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* Perl script to analyse kernel namespace pollution
@ 2004-05-20  6:22 Keith Owens
  0 siblings, 0 replies; only message in thread
From: Keith Owens @ 2004-05-20  6:22 UTC (permalink / raw)
  To: linux-kernel

The namespace.pl script below will analyse your kernel and modules and
report namespace polution.  It lists multiply defined symbols, which
tend to confuse debugging.

It also lists symbols that are externally visible but are not
referenced from outside the source in which they are defined.  All such
symbols are candidates for being defined as static.  But be careful
when making changes based on a single report, some symbols are only
used for certain combinations of config options.

This script has been recently updated to automatically detect
conglomerate objects, which reduces the manual list of objects that
have to be excluded from consideration.  The manual lists of excluded
objects and symbols was built from i386 and ia64 2.4 and 2.6 builds.  I
am sure that these lists will need tweaking for other configs and
architectures.

#!/usr/bin/perl -w
#
#	namespace.pl.  Thu May 20 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 source
#	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 2.6.6.
#
#	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.
#

require 5;	# at least perl 5
use strict;
use File::Find;

my $nm = "/usr/bin/nm -p";
my $objdump = "/usr/bin/objdump -s -j .comment";

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

&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$:
		|| m:/piggy.o$: || m:/bootsect.o$:
		|| m:/boot/setup.o$: || m:^modules/: || m:^scripts/:
		|| m:/compressed/: || m:/vmlinux-obj.o$:
		|| m:boot/bbootsect.o$: || m:boot/bsetup.o$:
		|| m:arch/ia64/scripts/check_gas_for_hint.o$:
		|| m:arch/ia64/lib/__divsi3.o$:
		|| m:arch/ia64/lib/__udivsi3.o$:
		|| m:arch/ia64/lib/__modsi3.o$:
		|| m:arch/ia64/lib/__umodsi3.o$:
		|| m:arch/ia64/lib/__divdi3.o$:
		|| m:arch/ia64/lib/__udivdi3.o$:
		|| m:arch/ia64/lib/__moddi3.o$:
		|| m:arch/ia64/lib/__umoddi3.o$:
		|| m:arch/ia64/ia32/ia32.o$:
		|| m:net/sched/sched.o$:
		|| m:fs/romfs/romfs.o$:
		|| m:fs/ramfs/ramfs.o$:
		|| m:fs/nls/nls.o$:
		|| m:drivers/video/video.o$:
		|| m:drivers/scsi/sd_mod.o$:
		|| m:drivers/media/media.o$:
		|| m:drivers/ide/ide-detect.o$:
		|| m:drivers/ide/pci/idedriver-pci.o$:
		|| m:drivers/cdrom/driver.o$:
		|| m:net/netlink/netlink.o$:
		|| m:fs/vfat/vfat.o$:
		|| m:fs/hugetlbfs/hugetlbfs.o$:
		|| m:fs/exportfs/exportfs.o$:
		|| m:fs/devpts/devpts.o$:
		|| m:arch/ia64/sn/kernel/xp.o$:
		|| m:arch/ia64/kernel/gate-syms.o$:
		|| m:^\.tmp_:
		|| m:^.*/\.tmp_:
		|| m:sound/pci/snd-intel8x0.o$:
		|| m:sound/drivers/mpu401/snd-mpu401-uart.o$:
		|| m:sound/core/snd-timer.o$:
		|| m:sound/core/snd-rawmidi.o$:
		|| m:sound/core/seq/snd-seq-device.o$:
		|| m:sound/core/seq/snd-seq-midi-event.o$:
		|| m:sound/core/seq/snd-seq-midi.o$:
		|| m:sound/core/oss/snd-mixer-oss.o$:
		|| m:init/mounts.o$:
		|| m:fs/msdos/msdos.o$:
		|| m:arch/i386/kernel/vsyscall-syms.o$:
		)
	) {
		do_nm($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;
	$source =~ s/\.o$//;
	if (! -e "$source.c" && ! -e "$source.S") {
		# No obvious source, exclude the object if it is conglomerate
		if (! open(OBJDUMPDATA, "$objdump $basename|")) {
			printf STDERR "$objdump $fullname failed $!\n";
			return;
		}
		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 $fullname\n";
		}
		return;
	}
	if (! open(NMDATA, "$nm $basename|")) {
		printf STDERR "$nm $fullname failed $!\n";
		return;
	}
	my @nmdata;
	while (<NMDATA>) {
		chop;
		($type, $name) = (split(/ +/, $_, 3))[1..2];
		# Expected types
		# B weak external reference to data that has been resolved
		# C global variable, uninitialised
		# D global variable, initialised
		# G global variable, initialised, small data section
		# R global array, initialised
		# S global variable, uninitialised, small bss
		# T global label/procedure
		# U external reference
		# W weak external reference to text that has been resolved
		# a assembler equate
		# b static variable, uninitialised
		# d static variable, initialised
		# g static variable, initialised, small data section
		# r static array, initialised
		# s static variable, uninitialised, small bss
		# t static label/procedures
		# w weak external reference to text that has not been resolved
		# ? undefined type, used a lot by modules
		if ($type !~ /^[BCDGRSTUWabdgrstw?]$/) {
			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
			$name =~ s/_R[a-f0-9]{8}$//;	# module versions adds this
			if ($type =~ /[BCDGRSTW]/ &&
				$name ne 'init_module' &&
				$name ne 'cleanup_module' &&
				$name ne 'Using_Versions' &&
				$name !~ /^Version_[0-9]+$/ &&
				$name !~ /^__parm_/ &&
				$name !~ /^__kstrtab/ &&
				$name !~ /^__ksymtab/ &&
				$name !~ /^__exitcall_/ &&
				$name !~ /^__initcall_/ &&
				$name !~ /^__kdb_initcall_/ &&
				$name !~ /^__kdb_exitcall_/ &&
				$name !~ /^__module_/ &&
				$name !~ /^__mod_/ &&
				$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) {
		if (
			$fullname ne "lib/brlock.o"
			&& $fullname ne "lib/dec_and_lock.o"
			&& $fullname ne "fs/xfs/xfs_macros.o"
			&& $fullname ne "drivers/ide/ide-probe-mini.o"
			&& $fullname ne "usr/initramfs_data.o"
			&& $fullname ne "drivers/acpi/executer/exdump.o"
			&& $fullname ne "drivers/acpi/resources/rsdump.o"
			&& $fullname ne "drivers/acpi/namespace/nsdumpdv.o"
			&& $fullname ne "drivers/acpi/namespace/nsdump.o"
			&& $fullname ne "arch/ia64/sn/kernel/sn2/io.o"
			&& $fullname ne "arch/ia64/kernel/gate-data.o"
			&& $fullname ne "drivers/ieee1394/oui.o"
			&& $fullname ne "security/capability.o"
			&& $fullname ne "sound/core/wrappers.o"
		) {
			printf "No nm data for $fullname\n";
		}
		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
{
	my ($name, $module);
	foreach $name (keys(%def)) {
		if ($#{$def{$name}} > 0) {
			# Special case for cond_syscall
			if ($#{$def{$name}} == 1 && $name =~ /^sys_/ &&
			    ($def{$name}[0] eq "kernel/sys.o" ||
			     $def{$name}[1] eq "kernel/sys.o")) {
				&drop_def("kernel/sys.o", $name);
				next;
			}
			# Special case for i386 entry code
			if ($#{$def{$name}} == 1 && $name =~ /^__kernel_/ &&
			    $def{$name}[0] eq "arch/i386/kernel/vsyscall-int80.o" &&
			    $def{$name}[1] eq "arch/i386/kernel/vsyscall-sysenter.o") {
				&drop_def("arch/i386/kernel/vsyscall-sysenter.o", $name);
				next;
			}
			printf "$name is multiply defined in :-\n";
			foreach $module (@{$def{$name}}) {
				printf "\t$module\n";
			}
		}
	}
}

