The 32-bitted Clipboard module

The 32-bitted Clipboard module still contains some 26-bit code that prevents it from working correctly.

The routine MySendMessage (in s.WimpMsg) checks if it’s called in SVC or User mode using:

         MOV     R14, PC
         ANDS    R14, R14, #SVC_mode     ; so EQ => USR, NE => SVC
         BNE     %FT01

To work on 32-bit systems it needs something like this:

         TEQ    r0, r0                   ; ensure Z is zet
         TEQ    pc, pc                   ; are we in 32-bit mode?

         MOVNE  r14, pc                  ; 26-bit => flags are in pc
         MRSEQ  r14, cpsr                ; 32-bit => flags are in cpsr
         MOVNE  r5, #SVC_mode            ; set up 26-bit SVC mask
         MOVEQ  r5, #2_1111              ; set up 32-bit SVC mask

         TST    r14, r5                  ; are we in user mode?
         BNE    %FT01                    ; if not, queue message

I’m raising this here rather than sending in a patch as James has indicated that further work would be done by someone else. If no-one has taken this up yet then I’d be happy to submit the required changes.

Ouch. What about:

MOV     R14, PC
AND     R14, R14, #SVC_mode  ; extract mode bits from 26-bit PC
MRS     R14, CPSR            ; NOP on ARM2/3, works in any mode on later ARMs
TST     R14, #&F             ; NE for any mode other than USR26 or USR32

Thanks Ben, that’s much better.