Upon exit, the emulator will now print a leak report of any malloc
allocations that are still live and don't have pointers to their base
address anywhere in either another live mallocation, or in one of the
non-malloc-block memory regions.
Note that the malloc-block memory region check is not fully functional
and this will work even better once we get that fixed.
This is pretty cool. :^)
This patch introduces a "MallocTracer" to the UserspaceEmulator.
If this object is present on the Emulator, it can be notified whenever
the emulated program does a malloc() or free().
The notifications come in via a magic instruction sequence that we
embed in the LibC malloc() and free() functions. The sequence is:
"salc x2, push reg32 x2, pop reg32 x3"
The data about the malloc/free operation is in the three pushes.
We make sure the sequence is harmless when running natively.
Memory accesses on MmapRegion are then audited to see if they fall
inside a known-to-be-freed malloc chunk. If so, we complain loud
and red in the debugger output. :^)
This is very, very cool! :^)
It's also a whole lot slower than before, since now we're auditing
memory accesses against a new set of metadata. This will need to be
optimized (and running in this mode should be opt-in, perhaps even
a separate program, etc.)
