linux-kernel - Re: [PATCH 2/2] exec: open code copy_string

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Message-ID: <20200501192639.GA25896@lst.de>
Date:   Fri, 1 May 2020 21:26:39 +0200
From:   Christoph Hellwig <hch@....de>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        aaw@...gle.com
Subject: Re: [PATCH 2/2] exec: open code copy_string_kernel

On Fri, May 01, 2020 at 01:50:49PM +0100, Al Viro wrote:
> On Fri, May 01, 2020 at 12:41:05PM +0200, Christoph Hellwig wrote:
> > Currently copy_string_kernel is just a wrapper around copy_strings that
> > simplifies the calling conventions and uses set_fs to allow passing a
> > kernel pointer.  But due to the fact the we only need to handle a single
> > kernel argument pointer, the logic can be sigificantly simplified while
> > getting rid of the set_fs.
> 
> I can live with that...  BTW, why do we bother with flush_cache_page() (by
> way of get_arg_page()) here and in copy_strings()?  How could *anything*
> have accessed that page by its address in new mm - what are we trying to
> flush here?

s/get_arg_page/flush_arg_page/ ?

No idea, what the use case is, but this comes from:

commit b6a2fea39318e43fee84fa7b0b90d68bed92d2ba
Author: Ollie Wild <aaw@...gle.com>
Date:   Thu Jul 19 01:48:16 2007 -0700

    mm: variable length argument support