From: Balbir Singh <bsingharora@gmail.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
Julien Thierry <julien.thierry@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.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 v6] arm64: implement ftrace with regs
Date: Mon, 14 Jan 2019 23:13:59 +1100 [thread overview]
Message-ID: <20190114121359.GB26056@350D> (raw)
In-Reply-To: <20190104175017.GA7157@lakrids.cambridge.arm.com>
On Fri, Jan 04, 2019 at 05:50:18PM +0000, Mark Rutland wrote:
> Hi Torsten,
>
> On Fri, Jan 04, 2019 at 03:10:53PM +0100, Torsten Duwe wrote:
> > Use -fpatchable-function-entry (gcc8) to add 2 NOPs at the beginning
> > of each function. Replace the first NOP thus generated with a quick LR
> > saver (move it to scratch reg x9), so the 2nd replacement insn, the call
> > to ftrace, does not clobber the value. Ftrace will then generate the
> > standard stack frames.
> >
Do we know what the overhead would be, if this was a link time change
for the first instruction?
Also, I was under the impression that some arch's do ftrace_call_replace
under stop_machine(), is that a possibility here?
Balbir Singh
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next prev parent reply other threads:[~2019-01-14 12:14 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-04 14:10 [PATCH v6] arm64: implement ftrace with regs Torsten Duwe
2019-01-04 17:50 ` Mark Rutland
2019-01-04 18:06 ` Steven Rostedt
2019-01-04 22:41 ` Torsten Duwe
2019-01-05 11:05 ` Torsten Duwe
2019-01-05 20:00 ` Steven Rostedt
2019-01-07 11:19 ` Mark Rutland
2019-01-14 12:13 ` Balbir Singh [this message]
2019-01-14 12:26 ` Mark Rutland
2019-01-16 15:56 ` Julien Thierry
2019-01-16 18:01 ` Julien Thierry
2019-01-07 4:57 ` Amit Daniel Kachhap
2019-01-16 9:57 ` Julien Thierry
2019-01-16 10:08 ` Julien Thierry
2019-01-17 15:48 ` Torsten Duwe
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