From: Steven Rostedt <rostedt@goodmis.org>
To: Torsten Duwe <duwe@lst.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
Petr Mladek <pmladek@suse.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
takahiro.akashi@linaro.org,
Jungseok Lee <jungseoklee85@gmail.com>,
Arnd Bergmann <arnd@arndb.de>, Li Bin <huawei.libin@huawei.com>,
Ingo Molnar <mingo@redhat.com>,
Christopher Li <sparse@chrisli.org>,
Jiri Kosina <jikos@kernel.org>,
andrew.wafaa@arm.com, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, live-patching@vger.kernel.org,
linux-arch@vger.kernel.org, linux-sparse@vger.kernel.org
Subject: Re: [PATCH v2 1/2] arm64: implement FTRACE_WITH_REGS
Date: Fri, 8 Jul 2016 17:08:08 -0400 [thread overview]
Message-ID: <20160708170808.1ab70ce3@gandalf.local.home> (raw)
In-Reply-To: <20160708202455.GA4580@lst.de>
On Fri, 8 Jul 2016 22:24:55 +0200
Torsten Duwe <duwe@lst.de> wrote:
> On Fri, Jul 08, 2016 at 11:57:10AM -0400, Steven Rostedt wrote:
> > On Fri, 8 Jul 2016 10:48:24 -0500
> > Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > >
> > > Here, with -fprolog-pad, it's already a nop, so no change is needed.
> > >
>
> Yes, exactly.
>
> > That's what I was thinking. But as I stated in another email (probably
> > in the air when you wrote this), the call to ftrace_modify_code() may be
> > completely circumvented by ftrace_make_nop() if the addr is MCOUNT_ADDR.
>
> Only on the _first_ invocation. Later on, tracing can be switched on and off,
> and then the instructions need to be changed just like with fentry (or
> profile-kernel ;-)
>
Understood, but ftrace_modify_code() will only receive addr ==
MCOUNT_ADDR on boot up or when a module is loaded. In both cases, with
-fprolog-pad it will already be a nop, hence no need to call
ftrace_modify_code(), in those cases.
In all other cases, addr will point to a ftrace trampoline.
-- Steve
next prev parent reply other threads:[~2016-07-08 21:08 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-27 15:15 [PATCH v2 0/2] arm64 live patching Torsten Duwe
2016-06-27 15:15 ` Torsten Duwe
2016-06-27 15:17 ` [PATCH v2 1/2] arm64: implement FTRACE_WITH_REGS Torsten Duwe
2016-06-27 15:17 ` Torsten Duwe
2016-07-01 12:53 ` Josh Poimboeuf
2016-07-01 12:53 ` Josh Poimboeuf
2016-07-04 9:18 ` Torsten Duwe
2016-07-04 9:18 ` Torsten Duwe
2016-07-03 5:17 ` kbuild test robot
2016-07-08 14:58 ` Petr Mladek
2016-07-08 14:58 ` Petr Mladek
2016-07-08 15:07 ` Torsten Duwe
2016-07-08 15:24 ` Petr Mladek
2016-07-08 15:24 ` Petr Mladek
2016-07-08 15:48 ` Josh Poimboeuf
2016-07-08 15:48 ` Josh Poimboeuf
2016-07-08 15:57 ` Steven Rostedt
2016-07-08 20:24 ` Torsten Duwe
2016-07-08 20:24 ` Torsten Duwe
2016-07-08 21:08 ` Steven Rostedt [this message]
2016-07-09 9:06 ` Torsten Duwe
2016-07-09 9:06 ` Torsten Duwe
2016-07-15 18:36 ` Steven Rostedt
2016-07-15 18:36 ` Steven Rostedt
2016-07-08 15:49 ` Steven Rostedt
2016-06-27 15:17 ` [PATCH v2 2/2] arm64: implement live patching Torsten Duwe
2016-06-27 15:17 ` Torsten Duwe
2016-07-11 14:03 ` Miroslav Benes
2016-07-11 14:03 ` Miroslav Benes
2016-07-11 21:58 ` Jessica Yu
2016-07-12 9:47 ` Miroslav Benes
2016-07-13 0:11 ` [PATCH] arm64: take SHN_LIVEPATCH syms into account when calculating plt_max_entries Jessica Yu
2016-07-13 0:11 ` Jessica Yu
2016-08-17 9:38 ` Miroslav Benes
2016-08-17 9:38 ` Miroslav Benes
2016-08-11 16:46 ` [PATCH v2 2/2] arm64: implement live patching Torsten Duwe
2016-08-11 16:46 ` Torsten Duwe
2016-07-15 16:03 ` Paul Gortmaker
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