From: Steven Rostedt <rostedt@goodmis.org>
To: Julien Thierry <julien.thierry@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Arnd Bergmann <arnd@arndb.de>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org,
AKASHI Takahiro <takahiro.akashi@linaro.org>,
Ingo Molnar <mingo@redhat.com>, Torsten Duwe <duwe@lst.de>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Amit Daniel Kachhap <amit.kachhap@arm.com>,
live-patching@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v7 2/3] arm64: implement ftrace with regs
Date: Thu, 7 Feb 2019 09:51:57 -0500 [thread overview]
Message-ID: <20190207095157.3dea1086@gandalf.local.home> (raw)
In-Reply-To: <198550d8-78d4-6e30-0179-b5e07dd140f8@arm.com>
On Thu, 7 Feb 2019 10:33:50 +0000
Julien Thierry <julien.thierry@arm.com> wrote:
> I don't see really much documentation on that function. As far as I can
> tell it is only called once for each site (and if it didn't, we'd always
> be placing the same instruction, but I agree it wouldn't be nice). It
> could depend on how far you can expand the notion of "adjusting" :) .
>
> Steven, do you have an opinion on whether it would be acceptable to
> modify function entry code in ftrace_call_adjust() ?
Just to make sure I'm on the same page as you are. You want to modify
the function entry code at the time of the ftrace_call_adjust()?
I would update the rec->ip to the offset you want at
ftrace_call_adjust() but not do any modifications. It really isn't safe
to do it there. But right after that is called, you will have the arch
specific call of ftrace_make_nop() called with MCOUNT_ADDR as the
second parameter to let you know that this is the first time the call
is made at this address. This is where you can do that initial
modifications.
-- Steve
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next prev parent reply other threads:[~2019-02-07 14:52 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-18 16:37 [PATCH v7 0/3] arm64: ftrace with regs Torsten Duwe
2019-01-18 16:39 ` [PATCH v7 1/3] arm64: replace -pg with CC_FLAGS_FTRACE in Makefiles Torsten Duwe
2019-01-18 17:24 ` Mark Rutland
2019-01-18 16:39 ` [PATCH v7 2/3] arm64: implement ftrace with regs Torsten Duwe
2019-01-22 1:39 ` Singh, Balbir
2019-01-22 13:09 ` Torsten Duwe
2019-01-23 20:38 ` Singh, Balbir
2019-01-22 10:18 ` Julien Thierry
2019-01-22 13:28 ` Torsten Duwe
2019-01-22 13:49 ` Julien Thierry
2019-01-22 13:55 ` Ard Biesheuvel
2019-02-04 12:03 ` Torsten Duwe
2019-02-04 13:43 ` Ard Biesheuvel
2019-02-06 8:59 ` Julien Thierry
2019-02-06 9:30 ` Julien Thierry
2019-02-06 14:09 ` Steven Rostedt
2019-02-06 15:05 ` Torsten Duwe
2019-02-07 10:33 ` Julien Thierry
2019-02-07 12:51 ` Torsten Duwe
2019-02-07 13:47 ` Julien Thierry
2019-02-07 14:51 ` Steven Rostedt [this message]
2019-02-07 14:58 ` Julien Thierry
2019-02-07 15:00 ` Torsten Duwe
2019-04-03 2:48 ` Mark Rutland
2019-04-03 12:30 ` Steven Rostedt
2019-04-03 13:05 ` Torsten Duwe
2019-01-18 16:39 ` [PATCH v7 3/3] arm64: use -fpatchable-function-entry if available Torsten Duwe
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