On Thu, Jan 24, 2019 at 04:32:56PM +0000, James Morse wrote:
> The hyp-stub is loaded by the kernel's early startup code at EL2
> during boot, before KVM takes ownership later. The hyp-stub's
> text is part of the regular kernel text, meaning it can be kprobed.
>
> A breakpoint in the hyp-stub causes the CPU to spin in el2_sync_invalid.
>
> Add it to the __hyp_text.
>
> Signed-off-by: James Morse <james.morse@xxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>
> This has been a problem since kprobes was merged, it should
> probably have been covered in 888b3c8720e0.
>
> I'm not sure __hyp_text is the right place. Its not idmaped,
> and as it contains a set of vectors, adding it to the host/hyp
> idmap sections could grow them beyond a page... but it does
> run with the MMU off, so does need to be cleaned to PoC when
> anything wacky, like hibernate happens. With this patch,
> hibernate should clean the __hyp_text to PoC too.
How did this code get cleaned before?
Is there a problem you can identify with putting it in __hyp_text?
Seems to me we should just stick it there if it has no negative
side-effects and otherwise we have to make up a separate section with a
specialized meaning.
Thanks,
Christoffer
> ---
> arch/arm64/kernel/hyp-stub.S | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
> index e1261fbaa374..17f325ba831e 100644
> --- a/arch/arm64/kernel/hyp-stub.S
> +++ b/arch/arm64/kernel/hyp-stub.S
> @@ -28,6 +28,8 @@
> #include <asm/virt.h>
>
> .text
> + .pushsection .hyp.text, "ax"
> +
> .align 11
>
> ENTRY(__hyp_stub_vectors)
> --
> 2.20.1
>
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