Determining if rotated loads are supported

Is there an OS call to determine if rotated loads are supported on the current platform? OS_PlatformFeatures 0 doesn’t look like it has a flag for it.

No, there isn’t an OS call for it. It’s probably easiest to just read the current setting from the system control register. Bit 1 will be set if alignment exceptions are enabled, and bit 22 will be set if ARMv7-style unaligned loads are in use (with bit 1 taking priority if they’re both set).

I guess if you did want to use an OS SWI, OS_MMUControl 0 would be what you want.

just read the current setting from the system control register

I’ve purposely avoided that method, as ARM have a habit of breaking backward compatibility. The route I’ve now taken is to turn IRQ/FIQ off, claim the Abort vector and try an unaligned load – its the only method I could think of that doesn’t touch bare metal.