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From: Jiri Kosina <jikos@kernel.org>
To: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Torsten Duwe <duwe@lst.de>, Steven Rostedt <rostedt@goodmis.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
	live-patching@vger.kernel.org
Subject: Re: [PATCH v6 1/9] ppc64 (le): prepare for -mprofile-kernel
Date: Thu, 4 Feb 2016 22:47:56 +0100 (CET)	[thread overview]
Message-ID: <alpine.LNX.2.00.1602042244430.22727@cbobk.fhfr.pm> (raw)
In-Reply-To: <56B31A7C.2050803@linaro.org>

On Thu, 4 Feb 2016, AKASHI Takahiro wrote:

> On arm/arm64, link register must be saved before any function call. So anyhow
> we will have to add something, 3 instructions at the minimum, like:
>    save lr
>    branch _mcount
>    restore lr
>    <prologue>
>    ...
>    <body>
>    ...

This means that we have at least two architectures that need one 
instruction before the mcount/mfentry call, and the rest of the prologue 
to follow afterwards. On x86, we don't need any "pre-prologue".

Persumably the corresponding opcodes have different sizes. This nicely 
demonstrates my point -- if this one-gcc-option-to-rule-them-all would 
exist, it needs to be generic enough to describe these kinds of 
constraints (who knows what other restrictions will pop up when exploring 
other, more exotic, architectures later).

Thanks,

-- 
Jiri Kosina
SUSE Labs

  parent reply	other threads:[~2016-02-04 21:48 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-25 15:38 [PATCH v6 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2) Torsten Duwe
2016-01-25 15:26 ` [PATCH v6 1/9] ppc64 (le): prepare for -mprofile-kernel Torsten Duwe
2016-01-27 10:19   ` Michael Ellerman
2016-01-27 10:44     ` Torsten Duwe
2016-01-28  4:26       ` Michael Ellerman
2016-01-28  4:26         ` Michael Ellerman
2016-01-28 11:50         ` Torsten Duwe
2016-01-27 12:58     ` Alan Modra
2016-01-27 13:45       ` Torsten Duwe
2016-01-28  3:39       ` Michael Ellerman
2016-01-28  3:39         ` Michael Ellerman
2016-02-03  7:23   ` AKASHI Takahiro
2016-02-03  8:55     ` Jiri Kosina
2016-02-03 11:24       ` Torsten Duwe
2016-02-04  9:31         ` AKASHI Takahiro
2016-02-04 11:02           ` Petr Mladek
2016-02-05  4:40             ` Balbir Singh
2016-02-05 10:22               ` Petr Mladek
2016-02-04 21:47           ` Jiri Kosina [this message]
2016-01-25 15:27 ` [PATCH v6 2/9] ppc64le FTRACE_WITH_REGS implementation Torsten Duwe
2016-01-25 15:29 ` [PATCH v6 3/9] ppc use ftrace_modify_all_code default Torsten Duwe
2016-01-25 15:29 ` [PATCH v6 4/9] ppc64 ftrace_with_regs configuration variables Torsten Duwe
2016-01-25 15:30 ` [PATCH v6 5/9] ppc64 ftrace_with_regs: spare early boot and low level Torsten Duwe
2016-01-25 15:31 ` [PATCH v6 6/9] ppc64 ftrace: disable profiling for some functions Torsten Duwe
2016-01-25 15:31 ` [PATCH v6 7/9] ppc64 ftrace: disable profiling for some files Torsten Duwe
2016-01-25 15:33 ` [PATCH v6 8/9] Implement kernel live patching for ppc64le (ABIv2) Torsten Duwe
2016-01-26 10:50   ` Miroslav Benes
2016-01-26 12:48     ` Petr Mladek
2016-01-26 13:56       ` Torsten Duwe
2016-02-02 12:12       ` Petr Mladek
2016-02-02 15:45         ` Torsten Duwe
2016-02-02 16:47           ` Petr Mladek
2016-02-02 20:39             ` Jiri Kosina
2016-01-26 14:00     ` Torsten Duwe
2016-01-26 14:14       ` Miroslav Benes
2016-01-27  1:53         ` Jessica Yu
2016-02-02 13:46   ` [PATCH v6 8/9] " Denis Kirjanov
2016-02-10 18:03     ` Torsten Duwe
2016-01-25 15:33 ` [PATCH v6 9/9] Enable LIVEPATCH to be configured on ppc64le and add livepatch.o if it is selected Torsten Duwe
2016-01-27 10:51 ` [PATCH v6 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2) Balbir Singh
2016-01-27 12:19   ` Torsten Duwe
2016-01-28  2:41     ` Balbir Singh
2016-01-28  3:31       ` Michael Ellerman
2016-01-28 11:19         ` Torsten Duwe

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