From: Steven Rostedt <rostedt@goodmis.org>
To: Alexei Starovoitov <ast@fb.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Josef Bacik <jbacik@fb.com>, <mingo@redhat.com>,
<davem@davemloft.net>, <netdev@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <ast@kernel.org>,
<kernel-team@fb.com>, <daniel@iogearbox.net>,
<linux-btrfs@vger.kernel.org>, <darrick.wong@oracle.com>,
Josef Bacik <josef@toxicpanda.com>,
Akinobu Mita <akinobu.mita@gmail.com>
Subject: Re: [RFC PATCH bpf-next v2 1/4] tracing/kprobe: bpf: Check error injectable event is on function entry
Date: Wed, 27 Dec 2017 23:16:44 -0500 [thread overview]
Message-ID: <20171227231644.168abc0f@vmware.local.home> (raw)
In-Reply-To: <03e0ebb7-0b2a-4235-3408-c0d59a1ba4c2@fb.com>
On Wed, 27 Dec 2017 19:45:42 -0800
Alexei Starovoitov <ast@fb.com> wrote:
> I don't think that's the case. My reading of current
> trace_kprobe_ftrace() -> arch_check_ftrace_location()
> is that it will not be true for old mcount case.
In the old mcount case, you can't use ftrace to return without calling
the function. That is, no modification of the return ip, unless you
created a trampoline that could handle arbitrary stack frames, and
remove them from the stack before returning back to the function.
>
> As far as the rest of your arguments it very much puzzles me that
> you claim that this patch suppose to work based on historical
> reasoning whereas you did NOT test it.
I believe that Masami is saying that the modification of the IP from
kprobes has been very well tested. But I'm guessing that you still want
a test case for using kprobes in this particular instance. It's not the
implementation of modifying the IP that you are worried about, but the
implementation of BPF using it in this case. Right?
-- Steve
next prev parent reply other threads:[~2017-12-28 4:16 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-26 7:46 [RFC PATCH bpf-next v2 0/4] Separate error injection table from kprobes Masami Hiramatsu
2017-12-26 7:46 ` [RFC PATCH bpf-next v2 1/4] tracing/kprobe: bpf: Check error injectable event is on function entry Masami Hiramatsu
2017-12-27 1:57 ` Alexei Starovoitov
2017-12-27 5:56 ` Masami Hiramatsu
2017-12-27 22:46 ` Alexei Starovoitov
2017-12-28 2:34 ` Masami Hiramatsu
2017-12-28 3:45 ` Alexei Starovoitov
2017-12-28 4:16 ` Steven Rostedt [this message]
2017-12-28 4:32 ` Alexei Starovoitov
2017-12-28 8:20 ` Masami Hiramatsu
2017-12-29 1:03 ` Alexei Starovoitov
2017-12-29 8:20 ` Masami Hiramatsu
2018-01-08 3:01 ` Alexei Starovoitov
2018-01-08 13:21 ` Masami Hiramatsu
2017-12-28 7:56 ` Masami Hiramatsu
2017-12-26 7:47 ` [RFC PATCH bpf-next v2 2/4] tracing/kprobe: bpf: Compare instruction pointer with original one Masami Hiramatsu
2017-12-27 2:00 ` Alexei Starovoitov
2017-12-26 7:47 ` [RFC PATCH bpf-next v2 3/4] error-injection: Separate error-injection from kprobe Masami Hiramatsu
2017-12-27 2:07 ` Alexei Starovoitov
2017-12-26 7:48 ` [RFC PATCH bpf-next v2 4/4] error-injection: Support fault injection framework Masami Hiramatsu
2017-12-27 2:12 ` Alexei Starovoitov
2017-12-27 8:09 ` Masami Hiramatsu
2017-12-27 22:49 ` Alexei Starovoitov
2017-12-28 1:38 ` Masami Hiramatsu
2017-12-28 3:49 ` Alexei Starovoitov
2017-12-28 7:51 ` Masami Hiramatsu
2017-12-29 1:11 ` Alexei Starovoitov
2017-12-29 7:34 ` Masami Hiramatsu
2018-01-04 16:07 ` [RFC PATCH bpf-next v2 0/4] Separate error injection table from kprobes Josef Bacik
2018-01-09 1:17 ` Masami Hiramatsu
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