linux-kernel - Re: Sparc miss chance to fix recoverable fault in copy_from

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Date:	Thu, 13 Aug 2009 20:29:25 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	heyongli@...il.com
Cc:	linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org
Subject: Re: Sparc miss chance to fix recoverable fault in copy_from_user

From: hyl <heyongli@...il.com>
Date: Fri, 14 Aug 2009 11:16:41 +0800

> console is: (access the address 0xffff fff0 )
>     SUN4V-DTLB: Error at TPC[5f2cc8], tl 1
>     SUN4V-DTLB: TPC<memcpy_user_stub+0x8/0x40>
>     SUN4V-DTLB: O7[4af23c]
>     SUN4V-DTLB: O7<probe_kernel_read+0x3c/0xa0>
>     SUN4V-DTLB: vaddr[ffffffffffffe000] ctx[0] pte[800007ffffffe743] error[2]
> 
> 
> the problem is :
> this DTLB fault can be fixed by search extable, by fall to the
> do_sparc64_fault, my draft proposal can verify this:  with this patch, this kind
> of fault is recovery, so enable copy_from_user  return error instead of halt.
> 
> in addition, it is triggered in kernel space, search the extable is mandatory .

No, that's not the problem.

The problem is that the virtual address validation done in the TLB
miss path accepts the address printed in:

>     SUN4V-DTLB: vaddr[ffffffffffffe000] ctx[0] pte[800007ffffffe743] error[2]

That's the real bug, not any of the other things you are talking
about.

Your "fix" would only paper over this problem.
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