From mboxrd@z Thu Jan  1 00:00:00 1970
From: Richard Knutsson <ricknu-0@student.ltu.se>
Date: Sun, 28 Jan 2007 15:51:28 +0000
Subject: Re: [KJ] clear_page() and copy_page()
Message-Id: <45BCC680.5060601@student.ltu.se>
List-Id: <kernel-janitors.vger.kernel.org>
References: <Pine.LNX.4.64.0701280332020.29915@CPE00045a9c397f-CM001225dbafb6>
In-Reply-To: <Pine.LNX.4.64.0701280332020.29915@CPE00045a9c397f-CM001225dbafb6>
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To: kernel-janitors@vger.kernel.org

Robert P. J. Day wrote:
>   there are numerous instances of calls to memset() of the form
>
>   memset(<addr>, 0, PAGE_SIZE);
>
> to clear a single page, as you can see sprinkled throughout the output
> here (obviously, not every line of output represents one of those
> cases, the grep pattern is overly general):
>   
[snip]
> same questions here -- any issues with standardizing on calls to
> copy_page()?
>   
> rday
>
> p.s.  obviously, rewriting to use those simpler macros would imply
> that *every* architecture would need to define those macros, and i
> don't think that's the case at the moment.
>   

include]$ grep -L clear_page asm-*/page.h
asm-generic/page.h
asm-powerpc/page.h
include]$ grep -L copy_page asm-*/page.h
asm-generic/page.h
asm-powerpc/page.h

so it seems it only needs to be defined on PowerPC. But what confuses me is:
...
asm-x86_64/page.h:48:void clear_page(void *);
asm-x86_64/page.h:51:#define clear_user_page(page, vaddr, pg)   clear_page(page)
...

Is x86_64 setting all its memory to zero before giving it to the caller, or what?

Well, just my 2 cents...
Richard Knutsson

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