Re: ldd runs linux programs

On 7/30/13 4:54 AM, Mateusz Guzik wrote:
> On Mon, Jul 29, 2013 at 11:56:25AM -0400, Mark Johnston wrote:
>>> 127276 suggests running the binary as is (which I don't like) and
>>> achieves this with a hacky way. So if we really want to do this, the
>>> patch should be reworked to detect Linux binaries properly.
>>>
>>> In general we should gain linux_ldd (like linux_kdump) and our ldd
>>> should work only on FreeBSD binaries. The last part is achieved with my
>>> patch.
>>>
>>> markj, are you working on this?
>> Not really; my original fix for this problem was essentially the same as
>> yours. That is, just change ldd(1) to bail if the OS ABI byte isn't
>> equal to ELFOSABI_FREEBSD. That's the change I have committed in my
>> local tree right now.
>>
>> Then I thought I'd try to get ldd to work properly with Linux binaries
>> as well, but wasn't sure what the right approach should be. As the above
>> PR suggests, the easy thing to do is to just pass
>> LD_TRACE_LOADED_OBJECTS and not LD_32_TRACE_LOADED_OBJECTS for 32-bit
>> ELF objects if the OS isn't FreeBSD. This feels somewhat hacky to me,
>> but I didn't really see another approach.
>>
>> That said, I think your patch should be committed since it's clearly an
>> improvement over the current behaviour. I'm willing to test and commit
>> it, and clean up the open PRs. If you could expand on the right way to
>> handle Linux binaries, I'd be willing to implement and commit that too.
>> I don't quite understand your reference to linux_kdump though - I have
>> no such program on my laptop running CURRENT, and ktrace+kdump seem to
>> work fine with the Linux binaries under /compat/linux.
>>
> Well, there was linux_kdump in ports but it apparently got obsolete as
> necessary support for included in our regular kdump.
>
> So it may make sense to teach our ldd how to deal with Linux binaries
> for consistency, but its unclear for me if this is better than providing
> linux_ldd. Also there is the problem of (not) appending /compat/linux to
> printed paths (for Linux binaries the kernel performs file lookups against
> /compat/linux first). I'm not that interested in this problem though. :P
>
> That being said, if you want to do something with this, I suggest
> cleaning up PRs and reviving discussion in
> http://www.freebsd.org/cgi/query-pr.cgi?pr=bin/127276

if linux binaries are installed then chain to libexec/linux-ldd just 
like fsck chains to various specific fsck binaries.  If there is no 
such chain loadable ldd, then just refuse to do anything.
>