[Bug uprobes/5273] New: x86 arch_validate_probed_insn(): lighten up?

[Bug uprobes/5273] New: x86 arch_validate_probed_insn(): lighten up?

[jkenisto at us dot ibm dot com]

In uprobes_i386.c and uprobes_x86_64.c, we spend quite a bit of code on refusing
to probe certain types of instructions, such as undefined opcodes and other
instructions that are likely to yield SIGILL when single-stepped in user mode. 
There's also some paranoia about how instruction prefixes and such might affect
our decisions about which instructions need to be treated specially when
single-stepping them out of line.

We could probably lighten up here.  One disadvantage of the paranoia is that
tests that try to probe (say) EVERY instruction in a .o file will choke on
things like hlt.

For illegal instructions, if the SIGILL kills the task before the SIGTRAP from
the single-step is reported to us -- we need to test this -- then we should be
OK.  Testing suggests that we know how to handle tasks that die of other causes
during probepoint processing.

And I think we've successfully identified instructions that need special
attention during SSOL.  It's probably just a matter of testing each currently
banned instruction type to verify that it doesn't present an unforeseen problem.

-- 
           Summary: x86 arch_validate_probed_insn(): lighten up?
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: minor
          Priority: P3
         Component: uprobes
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: jkenisto at us dot ibm dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=5273

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[Bug uprobes/5273] x86 arch_validate_probed_insn(): lighten up?

[jkenisto at us dot ibm dot com]

------- Additional Comments From jkenisto at us dot ibm dot com  2009-04-24 21:00 -------
uprobes/uprobes_i386.c has been brought back into sync with the (more tolerant)
uprobes2/uprobes_x86.c.  A couple of changes were ad hoc to address specific
test failures.  Commit af6b060 completes the resync.

We still haven't done any exhaustive testing of the whole instruction set.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=5273

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[Bug uprobes/5273] x86 arch_validate_probed_insn(): lighten up?

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2009-08-13 17:47 -------
*** Bug 10324 has been marked as a duplicate of this bug. ***

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           What    |Removed                     |Added
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                 CC|                            |fche at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=5273

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