scripts/recordmcount.pl - arm/linux - Git at Google

 #!/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\n";
 	print "version: $V\n";
 	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'\n";

 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 && $print_warning) {
 	print STDERR "WARNING: could not find objcopy version or version " .
 	    "is less than 2.17.\n" .
 	    "\tLocal function references are disabled.\n";
 	open (QUIET, ">$quiet_recordmcount");
 	printf QUIET "Disables the warning from recordmcount.pl\n";
 	close QUIET;
     }
 }

 if ($arch eq 'x86') {
     $arch = ($bits == 64) ? 'x86_64' : '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\n";
     }

     # 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\n";
 	$opened = 1;
 	print FILE "\t.section $mcount_section,\"a\",$section_type\n";
 	print FILE "\t.align $alignment\n" if (defined($alignment));
     }
     foreach my $cur_offset (@offsets) {
 	printf FILE "\t%s %s + %d\n", $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\n" .
 	    "\tThis may be an indication that your build is corrupted.\n" .
 	    "\tDelete $inputfile and try again. If the same object file\n" .
 	    "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
 	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);
	#!/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\n";
	print "version: $V\n";
	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'\n";

	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 && $print_warning) {
	print STDERR "WARNING: could not find objcopy version or version " .
	"is less than 2.17.\n" .
	"\tLocal function references are disabled.\n";
	open (QUIET, ">$quiet_recordmcount");
	printf QUIET "Disables the warning from recordmcount.pl\n";
	close QUIET;
	}
	}

	if ($arch eq 'x86') {
	$arch = ($bits == 64) ? 'x86_64' : '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]+):\\sR_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]+):\\sR_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\n";
	}

	# 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\n";
	$opened = 1;
	print FILE "\t.section $mcount_section,\"a\",$section_type\n";
	print FILE "\t.align $alignment\n" if (defined($alignment));
	}
	foreach my $cur_offset (@offsets) {
	printf FILE "\t%s %s + %d\n", $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\n" .
	"\tThis may be an indication that your build is corrupted.\n" .
	"\tDelete $inputfile and try again. If the same object file\n" .
	"\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
	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);