text: #!/usr/bin/env perl
  #
  #	namespace.pl.  Mon Aug 30 2004
  #
  #	Perform a name space analysis on the linux kernel.
  #
  #	Copyright Keith Owens <kaos@ocs.com.au>.  GPL.
  #
  #	Invoke by changing directory to the top of the kernel object
  #	tree then namespace.pl, no parameters.
  #
  #	Tuned for 2.1.x kernels with the new module handling, it will
  #	work with 2.0 kernels as well.
  #
  #	Last change 2.6.9-rc1, adding support for separate source and object
  #	trees.
  #
  #	The source must be compiled/assembled first, the object files
  #	are the primary input to this script.  Incomplete or missing
  #	objects will result in a flawed analysis.  Compile both vmlinux
  #	and modules.
  #
  #	Even with complete objects, treat the result of the analysis
  #	with caution.  Some external references are only used by
  #	certain architectures, others with certain combinations of
  #	configuration parameters.  Ideally the source should include
  #	something like
  #
  #	#ifndef CONFIG_...
  #	static
  #	#endif
  #	symbol_definition;
  #
  #	so the symbols are defined as static unless a particular
  #	CONFIG_... requires it to be external.
  #
  #	A symbol that is suffixed with '(export only)' has these properties
  #
  #	* It is global.
  #	* It is marked EXPORT_SYMBOL or EXPORT_SYMBOL_GPL, either in the same
  #	  source file or a different source file.
  #	* Given the current .config, nothing uses the symbol.
  #
  #	The symbol is a candidate for conversion to static, plus removal of the
  #	export.  But be careful that a different .config might use the symbol.
  #
  #
  #	Name space analysis and cleanup is an iterative process.  You cannot
  #	expect to find all the problems in a single pass.
  #
  #	* Identify possibly unnecessary global declarations, verify that they
  #	  really are unnecessary and change them to static.
  #	* Compile and fix up gcc warnings about static, removing dead symbols
  #	  as necessary.
  #	* make clean and rebuild with different configs (especially
  #	  CONFIG_MODULES=n) to see which symbols are being defined when the
  #	  config does not require them.  These symbols bloat the kernel object
  #	  for no good reason, which is frustrating for embedded systems.
  #	* Wrap config sensitive symbols in #ifdef CONFIG_foo, as long as the
  #	  code does not get too ugly.
  #	* Repeat the name space analysis until you can live with with the
  #	  result.
  #
  
  use warnings;
  use strict;
  use File::Find;
  
  my $nm = ($ENV{'NM'} || "nm") . " -p";
  my $objdump = ($ENV{'OBJDUMP'} || "objdump") . " -s -j .comment";
  my $srctree = "";
  my $objtree = "";
  $srctree = "$ENV{'srctree'}/" if (exists($ENV{'srctree'}));
  $objtree = "$ENV{'objtree'}/" if (exists($ENV{'objtree'}));
  
  if ($#ARGV != -1) {
  	print STDERR "usage: $0 takes no parameters\n";
  	die("giving up\n");
  }
  
  my %nmdata = ();	# nm data for each object
  my %def = ();		# all definitions for each name
  my %ksymtab = ();	# names that appear in __ksymtab_
  my %ref = ();		# $ref{$name} exists if there is a true external reference to $name
  my %export = ();	# $export{$name} exists if there is an EXPORT_... of $name
  
  my %nmexception = (
      'fs/ext3/bitmap'			=> 1,
      'fs/ext4/bitmap'			=> 1,
      'arch/x86/lib/thunk_32'		=> 1,
      'arch/x86/lib/cmpxchg'		=> 1,
      'arch/x86/vdso/vdso32/note'		=> 1,
      'lib/irq_regs'			=> 1,
      'usr/initramfs_data'		=> 1,
      'drivers/scsi/aic94xx/aic94xx_dump'	=> 1,
      'drivers/scsi/libsas/sas_dump'	=> 1,
      'lib/dec_and_lock'			=> 1,
      'drivers/ide/ide-probe-mini'	=> 1,
      'usr/initramfs_data'		=> 1,
      'drivers/acpi/acpia/exdump'		=> 1,
      'drivers/acpi/acpia/rsdump'		=> 1,
      'drivers/acpi/acpia/nsdumpdv'	=> 1,
      'drivers/acpi/acpia/nsdump'		=> 1,
      'arch/ia64/sn/kernel/sn2/io'	=> 1,
      'arch/ia64/kernel/gate-data'	=> 1,
      'security/capability'		=> 1,
      'fs/ntfs/sysctl'			=> 1,
      'fs/jfs/jfs_debug'			=> 1,
  );
  
