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From: "mjw at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: systemtap@sourceware.org
Subject: [Bug runtime/13467] New: user array indexing pointer_array.exp testcase fails on s390x needs @user($ptr)
Date: Fri, 02 Dec 2011 19:36:00 -0000
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http://sourceware.org/bugzilla/show_bug.cgi?id=13467

             Bug #: 13467
           Summary: user array indexing pointer_array.exp testcase fails
                    on s390x needs @user($ptr)
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
        AssignedTo: systemtap@sourceware.org
        ReportedBy: mjw@redhat.com
    Classification: Unclassified


pointer_array.stp basically does:

probe syscall.execve { println(user_string($argv[0])) }

The $argv[0] is evaluated in kernel context, but is really a user pointer.
So you will get a ERROR: kernel read fault at 0x00000000859fa100 (addr) near
identifier '$argv'.

The following would "fix" it:

probe syscall.execve { println(user_string(user_long($argv))) }

But the test really is about array indexing. The next tests try to extract the
individual chars with $argv[0][1], etc.

We could rewrite the testcase to use a user array in a user probe context.
But maybe we need some kind of @user($ptr) construct, which would then give you
an object that can be evaluated through []/-> as if in a user probe context?

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