Re: [RFC PATCH] Fix: x86 unaligned __memcpy to/from virtual memory

From	Linus Torvalds <torvalds@linux-foundation.org>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH] Fix: x86 unaligned __memcpy to/from virtual memory
Date	2015-06-25 02:40 +0200
Message-ID	<pF3mW-KX-13@gated-at.bofh.it> (permalink)
References	<pEVz4-6x6-15@gated-at.bofh.it> <pEWls-7H7-13@gated-at.bofh.it> <pEXUd-1jL-7@gated-at.bofh.it> <pEYng-26P-9@gated-at.bofh.it> <pF2Ke-8e7-3@gated-at.bofh.it>
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On Wed, Jun 24, 2015 at 4:54 PM, Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
>
> OK, see below. This time the fault occurred at an unaligned address.
> It fails on the !pte_present(*pte_ref) check.

So every time, %rcx is 0x001fb.

Once, your rdx value (which is remaining bytes after the movsq) was 3,
the other two times it's 0.

What's so magical about that 4056-byte copy (+3 bytes once)? Are you
*sure* that copy is valid?

                   Linus
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Re: [RFC PATCH] Fix: x86 unaligned __memcpy to/from virtual memory Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2015-06-25 02:00 +0200
  Re: [RFC PATCH] Fix: x86 unaligned __memcpy to/from virtual memory Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2015-06-25 02:40 +0200
  Re: [RFC PATCH] Fix: x86 unaligned __memcpy to/from virtual memory Linus Torvalds <torvalds@linux-foundation.org> - 2015-06-25 02:40 +0200

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