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SubjectRe: [PATCH v8 7/7] powerpc: add machine check safe copy_to_user
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Santosh Sivaraj <santosh@fossix.org> writes:
> Use memcpy_mcsafe() implementation to define copy_to_user_mcsafe()
>
> Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
> ---
> arch/powerpc/Kconfig | 1 +
> arch/powerpc/include/asm/uaccess.h | 14 ++++++++++++++
> 2 files changed, 15 insertions(+)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 77f6ebf97113..4316e36095a2 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -137,6 +137,7 @@ config PPC
> select ARCH_HAS_STRICT_KERNEL_RWX if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
> select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
> select ARCH_HAS_UACCESS_FLUSHCACHE if PPC64
> + select ARCH_HAS_UACCESS_MCSAFE if PPC64
> select ARCH_HAS_UBSAN_SANITIZE_ALL
> select ARCH_HAVE_NMI_SAFE_CMPXCHG
> select ARCH_KEEP_MEMBLOCK
> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> index 8b03eb44e876..15002b51ff18 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -387,6 +387,20 @@ static inline unsigned long raw_copy_to_user(void __user *to,
> return ret;
> }
>
> +static __always_inline unsigned long __must_check
> +copy_to_user_mcsafe(void __user *to, const void *from, unsigned long n)
> +{
> + if (likely(check_copy_size(from, n, true))) {
> + if (access_ok(to, n)) {
> + allow_write_to_user(to, n);
> + n = memcpy_mcsafe((void *)to, from, n);
> + prevent_write_to_user(to, n);
> + }
> + }
> +
> + return n;
> +}

This looks OK to me.

It would be nice though if copy_to_user_mcsafe() followed the pattern of
the other copy_to_user() etc. routines where the arch code is only
responsible for the actual arch details, and all the checks are done in
the generic code. That would be a good cleanup to do after this has gone
in, as the 2nd implementation of the API.

cheers

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