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Subject: Re: [PATCH v5 11/23] powerpc/book3s64/pkeys: Store/restore userspace
 AMR/IAMR correctly on entry and exit from kernel
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
References: <20200827040931.297759-1-aneesh.kumar@linux.ibm.com>
 <20200827040931.297759-12-aneesh.kumar@linux.ibm.com>
From: Sandipan Das <sandipan.osd@gmail.com>
Message-ID: <ef174ccb-62b1-9385-b213-42c1718d5cfa@gmail.com>
Date: Sun, 18 Oct 2020 09:19:09 +0530
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On 27/08/20 9:39 am, Aneesh Kumar K.V wrote:
> This prepare kernel to operate with a different value than userspace AMR/IAMR.
> For this, AMR/IAMR need to be saved and restored on entry and return from the
> kernel.
> 
> With KUAP we modify kernel AMR when accessing user address from the kernel
> via copy_to/from_user interfaces. We don't need to modify IAMR value in
> similar fashion.
> 
> If MMU_FTR_PKEY is enabled we need to save AMR/IAMR in pt_regs on entering
> kernel from userspace. If not we can assume that AMR/IAMR is not modified
> from userspace.
> 
> We need to save AMR if we have MMU_FTR_KUAP feature enabled and we are
> interrupted within kernel. This is required so that if we get interrupted
> within copy_to/from_user we continue with the right AMR value.
> 
> If we hae MMU_FTR_KUEP enabled we need to restore IAMR on return to userspace
> beause kernel will be running with a different IAMR value.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
>  arch/powerpc/include/asm/book3s/64/kup.h | 177 ++++++++++++++++++++---
>  arch/powerpc/include/asm/ptrace.h        |   4 +-
>  arch/powerpc/kernel/asm-offsets.c        |   2 +
>  arch/powerpc/kernel/entry_64.S           |   6 +-
>  arch/powerpc/kernel/exceptions-64s.S     |   4 +-
>  arch/powerpc/kernel/syscall_64.c         |  30 +++-
>  6 files changed, 192 insertions(+), 31 deletions(-)
> 

Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>