[Bug runtime/4633] New: backtracing broken

["fche at redhat dot com" <sourceware-bugzilla@sourceware.org>]

Bug #3050 may have been closed but the bug did not stay dead.  The same code on
current fc7 kernels gives the usual single line of backtrace info.
The kernel backtracer always seems to do a better job than the code in the runtime.

There are several problems with the code.  It uses unprotected dereference code
like "*stack++", even though the stack values are not completely reliable.  It
does not know how to distinguish between alternative stacks such as the trap stack,
the normal kernel stack, or whatever happens to come in pt_regs.  This is key
because backtrace() should from both kprobes and from ordinary hook calls
such as timers, begin/end, and markers.  The backtrace() function should not
include the "Inexact backtrace:" string, as this breaks subsequent tokenizing 
with print_stack().

-- 
           Summary: backtracing broken
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: fche at redhat dot com
  GCC host triplet: x86-64


http://sourceware.org/bugzilla/show_bug.cgi?id=4633

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