Re: [Libguestfs] alternatives for hooking dlopen() without LD_LIBRARY_PATH or LD_AUDIT?

* Richard W. M. Jones: > On Fri, Feb 21, 2020 at 04:00:30PM +0100, Florian Weimer wrote: >> * Richard W. M. Jones: >> >> > On Fri, Feb 21, 2020 at 01:19:34PM +0100, Florian Weimer wrote: >> >> I think what confuses me is that keep talking about a single binary, but >> >> clearly there is this separate vddk DSO, and there is talk of plugins. >> >> So it seems to me that multiple files are involved already? >> > >> > nbdkit is a standalone binary that happens to be able to load plugins >> > from a well-known path, eg nbdkit-vddk-plugin.so. nbdkit knows the >> > path for plugins, and there's a wrapper allowing it to get local >> > plugins even when it's still in the build directory. Adding another >> > file would mean another path (or overloading the meaning of the plugin >> > path) and just makes the whole thing more fragile and complex. >> > >> > Having said all that, what would also solve this is either an API for >> > updating LD_LIBRARY_PATH after the program has started; or making >> > setenv ("LD_LIBRARY_PATH",...) DTRT*; or some kind of dlopen() variant >> > which takes a library path as an extra parameter. >> >> Have you tried adding DT_RUNPATH or DT_RPATH to nbdkit-vddk-plugin.so? >> Or does the path have to be chosen dynamically? > > To be clear, the situation is: > > nbdkit (free) > -> dlopens nbdkit-vddk-plugin.so (free) > -> dlopens libvixDiskLib.so (proprietary) > -> dlopens other proprietary plugins > -> both libvixDiskLib.so and its plugins have DT_NEEDED > "libstdc++.so.X" and other objects that have odd/old > compiled versions in its own directory > > It's the proprietary library libvixDiskLib.so (colloquially known as "VDDK") > which has trouble opening its own plugins. I guess you mean adding > DT_* to the proprietary library? No, to nbdkit-vddk-plugin.so. But it looks like have misunderstood the request. Do you want to inhibit loading the libstdc++.so.X from vddk, or the opposite—ensure that it is loaded? The latter obviously taints the process. But maybe that's what you want?