From: Peter Zijlstra <peterz@infradead.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Jiri Olsa <olsajiri@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Ingo Molnar <mingo@redhat.com>, bpf <bpf@vger.kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [RFC] ftrace: Add support to keep some functions out of ftrace
Date: Mon, 15 Aug 2022 17:02:03 +0200 [thread overview]
Message-ID: <Yvpf67eCerqaDmlE@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <CAADnVQKyfrFTZOM9F77i0NbaXLZZ7KbvKBvu7p6kgdnRgG+2=Q@mail.gmail.com>
On Mon, Aug 15, 2022 at 07:45:16AM -0700, Alexei Starovoitov wrote:
> On Mon, Aug 15, 2022 at 7:33 AM Peter Zijlstra <peterz@infradead.org> wrote:
> > It is in full control of the 'call __fentry__'. Absolute full NAK on you
> > trying to make it otherwise.
>
> Don't mix 'call fentry' generated by the compiler with nop5 inserted
> by macroses or JITs.
Looking at:
https://lore.kernel.org/all/20191211123017.13212-3-bjorn.topel@gmail.com/
this seems to want to prod at the __fentry__ sites.
> > > Soon we will have nop5 in the middle of the function.
> > > ftrace must not touch it.
> >
> > How are you generating that NOP and what for?
>
> We're generating nop5-s in JITed code to further
> attach to.
Ftrace doesn't know about those; so how can it break that?
Likewise it doesn't know about the static_branch/static_call NOPs and
nothing is broken.
Ftrace only knows about the __fentry__ sites, and it *does* own them.
Are you saying ftrace is writing to a code location not a __fentry__
site?
next prev parent reply other threads:[~2022-08-15 15:02 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220722110811.124515-1-jolsa@kernel.org>
[not found] ` <20220722072608.17ef543f@rorschach.local.home>
[not found] ` <CAADnVQ+hLnyztCi9aqpptjQk-P+ByAkyj2pjbdD45dsXwpZ0bw@mail.gmail.com>
[not found] ` <20220722120854.3cc6ec4b@gandalf.local.home>
[not found] ` <20220722122548.2db543ca@gandalf.local.home>
[not found] ` <YtsRD1Po3qJy3w3t@krava>
[not found] ` <20220722174120.688768a3@gandalf.local.home>
[not found] ` <YtxqjxJVbw3RD4jt@krava>
[not found] ` <YvbDlwJCTDWQ9uJj@krava>
2022-08-13 19:02 ` [RFC] ftrace: Add support to keep some functions out of ftrace Steven Rostedt
2022-08-14 11:32 ` Steven Rostedt
2022-08-14 15:22 ` Jiri Olsa
2022-08-15 2:07 ` Chen Zhongjin
2022-08-15 8:04 ` Jiri Olsa
2022-08-15 11:01 ` Björn Töpel
2022-08-15 11:29 ` Jiri Olsa
2022-08-15 12:19 ` Björn Töpel
2022-08-15 12:30 ` Björn Töpel
2022-08-15 8:03 ` Peter Zijlstra
2022-08-15 9:44 ` Jiri Olsa
2022-08-15 12:37 ` Peter Zijlstra
2022-08-15 14:25 ` Alexei Starovoitov
2022-08-15 14:33 ` Peter Zijlstra
2022-08-15 14:45 ` Alexei Starovoitov
2022-08-15 15:02 ` Peter Zijlstra [this message]
2022-08-15 15:17 ` Alexei Starovoitov
2022-08-15 15:28 ` Peter Zijlstra
2022-08-15 15:35 ` Alexei Starovoitov
2022-08-15 15:44 ` Steven Rostedt
2022-08-15 15:53 ` Alexei Starovoitov
2022-08-15 16:13 ` Steven Rostedt
2022-08-15 15:48 ` Peter Zijlstra
2022-08-16 6:56 ` Jiri Olsa
2022-08-17 9:29 ` Jiri Olsa
2022-08-17 16:57 ` Alexei Starovoitov
2022-08-17 19:39 ` Jiri Olsa
2022-08-15 15:41 ` Peter Zijlstra
2022-08-15 15:49 ` Alexei Starovoitov
2022-08-15 16:08 ` Steven Rostedt
2022-08-18 20:27 ` Jiri Olsa
2022-08-18 20:50 ` Steven Rostedt
2022-08-18 21:00 ` Alexei Starovoitov
2022-08-18 21:05 ` Steven Rostedt
2022-08-18 21:32 ` Jiri Olsa
2022-08-19 11:45 ` Jiri Olsa
2022-08-23 17:23 ` Alexei Starovoitov
2022-08-26 8:00 ` Jiri Olsa
2022-08-18 21:14 ` Jiri Olsa
2022-08-15 15:32 ` Steven Rostedt
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