Re: arm thumb interworking funkyness.

[Khem Raj <kraj at mvista dot com>]

Duane Ellis wrote:
> Hello,
>
> I'm trying to write a small bit of ARM asm, that is callable from 
> mixed code.
>
> that is: I don't want the LD to create a "_from_thumb" symbol 
> (wrapper) for it.
> I want to include that in my hand written assembler code.
>
> GCC version: gcc version 4.1.2
> binutils version 2.17
>
> C code is compiled with -mcpu=arm7tdmi -mthumb -mthumb-interwork
> ASM code is (really .S, through GCC) is compiled with the same options.
>
> In C, code, I'm doing this:
>
>   void
>   my_function( void )
>  {       printf("Turn interrupts on\n");
>       ARM_enable_IRQ();
>       process_run();
>   }
>
> After linking, instead of calling my ARM/THUMB code, I get this in the 
> disassembly output:
>
>  200558:    f001 f962     bl    201820 <printf>
>  20055c:    f007 f9c6     bl    2078ec <____floatsidf_from_thumb>
>  200560:    f000 f8e8     bl    200734 <process_run>
Can you make sure that you are looking at the right location in the 
disassembly. From what you provided it works correctly. You might have 
to give more information if you still are stuck.


> yea, it is literally calling the *WRONG* function.
>
> The Assembler code (a .S file) looks like this:
>
> #define DUAL_HEAD( X )  \
>    .global    __ ## X ## _from_thumb     ; \
>    .code 16             ; \
>    .thumb_func            ; \
>    .type    __ ## X ## _from_thumb,function ;  \
> __ ## X  ## _from_thumb:            ; \
>    bx    pc             ; \
>    nop                ; \
>    .global    X             ; \
>    .type    X ,function         ; \
>    .code 32            ; \
> X :                    ; \
>
>    DUAL_HEAD( ARM_disable_IRQ    )
>    mrs    r0,cpsr
>    orr    r1,r0,#I_BIT
>    msr    cpsr_c,r1
>    bx    lr
>    .size    ARM_disable_IRQ,(.-ARM_disable_IRQ)
>
> ==========================
>
> From what I can see, I believe I'm constructing the veneer correctly.
> But -- Either I'm doing something wrong or - there's a bug in the linker.
> I suspect it is me... But... well, I'm not getting anywhere.
>
> ==========================
>
> Any suggestions?
>
> Sadly, It is not very simple to reduce this to a _small_ set of code.
>
>
> --Duane.
>
>
>
> --
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