Caret X does not use readlink() when coreutils are compiled with multicall support

[p5pRT]

Migrated from rt.perl.org#130997 (status was 'open')

Searchable as RT130997$

[p5pRT]

From kabel@blackhole.sk

Created by kabel@blackhole.sk

When coreutils are compiled with multicall support, the command
ls -l /proc/self/exe outputs something like​:

  lrwxrwxrwx 1 user group 0 Jan 1 00​:00 /proc/self/exe -> /usr/bin/coreutils

But when determining the HAS_PROCSELFEXE macro, perl's Configure script
checks if the result of the ls command contains string '/ls'. It this case
this fails, because there is no /bin/ls, rather /usr/bin/coreutils.

Thus when perl is compiled on systems with multicall coreutils, it cannot
check the path to its own executable, and thus the $^X variable return argv[0].

I encountered this issue when compiling OpenWRT/LEDE on my Gentoo system with
multicall coreutils​: when perl is cross compiled, miniperl is just a symlink
to host's perl, which, in this case, is built to be relocatable. But the code
which searches for modules could not find the XXX/usr/lib/perl5 directory,
because instead of "XXX/usr/bin/perl", it had just "./miniperl" in $^X.

I think the best way to check for /proc/self/exe and similar symlinks in
Configure would be to compile a small test.c which check for this, ie. something
like

  #include <unistd.h>
  int main(int argc, char ** argv) {
  char r[1024];
  size_t l = readlink(argv[1], r, 1024);
  return l < 1024 && !strcmp(r, argv[2]));
  }

Then Configure could just call /PATH/test /proc/self/exe /PATH/test to check
if /proc/self/exe works as intended.

Perl Info

Flags:
    category=core
    severity=low

Site configuration information for perl 5.24.1:

Configured by Gentoo at Fri Mar 10 18:00:40 CET 2017.

Summary of my perl5 (revision 5 version 24 subversion 1) configuration:
   
  Platform:
    osname=linux, osvers=4.9.13-gentoo, archname=x86_64-linux
    uname='linux thinkpad 4.9.13-gentoo #1 smp thu mar 9 11:43:35 cet 2017 x86_64 intel(r) core(tm) i7-3520m cpu @ 2.90ghz genuineintel gnulinux '
    config_args='-des -Dinstallprefix=/usr -Dinstallusrbinperl=n -Di_ndbm -Di_gdbm -Di_db -DDEBUGGING=none -Dinc_version_list=5.24.0/x86_64-linux 5.24.0  -Dlibpth=/usr/local/lib64 /lib64 /usr/lib64 -Dnoextensions=ODBM_File -Duseshrplib -Darchname=x86_64-linux -Dcc=x86_64-pc-linux-gnu-gcc -Doptimize=-march=native -O3 -pipe -fPIC -flto=4 -fuse-linker-plugin -Wl,-fuse-ld=gold -Dldflags=-Wl,-O1 -Wl,--as-needed -Dprefix=/usr -Dsiteprefix=/usr/local -Dvendorprefix=/usr -Dscriptdir=/usr/bin -Dprivlib=/usr/lib64/perl5/5.24.1 -Darchlib=/usr/lib64/perl5/5.24.1/x86_64-linux -Dsitelib=/usr/local/lib64/perl5/5.24.1 -Dsitearch=/usr/local/lib64/perl5/5.24.1/x86_64-linux -Dvendorlib=/usr/lib64/perl5/vendor_perl/5.24.1 -Dvendorarch=/usr/lib64/perl5/vendor_perl/5.24.1/x86_64-linux -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Dvendorman1dir=/usr/share/man/man1 -Dvendorman3dir=/usr/share/man/man3 -Dman1ext=1
                 -Dman3ext=3pm -Dlibperl=libperl.so.5.24.1 -Dlocincpth=/usr/include  -Dglibpth=/lib64 /usr/lib64  -Duselargefiles -Dd_semctl_semun -Dcf_by=Gentoo -Dmyhostname=localhost -Dperladmin=root@localhost -Ud_csh -Dsh=/bin/sh -Dtargetsh=/bin/sh -Uusenm -Di_ndbm -Di_gdbm -Di_db -DDEBUGGING=none -Dinc_version_list=5.24.0/x86_64-linux 5.24.0  -Dlibpth=/usr/local/lib64 /lib64 /usr/lib64 -Dnoextensions=ODBM_File'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=undef, usemultiplicity=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='x86_64-pc-linux-gnu-gcc', ccflags ='-fwrapv -fno-strict-aliasing -pipe -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-march=native -O3 -pipe -fPIC -flto=4 -fuse-linker-plugin -Wl,-fuse-ld=gold',
    cppflags='-fwrapv -fno-strict-aliasing -pipe'
    ccversion='', gccversion='5.4.0', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678, doublekind=3
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16, longdblkind=3
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='x86_64-pc-linux-gnu-gcc', ldflags ='-Wl,-O1 -Wl,--as-needed'
    libpth=/usr/local/lib64 /lib64 /usr/lib64 /usr/lib/gcc/x86_64-pc-linux-gnu/5.4.0/include-fixed /usr/lib /lib/../lib64 /usr/lib/../lib64 /lib
    libs=-lpthread -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
    perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    libc=libc-2.23.so, so=so, useshrplib=true, libperl=libperl.so.5.24.1
    gnulibc_version='2.23'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -march=native -O3 -pipe -fPIC -flto=4 -fuse-linker-plugin -Wl,-fuse-ld=gold -Wl,-O1 -Wl,--as-needed'

