linux-kernel - Re: [PATCH] asm-generic: uaccess: fix up local access

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Message-Id: <200906141210.17922.arnd@arndb.de>
Date:	Sun, 14 Jun 2009 12:10:17 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Mike Frysinger <vapier.adi@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] asm-generic: uaccess: fix up local access_ok() usage

On Sunday 14 June 2009, Mike Frysinger wrote:
> well, if you dont mind a bit of cruft, you can undef it ;)
> #include <asm-generic/uaccess.h>
> #undef access_ok

That will only work for the users outside of uaccess.h, so it doesn't
solve this problem.

> the Blackfin port does have hardware memory protection (MPU) and it
> does handle r/w/x bits, but we havent merged this into access_ok yet,
> just the vma lists

Hmm, if the hardware can catch memory protection errors, why would
you want to check them again in access_ok()? Are the checks disabled
in kernel mode? Most implementations of access_ok only check if the
address is a kernel or user pointer, because the kernel can access
both on most architectures, and the MMU only protects you from
passing invalid pointers, not valid kernel pointers.

> > What I really got wrong was the prototype for __access_ok(), as you
> > showed in your follow-up. I only tested this with the microblaze
> > patch that overrides __access_ok() with an architecture specific
> > version that gets this part right.
> 
> yeah, that looks good, but i'd still like the __access_ok -> access_ok

Ok, no problem. I can take that change as well, don't care much either way.

	Arnd <><
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