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.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org