From: Peter Zijlstra <peterz@infradead.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
alexei.starovoitov@gmail.com, netdev@vger.kernel.org,
bpf@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH bpf] bpf: avoid setting bpf insns pages read-only when prog is jited
Date: Mon, 2 Dec 2019 09:30:06 +0100 [thread overview]
Message-ID: <20191202083006.GJ2844@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <adc89dbf-361a-838f-a0a5-8ef7ea619848@gmail.com>
On Sun, Dec 01, 2019 at 06:49:32PM -0800, Eric Dumazet wrote:
> Thanks for the link !
>
> Having RO protection as a debug feature would be useful.
>
> I believe we have CONFIG_STRICT_MODULE_RWX (and CONFIG_STRICT_KERNEL_RWX) for that already.
>
> Or are we saying we also want to get rid of them ?
No, in fact I'm working on making that stronger. We currently still have
a few cases that violate the W^X rule.
The thing is, when the BPF stuff is JIT'ed, the actual BPF instruction
page is not actually executed at all, so making it RO serves no purpose,
other than to fragment the direct map.
All actual code lives in the 2G range that x86_64 can directly branch
to, but this BPF instruction stuff lives in the general data heap and
can thus cause much more fragmentation of the direct map.
next prev parent reply other threads:[~2019-12-02 8:30 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-29 22:29 [PATCH bpf] bpf: avoid setting bpf insns pages read-only when prog is jited Daniel Borkmann
2019-11-30 1:37 ` Eric Dumazet
2019-11-30 9:52 ` Daniel Borkmann
2019-12-01 17:54 ` Alexei Starovoitov
2019-12-02 2:49 ` Eric Dumazet
2019-12-02 3:44 ` hpa
2019-12-02 8:30 ` Peter Zijlstra [this message]
2019-12-02 9:17 ` Daniel Borkmann
2019-12-02 16:19 ` Alexei Starovoitov
2019-12-02 20:09 ` Daniel Borkmann
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191202083006.GJ2844@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=alexei.starovoitov@gmail.com \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=eric.dumazet@gmail.com \
--cc=hpa@zytor.com \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).