linux-kernel - Re: [PATCH v2 5/6] powerpc/32s: prepare prevent_user_access() for user_access

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Date:   Thu, 23 Jan 2020 21:59:07 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christophe Leroy <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 5/6] powerpc/32s: prepare prevent_user_access() for user_access_end()

Christophe Leroy <christophe.leroy@....fr> writes:
> In preparation of implementing user_access_begin and friends
> on powerpc, the book3s/32 version of prevent_user_access() need
> to be prepared for user_access_end().
>
> user_access_end() doesn't provide the address and size which
> were passed to user_access_begin(), required by prevent_user_access()
> to know which segment to modify.
>
> The list of segments which where unprotected by allow_user_access()
> are available in current->kuap. But we don't want prevent_user_access()
> to read this all the time, especially everytime it is 0 (for instance
> because the access was not a write access).
>
> Implement a special direction case named KUAP_SELF. In this case only,
> the addr and end are retrieved from current->kuap.

Can we call it KUAP_CURRENT?

ie. "use the KUAP state in current"

cheers