Re: Compiling kernel with -g may confuse binutils

From: H. J. Lu (hjl@lucon.org)
Date: Mon Jul 29 2002 - 20:15:52 EST


On Tue, Jul 30, 2002 at 10:35:16AM +1000, Keith Owens wrote:
> 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.

Please show how to exactly reproduce it with gcc 3.1.1.

>
> 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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