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.)
Use some template hacks to force GCC to inline more of the instruction
decoding stuff into the UserspaceEmulator main execution loop.
This is my last optimization for today, and we've gone from ~60 seconds
when running "UserspaceEmulator UserspaceEmulator id" to ~8 seconds :^)
To avoid MMU region lookup on every single instruction fetch, we now
cache a raw pointer to the current instruction. This gets automatically
invalidated when we jump somewhere, but as long as we're executing
sequentially, instruction fetches will hit the cache and bypass all
the region lookup stuff.
This is about a ~2x speedup. :^)
This patch adds a basic ELF program loader to the UserspaceEmulator and
creates MMU regions for each PT_LOAD header. (Note that we don't yet
respect the R/W/X flags etc.)
We also turn the SoftCPU into an X86::InstructionStream and give it an
EIP register so we can actually execute code by fetching memory through
our MMU abstraction.
Let's use C++ templates to implement the generic parts of instructions.
There are tons of them with the same set of inputs, just different
behavior. Templates are perfect for this.
This patch adds a PartAddressableRegister type, which divides a 32-bit
value into separate parts needed for the EAX/AX/AL/AH register splits.
Clean up the code around register access to make it a little less
cumbersome to use.
This introduces a new X86 CPU emulator for running SerenityOS userspace
programs in a virtualized interpreter environment.
The main goal is to be able to instrument memory accesses and catch
interesting bugs that are very hard to find otherwise. But before we
can do fancy things like that, we have to build a competent emulator
able to actually run programs.
This initial version is able to run a very small program that makes
some tiny syscalls, but nothing more.
