From: Christoph Hellwig <hch@infradead.org>
To: Yonghong Song <yhs@fb.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Christoph Hellwig <hch@infradead.org>,
Alan Maguire <alan.maguire@oracle.com>,
Yixun Lan <dlan@gentoo.org>, Palmer Dabbelt <palmer@dabbelt.com>,
linux-riscv@lists.infradead.org,
Paul Walmsley <paul.walmsley@sifive.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
open list <linux-kernel@vger.kernel.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH] RISC-V/bpf: Enable bpf_probe_read{, str}()
Date: Wed, 6 Jul 2022 00:01:51 -0700 [thread overview]
Message-ID: <YsUzX2IeNb/u9VmN@infradead.org> (raw)
In-Reply-To: <712c8fac-6784-2acd-66ca-d1fd393aef23@fb.com>
On Tue, Jul 05, 2022 at 11:41:30PM -0700, Yonghong Song wrote:
>
>
> On 7/5/22 10:00 PM, Andrii Nakryiko wrote:
> > On Sun, Jul 3, 2022 at 10:53 PM Christoph Hellwig <hch@infradead.org> wrote:
> > >
> > > On Sun, Jul 03, 2022 at 09:09:24PM +0800, Yixun Lan wrote:
> > > > Enable this option to fix a bcc error in RISC-V platform
> > > >
> > > > And, the error shows as follows:
> > >
> > > These should not be enabled on new platforms. Use the proper helpers
> > > to probe kernel vs user pointers instead.
> >
> > riscv existed as of [0], so I'd argue it is a proper bug fix, as
> > corresponding select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE should
> > have been added back then.
> >
> > But I also agree that BCC tools should be updated to use proper
> > bpf_probe_read_{kernel,user}[_str()] helpers, please contribute such
> > fixes to BCC tools and BCC itself as well. Cc'ed Alan as his ksnoop in
> > libbpf-tools seems to be using bpf_probe_read() as well and needs to
> > be fixed.
>
> Yixun, the bcc change looks like below:
No, this is broken. bcc needs to stop using bpf_probe_read entirely
for user addresses and unconditionally use bpf_probe_read_user first
and only fall back to bpf_probe_read if not supported.
next prev parent reply other threads:[~2022-07-06 7:02 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-03 13:09 [PATCH] RISC-V/bpf: Enable bpf_probe_read{, str}() Yixun Lan
2022-07-03 13:12 ` Conor Dooley
2022-07-04 2:20 ` Yixun Lan
2022-07-04 6:29 ` Conor.Dooley
2022-07-04 5:53 ` Christoph Hellwig
2022-07-06 5:00 ` Andrii Nakryiko
2022-07-06 6:41 ` Yonghong Song
2022-07-06 7:01 ` Christoph Hellwig [this message]
2022-07-09 1:01 ` Yixun Lan
2022-07-09 6:24 ` Christoph Hellwig
2022-07-09 8:48 ` Yixun Lan
2022-07-11 3:58 ` Christoph Hellwig
2022-07-06 7:00 ` Christoph Hellwig
2022-07-08 22:22 ` Andrii Nakryiko
2022-07-09 6:25 ` Christoph Hellwig
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