Locally applied patches:
    gentoo/hints_hpux - Fix hpux hints
    gentoo/aix_soname - aix gcc detection and shared library soname support
    gentoo/EUMM-RUNPATH - https://bugs.gentoo.org/105054 cpan/ExtUtils-MakeMaker: drop $PORTAGE_TMPDIR from LD_RUN_PATH
    gentoo/config_over - Remove -rpath and append LDFLAGS to lddlflags
    gentoo/opensolaris_headers - Add headers for opensolaris
    gentoo/patchlevel - List packaged patches for perl-5.24.1-r1(#3) in patchlevel.h
    gentoo/cleanup-paths - Cleanup PATH and shrpenv
    gentoo/enc2xs - Tweak enc2xs to follow symlinks and ignore missing @INC directories.
    gentoo/darwin-cc-ld - https://bugs.gentoo.org/297751 darwin: Use $CC to link
    gentoo/cpan_definstalldirs - Provide a sensible INSTALLDIRS default for modules installed from CPAN.
    gentoo/interix - Fix interix hints
    gentoo/create_libperl_soname - https://bugs.gentoo.org/286840 Set libperl soname
    gentoo/mod_paths - Add /etc/perl to @INC
    gentoo/EUMM_perllocalpod - cpan/ExtUtils-MakeMaker: remove targets that generate perllocal.pod
    gentoo/drop_fstack_protector - https://bugs.gentoo.org/348557 Don't force -fstack-protector on everyone
    gentoo/usr_local - Configure: Don't include sources in /usr/local/ for compiling perl
    gentoo/D-SHA-CFLAGS - https://bugs.gentoo.org/506818 Do not set custom CFLAGS in cpan/Digest-SHA
    gentoo/io_socket_ip_tests - cpan/IO-Socket-IP: Disable network tests
    gentoo/cygwin-libperl - Cygwin: avoid libperl.dll.dll.a
    gentoo/tests - Fixup EUMM perlocal.pod tests and customised SHA1s
    gentoo/basepm-dot-inc - base.pm: Protect against . in @INC
    gentoo/zlib-1.2.9-backported-fixes - [rt#119762] Compress-Raw-Zlib: backport zlib 1.2.9+ fixes from upstream 2.073
    gentoo/gcc6-lto-configure - [RT#128131] fix symbol detection with gcc 6 link-time optimization
    debian/cpan-missing-site-dirs - Fix CPAN::FirstTime defaults with nonexisting site dirs if a parent is writable
    debian/makemaker-pasthru - Pass LD settings through to subdirectories
    fixes/memoize_storable_nstore - [rt.cpan.org #77790] Memoize::Storable: respect 'nstore' option not respected
    fixes/podman-pipe - Better errors for man pages from standard input
    fixes/respect_umask - Respect umask during installation
    fixes/net_smtp_docs - [rt.cpan.org #36038] Document the Net::SMTP 'Port' option
    fixes/document_makemaker_ccflags - [rt.cpan.org #68613] Document that CCFLAGS should include $Config{ccflags}
    fixes/parallel-manisort.patch - Fix parallel building


