Currently our 32-bit code only gave one TLS slot and crashed
if you needed more.
First switch over to the same initial slot as the Linux kernel.
Then allow searching the slots for a free spot.
This allows us to more closely match the behaviour of the Linux kernel just in case
anything has hardcoded the TLS slots
This makes it so Saints Row: The Third stops crashing at boot, plays a few intro videos, then hangs instead.
Syscall entry points still have different argument orders,
Moves the arguments to the clone3 argument structure and passes to generic handler.
Also implements clone3 while doing this
C++ no-op functions can't optimize out the predicate arguments in all cases.
This was causing a problem where zero cost assertions weren't actually zero cost.
The only way to resolve this is to actually use macros sadly enough.
This will give a fairly hefty performance uplift with anything operating on IR.
Notably this allows applications to work that don't require the namespace but check up front if they are able to clone with it.
Civ 6's launcher checks this as an example
The vast majoirty of syscalls don't need anything in thread or frame.
So lets save an indirection for all those syscalls.
Most of the syscalls which do need Thread (or CTX via
Thread are in Thread.cpp or Memory.cpp
These have all been modifiy to fetch Thread from Frame
We need to check to see if the application wanting to be executed is in
the rootfs first. Otherwise we end up in a case where we either lose
tracking of applications in FEX, or applications fail to launch since
they don't exist in the global filesystem
Sadly these things can't be split without breaking functionality so it
turns in to a bit of a mess.
SyscallHandler is very much something that is a Linux only construct and
shouldn't be in FEXCore itself. Lets the frontend register a
Syscallhandler with FEXCore. FEXCore itself is then aware of the current
syscall ABI and handles the ABI in an optimal fashion.
So it is not a 100% clean break otherwise we would lose performance.
The SignalDelegator then needs to move to the frontend since the
SyscallHandler requires it for signal based syscalls.
The CPU backend signal handling still needs to happen in FEXCore because
it is a very tight coupling with the CPU backend.
Once we need to support more Signal handling we can give the backends
cleaner support to select which specific OS handler to handle.
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