From: Daniel Borkmann <daniel@iogearbox.net>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
the arch/x86 maintainers <x86@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
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>,
bgregg@netflix.com
Subject: Re: [PATCH 11/18] maccess: remove strncpy_from_unsafe
Date: Thu, 14 May 2020 01:58:33 +0200 [thread overview]
Message-ID: <866cbe54-a027-04eb-65db-c6423d16b924@iogearbox.net> (raw)
In-Reply-To: <20200513232816.GZ23230@ZenIV.linux.org.uk>
On 5/14/20 1:28 AM, Al Viro wrote:
> On Thu, May 14, 2020 at 12:36:28AM +0200, Daniel Borkmann wrote:
>
>>> So on say s390 TASK_SIZE_USUALLy is (-PAGE_SIZE), which means we'd alway
>>> try the user copy first, which seems odd.
>>>
>>> I'd really like to here from the bpf folks what the expected use case
>>> is here, and if the typical argument is kernel or user memory.
>>
>> It's used for both. Given this is enabled on pretty much all program types, my
>> assumption would be that usage is still more often on kernel memory than user one.
>
> Then it needs an argument telling it which one to use. Look at sparc64.
> Or s390. Or parisc. Et sodding cetera.
>
> The underlying model is that the kernel lives in a separate address space.
> Yes, on x86 it's actually sharing the page tables with userland, but that's
> not universal. The same address can be both a valid userland one _and_
> a valid kernel one. You need to tell which one do you want.
Yes, see also 6ae08ae3dea2 ("bpf: Add probe_read_{user, kernel} and probe_read_{user,
kernel}_str helpers"), and my other reply wrt bpf_trace_printk() on how to address
this. All I'm trying to say is that both bpf_probe_read() and bpf_trace_printk() do
exist in this form since early [e]bpf days for ~5yrs now and while broken on non-x86
there are a lot of users on x86 for this in the wild, so they need to have a chance
to migrate over to the new facilities before they are fully removed.
next prev parent reply other threads:[~2020-05-13 23:58 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-13 16:00 clean up and streamline probe_kernel_* and friends v2 Christoph Hellwig
2020-05-13 16:00 ` [PATCH 01/18] maccess: unexport probe_kernel_write and probe_user_write Christoph Hellwig
2020-05-13 16:00 ` [PATCH 02/18] maccess: remove various unused weak aliases Christoph Hellwig
2020-05-13 16:00 ` [PATCH 03/18] maccess: remove duplicate kerneldoc comments Christoph Hellwig
2020-05-13 16:00 ` [PATCH 04/18] maccess: clarify " Christoph Hellwig
2020-05-13 16:00 ` [PATCH 05/18] maccess: update the top of file comment Christoph Hellwig
2020-05-13 16:00 ` [PATCH 06/18] maccess: rename strncpy_from_unsafe_user to strncpy_from_user_nofault Christoph Hellwig
2020-05-13 16:00 ` [PATCH 07/18] maccess: rename strncpy_from_unsafe_strict to strncpy_from_kernel_nofault Christoph Hellwig
2020-05-13 16:00 ` [PATCH 08/18] maccess: rename strnlen_unsafe_user to strnlen_user_nofault Christoph Hellwig
2020-05-13 16:00 ` [PATCH 09/18] maccess: remove probe_read_common and probe_write_common Christoph Hellwig
2020-05-13 16:00 ` [PATCH 10/18] maccess: unify the probe kernel arch hooks Christoph Hellwig
2020-05-14 1:13 ` Masami Hiramatsu
2020-05-19 5:46 ` Christoph Hellwig
2020-05-13 16:00 ` [PATCH 11/18] maccess: remove strncpy_from_unsafe Christoph Hellwig
2020-05-13 19:11 ` Linus Torvalds
2020-05-13 19:28 ` Christoph Hellwig
2020-05-13 22:36 ` Daniel Borkmann
2020-05-13 23:03 ` Linus Torvalds
2020-05-13 23:24 ` Daniel Borkmann
2020-05-13 23:20 ` Masami Hiramatsu
2020-05-13 23:59 ` Linus Torvalds
2020-05-14 1:00 ` Masami Hiramatsu
2020-05-14 2:43 ` Linus Torvalds
2020-05-14 9:44 ` Masami Hiramatsu
2020-05-14 10:27 ` Daniel Borkmann
2020-05-13 23:28 ` Al Viro
2020-05-13 23:58 ` Daniel Borkmann [this message]
2020-05-14 10:01 ` David Laight
2020-05-14 10:21 ` Daniel Borkmann
2020-05-13 16:00 ` [PATCH 12/18] maccess: always use strict semantics for probe_kernel_read Christoph Hellwig
2020-05-13 16:00 ` [PATCH 13/18] maccess: move user access routines together Christoph Hellwig
2020-05-13 16:00 ` [PATCH 14/18] maccess: allow architectures to provide kernel probing directly Christoph Hellwig
2020-05-13 19:36 ` Linus Torvalds
2020-05-13 19:40 ` Christoph Hellwig
2020-05-13 19:48 ` Linus Torvalds
2020-05-13 19:54 ` Christoph Hellwig
2020-05-16 3:42 ` Masami Hiramatsu
2020-05-18 15:09 ` Christoph Hellwig
2020-05-13 16:00 ` [PATCH 15/18] x86: use non-set_fs based maccess routines Christoph Hellwig
2020-05-13 16:00 ` [PATCH 16/18] maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault Christoph Hellwig
2020-05-13 16:00 ` [PATCH 17/18] maccess: rename probe_user_{read,write} to copy_{from,to}_user_nofault Christoph Hellwig
2020-05-13 16:00 ` [PATCH 18/18] maccess: rename probe_kernel_address to get_kernel_nofault Christoph Hellwig
2020-05-13 19:37 ` clean up and streamline probe_kernel_* and friends v2 Linus Torvalds
2020-05-13 23:04 ` Daniel Borkmann
2020-05-13 23:20 ` Linus Torvalds
2020-05-19 5:50 ` Christoph Hellwig
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