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From: Torsten Duwe <duwe@lst.de>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Julien Thierry <julien.thierry@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Ingo Molnar <mingo@redhat.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>,
	AKASHI Takahiro <takahiro.akashi@linaro.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, live-patching@vger.kernel.org
Subject: Re: [PATCH v3 2/4] arm64: implement ftrace with regs
Date: Tue, 2 Oct 2018 14:18:17 +0200	[thread overview]
Message-ID: <20181002121817.GB2398@lst.de> (raw)
In-Reply-To: <20181002112741.mvav4ar4v25gj46e@lakrids.cambridge.arm.com>

Hi Mark,

thank you for your very detailed feedback, I'll incorporate it
all into the next version, besides one issue:

On Tue, Oct 02, 2018 at 12:27:41PM +0100, Mark Rutland wrote:
> 
> Please use the insn framework, as we do to generate all the other
> instruction sequences in ftrace.
> 
> MOV (register) is an alias of ORR (shifted register), i.e.
> 
> 	mov	<xd>, <xm>
> 
> ... is:
> 
> 	orr	<xd>, xzr, <xm>
> 
> ... and we have code to generate ORR, so we can add a trivial wrapper to
> generate MOV.

I had something similar in v2; but it was hardly any better to read or
understand. My main question however is: how do you justify the runtime
overhead of aarch64_insn_gen_logical_shifted_reg for every function that
gets its tracing switched on or off? The result is always the same 4-byte
constant, so why not use a macro and a comment that says what it does?

	Torsten


  reply	other threads:[~2018-10-02 12:18 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-01 14:09 [PATCH v3 0/4] arm64 live patching Torsten Duwe
2018-10-01 14:16 ` [PATCH v3 1/4] DYNAMIC_FTRACE configurable with and without REGS Torsten Duwe
2018-10-01 14:52   ` Ard Biesheuvel
2018-10-01 15:03     ` Torsten Duwe
2018-10-01 15:06       ` Ard Biesheuvel
2018-10-01 15:10         ` Torsten Duwe
2018-10-01 15:14           ` Steven Rostedt
2018-10-01 14:16 ` [PATCH v3 2/4] arm64: implement ftrace with regs Torsten Duwe
2018-10-01 15:57   ` Ard Biesheuvel
2018-10-02 10:02     ` Torsten Duwe
2018-10-02 10:39       ` Ard Biesheuvel
2018-10-02 11:27   ` Mark Rutland
2018-10-02 12:18     ` Torsten Duwe [this message]
2018-10-02 12:57       ` Mark Rutland
2018-10-01 14:16 ` [PATCH v3 3/4] arm64: implement live patching Torsten Duwe
2018-10-17 13:39   ` Miroslav Benes
2018-10-18 12:58     ` Jessica Yu
2018-10-19 11:59       ` Miroslav Benes
2018-10-19 12:18         ` Jessica Yu
2018-10-19 15:14           ` Miroslav Benes
2018-10-19 13:46         ` Torsten Duwe
2018-10-19 13:52       ` Ard Biesheuvel
2018-10-19 15:21         ` Miroslav Benes
2018-10-20 14:10           ` Ard Biesheuvel
2018-10-22 12:53             ` Miroslav Benes
2018-10-22 14:54               ` Torsten Duwe
2018-10-23 17:55   ` [PATCH] arm64/module: use mod->klp_info section header information Jessica Yu
2018-10-23 19:32     ` kbuild test robot
2018-10-24 11:57     ` Miroslav Benes
2018-10-25  8:08     ` Petr Mladek
2018-10-25  9:00       ` Miroslav Benes
2018-10-25 11:42         ` Jessica Yu
2018-10-26 17:25     ` [PATCH v2] arm64/module: use mod->klp_info section header information for livepatch modules Jessica Yu
2018-10-29 13:24       ` Miroslav Benes
2018-10-29 13:32         ` Jessica Yu
2018-10-29 15:28       ` Will Deacon
2018-10-30 13:19         ` Jessica Yu
2018-11-01 15:18           ` Miroslav Benes
2018-11-01 16:07           ` Will Deacon
2018-11-05 12:30             ` Ard Biesheuvel
2018-11-05 17:57   ` [PATCH] arm64/module: use plt section indices for relocations Jessica Yu
2018-11-05 18:04     ` Ard Biesheuvel
2018-11-05 18:53     ` [PATCH v2] " Jessica Yu
2018-11-05 18:56       ` Ard Biesheuvel
2018-11-05 19:26       ` Will Deacon
2018-11-05 19:49         ` Jessica Yu
2018-11-06  9:44         ` Miroslav Benes
2018-10-01 14:16 ` [PATCH v3 4/4] arm64: reliable stacktraces Torsten Duwe

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