From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
x86@kernel.org, Kostya Serebryany <kcc@google.com>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Alexander Potapenko <glider@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
"H . J . Lu" <hjl.tools@gmail.com>,
Andi Kleen <ak@linux.intel.com>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv3 5/8] x86/uaccess: Provide untagged_addr() and remove tags before address check
Date: Thu, 16 Jun 2022 19:48:54 +0300 [thread overview]
Message-ID: <20220616164854.oyvfpl3tzqj54rd6@black.fi.intel.com> (raw)
In-Reply-To: <Yqr/qBeIbLZYzgXi@hirez.programming.kicks-ass.net>
On Thu, Jun 16, 2022 at 12:02:16PM +0200, Peter Zijlstra wrote:
> On Fri, Jun 10, 2022 at 05:35:24PM +0300, Kirill A. Shutemov wrote:
> > +#ifdef CONFIG_X86_64
> > +/*
> > + * Mask out tag bits from the address.
> > + *
> > + * Magic with the 'sign' allows to untag userspace pointer without any branches
> > + * while leaving kernel addresses intact.
> > + */
> > +#define untagged_addr(mm, addr) ({ \
> > + u64 __addr = (__force u64)(addr); \
> > + s64 sign = (s64)__addr >> 63; \
> > + __addr ^= sign; \
> > + __addr &= (mm)->context.untag_mask; \
> > + __addr ^= sign; \
> > + (__force __typeof__(addr))__addr; \
> > +})
>
> Can't we make that mask a constant and *always* unmask U57 irrespective
> of LAM being on?
We can do this if we give up on LAM_U48.
It would also needlessly relax canonical check. I'm not sure it is a good
idea.
--
Kirill A. Shutemov
next prev parent reply other threads:[~2022-06-16 16:48 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-10 14:35 [PATCHv3 0/8] Linear Address Masking enabling Kirill A. Shutemov
2022-06-10 14:35 ` [PATCHv3 1/8] x86/mm: Fix CR3_ADDR_MASK Kirill A. Shutemov
2022-06-10 23:32 ` Edgecombe, Rick P
2022-06-10 14:35 ` [PATCHv3 2/8] x86: CPUID and CR3/CR4 flags for Linear Address Masking Kirill A. Shutemov
2022-06-10 14:35 ` [PATCHv3 3/8] mm: Pass down mm_struct to untagged_addr() Kirill A. Shutemov
2022-06-10 23:33 ` Edgecombe, Rick P
2022-06-17 15:27 ` Alexander Potapenko
2022-06-17 22:38 ` Kirill A. Shutemov
2022-06-10 14:35 ` [PATCHv3 4/8] x86/mm: Handle LAM on context switch Kirill A. Shutemov
2022-06-10 23:55 ` Edgecombe, Rick P
2022-06-15 15:54 ` Kirill A. Shutemov
2022-06-16 9:08 ` Peter Zijlstra
2022-06-16 16:40 ` Kirill A. Shutemov
2022-06-17 15:35 ` Alexander Potapenko
2022-06-17 22:39 ` Kirill A. Shutemov
2022-06-28 23:33 ` Andy Lutomirski
2022-06-29 0:34 ` Kirill A. Shutemov
2022-06-30 1:51 ` Andy Lutomirski
2022-06-10 14:35 ` [PATCHv3 5/8] x86/uaccess: Provide untagged_addr() and remove tags before address check Kirill A. Shutemov
2022-06-13 17:36 ` Edgecombe, Rick P
2022-06-15 16:58 ` Kirill A. Shutemov
2022-06-15 19:06 ` Edgecombe, Rick P
2022-06-16 9:30 ` Peter Zijlstra
2022-06-16 16:44 ` Kirill A. Shutemov
2022-06-17 11:36 ` Peter Zijlstra
2022-06-17 14:22 ` H.J. Lu
2022-06-17 14:28 ` Peter Zijlstra
2022-06-16 9:34 ` Peter Zijlstra
2022-06-16 10:02 ` Peter Zijlstra
2022-06-16 16:48 ` Kirill A. Shutemov [this message]
2022-06-28 23:40 ` Andy Lutomirski
2022-06-29 0:42 ` Kirill A. Shutemov
2022-06-30 2:38 ` Andy Lutomirski
2022-07-05 0:13 ` Kirill A. Shutemov
2022-06-10 14:35 ` [PATCHv3 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED_ADDR Kirill A. Shutemov
2022-06-10 15:25 ` Edgecombe, Rick P
2022-06-10 18:04 ` Kirill A. Shutemov
2022-06-10 16:16 ` Edgecombe, Rick P
2022-06-10 18:06 ` Kirill A. Shutemov
2022-06-10 18:08 ` Edgecombe, Rick P
2022-06-10 22:18 ` Edgecombe, Rick P
2022-06-11 1:12 ` Kirill A. Shutemov
2022-06-11 2:36 ` Edgecombe, Rick P
2022-06-12 21:03 ` Andy Lutomirski
2022-06-16 9:44 ` Peter Zijlstra
2022-06-16 16:54 ` Kirill A. Shutemov
2022-06-30 2:04 ` Andy Lutomirski
2022-06-13 14:42 ` Michal Hocko
2022-06-16 17:05 ` Kirill A. Shutemov
2022-06-19 23:40 ` Kirill A. Shutemov
2022-06-16 9:39 ` Peter Zijlstra
2022-06-28 23:42 ` Andy Lutomirski
2022-06-29 0:53 ` Kirill A. Shutemov
2022-06-30 2:29 ` Andy Lutomirski
2022-07-01 15:38 ` Kirill A. Shutemov
2022-07-02 23:55 ` Andy Lutomirski
2022-07-04 13:43 ` Kirill A. Shutemov
2022-06-10 14:35 ` [PATCHv3 7/8] x86: Expose untagging mask in /proc/$PID/arch_status Kirill A. Shutemov
2022-06-10 15:24 ` Dave Hansen
2022-06-11 1:28 ` Kirill A. Shutemov
2022-06-27 12:00 ` Catalin Marinas
2022-06-10 14:35 ` [PATCHv3 OPTIONAL 8/8] x86/mm: Extend LAM to support to LAM_U48 Kirill A. Shutemov
2022-06-16 10:00 ` Peter Zijlstra
2022-06-10 20:22 ` [PATCHv3 0/8] Linear Address Masking enabling Kostya Serebryany
2022-06-16 22:52 ` Edgecombe, Rick P
2022-06-16 23:43 ` Kirill A. Shutemov
2022-06-16 23:48 ` Edgecombe, Rick P
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