This was partially implemented before but it had some bugs still.
This fixes those bugs and also implements mremap, shmat, and shmdt.
This now works well enough for 32bit graphical applications
Base size is now only one page in size. We will then increment that BRK
size by 8MB alignments. 256MB for 32bit applications was causing some
applications on the edge to run out of virtual memory
I was hitting some 32bit applications that were being fairly mean with
BRK. They were allocating all of BRK space then running out of virtual
memory space with its mmap handler fallback after freeing BRK space.
This means we now munmap BRK pages on release for the guest, similar to
behaviour that Linux does.
Additionally I had an application that was getting very upset that BRK
wasn't actually at the end of program space. So allocate at the end of
program space like expected.
brk test now passes from gvisor
The glibc and kernel timer interfaces are sufficiently different enough
that unwrapping this through glibc is impossible.
Pass it directly through to the kernel.
This was being checked by an application for kernel version. Which was
seeing too new of a kernel and using things that were unsupported.
Also removes the EmulatedMap which is an unnecessary lookup.
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.
