Re: [Xen-devel] [PATCH 5/7] xen/arm32: Invalidate BTB on guest exit for Cortex A17 and 12

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Jan 19, 2018 at 01:41:01PM +0000, Julien Grall wrote:
> In order to avoid aliasing attackes agains the branch predictor, let's
> invalidate the BTB on guest exist. This is made complicated by the fact
> that we cannot take a branch invalidating the BTB.
> 
> This is based on the first version posrted by Marc Zyngier on Linux-arm
> mailing list (see [1]).
> 
> This is part of XSA-254.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> 
> [1] https://www.spinics.net/lists/arm-kernel/msg627032.html
> ---
>  xen/arch/arm/arm32/entry.S | 55 
> ++++++++++++++++++++++++++++++++++++++++++++++
>  xen/arch/arm/cpuerrata.c   | 19 ++++++++++++++++
>  2 files changed, 74 insertions(+)
> 
> diff --git a/xen/arch/arm/arm32/entry.S b/xen/arch/arm/arm32/entry.S
> index 54a1733f87..c6ec0aa399 100644
> --- a/xen/arch/arm/arm32/entry.S
> +++ b/xen/arch/arm/arm32/entry.S
> @@ -160,6 +160,61 @@ GLOBAL(hyp_traps_vector)
>          b trap_irq                      /* 0x18 - IRQ */
>          b trap_fiq                      /* 0x1c - FIQ */
>  
> +        .align 5

Not .align 8?


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