[lldb-dev] mmx registers on Linux 32-bit inferior

Todd Fiala tfiala at google.com
Thu Feb 27 15:28:01 PST 2014

Hey all,

I just put up a patch earlier today to support lldb debugging 32-bit EXEs
on a 32-bit host (thanks to Matthew Gardiner for all the investigation and
motivation!)  In the process of fixing that, I saw what looked like it
might be the root cause of MMX registers being read incorrectly for a Linux
32-bit EXE debugged by a 64-bit host lldb.

Is there anybody out there who has a valid MMX debug scenario for a 32-bit
Linux app that they can test in these two scenarios?
(1) debugging on a 32-bit Linux host with top of tree lldb.
(2) debugging on a 64-bit Linux host with top of tree lldb.

Those two code paths will be different now.  I suspect it will work
correctly in (1) [32-bit exe debugged on 32-bit host].  But it might fail
on #2.  If it works on #1 and not on #2, I suspect I can now change the
32-bit exe debugging path on 64 bit host to mirror the 32-bit host path
now, which may fix it.  But I don't want to fiddle with it without a valid
test scenario.

In lieu of actually running the test, I'd be happy to consume somebody's
MMX code that they know works and can tell me what the values should be at
certain points in the code and I can run the tests over here.

Todd Fiala | Software Engineer | tfiala at google.com | 650-943-3180
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