Re: [PATCH v4 25/28] ARM: decompressor: Remove __hyp_get_vectors usage

Christoffer Dall
2017-03-24T14:34:40Z

On Tue, Mar 21, 2017 at 07:20:55PM +0000, Marc Zyngier wrote:
> When the compressed image needs to be relocated to avoid being
> overwritten by the decompression process, we need to relocate
> the hyp vectors as well so that we can find them once the
> decompression has taken effect.
>
> For that, we perform the following calculation:
> u32 v = __hyp_get_vectors();
> v += offset;
> __hyp_set_vectors(v);
>
> But we're guaranteed that the initial value of v as returned by
> __hyp_get_vectors is always __hyp_stub_vectors, because we have
> just set it by calling __hyp_stub_install.
>
> So let's remove the use of __hyp_get_vectors, and directly use
> __hyp_stub_vectors instead.
>
> Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> arch/arm/boot/compressed/head.S | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
> index 9150f9732785..d58bb104c6e8 100644
> --- a/arch/arm/boot/compressed/head.S
> +++ b/arch/arm/boot/compressed/head.S
> @@ -422,7 +422,10 @@ dtb_check_done:
> cmp r0, #HYP_MODE
> bne 1f
>
> - bl __hyp_get_vectors
> +0: adr r0, 0b
> + movw r1, #:lower16:__hyp_stub_vectors - 0b
> + movt r1, #:upper16:__hyp_stub_vectors - 0b
> + add r0, r0, r1

nit: you could add a comment explaining what r0 ends up containing,
because I'm pretty sure this will feel obscure when not read in the
context of this series with your commit message above.

> sub r0, r0, r5
> add r0, r0, r10
> bl __hyp_set_vectors
> --
> 2.11.0
>

Nevertheless:

Acked-by: Christoffer Dall <cdall@linaro.org>