From: Petr Mladek <pmladek@suse.com>
To: Torsten Duwe <duwe@lst.de>
Cc: Miroslav Benes <mbenes@suse.cz>,
Steven Rostedt <rostedt@goodmis.org>,
Michael Ellerman <mpe@ellerman.id.au>,
anton@samba.org, Jiri Kosina <jkosina@suse.cz>,
linuxppc-dev@lists.ozlabs.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
live-patching@vger.kernel.org
Subject: Re: [PATCH v6 8/9] Implement kernel live patching for ppc64le (ABIv2)
Date: Tue, 2 Feb 2016 17:47:14 +0100 [thread overview]
Message-ID: <20160202164714.GU3305@pathway.suse.cz> (raw)
In-Reply-To: <20160202154523.GF32095@lst.de>
On Tue 2016-02-02 16:45:23, Torsten Duwe wrote:
> On Tue, Feb 02, 2016 at 01:12:24PM +0100, Petr Mladek wrote:
> >
> > Hmm, the size of the offset is not a constant. In particular, leaf
> > functions do not set TOC before the mcount location.
>
> To be slightly more precise, a leaf function that additionally uses
> no global data. No global function calls, no global data access =>
> no need to load the TOC.
Thanks for explanation.
> > The result is that kernel crashes when trying to trace leaf function
>
> The trampoline *requires* a proper TOC pointer to find the remote function
> entry point. If you jump onto the trampoline with the TOC from the caller's
> caller you'll grab some address from somewhere and jump into nirvana.
The dmesg messages suggested someting like this.
> > By other words, it seems that the code generated with -mprofile-kernel
> > option has been buggy in all gcc versions.
>
> Either that or we need bigger trampolines for everybody.
>
> Michael, should we grow every module trampoline to always load R2,
> or fix GCC to recognise the generated bl _mcount as a global function call?
> Anton, what do you think?
BTW: Is the trampoline used also for classic probes? If not, we might need
a trampoline for them as well.
Note that TOC is not set only when the problematic functions are
compiled with --mprofile-kernel. I still see the TOC stuff when
compiling only with -pg.
Best Regards,
Petr
next prev parent reply other threads:[~2016-02-02 16:47 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
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 [this message]
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=20160202164714.GU3305@pathway.suse.cz \
--to=pmladek@suse.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=mbenes@suse.cz \
--cc=mpe@ellerman.id.au \
--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 NNTP newsgroup(s).