Capstone is an open source disassembler [1] already used by
other projects (like QEMU).
gem5 is already capable of disassembling instructions. Every StaticInst
is supposed to define a generateDisassembly method which returns the
instruction mnemonic (opcode + operand list) as a string.
This "distributed" implementation of a disassembler relies
on the developer to properly populate the metadata fields
of the base instruction class.
The growing complexity of the ISA code and the massive reuse
of base classes beyond their intended use has led to a
disassembling logic which contains several bugs.
By allowing a tracer to rely on a third party disassembler, we fill the
intruction trace with a more trustworthy instruction stream.
This will make any trace parsing tool to work better and it will
also allow us to spot/fix our own bugs by comparing instruction
traces with native vs custom disassembler
[1]: http://www.capstone-engine.org/
Change-Id: I3c4db5072c03d2731265d0398d3863c101dcb180
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
The BaseCPU type had been specializing itself based on the value of
TARGET_ISA, which is not compatible with building more than one ISA at a
time.
This change refactors the CPU models so that the BaseCPU is more
general, and the ISA specific components are added to the CPU when the
CPU types are fully specialized. For instance, The AtomicSimpleCPU has a
version called X86AtomicSimpleCPU which installs the X86 specific
aspects of the CPU.
This specialization is done in three ways.
1. The mmu parameter is assigned an instance of the architecture
specific MMU type. This provides a reasonable default, but also avoids
having having to use the ISA specific type when the parameter is
created.
2. The ISA specific types are made available as class attributes, and
the utility functions (including __init__!) in the BaseCPU class can
refer to them to get the types they need to set up the CPU at run time.
Because SimObjects have strange, unhelpful semantics as far as assigning
to their attributes, these types need to be set up in a non-SimObject
class, which is then brought in as a base of the actual SimObject type.
Because the metaclass of this other type is just "type", things work
like you would expect. The SimObject doesn't do any special processing
of base classes if they aren't also SimObjects, so these attributes
survive and are accessible using normal lookup in the BaseCPU class.
3. There are some methods like addCheckerCPU and properties like
needsTSO which have ISA specific values or behaviors. These are set in
the ISA specific subclass, where they are inherently specific to an ISA
and don't need to check TARGET_ISA.
Also, the DummyChecker which was set up for the BaseSimpleCPU which
doesn't actually do anything in either C++ or python was not carried
forward. The CPU type still exists, but it isn't installed in the
simple CPUs.
To provide backward compatibility, each ISA implements a .py file which
matches the original .py for a CPU, and the original is renamed with a
Base prefix. The ISA specific version creates an alias with the old CPU
name which maps to the ISA specific type. This way, old scripts which
refer to, for example, AtomicSimpleCPU, will get the X86AtomicSimpleCPU
if the x86 version was compiled in, the ArmAtomicSimpleCPU on arm, etc.
Unfortunately, because of how tags on PySource and by extension SimObjects
are implemented right now, if you set the tags on two SimObjects or
PySources which have the same module path, the later will overwrite the
former whether or not they both would be included. There are some
changes in review which would revamp this and make it work like you
would expect, without this central bookkeeping which has the conflict.
Since I can't use that here, I fell back to checking TARGET_ISA to
decide whether to tell SCons about those files at all.
In the long term, this mechanism should be revamped so that these
compatibility types are only available if there is exactly one ISA
compiled into gem5. After the configs have been updated and no longer
assume they can use AtomicSimpleCPU in all cases, then these types can
be deleted.
Also, because ISAs can now either provide subclasses for a CPU or not,
the CPU_MODELS variable has been removed, meaning the non-ISA
specialized versions of those CPU models will always be included in
gem5, except when building the NULL ISA.
In the future, a more granular config mechanism will hopefully be
implemented for *all* of gem5 and not just the CPUs, and these can be
conditional again in case you only need certain models, and want to
reduce build time or binary size by excluding the others.
Change-Id: I02fc3f645c551678ede46268bbea9f66c3f6c74b
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52490
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
The CpuModel class looks like it was originally intended to hold a lot
more information that it does now, which is just the name of a CPU, and
whether it should be enabled by default. All the built in configs in
build_opts already explicitly list a set of CPUs, and CPUs should not,
generally speaking, be enabled by default, since they almost always need
to be specifically supported by an ISA. This is mutual, since usually
ISAs definitions are not quite correct or complete, and this is often
exposed by plugging them into different, and/or more complex CPU models
which stress those short comings.
This change drops the idea of a "default" CPU, and since the only thing
being tracked at this point is a list of CPUs, it turns CpuModel() into
a simple function which adds a name to a set of supported CPUs.
Change-Id: Id7475d5dc8548802b5253f79839da8c76ef4d165
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/48963
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Use SConsopts files local to individual domains to pull
non-foundational build code out of SConstruct. This greatly simplifies
SConstruct, and also makes it easier to find build configuration having
to do with particular pieces of gem5.
This change also converts some python level variables, all_protocols,
protocol_dirs, and slicc_includes, into the environment where the timing
of their initialization is more flexible.
Change-Id: Ie61ceb75ae9e5557cc400603c972a9582e99c1ea
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/40872
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Gabe Black <gabe.black@gmail.com>