  my %nameexception = (
      'mod_use_count_'	 => 1,
      '__initramfs_end'	=> 1,
      '__initramfs_start'	=> 1,
      '_einittext'	=> 1,
      '_sinittext'	=> 1,
      'kallsyms_names'	=> 1,
      'kallsyms_num_syms'	=> 1,
      'kallsyms_addresses'=> 1,
      'kallsyms_offsets'	=> 1,
      'kallsyms_relative_base'=> 1,
      '__this_module'	=> 1,
      '_etext'		=> 1,
      '_edata'		=> 1,
      '_end'		=> 1,
      '__bss_start'	=> 1,
      '_text'		=> 1,
      '_stext'		=> 1,
      '__gp'		=> 1,
      'ia64_unw_start'	=> 1,
      'ia64_unw_end'	=> 1,
      '__init_begin'	=> 1,
      '__init_end'	=> 1,
      '__bss_stop'	=> 1,
      '__nosave_begin'	=> 1,
      '__nosave_end'	=> 1,
      'pg0'		=> 1,
      'vdso_enabled'	=> 1,
      '__stack_chk_fail'  => 1,
      'VDSO32_PRELINK'	=> 1,
      'VDSO32_vsyscall'	=> 1,
      'VDSO32_rt_sigreturn'=>1,
      'VDSO32_sigreturn'	=> 1,
  );
  
  
  &find(\&linux_objects, '.');	# find the objects and do_nm on them
  &list_multiply_defined();
  &resolve_external_references();
  &list_extra_externals();
  
  exit(0);
  
  sub linux_objects
  {
  	# Select objects, ignoring objects which are only created by
  	# merging other objects.  Also ignore all of modules, scripts
  	# and compressed.  Most conglomerate objects are handled by do_nm,
  	# this list only contains the special cases.  These include objects
  	# that are linked from just one other object and objects for which
  	# there is really no permanent source file.
  	my $basename = $_;
  	$_ = $File::Find::name;
  	s:^\./::;
  	if (/.*\.o$/ &&
  		! (
  		m:/built-in.o$:
  		|| m:arch/x86/vdso/:
  		|| m:arch/x86/boot/:
  		|| m:arch/ia64/ia32/ia32.o$:
  		|| m:arch/ia64/kernel/gate-syms.o$:
  		|| m:arch/ia64/lib/__divdi3.o$:
  		|| m:arch/ia64/lib/__divsi3.o$:
  		|| m:arch/ia64/lib/__moddi3.o$:
  		|| m:arch/ia64/lib/__modsi3.o$:
  		|| m:arch/ia64/lib/__udivdi3.o$:
  		|| m:arch/ia64/lib/__udivsi3.o$:
  		|| m:arch/ia64/lib/__umoddi3.o$:
  		|| m:arch/ia64/lib/__umodsi3.o$:
  		|| m:arch/ia64/scripts/check_gas_for_hint.o$:
  		|| m:arch/ia64/sn/kernel/xp.o$:
  		|| m:boot/bbootsect.o$:
  		|| m:boot/bsetup.o$:
  		|| m:/bootsect.o$:
  		|| m:/boot/setup.o$:
  		|| m:/compressed/:
  		|| m:drivers/cdrom/driver.o$:
  		|| m:drivers/char/drm/tdfx_drv.o$:
  		|| m:drivers/ide/ide-detect.o$:
  		|| m:drivers/ide/pci/idedriver-pci.o$:
  		|| m:drivers/media/media.o$:
  		|| m:drivers/scsi/sd_mod.o$:
  		|| m:drivers/video/video.o$:
  		|| m:fs/devpts/devpts.o$:
  		|| m:fs/exportfs/exportfs.o$:
  		|| m:fs/hugetlbfs/hugetlbfs.o$:
  		|| m:fs/msdos/msdos.o$:
  		|| m:fs/nls/nls.o$:
  		|| m:fs/ramfs/ramfs.o$:
  		|| m:fs/romfs/romfs.o$:
  		|| m:fs/vfat/vfat.o$:
  		|| m:init/mounts.o$:
  		|| m:^modules/:
  		|| m:net/netlink/netlink.o$:
  		|| m:net/sched/sched.o$:
  		|| m:/piggy.o$:
  		|| m:^scripts/:
  		|| m:sound/.*/snd-:
  		|| m:^.*/\.tmp_:
  		|| m:^\.tmp_:
  		|| m:/vmlinux-obj.o$:
  		|| m:^tools/:
  		)
  	) {
  		do_nm($basename, $_);
  	}
  	$_ = $basename;		# File::Find expects $_ untouched (undocumented)
  }
  
