From: Peter Zijlstra <peterz@infradead.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Petr Pavlu <petr.pavlu@suse.com>,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, hpa@zytor.com,
samitolvanen@google.com, x86@kernel.org,
linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] x86/retpoline,kprobes: Avoid treating rethunk as an indirect jump
Date: Thu, 6 Jul 2023 09:17:05 +0200 [thread overview]
Message-ID: <20230706071705.GD2833176@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20230706094723.6934105e03f652923796bf7e@kernel.org>
On Thu, Jul 06, 2023 at 09:47:23AM +0900, Masami Hiramatsu wrote:
> > > If I understand correctly, all indirect jump will be replaced with JMP_NOSPEC.
> > > If you read the insn_jump_into_range, I onlu jecks the jump code, not call.
> > > So the functions only have indirect call still allow optprobe.
> >
> > With the introduction of kCFI JMP_NOSPEC is no longer an equivalent to a
> > C indirect jump.
>
> If I understand correctly, kCFI is enabled by CFI_CLANG, and clang is not
> using jump-tables by default, so we can focus on gcc. In that case
> current check still work, correct?
IIRC clang can use jump tables, but like GCC needs RETPOLINE=n and
IBT=n, so effectively nobody has them.
The reason I did mention kCFI though is that kCFI has a larger 'indirect
jump' sequence, and I'm not sure we've thought about what can go
sideways if that's optprobed.
I suspect the UD2 that's in there will go 'funny' if it's relocated into
an optprobe, as in, it'll not be recognised as a CFI fail.
next prev parent reply other threads:[~2023-07-06 7:17 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-05 8:15 [PATCH 0/2] x86/retpoline,kprobes: Fix the [__indirect_thunk_start, ..end] range Petr Pavlu
2023-07-05 8:15 ` [PATCH 1/2] x86/retpoline,kprobes: Fix position of thunk sections with CONFIG_LTO_CLANG Petr Pavlu
2023-07-05 8:52 ` Peter Zijlstra
2023-07-05 8:15 ` [PATCH 2/2] x86/retpoline,kprobes: Avoid treating rethunk as an indirect jump Petr Pavlu
2023-07-05 8:58 ` Peter Zijlstra
2023-07-05 14:20 ` Masami Hiramatsu
2023-07-05 14:50 ` Peter Zijlstra
2023-07-06 0:47 ` Masami Hiramatsu
2023-07-06 7:17 ` Peter Zijlstra [this message]
2023-07-06 9:00 ` Masami Hiramatsu
2023-07-06 11:34 ` Peter Zijlstra
2023-07-07 14:39 ` Masami Hiramatsu
2023-07-08 14:18 ` Petr Pavlu
2023-07-09 15:25 ` Masami Hiramatsu
2023-07-05 9:02 ` Peter Zijlstra
2023-07-05 14:40 ` Masami Hiramatsu
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=20230706071705.GD2833176@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-trace-kernel@vger.kernel.org \
--cc=mhiramat@kernel.org \
--cc=mingo@redhat.com \
--cc=petr.pavlu@suse.com \
--cc=samitolvanen@google.com \
--cc=tglx@linutronix.de \
--cc=x86@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