@INC for perl 5.24.1:
    /etc/perl
    /usr/local/lib64/perl5/5.24.1/x86_64-linux
    /usr/local/lib64/perl5/5.24.1
    /usr/lib64/perl5/vendor_perl/5.24.1/x86_64-linux
    /usr/lib64/perl5/vendor_perl/5.24.1
    /usr/local/lib64/perl5
    /usr/lib64/perl5/vendor_perl/5.24.0/x86_64-linux
    /usr/lib64/perl5/vendor_perl/5.24.0
    /usr/lib64/perl5/vendor_perl
    /usr/lib64/perl5/5.24.1/x86_64-linux
    /usr/lib64/perl5/5.24.1


Environment for perl 5.24.1:
    HOME=/home/kabel
    LANG=en_US.UTF-8
    LANGUAGE=en_US.UTF-8
    LC_ALL=en_US.UTF-8
    LC_MESSAGES=en_US.UTF-8
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=.:/usr/local/bin:/usr/bin:/bin:/opt/bin:/usr/x86_64-pc-linux-gnu/gcc-bin/5.4.0:/usr/x86_64-pc-linux-gnu/aarch64-unknown-linux-gnu/gcc-bin/5.4.0:/usr/x86_64-pc-linux-gnu/armv7a-hardfloat-linux-gnueabi/gcc-bin/4.9.4:/usr/x86_64-pc-linux-gnu/mipsel-softfloat-linux-gnu/gcc-bin/5.4.0:/usr/x86_64-pc-linux-gnu/mipsel-softfloat-linux-musl/gcc-bin/4.9.4:/sbin:/usr/sbin:/home/kabel/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

[p5pRT]

From @jkeenan

Are there any 'Configure' experts who could evaluate this bug report?

Thank you very much.

--
James E Keenan (jkeenan@​cpan.org)

[p5pRT]

The RT System itself - Status changed from 'new' to 'open'

[zwizwa]

I ran into the same problem compiling perl-5.40.0 as part of OpenWRT on my NixOS system.

[jkeenan]

OpenWRT

Some references:

• OpenWRT
• NixOS

[jkeenan]

From kabel@blackhole.sk

Created by kabel@blackhole.sk

When coreutils are compiled with multicall support, the command ls -l /proc/self/exe outputs something like​:

lrwxrwxrwx 1 user group 0 Jan 1 00​:00 /proc/self/exe -> /usr/bin/coreutils

But when determining the HAS_PROCSELFEXE macro, perl's Configure script checks if the result of the ls command contains string '/ls'. It this case this fails, because there is no /bin/ls, rather /usr/bin/coreutils.

Thus when perl is compiled on systems with multicall coreutils, it cannot check the path to its own executable, and thus the $^X variable return argv[0].

I encountered this issue when compiling OpenWRT/LEDE on my Gentoo system with multicall coreutils​: when perl is cross compiled, miniperl is just a symlink to host's perl, which, in this case, is built to be relocatable. But the code which searches for modules could not find the XXX/usr/lib/perl5 directory, because instead of "XXX/usr/bin/perl", it had just "./miniperl" in $^X.

I think the best way to check for /proc/self/exe and similar symlinks in Configure would be to compile a small test.c which check for this, ie. something like

#include <unistd.h> int main(int argc, char ** argv) { char r[1024]; size_t l = readlink(argv[1], r, 1024); return l < 1024 && !strcmp(r, argv[2])); }

Then Configure could just call /PATH/test /proc/self/exe /PATH/test to check if /proc/self/exe works as intended.
Perl Info

I got warnings and errors when I attempted to compile the C program submitted by the OP back in 2017. With my limited C skills, I modified the probe program as follows:

$ cat gh-15922-readlink.c 
#include <unistd.h>
#include <string.h>
int main(int argc, char ** argv) {
    char r[1024];
    size_t l = readlink(argv[1], r, 1024);
    return l < 1024 && !strcmp(r, argv[2]);
}

Can someone compile and run this program on a system with /usr/bin/coreutils or otherwise similar to the OP's platform? Thanks.