[PATCH v5 11/23] powerpc/book3s64/pkeys: Store/restore userspace AMR/IAMR correctly on entry and exit from kernel

[Sandipan Das]

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 at 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 at linux.ibm.com>