linux-kernel - Re: kgdb: fix optional arch functions and probe_kernel

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Message-ID: <20080421140058.GO9554@elte.hu>
Date:	Mon, 21 Apr 2008 16:00:59 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jason Wessel <jason.wessel@...driver.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: kgdb: fix optional arch functions and probe_kernel_*


* Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Fri, 18 Apr 2008 17:42:54 GMT
> Linux Kernel Mailing List <linux-kernel@...r.kernel.org> wrote:
> 
> > --- a/mm/maccess.c
> > +++ b/mm/maccess.c
> > @@ -17,11 +17,14 @@
> >  long probe_kernel_read(void *dst, void *src, size_t size)
> >  {
> >  	long ret;
> > +	mm_segment_t old_fs = get_fs();
> >  
> > +	set_fs(KERNEL_DS);
> >  	pagefault_disable();
> >  	ret = __copy_from_user_inatomic(dst,
> >  			(__force const void __user *)src, size);
> >  	pagefault_enable();
> > +	set_fs(old_fs);
> >  
> >  	return ret ? -EFAULT : 0;
> >  }
> 
> Oh.  Well that rather invalidates my earlier comments.  It looks like 
> this change could have been folded, but I understand that this 
> sometimes gets wearisome and isn't terribly important if
> 
> a) the fix doesn't repair build breakage and
> 
> b) the fix doesn't fix runtime breakage and
> 
> c) the fix fixes code which the git-bisect user won't have enabled in
>    config anyway.

yeah. I mentioned it in the pull request that i kept the fixes apart to 
demonstrate the overall fix dynamics of the KGDB tree over a full kernel 
cycle. I normally backmerge and create a clean queue - but that creates 
a false perception that the tree is 'too fresh' and trust is harder to 
be expressed.

> Still.  Do we need the set_fs() in there?  __copy_from_user_inatomic() 
> is a "__" uaccess function and hence shouldn't be running access_ok()?

yeah, i guess that's true. Jason?

	Ingo
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