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.
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