Rather than make a global accessor for this sort of thing. We can make
it a part of the thread interface itself. This allows getting rid of a
hidden global accessor in the kernel code.
This condition was checking against the nominal thread priority, whereas
the kernel itself checks against the current priority instead. We were
also assigning the nominal priority, when we should be assigning
current_priority, which takes priority inheritance into account.
This can lead to the incorrect priority being assigned to a thread.
Given we recursively update the relevant threads, we don't need to go
through the whole mutex waiter list. This matches what the kernel does
as well (only accessing the first entry within the waiting list).
* gdbstub: fix IsMemoryBreak() returning false while connected to client
As a result, the only existing codepath for a memory watchpoint hit to break into GDB (InterpeterMainLoop, GDB_BP_CHECK, ARMul_State::RecordBreak) is finally taken,
which exposes incorrect logic* in both RecordBreak and ServeBreak.
* a blank BreakpointAddress structure is passed, which sets r15 (PC) to NULL
* gdbstub: DynCom: default-initialize two members/vars used in conditionals
* gdbstub: DynCom: don't record memory watchpoint hits via RecordBreak()
For now, instead check for GDBStub::IsMemoryBreak() in InterpreterMainLoop and ServeBreak.
Fixes PC being set to a stale/unhit breakpoint address (often zero) when a memory watchpoint (rwatch, watch, awatch) is handled in ServeBreak() and generates a GDB trap.
Reasons for removing a call to RecordBreak() for memory watchpoints:
* The``breakpoint_data`` we pass is typed Execute or None. It describes the predicted next code breakpoint hit relative to PC;
* GDBStub::IsMemoryBreak() returns true if a recent Read/Write operation hit a watchpoint. It doesn't specify which in return, nor does it trace it anywhere. Thus, the only data we could give RecordBreak() is a placeholder BreakpointAddress at offset NULL and type Access. I found the idea silly, compared to simply relying on GDBStub::IsMemoryBreak().
There is currently no measure in the code that remembers the addresses (and types) of any watchpoints that were hit by an instruction, in order to send them to GDB as "extended stop information."
I'm considering an implementation for this.
* gdbstub: Change an ASSERT to DEBUG_ASSERT
I have never seen the (Reg[15] == last_bkpt.address) assert fail in practice, even after several weeks of (locally) developping various branches around GDB. Only leave it inside Debug builds.
Makes it an instantiable class like it is in the actual kernel. This
will also allow removing reliance on global accessors in a following
change, now that we can encapsulate a reference to the system instance
in the class.
Within the kernel, shared memory and transfer memory facilities exist as
completely different kernel objects. They also have different validity
checking as well. Therefore, we shouldn't be treating the two as the
same kind of memory.
They also differ in terms of their behavioral aspect as well. Shared
memory is intended for sharing memory between processes, while transfer
memory is intended to be for transferring memory to other processes.
This breaks out the handling for transfer memory into its own class and
treats it as its own kernel object. This is also important when we
consider resource limits as well. Particularly because transfer memory
is limited by the resource limit value set for it.
While we currently don't handle resource limit testing against objects
yet (but we do allow setting them), this will make implementing that
behavior much easier in the future, as we don't need to distinguish
between shared memory and transfer memory allocations in the same place.
The previous code had some minor issues with it, really not a big deal,
but amending it is basically 'free', so I figured, "why not?".
With the standard container maps, when:
map[key] = thing;
is done, this can cause potentially undesirable behavior in certain
scenarios. In particular, if there's no value associated with the key,
then the map constructs a default initialized instance of the value
type.
In this case, since it's a std::shared_ptr (as a type alias) that is
the value type, this will construct a std::shared_pointer, and then
assign over it (with objects that are quite large, or actively heap
allocate this can be extremely undesirable).
We also make the function take the region by value, as we can avoid a
copy (and by extension with std::shared_ptr, a copy causes an atomic
reference count increment), in certain scenarios when ownership isn't a
concern (i.e. when ReserveGlobalRegion is called with an rvalue
reference, then no copy at all occurs). So, it's more-or-less a "free"
gain without many downsides.
With this, all kernel objects finally have all of their data members
behind an interface, making it nicer to reason about interactions with
other code (as external code no longer has the freedom to totally alter
internals and potentially messing up invariants).
Lioncash