Subject: Re: [PATCH 2/3] Detect instruction fetch denied and report

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Tue, 08 Nov 2016 21:46:58 +0530

Balbir Singh <[email-masked]> writes:

> ISA 3 allows for prevention of instruction fetch and execution
> of user mode pages. If such an error occurs, SRR1 bit 35
> reports the error. We catch and report the error in do_page_fault()
>
> Signed-off-by: Balbir Singh <[email-masked]>
> ---
>  arch/powerpc/mm/fault.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index d0b137d..835fd03 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -404,6 +404,10 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
>  		    (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
>  		     !(vma->vm_flags & (VM_READ | VM_WRITE))))
>  			goto bad_area;
> +
> +		if (radix_enabled() && (regs->msr & SRR1_ISI_N_OR_G))
> +			goto bad_area;
> +

Can we also do this check early, ie, before down_read(mmap_sem)

-aneesh