From: "hch@lst•de" <hch@lst•de>
To: Arnd Bergmann <arnd@kernel•org>
Cc: Vineet Gupta <Vineet.Gupta1@synopsys•com>,
Matthew Wilcox <willy@infradead•org>,
"grygorii.strashko@ti•com" <grygorii.strashko@ti•com>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>,
"ilias.apalodimas@linaro•org" <ilias.apalodimas@linaro•org>,
"linux-kernel@vger•kernel.org" <linux-kernel@vger•kernel.org>,
"linux-mips@vger•kernel.org" <linux-mips@vger•kernel.org>,
"mhocko@kernel•org" <mhocko@kernel•org>,
"linux-mm@kvack•org" <linux-mm@kvack•org>,
"mgorman@suse•de" <mgorman@suse•de>,
"brouer@redhat•com" <brouer@redhat•com>,
"mcroce@linux•microsoft.com" <mcroce@linux•microsoft.com>,
"linux-snps-arc@lists•infradead.org"
<linux-snps-arc@lists•infradead.org>,
"linuxppc-dev@lists•ozlabs.org" <linuxppc-dev@lists•ozlabs.org>,
"hch@lst•de" <hch@lst•de>,
"linux-arm-kernel@lists•infradead.org"
<linux-arm-kernel@lists•infradead.org>
Subject: Re: [PATCH 1/2] mm: Fix struct page layout on 32-bit systems
Date: Wed, 21 Apr 2021 07:50:28 +0200 [thread overview]
Message-ID: <20210421055028.GA28910@lst.de> (raw)
In-Reply-To: <CAK8P3a3rzz1gfNLoGC8aZJiAC-tgZYD6P8pQsoEfgCAmQK=FAw@mail.gmail.com>
On Tue, Apr 20, 2021 at 11:20:19PM +0200, Arnd Bergmann wrote:
> In that case, there should be no problem for you.
>
> The main issue is with system calls and ioctls that contain a misaligned
> struct member like
>
> struct s {
> u32 a;
> u64 b;
> };
>
> Passing this structure by reference from a 32-bit user space application
> to a 64-bit kernel with different alignment constraints means that the
> kernel has to convert the structure layout. See
> compat_ioctl_preallocate() in fs/ioctl.c for one such example.
We've also had this problem with some on-disk structures in the past,
but hopefully people desining those have learnt the lesson by now.
next prev parent reply other threads:[~2021-04-21 5:50 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-16 23:07 [PATCH 0/2] Change struct page layout for page_pool Matthew Wilcox (Oracle)
2021-04-16 23:07 ` [PATCH 1/2] mm: Fix struct page layout on 32-bit systems Matthew Wilcox (Oracle)
2021-04-17 1:08 ` kernel test robot
2021-04-17 2:45 ` Matthew Wilcox
2021-04-17 18:32 ` Ilias Apalodimas
2021-04-17 20:22 ` Matthew Wilcox
2021-04-18 11:21 ` Ilias Apalodimas
2021-04-17 21:18 ` David Laight
2021-04-17 22:45 ` Matthew Wilcox
2021-04-20 2:48 ` Vineet Gupta
2021-04-20 3:10 ` Matthew Wilcox
2021-04-20 7:07 ` Arnd Bergmann
2021-04-20 21:14 ` Vineet Gupta
2021-04-20 21:20 ` Arnd Bergmann
2021-04-21 5:50 ` hch [this message]
2021-04-21 8:43 ` David Laight
2021-04-21 8:58 ` Arnd Bergmann
2021-04-20 7:39 ` Geert Uytterhoeven
2021-04-20 8:39 ` David Laight
2021-04-20 11:32 ` Matthew Wilcox
2021-04-17 7:34 ` Jesper Dangaard Brouer
2021-04-20 7:21 ` Rasmus Villemoes
2021-04-16 23:07 ` [PATCH 2/2] mm: Indicate pfmemalloc pages in compound_head Matthew Wilcox (Oracle)
2021-04-17 21:13 ` David Laight
2021-04-17 21:28 ` Matthew Wilcox
2021-04-20 4:03 ` [PATCH 0/2] Change struct page layout for page_pool Michael Ellerman
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