Currently, the wire format of register values in g- and G-packets is
modelled using a union of uint8/16/32/64 arrays. The offset positions
of each register are expressed as a "register count" scaled according
to the width of the register in question. This results in counter-
intuitive and error-prone "register count arithmetic", and some
formats would even be altogether unrepresentable in such model, e.g.
a 64-bit register following a 32-bit one would have a fractional index
in the regs64 array.
Another difficulty is that the array is allocated before the actual
architecture of the workload is known (and therefore before the correct
size for the array can be calculated).
With this patch I propose a simpler mechanism for expressing the
register set structure. In the new code, GdbRegCache is an abstract
class; its subclasses contain straightforward structs reflecting the
register representation. The determination whether to use e.g. the
AArch32 vs. AArch64 register set (or SPARCv8 vs SPARCv9, etc.) is made
by polymorphically dispatching getregs() to the concrete subclass.
The subclass is not instantiated until it is needed for actual
g-/G-packet processing, when the mode is already known.
This patch is not meant to be merged in on its own, because it changes
the contract between src/base/remote_gdb.* and src/arch/*/remote_gdb.*,
so as it stands right now, it would break the other architectures.
In this patch only the base and the ARM code are provided for review;
once we agree on the structure, I will provide src/arch/*/remote_gdb.*
for the other architectures; those patches could then be merged in
together.
Review Request: http://reviews.gem5.org/r/3207/
Pushed by Joel Hestness <jthestness@gmail.com>
The new single stepping implementation for x86 doesn't rely on any ISA
specific properties or functionality. This change pulls out the per ISA
implementation of those functions and promotes the X86 implementation to the
base class.
One drawback of that implementation is that the CPU might stop on an
instruction twice if it's affected by both breakpoints and single stepping.
While that might be a little surprising, it's harmless and would only happen
under somewhat unlikely circumstances.
This patch removes the assumption on having on single instance of
PhysicalMemory, and enables a distributed memory where the individual
memories in the system are each responsible for a single contiguous
address range.
All memories inherit from an AbstractMemory that encompasses the basic
behaviuor of a random access memory, and provides untimed access
methods. What was previously called PhysicalMemory is now
SimpleMemory, and a subclass of AbstractMemory. All future types of
memory controllers should inherit from AbstractMemory.
To enable e.g. the atomic CPU and RubyPort to access the now
distributed memory, the system has a wrapper class, called
PhysicalMemory that is aware of all the memories in the system and
their associated address ranges. This class thus acts as an
infinitely-fast bus and performs address decoding for these "shortcut"
accesses. Each memory can specify that it should not be part of the
global address map (used e.g. by the functional memories by some
testers). Moreover, each memory can be configured to be reported to
the OS configuration table, useful for populating ATAG structures, and
any potential ACPI tables.
Checkpointing support currently assumes that all memories have the
same size and organisation when creating and resuming from the
checkpoint. A future patch will enable a more flexible
re-organisation.
--HG--
rename : src/mem/PhysicalMemory.py => src/mem/AbstractMemory.py
rename : src/mem/PhysicalMemory.py => src/mem/SimpleMemory.py
rename : src/mem/physical.cc => src/mem/abstract_mem.cc
rename : src/mem/physical.hh => src/mem/abstract_mem.hh
rename : src/mem/physical.cc => src/mem/simple_mem.cc
rename : src/mem/physical.hh => src/mem/simple_mem.hh
A recent changeset (aae12ce9f34c) removed support for
PAL-mode breakpoints in Alpha, since it was awkward
and likely unused. This patch lets a user know if they
potentially run into this limitation.
