From: ebiederm@xmission.com (Eric W. Biederman)
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
kernel-hardening@lists.openwall.com,
Catalin Marinas <catalin.marinas@arm.com>,
x86@kernel.org, Will Deacon <will.deacon@arm.com>,
Alexei Starovoitov <ast@kernel.org>,
Russell King <linux@armlinux.org.uk>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
tglx@linutronix.de, torvalds@linux-foundation.org,
akpm@linux-foundation.org, alan@linux.intel.com
Subject: Re: [PATCH v2 06/19] asm-generic/barrier: mask speculative execution flows
Date: Thu, 11 Jan 2018 20:42:41 -0600 [thread overview]
Message-ID: <8760874x26.fsf@xmission.com> (raw)
In-Reply-To: <151571801681.27429.15417813964230837664.stgit@dwillia2-desk3.amr.corp.intel.com> (Dan Williams's message of "Thu, 11 Jan 2018 16:46:56 -0800")
Dan Williams <dan.j.williams@intel.com> writes:
> diff --git a/include/linux/nospec.h b/include/linux/nospec.h
> new file mode 100644
> index 000000000000..5c66fc30f919
> --- /dev/null
> +++ b/include/linux/nospec.h
> @@ -0,0 +1,71 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright(c) 2018 Intel Corporation. All rights reserved.
> +
> +#ifndef __NOSPEC_H__
> +#define __NOSPEC_H__
> +
> +#include <linux/jump_label.h>
> +#include <asm/barrier.h>
> +
> +#ifndef array_ptr_mask
> +#define array_ptr_mask(idx, sz) \
> +({ \
> + unsigned long mask; \
> + unsigned long _i = (idx); \
> + unsigned long _s = (sz); \
> + \
> + mask = ~(long)(_i | (_s - 1 - _i)) >> (BITS_PER_LONG - 1); \
> + mask; \
> +})
> +#endif
This could really use a comment that explains it generates 0
for out of bound accesses and -1L aka 0xffffffffffffffff for
all other accesses.
The code is clever enough which values it generates is not obvious.
Eric
next prev parent reply other threads:[~2018-01-12 2:43 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-12 0:46 [PATCH v2 00/19] prevent bounds-check bypass via speculative execution Dan Williams
2018-01-12 0:46 ` Dan Williams
2018-01-12 0:46 ` [PATCH v2 01/19] Documentation: document array_ptr Dan Williams
2018-01-12 0:46 ` Dan Williams
2018-01-12 10:38 ` Geert Uytterhoeven
2018-01-12 10:38 ` Geert Uytterhoeven
2018-01-16 21:01 ` Kees Cook
2018-01-16 21:01 ` Kees Cook
2018-01-12 0:46 ` [PATCH v2 02/19] arm64: implement ifence_array_ptr() Dan Williams
2018-01-12 0:46 ` Dan Williams
2018-01-12 0:46 ` [PATCH v2 03/19] arm: " Dan Williams
2018-01-12 0:46 ` [PATCH v2 04/19] x86: implement ifence() Dan Williams
2018-01-12 0:46 ` Dan Williams
2018-01-12 2:27 ` Eric W. Biederman
2018-01-12 2:27 ` Eric W. Biederman
2018-01-12 3:39 ` Dan Williams
2018-01-12 0:46 ` [PATCH v2 05/19] x86: implement ifence_array_ptr() and array_ptr_mask() Dan Williams
2018-01-12 0:46 ` Dan Williams
2018-01-12 0:46 ` [PATCH v2 06/19] asm-generic/barrier: mask speculative execution flows Dan Williams
2018-01-12 2:42 ` Eric W. Biederman [this message]
2018-01-12 9:12 ` Peter Zijlstra
2018-01-13 0:41 ` Dan Williams
2018-01-15 8:46 ` Peter Zijlstra
2018-01-12 0:47 ` [PATCH v2 07/19] x86: introduce __uaccess_begin_nospec and ASM_IFENCE Dan Williams
