[PATCH RFC v9 01/25] mm: Introduce kpkeys

[Mike Rapoport]

Hi Kevin,

> kpkeys is a simple framework to enable the use of protection keys
> (pkeys) to harden the kernel itself. This patch introduces the basic
> API in <linux/kpkeys.h>: a couple of functions to enter/leave a
> kpkeys context and macros to define guard objects.
> 
> kpkeys introduces a new concept on top of pkeys: the kpkeys context.
> Each context is associated with a set of permissions for the pkeys
> managed by the kpkeys framework. kpkeys_enter_context(ctx) sets
> those permissions according to ctx, and returns the original kpkeys
> state (typically the arch-specific pkeys register) that is later
> restored by calling kpkeys_leave_context(). To start with, only
> KPKEYS_CTX_DEFAULT is available, which is meant to grant RW access
> to KPKEYS_PKEY_DEFAULT (i.e. all memory since this is the only
> available pkey for now).
> 
> The underlying representation of each kpkeys context is entirely
> architecture-specific. Support for kpkeys must be explicitly
> indicated by selecting ARCH_HAS_KPKEYS and defining the following
> functions in <asm/kpkeys.h>:
> 
> * arch_kpkeys_enter_context()
> * arch_kpkeys_leave_context()
> * arch_supports_kpkeys()
> 
> Additionally, <asm/kpkeys_types.h> must define struct arch_kpkeys_state,
> which typically provides storage for the pkeys register.
> 
> Signed-off-by: Kevin Brodsky <kevin.brodsky at arm.com>
>
> diff --git a/include/linux/kpkeys.h b/include/linux/kpkeys.h
> new file mode 100644
> index 0000000000000..eac522f552141
> --- /dev/null
> +++ b/include/linux/kpkeys.h
> @@ -0,0 +1,104 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef _LINUX_KPKEYS_H
> +#define _LINUX_KPKEYS_H
> +
> +#include <linux/bug.h>
> +#include <linux/cleanup.h>
> +#include <linux/kpkeys_types.h>
> +
> +/**
> + * KPKEYS_GUARD_NOOP() - define a guard type that does nothing

Nit: I'd suggest to drop "define" from all the descriptions, they would
read better without it IMHO.

-- 
Sincerely yours,
Mike.