From: Andi Kleen <andi@firstfloor.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Seth Jennings <sjenning@redhat.com>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
Steven Rostedt <rostedt@goodmis.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@redhat.com>, Jiri Slaby <jslaby@suse.cz>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 0/2] kpatch: dynamic kernel patching
Date: Thu, 01 May 2014 13:45:33 -0700 [thread overview]
Message-ID: <87ppjxcjo2.fsf@tassilo.jf.intel.com> (raw)
In-Reply-To: <cover.1398958771.git.jpoimboe@redhat.com> (Josh Poimboeuf's message of "Thu, 1 May 2014 10:52:04 -0500")
Josh Poimboeuf <jpoimboe@redhat.com> writes:
>
> kpatch checks the backtraces of all tasks in stop_machine() to ensure
> that no instances of the old function are running when the new function
> is applied.
How does that work for tail calls?
call foo
foo:
...
jmp bar
bar:
... code executing ...
When you backtrace you will see foo, but you are running in bar.
Note that tail calls can be indirect, so they cannot be resolved
statically.
CONFIG_DEBUG_INFO usually disables tail calls, but not supporting
it would seem like a large limitation, as the cost can be high.
It wouldn't surprise me if there are some similar special cases that
can even happen with them disabled.
In theory you could read LBRs, but even that may miss some extreme
cases.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
next prev parent reply other threads:[~2014-05-01 20:45 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-01 15:52 [RFC PATCH 0/2] kpatch: dynamic kernel patching Josh Poimboeuf
2014-05-01 15:52 ` [RFC PATCH 1/2] kpatch: add TAINT_KPATCH flag Josh Poimboeuf
2014-05-01 15:52 ` [RFC PATCH 2/2] kpatch: add kpatch core module Josh Poimboeuf
2014-05-01 20:45 ` Andi Kleen [this message]
2014-05-01 21:01 ` [RFC PATCH 0/2] kpatch: dynamic kernel patching Josh Poimboeuf
2014-05-01 21:06 ` Andi Kleen
2014-05-01 21:27 ` Josh Poimboeuf
2014-05-01 21:39 ` Josh Poimboeuf
2014-05-02 1:30 ` Masami Hiramatsu
2014-05-02 8:37 ` Jiri Kosina
2014-05-02 13:29 ` Josh Poimboeuf
2014-05-02 13:10 ` Jiri Kosina
2014-05-02 13:37 ` Josh Poimboeuf
2014-05-05 23:34 ` David Lang
2014-05-05 23:52 ` Jiri Kosina
2014-05-06 1:59 ` David Lang
2014-05-06 12:17 ` Josh Poimboeuf
2014-05-06 7:32 ` Ingo Molnar
2014-05-06 8:03 ` Jiri Kosina
2014-05-06 12:23 ` Josh Poimboeuf
2014-05-07 12:19 ` Ingo Molnar
2014-05-09 1:46 ` David Lang
2014-05-09 2:45 ` Steven Rostedt
2014-05-09 4:07 ` Masami Hiramatsu
2014-05-05 8:55 ` Ingo Molnar
2014-05-05 13:26 ` Josh Poimboeuf
2014-05-05 14:10 ` Frederic Weisbecker
2014-05-05 18:43 ` Ingo Molnar
2014-05-05 21:49 ` Frederic Weisbecker
2014-05-06 12:12 ` Josh Poimboeuf
2014-05-06 12:33 ` Steven Rostedt
2014-05-06 22:49 ` Masami Hiramatsu
2014-05-06 14:05 ` Frederic Weisbecker
2014-05-06 14:50 ` Josh Poimboeuf
2014-05-07 12:24 ` Ingo Molnar
2014-05-07 15:41 ` Josh Poimboeuf
2014-05-07 15:57 ` Ingo Molnar
2014-05-07 16:43 ` Josh Poimboeuf
2014-05-07 22:56 ` David Lang
2014-05-08 6:12 ` Ingo Molnar
2014-05-08 6:50 ` David Lang
2014-05-08 7:08 ` Ingo Molnar
2014-05-08 7:29 ` Masami Hiramatsu
2014-05-08 12:48 ` Josh Poimboeuf
2014-05-09 6:21 ` Masami Hiramatsu
2014-06-14 20:31 ` Pavel Machek
2014-06-15 6:57 ` Ingo Molnar
2014-05-06 11:45 ` Masami Hiramatsu
2014-05-06 12:26 ` Steven Rostedt
2014-05-06 22:33 ` Masami Hiramatsu
2014-05-16 16:27 ` Jiri Kosina
2014-05-16 17:14 ` Josh Poimboeuf
2014-05-20 9:37 ` Jiri Kosina
2014-05-20 12:59 ` Josh Poimboeuf
2014-05-16 18:09 ` Masami Hiramatsu
2014-05-17 22:46 ` Vojtech Pavlik
2014-05-16 18:55 ` Steven Rostedt
2014-05-16 22:32 ` Jiri Kosina
2014-05-17 0:27 ` Steven Rostedt
2014-05-17 7:10 ` Jiri Kosina
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