Re: [PATCHv2 4/4] pmdinfo.py: Add tool to query binaries for hw and other support information

[Panu Matilainen <pmatilai@redhat.com>]

On 05/19/2016 12:08 AM, Neil Horman wrote:
> This tool searches for the primer sting PMD_DRIVER_INFO= in any ELF binary,
> and, if found parses the remainder of the string as a json encoded string,
> outputting the results in either a human readable or raw, script parseable
> format
>
> Note that, in the case of dynamically linked applications, pmdinfo.py will scan
> for implicitly linked PMDs by searching the specified binaries .dynamic section
> for DT_NEEDED entries that contain the substring librte_pmd.  The DT_RUNPATH,
> LD_LIBRARY_PATH, /usr/lib and /lib are searched for these libraries, in that
> order

Scanning /usr/lib and /lib does little good on systems where /usr/lib64 
and /lib64 are the standard path, such as x86_64 Fedora / RHEL and 
derivates.

With the path changed (or LD_LIBRARY_PATH set manually), I can confirm 
it works for a shared binary which is --whole-archive linked to all of 
DPDK such as ovs-vswitchd currently is (because it needs to for static 
DPDK linkage and is not aware of plugin autoloading).

It doesn't help testpmd though because its not linked with 
--whole-archive in the shared case, so its not working for the main DPDK 
executable...

In any case, using --whole-archive is a sledgehammer solution at best, 
and against the spirit of shared libs and plugins in particular.

I think the shared linkage case can be solved by exporting the PMD path 
from librte_eal (either through an elf section or c-level symbol) and 
teach the script to detect the case of an executable dynamically linked 
to librte_eal, fish the path from there and then process everything in 
that path.

>
> If a file is specified with no path, it is assumed to be a PMD DSO, and the
> LD_LIBRARY_PATH, /usr/lib/ and /lib is searched for it

Same as above, /usr/lib/ and /lib is incorrect for a large number of 
systems.

>
> Currently the tool can output data in 3 formats:
>
> a) raw, suitable for scripting, where the raw JSON strings are dumped out
> b) table format (default) where hex pci ids are dumped in a table format
> c) pretty, where a user supplied pci.ids file is used to print out vendor and
> device strings

c) is a nice addition. Would be even nicer if it knew the most common 
pci.ids locations so it doesn't need extra arguments in those cases, ie 
see if /usr/share/hwdata/pci.ids or /usr/share/misc/pci.ids exists and 
use that unless overridden on the cli.

	- Panu -