From: Mark Rutland <mark.rutland@arm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: "Wangshaobo (bobo)" <bobo.shaobowang@huawei.com>,
cj.chengjian@huawei.com, huawei.libin@huawei.com,
xiexiuqi@huawei.com, liwei391@huawei.com,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com,
will@kernel.org, zengshun.wu@outlook.com
Subject: Re: [RFC PATCH -next v2 0/4] arm64/ftrace: support dynamic trampoline
Date: Wed, 25 May 2022 18:26:04 +0100 [thread overview]
Message-ID: <Yo5mrDnNctKmG2PQ@FVFF77S0Q05N> (raw)
In-Reply-To: <20220525095845.53ec8fe0@gandalf.local.home>
On Wed, May 25, 2022 at 09:58:45AM -0400, Steven Rostedt wrote:
> On Wed, 25 May 2022 13:45:13 +0100
> Mark Rutland <mark.rutland@arm.com> wrote:
>
> > ... the compiler places 3 NOPs *before* any BTI, and 2 NOPs *after* any BTI,
> > still recording the location of the first NOP. So in the two cases we get:
> >
> > NOP <--- recorded location
> > NOP
> > NOP
> > __func_without_bti:
> > NOP
> > NOP
> >
> > NOP <--- recorded location
> > NOP
> > NOP
> > __func_with_bti:
> > BTI
> > NOP
> > NOP
>
> Are you saying that the above "recorded location" is what we have in
> mcount_loc section?
Yes; I'm saying that with this series, the compiler would record that into the
mcount_loc section.
Note that's not necessarily what goes into rec->ip, which we can adjust at
initialization time to be within the function. We'd need to record the
presence/absence of the BTI somewhere (I guess in dyn_arch_ftrace).
> If that's the case, we will need to modify it to point to something that
> kallsyms will recognize (ie. sym+0 or greater). Because that will cause
> set_ftrace_filter to fail as well.
Yup, understood. Like I mentioned it also wrecks the unwinder and would make it
really hard to implement RELIABLE_STACKTRACE.
Just to be clear, I don't think we should follow this specific approach. I just
wrote the examples to clarify what was being proposed.
Thanks,
Mark.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-05-25 17:27 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-16 10:01 [RFC PATCH -next v2 0/4] arm64/ftrace: support dynamic trampoline Wang ShaoBo
2022-03-16 10:01 ` [RFC PATCH -next v2 1/4] arm64: introduce aarch64_insn_gen_load_literal Wang ShaoBo
2022-03-16 10:01 ` [RFC PATCH -next v2 2/4] arm64/ftrace: introduce ftrace dynamic trampoline entrances Wang ShaoBo
2022-03-16 10:01 ` [RFC PATCH -next v2 3/4] arm64/ftrace: support dynamically allocated trampolines Wang ShaoBo
2022-04-21 13:10 ` Mark Rutland
2022-04-21 14:06 ` Steven Rostedt
2022-04-21 14:08 ` Steven Rostedt
2022-04-21 15:14 ` Mark Rutland
2022-04-21 15:42 ` Steven Rostedt
2022-04-21 16:27 ` Mark Rutland
2022-04-21 17:06 ` Steven Rostedt
2022-04-22 10:12 ` Mark Rutland
2022-04-22 15:45 ` Steven Rostedt
2022-04-22 17:27 ` Mark Rutland
2022-04-26 8:47 ` Masami Hiramatsu
2022-05-04 10:24 ` Mark Rutland
2022-05-05 3:15 ` Masami Hiramatsu
2022-05-09 18:22 ` Steven Rostedt
2022-05-10 9:10 ` Masami Hiramatsu
2022-05-10 14:44 ` Steven Rostedt
2022-05-11 14:34 ` Masami Hiramatsu
2022-05-11 15:12 ` Steven Rostedt
2022-05-12 12:02 ` Masami Hiramatsu
2022-05-12 13:50 ` Steven Rostedt
2022-05-25 12:17 ` Mark Rutland
2022-05-25 13:43 ` Steven Rostedt
2022-05-25 17:12 ` Mark Rutland
2022-05-30 1:03 ` Masami Hiramatsu
2022-05-30 12:38 ` Jiri Olsa
2022-05-31 1:00 ` Masami Hiramatsu
2022-05-04 12:43 ` Mark Rutland
2022-05-05 2:57 ` Wangshaobo (bobo)
2022-05-25 12:27 ` Mark Rutland
2022-04-27 8:54 ` Wangshaobo (bobo)
2022-03-16 10:01 ` [RFC PATCH -next v2 4/4] arm64/ftrace: implement long jump for dynamic trampolines Wang ShaoBo
2022-04-21 13:47 ` Mark Rutland
2022-03-16 14:29 ` [RFC PATCH -next v2 0/4] arm64/ftrace: support dynamic trampoline Steven Rostedt
2022-04-20 18:11 ` Steven Rostedt
2022-04-21 1:13 ` Wangshaobo (bobo)
2022-04-21 12:37 ` Steven Rostedt
2022-05-25 12:45 ` Mark Rutland
2022-05-25 13:58 ` Steven Rostedt
2022-05-25 17:26 ` Mark Rutland [this message]
2022-04-21 12:53 ` Mark Rutland
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=Yo5mrDnNctKmG2PQ@FVFF77S0Q05N \
--to=mark.rutland@arm.com \
--cc=bobo.shaobowang@huawei.com \
--cc=catalin.marinas@arm.com \
--cc=cj.chengjian@huawei.com \
--cc=huawei.libin@huawei.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=liwei391@huawei.com \
--cc=rostedt@goodmis.org \
--cc=will@kernel.org \
--cc=xiexiuqi@huawei.com \
--cc=zengshun.wu@outlook.com \
/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).