text;

  		$offset = hex $1;

  	    }

  	}

      }

      # is this a call site to mcount? If so, record it to print later
      if ($text_found && /$mcount_regex/) {

  	push(@offsets, hex $1);

      }
  }

  # dump out anymore offsets that may have been found

  update_funcs();

  # 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);