[Bugme-janitors] [Bug 6949] New: Linux does not differentiate between memory faults and privileged instruction faults

[bugme-daemon at bugzilla.kernel.org]

http://bugzilla.kernel.org/show_bug.cgi?id=6949

           Summary: Linux does not differentiate between memory faults and
                    privileged instruction faults
    Kernel Version: 2.6.17
            Status: NEW
          Severity: normal
             Owner: other_other at kernel-bugs.osdl.org
         Submitter: eteran at alum.rit.edu


Intel(R) Pentium(R) M processor 2.00GHz

Linux does not differentiate between memory faults and privileged instruction
faults. I am not sure if this is truly a bug, as it is more a matter of taste. 

However, I am currently developing a debugger with Linux as my primary platform,
and i noticed that when a faulty program attempts to execute an instruction
which is not allowed in ring3 (HLT for example), a SIGSEGV signal is produced. I
found this to be unintuitive at best.

My initial feeling would be that it would be more closely matched to the SIGILL
(illegal instruction signal), even though that is for op-codes which are not
legal in any context, it is a bit of a closer match to what is really happening.

Obviously, in a perfect world, there would be a separate signal for this sort of
situation, but I can see that being an issue with regard to backwards
compatibility if any programs count on this behaviour.

Like I said, it's arguable whether it's a bug at all, but I thought I'd at least
mention it.

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