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From: Keith Owens <kaos@ocs.com.au>
To: linux-kernel@vger.kernel.org
Cc: hjl@gnu.ai.mit.edu
Subject: Compiling kernel with -g may confuse binutils
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Date: Tue, 30 Jul 2002 10:35:16 +1000
Message-ID: <16624.1027989316@ocs3.intra.ocs.com.au>
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Building the kernel with -g confuses binutils 2.12.90.0.1-4.  This
error message (reported by Ramesh Panuganty)

drivers/built-in.o: In function `isapnp_peek':
/usr/src/linux-2.5.28/drivers/pnp/isapnp.c:267: undefined reference to
`local symbols in discarded section .text.exit'

was really caused by de_remove_one() in drivers/net/tulip/de2104x.c.

Building with -g also generates false positives in my script that homes
in on which object is causing the problem.  New version of
reference_discarded.pl below, run it when you get 'discarded section'
messages.

#!/usr/bin/perl -w
#
# reference_discarded.pl (C) Keith Owens 2001 <kaos@ocs.com.au>
#
# List dangling references to vmlinux discarded sections.

use strict;
die($0 . " takes no arguments\n") if($#ARGV >= 0);

my %object;
my $object;
my $line;
my $ignore;

$| = 1;

printf("Finding objects, ");
open(OBJDUMP_LIST, "find . -name '*.o' | xargs objdump -h |") || die "getting objdump list failed";
while (defined($line = <OBJDUMP_LIST>)) {
	chomp($line);
	if ($line =~ /:\s+file format/) {
		($object = $line) =~ s/:.*//;
		$object{$object}->{'module'} = 0;
		$object{$object}->{'size'} = 0;
		$object{$object}->{'off'} = 0;
	}
	if ($line =~ /^\s*\d+\s+\.modinfo\s+/) {
		$object{$object}->{'module'} = 1;
	}
	if ($line =~ /^\s*\d+\s+\.comment\s+/) {
		($object{$object}->{'size'}, $object{$object}->{'off'}) = (split(' ', $line))[2,5]; 
	}
}
close(OBJDUMP_LIST);
printf("%d objects, ", scalar keys(%object));
$ignore = 0;
foreach $object (keys(%object)) {
	if ($object{$object}->{'module'}) {
		++$ignore;
		delete($object{$object});
	}
}
printf("ignoring %d module(s)\n", $ignore);

# Ignore conglomerate objects, they have been built from multiple objects and we
# only care about the individual objects.  If an object has more than one GCC:
# string in the comment section then it is conglomerate.  This does not filter
# out conglomerates that consist of exactly one object, can't be helped.

printf("Finding conglomerates, ");
$ignore = 0;
foreach $object (keys(%object)) {
	if (exists($object{$object}->{'off'})) {
		my ($off, $size, $comment, $l);
		$off = hex($object{$object}->{'off'});
		$size = hex($object{$object}->{'size'});
		open(OBJECT, "<$object") || die "cannot read $object";
		seek(OBJECT, $off, 0) || die "seek to $off in $object failed";
		$l = read(OBJECT, $comment, $size);
		die "read $size bytes from $object .comment failed" if ($l != $size);
		close(OBJECT);
		if ($comment =~ /GCC\:.*GCC\:/m) {
			++$ignore;
			delete($object{$object});
		}
	}
}
printf("ignoring %d conglomerate(s)\n", $ignore);

printf("Scanning objects\n");
foreach $object (keys(%object)) {
	my $from;
	open(OBJDUMP, "objdump -r $object|") || die "cannot objdump -r $object";
	while (defined($line = <OBJDUMP>)) {
		chomp($line);
		if ($line =~ /RELOCATION RECORDS FOR /) {
			($from = $line) =~ s/.*\[([^]]*).*/$1/;
		}
		if (($line =~ /\.text\.exit$/ ||
		     $line =~ /\.data\.exit$/ ||
		     $line =~ /\.exitcall\.exit$/) &&
		    ($from !~ /\.text\.exit$/ &&
		     $from !~ /\.data\.exit$/ &&
		     $from !~ /\.exitcall\.exit$/ &&
		     $from !~ /\.stab$/)) {
			printf("Error: %s %s refers to %s\n", $object, $from, $line);
		}
	}
	close(OBJDUMP);
}
printf("Done\n");

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