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[Russell King - ARM Linux]

On Tue, Apr 21, 2015 at 12:10:43PM +0100, Dave P Martin wrote:
> On Tue, Apr 21, 2015 at 11:50:02AM +0100, Ard Biesheuvel wrote:
> > OK, that makes sense. But it does appear that the local cross-section
> > references are working just fine, i.e., references from other sections
> > in the same .o have the thumb bit set correctly even without BSYM()
> 
> For branch targets, the set of situations where BSYM must be used and
> the set of situations where it must not be used are mutually exclusive:
> 
>  * If the assembler resolves the address and the address will be used as a
>    branch target, BSYM() must be used.  This applies to non-cross-section
>    references within in single object only.
> 
>  * If the linker resolves the address, BSYM() must not be used and the
>    target label must be annotated with ENDPROC().  This applies to
>    all cross-section or cross-object references.

Yes, that agrees with the situation we have for the initfunc stuff.

> For any address that won't be used as a branch target, BSYM() must not
> be used.
> 
> Cross-section non-cross-object references where the target is missing
> ENDPROC() and BSYM _is_ used will also work, but this should be avoided
> -- it's an abuse really.

We should probably create a badr macro to complement the adr pseudo-op
which incorporates the BSYM thing so make this clearer - and a comment
before it.  This is really the case where BSYM should be used.

We have one case in the kernel source which is probably buggy:

arch/arm/kvm/interrupts.S:      ldr     r2, =BSYM(panic)

and killing BSYM in favour of a badr macro would prevent this.

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