This nearly gets FEX's TestHarnessRunner to be self-hosting inside of
FEX. The only thing blocking it currently is that our SBRK emulation
reserves the whole region, when it should be "soft-reserved" and mmap
with MAP_FIXED_NOREPLACE can override it. Plus an assert in
OpcodeDispatcher preventing any 32-bit code from running from a 64-bit
process.
In the most simple terms, gdt and ldt are setup to be unique per thread,
and modify_ldt then modifies that thread's ldt entry. On thread
creation, these values get inherited as a copy.
This allows installation of 32-bit code entries, which with the previous
PRs merged allows the code to attempt jumping to that 32-bit code entry.
It then will immediately explode with an assert in our OpcodeDispatcher.
We can't allow 32-bit code jumping yet until our OpDispatcher/X86Tables
allows runtime selection of 64-bit and 32-bit code entries which is
still a ways away.
With the assert removed and the SBRK code handling hacked out,
/technically/ the TestHarnessRunner can run some code, albeit anything
that changes behaviour between bitness is completely incorrect.
alternative to #3638. this is theoretically better for side-by-side diffs. in
practice it may make other diffs worse since all the \'s change when part of the
macro change.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Which requires moving LinuxEmulation to its own independent folder as
well. Since both IRLoader and FEXLoader rely on it.
No functional change, just moves the the code around.
Ryan Houdek