  sub do_nm
  {
  	my ($basename, $fullname) = @_;
  	my ($source, $type, $name);
  	if (! -e $basename) {
  		printf STDERR "$basename does not exist\n";
  		return;
  	}
  	if ($fullname !~ /\.o$/) {
  		printf STDERR "$fullname is not an object file\n";
  		return;
  	}
  	($source = $basename) =~ s/\.o$//;
  	if (-e "$source.c" || -e "$source.S") {
  		$source = "$objtree$File::Find::dir/$source";
  	} else {
  		$source = "$srctree$File::Find::dir/$source";
  	}
  	if (! -e "$source.c" && ! -e "$source.S") {
  		# No obvious source, exclude the object if it is conglomerate
  	        open(my $objdumpdata, "$objdump $basename|")
  		    or die "$objdump $fullname failed $!\n";
  
  		my $comment;
  		while (<$objdumpdata>) {
  			chomp();
  			if (/^In archive/) {
  				# Archives are always conglomerate
  				$comment = "GCC:GCC:";
  				last;
  			}
  			next if (! /^[ 0-9a-f]{5,} /);
  			$comment .= substr($_, 43);
  		}
  		close($objdumpdata);
  
  		if (!defined($comment) || $comment !~ /GCC\:.*GCC\:/m) {
  			printf STDERR "No source file found for $fullname\n";
  		}
  		return;
  	}
  	open (my $nmdata, "$nm $basename|")
  	    or die "$nm $fullname failed $!\n";
  
  	my @nmdata;
  	while (<$nmdata>) {
  		chop;
  		($type, $name) = (split(/ +/, $_, 3))[1..2];
  		# Expected types
  		# A absolute symbol
  		# B weak external reference to data that has been resolved
  		# C global variable, uninitialised
  		# D global variable, initialised
  		# G global variable, initialised, small data section
  		# R global array, initialised
  		# S global variable, uninitialised, small bss
  		# T global label/procedure
  		# U external reference
  		# W weak external reference to text that has been resolved
  		# V similar to W, but the value of the weak symbol becomes zero with no error.
  		# a assembler equate
  		# b static variable, uninitialised
  		# d static variable, initialised
  		# g static variable, initialised, small data section
  		# r static array, initialised
  		# s static variable, uninitialised, small bss
  		# t static label/procedures
  		# w weak external reference to text that has not been resolved
  		# v similar to w
  		# ? undefined type, used a lot by modules
  		if ($type !~ /^[ABCDGRSTUWVabdgrstwv?]$/) {
  			printf STDERR "nm output for $fullname contains unknown type '$_'\n";
  		}
  		elsif ($name =~ /\./) {
  			# name with '.' is local static
  		}
  		else {
  			$type = 'R' if ($type eq '?');	# binutils replaced ? with R at one point
  			# binutils keeps changing the type for exported symbols, force it to R
  			$type = 'R' if ($name =~ /^__ksymtab/ || $name =~ /^__kstrtab/);
  			$name =~ s/_R[a-f0-9]{8}$//;	# module versions adds this
  			if ($type =~ /[ABCDGRSTWV]/ &&
  				$name ne 'init_module' &&
  				$name ne 'cleanup_module' &&
  				$name ne 'Using_Versions' &&
  				$name !~ /^Version_[0-9]+$/ &&
  				$name !~ /^__parm_/ &&
  				$name !~ /^__kstrtab/ &&
  				$name !~ /^__ksymtab/ &&
  				$name !~ /^__kcrctab_/ &&
  				$name !~ /^__exitcall_/ &&
  				$name !~ /^__initcall_/ &&
  				$name !~ /^__kdb_initcall_/ &&
  				$name !~ /^__kdb_exitcall_/ &&
  				$name !~ /^__module_/ &&
  				$name !~ /^__mod_/ &&
  				$name !~ /^__crc_/ &&
  				$name ne '__this_module' &&
  				$name ne 'kernel_version') {
  				if (!exists($def{$name})) {
  					$def{$name} = [];
  				}
  				push(@{$def{$name}}, $fullname);
  			}
  			push(@nmdata, "$type $name");
  			if ($name =~ /^__ksymtab_/) {
  				$name = substr($name, 10);
  				if (!exists($ksymtab{$name})) {
  					$ksymtab{$name} = [];
  				}
  				push(@{$ksymtab{$name}}, $fullname);
  			}
  		}
  	}
  	close($nmdata);
  
