Fonctions utilisées d'une librairie statique - InCloudUs

Un bout de Perl avec la commande nm

Lors d’un récent entretien chez eNovance, ces derniers m’ont demandé de faire un script permettant de lister les fonctions actuellement en mémoire des librairies statiques présentes dans /usr/lib/.

Cet exercice était à faire en Perl, hors cela faisait un bout de temps que je n’avais pas pratiqué ce langage. Ils ont été plutôt sympas sur ce point et ils m’ont autorisé à le faire en Bash.

Pour le fun (oui pour le fun), j’ai tenté l’exercice en Perl. Les librairies statiques dans /usr/lib/ sont celles qui se terminent par .a. Une fois les librairies listées, la commande nm permet de lister les symboles (fonctions) en cours d’utilisation.

Exemple

$ nm /usr/lib/libasprintf.a

1	$ nm /usr/lib/libasprintf.a

 lib-asprintf.o:
nm: lib-asprintf.o: no symbols

autosprintf.o:
0000000000000000 t _GLOBAL__sub_I__ZN3gnu11autosprintfC2EPKcz
0000000000000000 T _ZN3gnu11autosprintfC1EPKcz
00000000000000b0 T _ZN3gnu11autosprintfC1ERKS0_
0000000000000000 T _ZN3gnu11autosprintfC2EPKcz
00000000000000b0 T _ZN3gnu11autosprintfC2ERKS0_
00000000000000d0 T _ZN3gnu11autosprintfD1Ev
00000000000000d0 T _ZN3gnu11autosprintfD2Ev
00000000000000e0 T _ZNK3gnu11autosprintfcvPcEv
0000000000000150 T _ZNK3gnu11autosprintfcvSsEv
                 U _ZNSsC1EPKcRKSaIcE
                 U _ZNSt8ios_base4InitC1Ev
                 U _ZNSt8ios_base4InitD1Ev
0000000000000000 b _ZStL8__ioinit
                 U _Znam
                 U __cxa_atexit
                 U __dso_handle
                 U __vasprintf_chk
                 U free
                 U memcpy
                 U strdup
                 U strlen

lib-asprintf.o:

nm: lib-asprintf.o: no symbols

autosprintf.o:

0000000000000000 t _GLOBAL__sub_I__ZN3gnu11autosprintfC2EPKcz

0000000000000000 T _ZN3gnu11autosprintfC1EPKcz

00000000000000b0 T _ZN3gnu11autosprintfC1ERKS0_

0000000000000000 T _ZN3gnu11autosprintfC2EPKcz

00000000000000b0 T _ZN3gnu11autosprintfC2ERKS0_

00000000000000d0 T _ZN3gnu11autosprintfD1Ev

00000000000000d0 T _ZN3gnu11autosprintfD2Ev

00000000000000e0 T _ZNK3gnu11autosprintfcvPcEv

0000000000000150 T _ZNK3gnu11autosprintfcvSsEv

U _ZNSsC1EPKcRKSaIcE

U _ZNSt8ios_base4InitC1Ev

U _ZNSt8ios_base4InitD1Ev

0000000000000000 b _ZStL8__ioinit

U _Znam

U __cxa_atexit

U __dso_handle

U __vasprintf_chk

U free

U memcpy

U strdup

U strlen

Ici les fonctions utilisées sont celles ayant le flag T.

T : le symbole est dans la zone mémoire .text (code)

Le script

#!/usr/bin/perl -w
#
######################################################################
#
# List all functions from static libraries currently used.
#
# Author : Gaetan Trellu (goldyfruit) <gaetan.trellu@incloudus.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
###########################################################################

use strict;
use warnings;

# Path to static libraries
my $libPath = "/usr/lib";

# Open the libraries path and read the content
opendir(DIR, $libPath) or die $!;

# Keep only library who finished by .a
my @libraries = grep { /\.a$/ } readdir(DIR);

# Define arrays (associative and normal)
my %array;
my @tab;

# Print the content at 70 chars from the left to the right for the first column
# and 50 chars from the first column for the second column
print "################################################################################\n";
printf("%-70s %-50s\n", "# Function currently used", "Library #");
print "################################################################################\n";

# For each librairy found
foreach my $library (@libraries) {

        # Find all functions used (T flag) in static library
        # "nm" command is used to list the status of a library
        # Result is push in a standard array
        my @functionsArray = grep { /T/ } `nm $libPath/$library`;

        # Explode the function by using space and push the result in the @tab array
        foreach my $function (@functionsArray) {
                @tab = split(/ /, $function);

                # If the second field is equal to T then space, chariot
                # are escaped with the chomp() function
                # Result is push in the associative array %array
                if ($tab[1] eq "T") {
                        chomp($tab[2]);
                        $array{$tab[2]}=$library;
                }
        }

}

# Each result in the %array array is display
foreach my $key (sort keys %array) {
        printf("%-70s %-50s\n", $key, $array{$key});
}

print "\n";

# Close the libraries directory
closedir(DIR);

exit 0;

#!/usr/bin/perl -w

######################################################################

# List all functions from static libraries currently used.

# Author : Gaetan Trellu (goldyfruit) <gaetan.trellu@incloudus.com>

# This program is free software: you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation, either version 3 of the License, or

# (at your option) any later version.

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License

# along with this program. If not, see <http://www.gnu.org/licenses/>.

###########################################################################

use strict;

use warnings;

# Path to static libraries

my $libPath = "/usr/lib";

# Open the libraries path and read the content

opendir(DIR, $libPath) or die $!;

# Keep only library who finished by .a

my @libraries = grep { /\.a$/ } readdir(DIR);

# Define arrays (associative and normal)

my %array;

my @tab;

# Print the content at 70 chars from the left to the right for the first column

# and 50 chars from the first column for the second column

print "################################################################################\n";

printf("%-70s %-50s\n", "# Function currently used", "Library #");

print "################################################################################\n";

# For each librairy found

foreach my $library (@libraries) {

# Find all functions used (T flag) in static library

# "nm" command is used to list the status of a library

# Result is push in a standard array

my @functionsArray = grep { /T/ } `nm $libPath/$library`;

# Explode the function by using space and push the result in the @tab array

foreach my $function (@functionsArray) {

@tab = split(/ /, $function);

# If the second field is equal to T then space, chariot

# are escaped with the chomp() function

# Result is push in the associative array %array

if ($tab[1] eq "T") {

chomp($tab[2]);

$array{$tab[2]}=$library;

}

# Each result in the %array array is display

foreach my $key (sort keys %array) {

printf("%-70s %-50s\n", $key, $array{$key});

}

print "\n";

# Close the libraries directory

closedir(DIR);

exit 0;

Gaëtan Trellu (goldyfruit)

Technical Operation Manager chez Ormuco

Autodidacte en informatique, depuis 2005 je parcours l’écosystème Unix à la recherche de nouvelles connaissances et de nouvelles rencontres.

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Fonctions utilisées d’une librairie statique

Un bout de Perl avec la commande nm

Exemple

Le script

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Gaëtan Trellu (goldyfruit)

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Un bout de Perl avec la commande nm

Exemple

Le script

Lien

Gaëtan Trellu (goldyfruit)

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