check_platform(...) is an API that can be used to:
- blacklist JIT/bytecode on just a very specific platform (not recommended)
- mask (with 0xf/0xff) some fields, and keep just the flags that uniquely
identify the system where a bug occurs (for example linux + ppc32).
- it returns a bool so you can do further checks if needed.
The bytecode also has access to all the information collected from the
environment, so it can make more detailed decisions (based on CPU, presence of
SELinux/PaX, etc.).
You can't introduce new detections via bytecode, but you can write new
conditions using existing ones.
The previously added builtin bytecode moved all the JIT disable logic to
bytecode for easy updating.
This bytecode will be run in interpreter mode on startup:
it can disable the JIT, or disable all further bytecodes.
There will be a builtin copy of it that is loaded if
no BC_STARTUP bytecodes were loaded (like filetypes_int.h and daily.ftm).
Only one BC_STARTUP bytecode is accepted, so as soon as bytecode.cvd will
contain one, it won't be overridable!
This bytecode will replace all the JIT checks (CPU, selinux, pax) etc.,
and allows to disable the JIT on just specific OS/arch/compiler/etc.
combinations. There are too many combinations to have a dconf flag for each.
Also fix the bytecode dconf so that the individual JIT_* flags actually work
(previously we could disable the entire JIT, or none at all).
Also introduce preliminary support for bytecode test mode (we already have
auto, jit and interpreter mode, introducing another mode here is easiest).
The test mode doesn't actually compare the outputs yet, but it does fail if
the JIT is disabled / falls back to interpreter.
