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From: Christoph Hellwig <hch@lst.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>,
	the arch/x86 maintainers <x86@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-parisc@vger.kernel.org,
	linux-um <linux-um@lists.infradead.org>,
	Netdev <netdev@vger.kernel.org>,
	bpf@vger.kernel.org, Linux-MM <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 15/15] x86: use non-set_fs based maccess routines
Date: Wed, 6 May 2020 20:15:43 +0200	[thread overview]
Message-ID: <20200506181543.GA7873@lst.de> (raw)
In-Reply-To: <CAHk-=wi6E5z_aKr9NX+QcEJqJvSyrDbO3ypPugxstcPV5EPSMQ@mail.gmail.com>

On Wed, May 06, 2020 at 10:51:51AM -0700, Linus Torvalds wrote:
> My private tree no longer has those __get/put_user_size() things,
> because "unsafe_get/put_user()" is the only thing that remains with my
> conversion to asm goto.
> 
> And we're actively trying to get rid of the whole __get_user() mess.
> Admittedly "__get_user_size()" is just the internal helper that
> doesn't have the problem, but it really is an internal helper for a
> legacy operation, and the new op that uses it is that
> "unsafe_get_user()".
> 
> Also, because you use __get_user_size(), you then have to duplicate
> the error handling logic that we already have in unsafe_get_user().
> 
> IOW - is there some reason why you didn't just make these use
> "unsafe_get/put_user()" directly, and avoid both of those issues?

That was the first prototype, and or x86 it works great, just the
__user cases in maccess.c are a little ugly.  And they point to
the real problem - for architectures like sparc and s390 that use
an entirely separate address space for the kernel vs userspace
I dont think just use unsafe_{get,put}_user will work, as they need
different instructions.

Btw, where is you magic private tree and what is the plan for it?

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-parisc@vger.kernel.org,
	Daniel Borkmann <daniel@iogearbox.net>,
	Netdev <netdev@vger.kernel.org>,
	the arch/x86 maintainers <x86@kernel.org>,
	linux-um <linux-um@lists.infradead.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>,
	bpf@vger.kernel.org, Masami Hiramatsu <mhiramat@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 15/15] x86: use non-set_fs based maccess routines
Date: Wed, 6 May 2020 20:15:43 +0200	[thread overview]
Message-ID: <20200506181543.GA7873@lst.de> (raw)
In-Reply-To: <CAHk-=wi6E5z_aKr9NX+QcEJqJvSyrDbO3ypPugxstcPV5EPSMQ@mail.gmail.com>

On Wed, May 06, 2020 at 10:51:51AM -0700, Linus Torvalds wrote:
> My private tree no longer has those __get/put_user_size() things,
> because "unsafe_get/put_user()" is the only thing that remains with my
> conversion to asm goto.
> 
> And we're actively trying to get rid of the whole __get_user() mess.
> Admittedly "__get_user_size()" is just the internal helper that
> doesn't have the problem, but it really is an internal helper for a
> legacy operation, and the new op that uses it is that
> "unsafe_get_user()".
> 
> Also, because you use __get_user_size(), you then have to duplicate
> the error handling logic that we already have in unsafe_get_user().
> 
> IOW - is there some reason why you didn't just make these use
> "unsafe_get/put_user()" directly, and avoid both of those issues?

That was the first prototype, and or x86 it works great, just the
__user cases in maccess.c are a little ugly.  And they point to
the real problem - for architectures like sparc and s390 that use
an entirely separate address space for the kernel vs userspace
I dont think just use unsafe_{get,put}_user will work, as they need
different instructions.

Btw, where is you magic private tree and what is the plan for it?

_______________________________________________
linux-um mailing list
linux-um@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-um


  reply	other threads:[~2020-05-06 18:15 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-06  6:22 clean up and streamline probe_kernel_* and friends Christoph Hellwig
2020-05-06  6:22 ` Christoph Hellwig
2020-05-06  6:22 ` [PATCH 01/15] maccess: unexport probe_kernel_write and probe_user_write Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06  6:22 ` [PATCH 02/15] maccess: remove various unused weak aliases Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06  6:22 ` [PATCH 03/15] maccess: remove duplicate kerneldoc commens Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06  6:22 ` [PATCH 04/15] maccess: clarify kerneldoc comments Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06  6:22 ` [PATCH 05/15] maccess: update the top of file comment Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06  6:22 ` [PATCH 06/15] maccess: rename strncpy_from_unsafe_user to strncpy_from_user_unsafe Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06  6:22 ` [PATCH 07/15] maccess: rename strncpy_from_unsafe_strict to strncpy_from_kernel_unsafe Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06  6:22 ` [PATCH 08/15] maccess: rename strnlen_unsafe_user to strnlen_user_unsafe Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06 17:44   ` Linus Torvalds
2020-05-06 17:44     ` Linus Torvalds
2020-05-06 17:47     ` Christoph Hellwig
2020-05-06 17:47       ` Christoph Hellwig
2020-05-06 17:57       ` Linus Torvalds
2020-05-06 17:57         ` Linus Torvalds
2020-05-06  6:22 ` [PATCH 09/15] maccess: remove probe_read_common and probe_write_common Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06  6:22 ` [PATCH 10/15] maccess: unify the probe kernel arch hooks Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06  6:22 ` [PATCH 11/15] maccess: remove strncpy_from_unsafe Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-11  5:34   ` Masami Hiramatsu
2020-05-11  5:34     ` Masami Hiramatsu
2020-05-06  6:22 ` [PATCH 12/15] maccess: always use strict semantics for probe_kernel_read Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-11  5:05   ` Masami Hiramatsu
2020-05-11  5:05     ` Masami Hiramatsu
2020-05-11  5:27     ` Masami Hiramatsu
2020-05-11  5:27       ` Masami Hiramatsu
2020-05-06  6:22 ` [PATCH 13/15] maccess: move user access routines together Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06  6:22 ` [PATCH 14/15] maccess: allow architectures to provide kernel probing directly Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06  6:22 ` [PATCH 15/15] x86: use non-set_fs based maccess routines Christoph Hellwig
2020-05-06  6:22   ` Christoph Hellwig
2020-05-06 17:51   ` Linus Torvalds
2020-05-06 17:51     ` Linus Torvalds
2020-05-06 18:15     ` Christoph Hellwig [this message]
2020-05-06 18:15       ` Christoph Hellwig
2020-05-06 19:01       ` Linus Torvalds
2020-05-06 19:01         ` Linus Torvalds
2020-05-07  5:12         ` Christoph Hellwig
2020-05-07  5:12           ` Christoph Hellwig

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