[Bug uprobes/12741] New: rip-relative instruction is not detected as such

[Bug uprobes/12741] New: rip-relative instruction is not detected as such

[jistone at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12741

           Summary: rip-relative instruction is not detected as such
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: uprobes
        AssignedTo: systemtap@sourceware.org
        ReportedBy: jistone@redhat.com


On Fedora 15 x86_64, uprobes handle_riprel_insn() is computing need_modrm:0 for
opcode 0x89, when the table says it should be 1.  Thus the instruction is not
properly being treated as rip-relative.

I noticed that with gcc 4.6, compiling uprobes gives a few warnings like:

    arch/x86/include/asm/bitops.h:319:2: warning: use of memory input
    without lvalue in asm operand 1 is deprecated [enabled by default]

That line is the asm statement in variable_test_bit().  The most obvious
difference is that test_bit takes const volatile, and our table is just const. 
It has always been thus, but apparently gcc 4.6 cares more about this, and is
generating code differently as a result.

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[Bug uprobes/12741] rip-relative instruction is not detected as such

[jistone at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12741

Josh Stone <jistone at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #1 from Josh Stone <jistone at redhat dot com> 2011-05-07 02:02:15 UTC ---
When our instruction tables are set const volatile to match test_bit(), the
warning goes away, and need_modrm is now computed correctly.  Commit 0746c987.

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[Bug uprobes/12741] rip-relative instruction is not detected as such

[jistone at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12741

--- Comment #2 from Josh Stone <jistone at redhat dot com> 2011-09-22 01:26:32 UTC ---
A similar asm warning cropped up in the uprobes patchset going upstream, and
this time I did a fuller analysis of why this warning makes a difference to the
test_bit result.  Link for posterity: https://lkml.org/lkml/2011/9/21/470

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