From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Le Bihan Date: Thu, 16 Jun 2016 21:45:22 +0200 Subject: [Buildroot] Allowing user to run ldconfig in post-build script In-Reply-To: <20160616153710.12ef9233@free-electrons.com> References: <1722059483.342813959.1466082436418.JavaMail.root@zimbra32-e6.priv.proxad.net> <1720572432.342833812.1466082726731.JavaMail.root@zimbra32-e6.priv.proxad.net> <20160616153710.12ef9233@free-electrons.com> Message-ID: <20160616214522.70ca9152@itchy> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: buildroot@busybox.net Le Thu, 16 Jun 2016 15:37:10 +0200, Thomas Petazzoni a ?crit : > > Since commit 9c40723, handling of ldconfig in the main Makefile as > > been dropped, and if /etc/ld.so.conf is found in the target root > > filesystem, the build fails. > > > > Not being able to run ldconfig and generate the ld.so cache has two > > drawbacks: > > > > - it prevents the user from installing some libraries in other > > locations than /lib and /usr/lib (e.g. /opt/foo/lib). This can be > > solved with symlinks, though. > > Does the dynamic linker uses /etc/ld.so.conf at runtime to find other > libraries, even if there is no /etc/ld.so.cache? If that's the case, > then our check for ld.so.conf being absent is somewhat wrong, as it > would be valid to have, independently of whether ldconfig has created > ld.so.cache or not. Inspecting the glibc source code shows that: - /etc/ld.so.conf is only read by ldconfig (see elf/ldconfig.c). - /etc/ld.so.cache is only read by the dynamic loader (see elf/dl-cache.c). This is confirmed when using strace. So, IMHO, this sanity check is of no use. > However, in order to merge something like this, I'd like to have a > solution that covers glibc, uClibc and musl, or at least takes those > different cases into account by making it available only for the C > libraries that support it (but that mean investigating how uClibc and > musl support ld.so.conf/ld.so.cache). >From the INSTALL file in musl source code, we learn that if dynamic linking is enabled, the dynamic linker will be /lib/ld-musl-$ARCH.so.1. It will look for libraries in the paths listed in /etc/ld-musl-$ARCH.path. Debian provides ld-musl-config, which aggregates the contents of the files found in /etc/ld-musl-$ARCH.d/ to create /etc/ld-musl-$ARCH.path. However musl is traditionally used for static linking. uclibc-ng also provides ldconfig, which behaves like the glibc version (see ldso/man/ldconfig.8 in the source tree). > Another thing that bothers me is why it is not possible to have a > cross-compilation aware ldconfig. This would really be much, much > nicer than running ldconfig under qemu. Yocto provides a recipe named ldconfig-native_2.12.1.bb [1], which contains a verbatim copy of the ldconfig source code from glibc, and a truck load of patches. It looks a bit hairy... [1] http://cgit.openembedded.org/openembedded-core/tree/meta/recipes-core/glibc/ldconfig-native_2.12.1.bb Regards, -- ELB