From: Linus Torvalds <torvalds@linux-foundation.org>
To: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
gregkh@linuxfoundation.org, pbonzini@redhat.com,
linux-kernel@vger.kernel.org, ojeda@kernel.org,
ndesaulniers@google.com, mingo@redhat.com, will@kernel.org,
longman@redhat.com, boqun.feng@gmail.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, vschneid@redhat.com, paulmck@kernel.org,
frederic@kernel.org, quic_neeraju@quicinc.com,
joel@joelfernandes.org, josh@joshtriplett.org,
mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com,
rcu@vger.kernel.org, tj@kernel.org, tglx@linutronix.de,
linux-toolchains@vger.kernel.org
Subject: Re: [PATCH v2 0/2] Lock and Pointer guards
Date: Tue, 6 Jun 2023 08:45:49 -0700 [thread overview]
Message-ID: <CAHk-=wh=vs298o0gewFH725pQAYQ57CAQzj05FOx_VZubZ3jiA@mail.gmail.com> (raw)
In-Reply-To: <202306060829.C2FD998CF@keescook>
On Tue, Jun 6, 2023 at 8:31 AM Kees Cook <keescook@chromium.org> wrote:
>
> nit: Linus's example was "(void *)8" (instead of 1) because we've had
> issues in the past with alignment warnings on archs that are sensitive
> to it. (e.g. see the __is_constexpr() macro which is doing NULL/!NULL
> comparisons.)
Note that I don't think we ever saw such a warning, it was just a
theoretical observation that depending on type, the compiler might
warn about known mis-aligned pointer bits.
So I'm not sure the 1-vs-8 actually matters. We do other things that
assume that low bits in a pointer are retained and valid, even if in
theory the C type system might have issues with it.
But maybe I mis-remember - if you did get an actual warning, maybe we
should document that warning just to keep the memory alive.
Linus
next prev parent reply other threads:[~2023-06-06 15:46 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20230526205204.861311518@infradead.org>
[not found] ` <CAHk-=wg2RHZKTN29Gr7MhgYfaNtzz58wry9jCNP75LAmQ9t8-A@mail.gmail.com>
[not found] ` <20230530092342.GA149947@hirez.programming.kicks-ass.net>
2023-06-06 9:42 ` [PATCH v2 0/2] Lock and Pointer guards Peter Zijlstra
2023-06-06 13:17 ` Linus Torvalds
2023-06-06 13:40 ` Peter Zijlstra
2023-06-06 14:50 ` Linus Torvalds
2023-06-06 16:06 ` Kees Cook
2023-06-06 18:08 ` Peter Zijlstra
2023-06-06 23:22 ` Linus Torvalds
2023-06-07 9:41 ` Peter Zijlstra
2023-06-08 8:52 ` Peter Zijlstra
2023-06-08 9:04 ` Greg KH
2023-06-08 15:45 ` Linus Torvalds
2023-06-08 16:47 ` Kees Cook
2023-06-08 16:59 ` Linus Torvalds
2023-06-08 17:20 ` Nick Desaulniers
2023-06-08 18:51 ` Peter Zijlstra
2023-06-08 20:14 ` Nick Desaulniers
2023-06-09 10:20 ` Paolo Bonzini
2023-06-08 20:06 ` Peter Zijlstra
2023-06-09 2:25 ` Linus Torvalds
2023-06-09 8:14 ` Peter Zijlstra
2023-06-09 21:18 ` Kees Cook
2023-06-09 8:27 ` Rasmus Villemoes
2023-06-06 15:31 ` Kees Cook
2023-06-06 15:45 ` Linus Torvalds [this message]
2023-06-06 16:08 ` Kees Cook
2023-06-08 16:25 ` David Laight
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