ARM/Thumb function attribute

["Albert Cahalan" <acahalan at gmail dot com>]

As far as I can tell, there is no way to declare
that a particular function pointer will point at
plain ARM code or at Thumb code. I'm more
than a little surprised actually, so maybe I just
missed something. How can I do this?

Some background: The function is in ROM.
I'm using a linker script to give it a symbol,
like so:

PROVIDE( tx_thread_create = 0xffff2718);

I'll be declaring it somewhat like this:

int __cdecl thread_create(void *thread, char *name, void (__cdecl
*fn)(int), int param, void *stack, int stack_size, int sched1, int
sched2, int sched3, int sched4);

Note that the function itself takes a pointer.
I might want to ability to enforce that the pointer
goes to Thumb code or to non-Thumb code.
Certainly I need to allow for a thread_create
function that can handle either kind of code.