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

On 2/14/20 1:02 PM, Eric Blake wrote: > Writing my own dlopen() wrapper directly in nbdkit seems like a > non-starter (my override has to come from a shared library before > it can replace the shared version that would be imported from -ldl, > at least for all subsequent shared library loads that want to bind > to the override). Maybe I spoke too soon. I've tried another approach that looks like it will do what I want: put my shim dlopen() in a shared library, but link nbdkit against that shared library PRIOR to -ldl (so that name lookup for dlopen resolves there first). The shim library in turn depends on -ldl so that dlsym(RTLD_NEXT, "dlopen") still lets me get to the real dlopen. And by linking it directly into nbdkit, rather than into the nbdkit-vddk-plugin.so that gets loaded later, the first bound dlopen() in use for all subsequent loads is from my shim. It's still a bit less clean than I'd like (it requires tighter coupling between nbdkit and nbdkit-vddk-plugin.so than what used to exist), but the fact that it works without dlmopen() or LD_LIBRARY_PATH is in its favor. I'm now polishing up the experiment, and will post the patch when it's ready.