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 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 < 6) {
 	print "usage: $P arch objdump objcopy cc ld nm rm mv inputfile\n";
 	print "version: $V\n";
 	exit(1);
 }

 my ($arch, $bits, $objdump, $objcopy, $cc,
     $ld, $nm, $rm, $mv, $inputfile) = @ARGV;

 # Acceptable sections to record.
 my %text_sections = (
      ".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'\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 $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

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

 if ($arch eq "x86_64") {
     $section_regex = "Disassembly of section\\s+(\\S+):";
     $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
     $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") {
     $section_regex = "Disassembly of section\\s+(\\S+):";
     $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
     $type = ".long";
     $alignment = 4;

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

 } 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.\n" .
 	"\tDisabling local function references.\n";
 }


 #
 # 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 (/^[0-9a-fA-F]+\s+t\s+(\S+)/) {
 	$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\n";
 	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\n";
 	    $opened = 1;
 	    print FILE "\t.section $mcount_section,\"a\",\@progbits\n";
 	    print FILE "\t.align $alignment\n";
 	}
 	printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
     }
 }

 #
 # Step 2: find the sections and mcount call sites
 #
 open(IN, "$objdump -dr $inputfile|") || die "error running $objdump";

 my $text;

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

 	# 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;
 	    }
 	}
     }

     # 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);
	#!/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 < 6) {
	print "usage: $P arch objdump objcopy cc ld nm rm mv inputfile\n";
	print "version: $V\n";
	exit(1);
	}

	my ($arch, $bits, $objdump, $objcopy, $cc,
	$ld, $nm, $rm, $mv, $inputfile) = @ARGV;

	# Acceptable sections to record.
	my %text_sections = (
	".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'\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 $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

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

	if ($arch eq "x86_64") {
	$section_regex = "Disassembly of section\\s+(\\S+):";
	$function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
	$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") {
	$section_regex = "Disassembly of section\\s+(\\S+):";
	$function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
	$mcount_regex = "^\\s([0-9a-fA-F]+):.\\smcount\$";
	$type = ".long";
	$alignment = 4;

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

	} 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.\n" .
	"\tDisabling local function references.\n";
	}


	#
	# 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 (/^[0-9a-fA-F]+\s+t\s+(\S+)/) {
	$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\n";
	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\n";
	$opened = 1;
	print FILE "\t.section $mcount_section,\"a\",\@progbits\n";
	print FILE "\t.align $alignment\n";
	}
	printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
	}
	}

	#
	# Step 2: find the sections and mcount call sites
	#
	open(IN, "$objdump -dr $inputfile\|") \|\| die "error running $objdump";

	my $text;

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

	# 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;
	}
	}
	}

	# 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);