From: Jeff Dike <jdike@addtoit.com>
To: Young Koh <young.koh@gmail.com>
Cc: user-mode-linux-devel@lists.sourceforge.net
Subject: Re: [uml-devel] a question about sigsetjmp() in copy_from/to_user()
Date: Tue, 27 Sep 2005 13:28:12 -0400 [thread overview]
Message-ID: <20050927172812.GA28528@ccure.user-mode-linux.org> (raw)
In-Reply-To: <3524bf1f050927070645b999bd@mail.gmail.com>
On Tue, Sep 27, 2005 at 10:06:53AM -0400, Young Koh wrote:
> my question is, if so, shouldn't the error be caught when UML kernel
> translates the user space address to the kernel space address? i mean,
> UML kernel must know the valid memory regions and if the address is
> out of the valid regions, then it knows the address is invalid before
> UML tries to access the address. why should it use sigsetjmp() and let
> a segfault occur?
Because the address may be fine, and an access may still cause a segfault.
UML memory is backed by a file on the host. You can map anything from
the file you want, but if you access it when the host filesystem is full
or you've exceeded your disk quota, the access will segfault.
Jeff
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next prev parent reply other threads:[~2005-09-27 18:12 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-27 14:06 [uml-devel] a question about sigsetjmp() in copy_from/to_user() Young Koh
2005-09-27 17:28 ` Jeff Dike [this message]
2005-09-28 11:59 ` Blaisorblade
2005-09-28 13:47 ` Young Koh
2005-09-28 14:50 ` Jeff Dike
2005-09-28 19:25 ` Young Koh
2005-09-29 12:09 ` Blaisorblade
2005-09-30 15:08 ` Young Koh
2005-09-30 15:44 ` Geert Uytterhoeven
2005-10-02 1:03 ` Jeff Dike
2005-10-02 10:23 ` Blaisorblade
2005-10-02 18:31 ` Jeff Dike
2005-10-03 18:35 ` Blaisorblade
2005-10-03 20:38 ` Jeff Dike
2005-09-28 16:09 ` Jeff Dike
2005-09-28 17:26 ` Blaisorblade
2005-09-28 18:43 ` Jeff Dike
2005-09-28 8:41 ` Blaisorblade
2005-09-28 14:22 ` Young Koh
2005-09-28 16:43 ` Blaisorblade
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