[PATCH 1/2] arm: semihosting: replace inline assembly with assembly file

Tom Rini trini at konsulko.com
Tue Mar 7 18:52:14 CET 2023

On Tue, Feb 07, 2023 at 03:21:04PM +0000, Andre Przywara wrote:

> So far we used inline assembly to inject the actual instruction that
> triggers the semihosting service. While this sounds elegant, as it's
> really only about one instruction, it has some serious downsides:
> - We need some barriers in place to force the compiler to issue writes
>   to a data structure before issuing the trap instruction.
> - We need to convince the compiler to actually fill the structures that
>   we use pointers to.
> - We need a memory clobber to avoid the compiler caching the data in
>   those structures, when semihosting writes data back.
> - We need register arguments to make sure the function ID and the
>   pointer land in the right registers.
> This is all doable, but fragile and somewhat cumbersome. Since we now
> have a separate function in an extra file anyway, we can do away with
> all the magic and just write that in an actual assembly file.
> This is much more readable and robust.
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> Reviewed-by: Sean Anderson <sean.anderson at seco.com>

Applied to u-boot/next, thanks!

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