From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Will Deacon <will@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Borislav Petkov <bp@alien8.de>,
Xiyu Yang <xiyuyang19@fudan.edu.cn>,
Alistair Popple <apopple@nvidia.com>,
Yang Shi <shy828301@gmail.com>,
Shakeel Butt <shakeelb@google.com>,
Hugh Dickins <hughd@google.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
yuanxzhang@fudan.edu.cn, Xin Tan <tanxin.ctf@gmail.com>,
Will Deacon <will.deacon@arm.com>,
David Howells <dhowells@redhat.com>,
keescook@chromium.org
Subject: Re: [PATCH] mm/rmap: Convert from atomic_t to refcount_t on anon_vma->refcount
Date: Fri, 20 Aug 2021 10:16:18 +0200 [thread overview]
Message-ID: <YR9k0hzMJpNF/0qL@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <YR9PHD+pWTelGKVd@hirez.programming.kicks-ass.net>
On Fri, Aug 20, 2021 at 08:43:40AM +0200, Peter Zijlstra wrote:
> Fine with me; although the immediate complaint from Andrew was about
> size, hence my UD1 hackery.
>
> > So if we do this, I think it should be something like
> >
> > static inline __must_check bool refcount_dec_and_test(refcount_t *r)
> > {
> > asm_volatile_goto (LOCK_PREFIX "decl %[var]\n\t"
> > "jz %l[cc_zero]\n\t"
> > "jl %l[cc_error]"
> > : : [var] "m" (r->refs.counter)
> > : "memory" : cc_zero, cc_error);
> >
> > return false;
> >
> > cc_zero:
> > return true;
> > cc_error:
> > refcount_warn_saturate(r, REFCOUNT_SUB_UAF);
> > return false;
> > }
> >
> > and we can discuss whether we could improve on the
> > refcount_warn_saturate() separately.
>
> I can do the refcount_warn_saturate() change separately.
>
> Let me go check how small I can get it...
gcc-10.2.1, x86_64-defconfig
kernel/event/core.o-inline-ud1: 96454
kernel/event/core.o-outofline-ud1: 96604
kernel/event/core.o-outofline-call: 97072
(42 refcount_warn_saturate/ud1 instances in that file,
10 of which are refcount_dec_and_test)
next prev parent reply other threads:[~2021-08-20 8:19 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-19 3:23 [PATCH] mm/rmap: Convert from atomic_t to refcount_t on anon_vma->refcount Xiyu Yang
2021-07-20 23:01 ` Andrew Morton
2021-08-19 13:21 ` Will Deacon
2021-08-19 14:06 ` Peter Zijlstra
2021-08-19 15:19 ` Peter Zijlstra
2021-08-19 19:09 ` Linus Torvalds
2021-08-20 6:43 ` Peter Zijlstra
2021-08-20 7:33 ` Kees Cook
2021-08-20 8:16 ` Peter Zijlstra [this message]
2021-08-20 8:24 ` Will Deacon
2021-08-20 9:03 ` Peter Zijlstra
2021-08-20 17:26 ` Kees Cook
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