From: Michael Ellerman <mpe@ellerman.id.au>
To: Alan Modra <amodra@gmail.com>
Cc: Torsten Duwe <duwe@lst.de>, 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: Thu, 28 Jan 2016 14:39:38 +1100 [thread overview]
Message-ID: <1453952378.4108.3.camel@ellerman.id.au> (raw)
In-Reply-To: <20160127125809.GN17028@bubble.grove.modra.org>
On Wed, 2016-01-27 at 23:28 +1030, Alan Modra wrote:
> On Wed, Jan 27, 2016 at 09:19:27PM +1100, Michael Ellerman wrote:
> > Hi Torsten,
> >
> > On Mon, 2016-01-25 at 16:26 +0100, Torsten Duwe wrote:
> > > The gcc switch -mprofile-kernel, available for ppc64 on gcc > 4.8.5,
> > > allows to call _mcount very early in the function, which low-level
> > > ASM code and code patching functions need to consider.
> > > Especially the link register and the parameter registers are still
> > > alive and not yet saved into a new stack frame.
> > >
> > > Signed-off-by: Torsten Duwe <duwe@suse.de>
> > > ---
> > > arch/powerpc/kernel/entry_64.S | 45 +++++++++++++++++++++++++++++++++++++++--
> > > arch/powerpc/kernel/ftrace.c | 12 +++++++++--
> > > arch/powerpc/kernel/module_64.c | 14 +++++++++++++
> > > 3 files changed, 67 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> > > index a94f155..e7cd043 100644
> > > --- a/arch/powerpc/kernel/entry_64.S
> > > +++ b/arch/powerpc/kernel/entry_64.S
> > > @@ -1206,7 +1206,12 @@ _GLOBAL(enter_prom)
> > > #ifdef CONFIG_DYNAMIC_FTRACE
> > > _GLOBAL(mcount)
> > > _GLOBAL(_mcount)
> > > - blr
> > > + std r0,LRSAVE(r1) /* gcc6 does this _after_ this call _only_ */
> > > + mflr r0
> > > + mtctr r0
> > > + ld r0,LRSAVE(r1)
> > > + mtlr r0
> > > + bctr
> >
> > 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.
OK, thanks for clarfiying. Pascal is not a big concern :D. But although I
don't think we use nested functions anywhere, someone somewhere could be, or at
least might one day.
> r12 might be a better choice for a temp reg.
Even better.
cheers
next prev parent reply other threads:[~2016-01-28 3:39 UTC|newest]
Thread overview: 42+ 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 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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1453952378.4108.3.camel@ellerman.id.au \
--to=mpe@ellerman.id.au \
--cc=amodra@gmail.com \
--cc=anton@samba.org \
--cc=duwe@lst.de \
--cc=jkosina@suse.cz \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=live-patching@vger.kernel.org \
--cc=rostedt@goodmis.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).