linux-kernel - RE: [PATCH v2 02/10] netfilter: Avoid assigning 'const' pointer to non-const pointer

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Message-ID: <16f131548042445fb557ecb027d4c2cd@AcuMS.aculab.com>
Date:   Mon, 27 Jan 2020 12:21:06 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Linus Torvalds' <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>
CC:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Will Deacon <will@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        kernel-team <kernel-team@...roid.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        "Florian Westphal" <fw@...len.de>,
        "David S. Miller" <davem@...emloft.net>
Subject: RE: [PATCH v2 02/10] netfilter: Avoid assigning 'const' pointer to
 non-const pointer

From: Linus Torvalds
> Sent: 24 January 2020 17:37
...
> (That also means that the compiler can't necessarily even optimize
> multiple accesses through a const pointer away, because the object
> might be modified through another pointer that aliases the const one -
> you'd need to also mark it "restrict" to tell the compiler that no
> other pointer will alias).

I've seen gcc cache a value read through a 'const' parameter pointer
across a function call.
Can't remember which version though.

	David

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