Exterminator- A ... with High Probability.pdf - DSpace at CUSAT ...

Exterminator
neither source code nor a large deployed user base in order to find errors, and
automatically generates runtime patches that correct them.
Delta debugging automates the process of identifying the smallest possible inputs that do
and do not exhibit a given error. Given these inputs, it is up to the software developer to
actually locate the bugs themselves. Exterminator focuses on a narrower class of errors, but
is able to isolate and correct an error given just one erroneous input, regardless of its size.
8.4 Fault Tolerance
Recently, there has been an increasing focus on approaches for tolerating hardware
transient errors that are becoming more common due to fabrication process limitations.
Work in this area ranges from proposed hardware support to software fault tolerance.While
Exterminator also uses redundancy as a method for detecting and correcting errors,
Exterminator goes beyond tolerating software errors, which are not transient, to correcting
them permanently. Like Exterminator, other efforts in the fault tolerance community seek
to gather data from multiple program executions to identify potential errors. For example,
Guo et al. use statistical techniques on internal monitoring data to probabilistically detect
faults, including memory leaks and deadlocks. Exterminator goes beyond this previous
work by characterizing each memory error so specifically that a correction can be
automatically generated for it.
Rinard et al. present a compiler-based approach called boundless buffers that caches
out-of-bound writes in a hash table for later reuse. This approach eliminates buffer
overflow errors (though not dangling pointer errors), but requires source code and imposes
higher performance overheads (1.05x to 8.9x).
Rx operates by checkpointing program execution and logging inputs. Rx rolls back
crashed applications and replays inputs to it in a new environment that pads all allocations
or defers all deallocations by some amount. If this new environment does not yield
success, Rx rolls back the application again and increases the pad values, up to some
threshold. Unlike Rx, Exterminator does not require checkpointing or rollback, and
precisely isolates and corrects memory errors.
8.5 Memory Managers
Conservative garbage collection prevents dangling pointer errors, but does not prevent
buffer overflows. Exterminator’s error isolation and correction is orthogonal to garbage
collection.
Finally, there have been numerous debugging memory allocators; the documentation
for one of them, mpatrol, includes a list of over ninety such systems. Notable recent
allocators with debugging features include dnmalloc, Heap Server, and version 2.8 of the
Lea allocator. Exterminator either prevents or corrects errors that these allocators can only
detect.
Dept. Of Computer Science & Engg. ~ 24 ~ Cochin University of Science & Technology