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[perl #108792] Since perl5.14, prctl is used to modify the process name through $0. prctl may have issues on older kernel

From:
Iker Salmón San Millán
Date:
January 22, 2012 15:16
Subject:
[perl #108792] Since perl5.14, prctl is used to modify the process name through $0. prctl may have issues on older kernel
Message ID:
rt-3.6.HEAD-14510-1327270650-208.108792-75-0@perl.org
# New Ticket Created by  Iker Salmón San Millán 
# Please include the string:  [perl #108792]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=108792 >


-----------------------------------------------------------------
[Please describe your issue here]
TRying to cross-debootstrap from x86 system to armhf i get an error
configuring cron:
Setting up cron (3.0pl1-120+b1) ...
Can't set $0 with prctl(): Bad address at /usr/sbin/addgroup line 86.

related /usr/sbin/addgroup lines:

85    my $nogroup_id = getgrnam("nogroup") || 65534;
86    $0 =~ s+.*/++;
87
88    our $verbose = 1;        # should we be verbose?

this does not happen if the target rootfs is armel instead of armhf.  I've
been discussing (asking for help better said),
in arm-debian-mailing list and they 've pointed me in this direction.

Dominic Dumont said:
Well, according to perlvar(1) (look for \$0), modifying $0 is not portable.
(In this case, I don't see the point: addgroup program is short lived, hence
shortening the process name is not likely to be useful.)

Since perl5.14, prctl is used to modify the process name through $0. prctl
may
have issues on older kernel.

This may be a perl 5.14 bug. OTOH, changing $0 in addgroup is a bad idea.

The weird thing is if i install and amd64 kernel in my x86 system and try
to debootstrap everithing works fine.
So, this bug may be only reproducible in x86 systems with 686 (or below)
kernels.

Thanks.

Iker


[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=medium
---
Site configuration information for perl 5.14.2:

Configured by Debian Project at Mon Nov 28 21:49:25 UTC 2011.

Summary of my perl5 (revision 5 version 14 subversion 2) configuration:

  Platform:
    osname=linux, osvers=2.6.32-5-686,
archname=i486-linux-gnu-thread-multi-64int
    uname='linux callisto 2.6.32-5-686 #1 smp mon oct 3 04:15:24 utc 2011
i686 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN
-Dcccdlflags=-fPIC -Darchname=i486-linux-gnu -Dprefix=/usr
-Dprivlib=/usr/share/perl/5.14 -Darchlib=/usr/lib/perl/5.14
-Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5
-Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local
-Dsitelib=/usr/local/share/perl/5.14.2
-Dsitearch=/usr/local/lib/perl/5.14.2 -Dman1dir=/usr/share/man/man1
-Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1
-Dsiteman3dir=/usr/local/man/man3 -Duse64bitint -Dman1ext=1 -Dman3ext=3perl
-Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm
-Ui_libutil -DDEBUGGING=-g -Doptimize=-O2 -Duseshrplib
-Dlibperl=libperl.so.5.14.2 -des'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=undef, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN
-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include
-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing
-pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.6.2', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t',
lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /lib/i386-linux-gnu /lib/../lib
/usr/lib/i386-linux-gnu /usr/lib/../lib /lib /usr/lib /usr/lib64
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=, so=so, useshrplib=true, libperl=libperl.so.5.14.2
    gnulibc_version='2.13'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -L/usr/local/lib
-fstack-protector'

Locally applied patches:


---
@INC for perl 5.14.2:
    /etc/perl
    /usr/local/lib/perl/5.14.2
    /usr/local/share/perl/5.14.2
    /usr/lib/perl5
    /usr/share/perl5
    /usr/lib/perl/5.14
    /usr/share/perl/5.14
    /usr/local/lib/site_perl
    .

---
Environment for perl 5.14.2:
    HOME=/root
    LANG=es_ES.UTF-8
    LANGUAGE=
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash



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