  	if ($#nmdata < 0) {
  	    printf "No nm data for $fullname\n"
  		unless $nmexception{$fullname};
  	    return;
  	}
  	$nmdata{$fullname} = \@nmdata;
  }
  
  sub drop_def
  {
  	my ($object, $name) = @_;
  	my $nmdata = $nmdata{$object};
  	my ($i, $j);
  	for ($i = 0; $i <= $#{$nmdata}; ++$i) {
  		if ($name eq (split(' ', $nmdata->[$i], 2))[1]) {
  			splice(@{$nmdata{$object}}, $i, 1);
  			my $def = $def{$name};
  			for ($j = 0; $j < $#{$def{$name}}; ++$j) {
  				if ($def{$name}[$j] eq $object) {
  					splice(@{$def{$name}}, $j, 1);
  				}
  			}
  			last;
  		}
  	}
  }
  
  sub list_multiply_defined
  {
  	foreach my $name (keys(%def)) {
  		if ($#{$def{$name}} > 0) {
  			# Special case for cond_syscall
  			if ($#{$def{$name}} == 1 &&
  			   ($name =~ /^sys_/ || $name =~ /^compat_sys_/ ||
  			    $name =~ /^sys32_/)) {
  				if($def{$name}[0] eq "kernel/sys_ni.o" ||
  				   $def{$name}[1] eq "kernel/sys_ni.o") {
  					&drop_def("kernel/sys_ni.o", $name);
  					next;
  				}
  			}
  
  			printf "$name is multiply defined in :-\n";
  			foreach my $module (@{$def{$name}}) {
  				printf "\t$module\n";
  			}
  		}
  	}
  }
  
  sub resolve_external_references
  {
  	my ($kstrtab, $ksymtab, $export);
  
  	printf "\n";
  	foreach my $object (keys(%nmdata)) {
  		my $nmdata = $nmdata{$object};
  		for (my $i = 0; $i <= $#{$nmdata}; ++$i) {
  			my ($type, $name) = split(' ', $nmdata->[$i], 2);
  			if ($type eq "U" || $type eq "w") {
  				if (exists($def{$name}) || exists($ksymtab{$name})) {
  					# add the owning object to the nmdata
  					$nmdata->[$i] = "$type $name $object";
  					# only count as a reference if it is not EXPORT_...
  					$kstrtab = "R __kstrtab_$name";
  					$ksymtab = "R __ksymtab_$name";
  					$export = 0;
  					for (my $j = 0; $j <= $#{$nmdata}; ++$j) {
  						if ($nmdata->[$j] eq $kstrtab ||
  						    $nmdata->[$j] eq $ksymtab) {
  							$export = 1;
  							last;
  						}
  					}
  					if ($export) {
  						$export{$name} = "";
  					}
  					else {
  						$ref{$name} = ""
  					}
  				}
  				elsif ( ! $nameexception{$name}
  					&& $name !~ /^__sched_text_/
  					&& $name !~ /^__start_/
  					&& $name !~ /^__end_/
  					&& $name !~ /^__stop_/
  					&& $name !~ /^__scheduling_functions_.*_here/
  					&& $name !~ /^__.*initcall_/
  					&& $name !~ /^__.*per_cpu_start/
  					&& $name !~ /^__.*per_cpu_end/
  					&& $name !~ /^__alt_instructions/
  					&& $name !~ /^__setup_/
  					&& $name !~ /^__mod_timer/
  					&& $name !~ /^__mod_page_state/
  					&& $name !~ /^init_module/
  					&& $name !~ /^cleanup_module/
  				) {
  					printf "Cannot resolve ";
  					printf "weak " if ($type eq "w");
  					printf "reference to $name from $object\n";
  				}
  			}
  		}
  	}
  }
  
  sub list_extra_externals
  {
  	my %noref = ();
  
  	foreach my $name (keys(%def)) {
  		if (! exists($ref{$name})) {
  			my @module = @{$def{$name}};
  			foreach my $module (@module) {
  				if (! exists($noref{$module})) {
  					$noref{$module} = [];
  				}
  				push(@{$noref{$module}}, $name);
  			}
  		}
  	}
  	if (%noref) {
  		printf "\nExternally defined symbols with no external references\n";
  		foreach my $module (sort(keys(%noref))) {
  			printf "  $module\n";
  			foreach (sort(@{$noref{$module}})) {
  			    my $export;
  			    if (exists($export{$_})) {
  				$export = " (export only)";
  			    } else {
  				$export = "";
  			    }
  			    printf "    $_$export\n";
  			}
  		}
  	}
  }
  