[PATCH] ARM: force linker to use PIC veneers

On 26 March 2015 at 13:53, Dave P Martin [off-list ref] wrote:

On Thu, Mar 26, 2015 at 12:24:01PM +0000, Ard Biesheuvel wrote:

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On 26 March 2015 at 13:22, Russell King - ARM Linux
[off-list ref] wrote:

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On Thu, Mar 26, 2015 at 01:20:16PM +0100, Ard Biesheuvel wrote:

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Any specific concerns? The --pic-veneer switch dates back to 2009, so
it's been around for a while

BX.  Not every CPU supports BX.

The bx is used for the Thumb -> ARM switch inside the veneer only, so
if you build for ARM these won't appear in the output

Agreed that's what's _supposed_ to happen.

Note that --use-blx is an override and might introduce BXs into a kernel
that otherwise doesn't have them.  But in any case, this option doesn't
show a benefit for the scenario under discussion, hence my dropping the
request (conditional on THUMB2_KERNEL in any case).

Actually, i am not quite sure. I hadn't realised that there is no
branch-without-link counterpart of 'blx <label>' so even if I still
potted a number of bx pc/nop sequences, I can't really say if there
were quite as many as before.

Ard, can you should build a couple of !THUMB2_KERNEL/pre-v5
configurations with your change and check, just to be sure?

Will do.