Date: Thu, 4 Jun 2020 15:48:49 -0400 From: Rich Felker <dalias@...c.org> To: Alexander Scherbatiy <alexander.scherbatiy@...l-sw.com> Cc: musl@...ts.openwall.com, Markus Wichmann <nullplan@....net> Subject: Re: Shared library loading On Thu, Jun 04, 2020 at 10:37:40PM +0300, Alexander Scherbatiy wrote: > On 25.05.2020 20:46, Rich Felker wrote: > > >On Mon, May 25, 2020 at 08:26:51PM +0300, Alexander Scherbatiy wrote: > >> What is the suggested way in musl to load $libdir/myapp/libfoo.so > >>from a custom directory so libbar.so can find it? > >Probably putting the dir in your application's rpath (or in the rpath > >of libbar). dlopen is not a tool for (effectively) adding additional > >directories to the library search path. > > OpenJDK can have several jvm variants (like server, client, minimal). > Each of variants contains its own version of libjvm.so lib. > jdk/bin/java > jdk/lib/server/libjvm.so > jdk/lib/client/libjvm.so > jdk/lib/minimal/libjvm.so > > When java is executed it first loads libjvm.so for the requested variant > using dlopen() with RTLD_NOW | RTLD_GLOBAL flags  and then > loads libraries from jdk/lib dir with dlopen() and RTLD_LAZY flag. > > To make it works with musl JDK implements workaround where > it puts libjvm.so into LD_LIBRARY_PATH  and re-executes itself. > > Is there a better way to handle the case where an application > with several lib variants can load common libraries > without changing LD_LIBRARY_PATH? > >  https://hg.openjdk.java.net/portola/portola/file/7ff60204a181/src/java.base/unix/native/libjli/java_md_solinux.c#l590 >  https://hg.openjdk.java.net/portola/portola/file/7ff60204a181/src/java.base/unix/native/libjli/java_md_solinux.c#l244 One way to do it would be to make dummy libraries libjvm_server.so, libjvm_client.so, and libjvm_minimal.so that contain no code or data but just a DT_NEEDED reference to libjvm.so and an appropriate DT_RUNPATH to find it. Rich
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