Re: [dpdk-dev] [PATCH] eal: don't use default library path for static binaries

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri, 26 Jun 2020 15:59:57 +0100
Bruce Richardson <bruce.richardson@intel.com> wrote:

> When using statically linked DPDK binaries, the EAL checks the default PMD
> path and tries to load any drivers there, despite the fact that all drivers
> are normally linked into the binary.  This behaviour can cause issues if
> the PMD path and lib dir is configured to a non-standard location which is
> not in the ld.so.conf paths, e.g. a build with prefix set to a home
> directory location. In a case such as this, EAL will try and
> (unnecessarily) load the .so driver files but that load will fail as their
> dependent libraries, such as ethdev, for example, will not be found.
> 
> Because of this, it is better if statically linked DPDK apps do not load
> drivers from the standard paths automatically. The user can always have
> this behaviour by explicitly specifying the path using -d flag, if so
> desired.
> 
> Not loading the libraries automatically can also prevent potential issues
> with a user building and running a statically-linked DPDK binary based off
> a private copy of DPDK, while there exists on the same machine a
> system-wide installation of DPDK in the default locations. Without this
> change, the system-installed drivers will be loaded to the binary alongside
> the statically-linked drivers, which is not what the user would have
> intended.
> 
> To detect whether we are in a statically or dynamically linked binary, we
> can have EAL try to get a dlopen handle to its own shared library, by
> calling dlopen with the RTLD_NOLOAD flag. This will return NULL if there is
> no such shared lib loaded i.e. the code is executing from a static library,
> or a handle to the lib if it is loaded.
> 
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>

But what if the majority of the DPDK is statically linked but the
application wants also load a dynamically linked driver?