2018-01-12 0:47 ` Dan Williams
2018-01-12 17:51 ` Josh Poimboeuf
2018-01-12 18:21 ` Dan Williams
2018-01-12 18:58 ` Josh Poimboeuf
2018-01-12 18:58 ` Josh Poimboeuf
2018-01-12 19:26 ` Dan Williams
2018-01-12 19:26 ` Dan Williams
2018-01-12 20:01 ` Linus Torvalds
2018-01-12 20:01 ` Linus Torvalds
2018-01-12 20:41 ` Josh Poimboeuf
2018-01-12 20:41 ` Josh Poimboeuf
2018-01-12 0:47 ` [PATCH v2 08/19] x86: use __uaccess_begin_nospec and ASM_IFENCE in get_user paths Dan Williams
2018-01-12 0:47 ` Dan Williams
2018-01-12 1:11 ` Linus Torvalds
2018-01-12 1:14 ` Dan Williams
2018-01-12 1:14 ` Dan Williams
2018-01-12 0:47 ` [PATCH v2 09/19] ipv6: prevent bounds-check bypass via speculative execution Dan Williams
2018-01-12 0:47 ` Dan Williams
2018-01-12 0:47 ` [PATCH v2 10/19] ipv4: " Dan Williams
2018-01-12 0:47 ` Dan Williams
2018-01-12 7:59 ` Greg KH
2018-01-12 7:59 ` Greg KH
2018-01-12 18:47 ` Dan Williams
2018-01-12 18:47 ` Dan Williams
2018-01-13 8:56 ` Greg KH
2018-01-13 8:56 ` Greg KH
2018-01-12 0:47 ` [PATCH v2 11/19] vfs, fdtable: " Dan Williams
2018-01-12 0:47 ` Dan Williams
2018-01-12 0:47 ` [PATCH v2 12/19] userns: " Dan Williams
2018-01-12 0:47 ` Dan Williams
2018-01-12 0:47 ` [PATCH v2 13/19] udf: " Dan Williams
2018-01-12 0:47 ` Dan Williams
2018-01-15 10:32 ` Jan Kara
2018-01-15 17:49 ` Dan Williams
2018-01-12 0:47 ` [PATCH v2 14/19] [media] uvcvideo: " Dan Williams
2018-01-12 0:47 ` Dan Williams
2018-08-06 21:40 ` Laurent Pinchart
2018-08-06 21:40 ` Laurent Pinchart
2018-01-12 0:47 ` [PATCH v2 15/19] carl9170: " Dan Williams
2018-01-12 0:47 ` Dan Williams
2018-01-12 14:42 ` Christian Lamparter
2018-01-12 14:42 ` Christian Lamparter
2018-01-12 18:39 ` Dan Williams
2018-01-12 20:01 ` Christian Lamparter
2018-01-12 20:01 ` Christian Lamparter
2018-01-12 23:05 ` Dan Williams
2018-01-12 23:05 ` Dan Williams
2018-01-12 0:47 ` [PATCH v2 16/19] p54: " Dan Williams
2018-01-12 0:47 ` [PATCH v2 17/19] qla2xxx: " Dan Williams
2018-01-12 0:47 ` Dan Williams
2018-01-12 1:19 ` James Bottomley
2018-01-12 1:19 ` James Bottomley
2018-01-12 5:38 ` Dan Williams
2018-01-12 5:38 ` Dan Williams
2018-01-12 6:05 ` James Bottomley
2018-01-12 0:48 ` [PATCH v2 18/19] cw1200: " Dan Williams
2018-01-12 0:48 ` Dan Williams
2018-01-12 0:48 ` [PATCH v2 19/19] net: mpls: " Dan Williams
2018-01-12 0:48 ` Dan Williams
2018-01-12 1:19 ` [PATCH v2 00/19] " Linus Torvalds
2018-01-12 1:19 ` Linus Torvalds
2018-01-12 1:41 ` Dan Williams
2018-01-12 1:41 ` Dan Williams
2018-01-18 13:18 ` Will Deacon
2018-01-18 13:18 ` Will Deacon
2018-01-18 16:58 ` Dan Williams
2018-01-18 16:58 ` Dan Williams
2018-01-18 17:05 ` Will Deacon
2018-01-18 17:05 ` Will Deacon
2018-01-18 21:41 ` Laurent Pinchart
2018-01-18 21:41 ` Laurent Pinchart
2018-01-13 0:15 ` Tony Luck
2018-01-13 0:15 ` Tony Luck
2018-01-13 18:51 ` Linus Torvalds
2018-01-13 18:51 ` Linus Torvalds
2018-01-16 19:21 ` Tony Luck
2018-01-16 19:21 ` Tony Luck
2018-01-12 10:02 ` Russell King - ARM Linux
2018-01-12 10:02 ` Russell King - ARM Linux
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