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From: Torsten Duwe <duwe@lst.de>
To: Alan Modra <amodra@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
	Steven Rostedt <rostedt@goodmis.org>,
	Anton Blanchard <anton@samba.org>, Jiri Kosina <jkosina@suse.cz>,
	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: Wed, 27 Jan 2016 14:45:02 +0100	[thread overview]
Message-ID: <20160127134502.GC32095@lst.de> (raw)
In-Reply-To: <20160127125809.GN17028@bubble.grove.modra.org>

On Wed, Jan 27, 2016 at 11:28:09PM +1030, Alan Modra wrote:
> On Wed, Jan 27, 2016 at 09:19:27PM +1100, Michael Ellerman wrote:
> > 
> > Can we use r11 instead? eg:
> > 
> > _GLOBAL(_mcount)
> > 	mflr	r11
> > 	mtctr	r11
> > 	mtlr	r0
> > 	bctr
> 
> Depends on what you need to support.  As Torsten says, the code to
> call _mcount when -mprofile-kernel is emitted before the prologue of a
> function (similar to -m32), but after the ELFv2 global entry point
> code.  If you trash r11 here you're killing the static chain pointer,
> used by C nested functions or other languages that use a static chain,
> eg. Pascal.  r11 has *not* been saved for ELFv2.

Even if nested functions aren't supported in the Linux kernel(?), I think
it was an earlier version of mcount when r11 usage ruined my day.

> r12 might be a better choice for a temp reg.

Good idea. r12 holds the function entry point and is used to calculate the
new TOC value just _before_ the call. It should be available.
I'll try, thanks for the hint.

	Torsten

  reply	other threads:[~2016-01-27 13:45 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 [this message]
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
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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