sub resolve_external_references
{
	my ($object, $type, $name, $i, $j, $kstrtab, $ksymtab, $export);
	printf "\n";
	foreach $object (keys(%nmdata)) {
		my $nmdata = $nmdata{$object};
		for ($i = 0; $i <= $#{$nmdata}; ++$i) {
			($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";
					$export = 0;
					for ($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 (    $name ne "mod_use_count_"
					&& $name ne "__initramfs_end"
					&& $name ne "__initramfs_start"
					&& $name ne "_einittext"
					&& $name ne "_sinittext"
					&& $name ne "kallsyms_names"
					&& $name ne "kallsyms_num_syms"
					&& $name ne "kallsyms_addresses"
					&& $name ne "__this_module"
					&& $name ne "_etext"
					&& $name ne "_edata"
					&& $name ne "_end"
					&& $name ne "__bss_start"
					&& $name ne "_text"
					&& $name ne "_stext"
					&& $name ne "__gp"
					&& $name ne "ia64_unw_start"
					&& $name ne "ia64_unw_end"
					&& $name ne "__setup_start"
					&& $name ne "__setup_end"
					&& $name ne "__init_begin"
					&& $name ne "__init_end"
					&& $name ne "__bss_stop"
					&& $name ne "__nosave_begin"
					&& $name ne "__nosave_end"
					&& $name ne "pg0"
					&& $name !~ /^__start_/
					&& $name !~ /^__end_/
					&& $name !~ /^__stop_/
					&& $name !~ /^__scheduling_functions_.*_here/
					&& $name !~ /^__.*initcall_/
					&& $name !~ /^__.*per_cpu_start/
					&& $name !~ /^__.*per_cpu_end/
					&& $name !~ /^__alt_instructions/
				) {

					printf "Cannot resolve ";
					printf "weak " if ($type eq "w");
					printf "reference to $name from $object\n";
				}
			}
		}
	}
}

sub list_extra_externals
{
	my %noref = ();
	my ($name, @module, $module, $export);
	foreach $name (keys(%def)) {
		if (! exists($ref{$name})) {
			@module = @{$def{$name}};
			foreach $module (@module) {
				if (! exists($noref{$module})) {
					$noref{$module} = [];
				}
				push(@{$noref{$module}}, $name);
			}
		}
	}
	if (%noref) {
		printf "\nExternally defined symbols with no external references\n";
		foreach $module (sort(keys(%noref))) {
			printf "  $module\n";
			foreach (sort(@{$noref{$module}})) {
				if (exists($export{$_})) {
					$export = " (export only)";
				}
				else {
					$export = "";
				}
				printf "    $_$export\n";
			}
		}
	}
}


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