From: Torsten Duwe <duwe@lst.de>
To: Jiri Kosina <jikos@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
Petr Mladek <pmladek@suse.com>,
Denis Kirjanov <kda@linux-powerpc.org>,
linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>,
live-patching@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v5 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2)
Date: Thu, 21 Jan 2016 22:56:38 +0100 [thread overview]
Message-ID: <20160121215638.GA5033@lst.de> (raw)
In-Reply-To: <alpine.LNX.2.00.1601212227200.21446@cbobk.fhfr.pm>
On Thu, Jan 21, 2016 at 10:29:13PM +0100, Jiri Kosina wrote:
> On Thu, 21 Jan 2016, Torsten Duwe wrote:
>
> > > mcount call sites looks normal on first sight...
> >
> > Not quite.
> > LR is not saved on the stack before the call.
> > Argh!
> >
> > Petr, this looks like 12 bytes offset for gcc-6.
> > I think I can work around the rest.
>
> Are we sure that gcc is doing the right thing here?
>
> I am far from claiming understanding of ppc64 ABI, but from what Vojtech
> told me I understood that saving link register is necessary for (at least)
> graph tracer to work properly.
It is held in R0 only, and saved right after _mcount. Thus, _mcount just
must not clobber R0 or save it the same way as it's done afterwards or
like gcc4 does it.
I'll make a v6 that's compiler agnostic. It's a few lines to change
for the kernel proper, and I'll have to have a look at the trampolines
for modules.
Torsten
prev parent reply other threads:[~2016-01-21 21:56 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-04 14:45 [PATCH v5 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2) Torsten Duwe
2015-12-04 13:36 ` [PATCH v5 1/9] ppc64 (le): prepare for -mprofile-kernel Torsten Duwe
2015-12-04 13:38 ` [PATCH v5 2/9] ppc64le FTRACE_WITH_REGS implementation Torsten Duwe
2015-12-04 13:39 ` [PATCH v5 3/9] ppc use ftrace_modify_all_code default Torsten Duwe
2015-12-04 13:50 ` [PATCH v5 4/9] ppc64 ftrace_with_regs configuration variables Torsten Duwe
2015-12-04 13:52 ` [PATCH v5 5/9] ppc64 ftrace_with_regs: spare early boot and low level Torsten Duwe
2015-12-04 13:55 ` [PATCH v5 6/9] ppc64 ftrace: disable profiling for some functions Torsten Duwe
2015-12-04 13:57 ` [PATCH v5 7/9] ppc64 ftrace: disable profiling for some files Torsten Duwe
2015-12-04 14:11 ` [PATCH v5 8/9] Implement kernel live patching for ppc64le (ABIv2) Torsten Duwe
2015-12-04 14:13 ` [PATCH v5 9/9] Enable LIVEPATCH to be configured on ppc64le and add livepatch.o if it is selected Torsten Duwe
2016-01-06 14:23 ` Petr Mladek
2016-01-06 14:17 ` [PATCH v5 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2) Petr Mladek
2016-01-20 6:03 ` Michael Ellerman
2016-01-20 9:07 ` Torsten Duwe
2016-01-20 9:48 ` Petr Mladek
2016-01-21 11:34 ` Petr Mladek
2016-01-21 9:33 ` Jiri Kosina
2016-01-21 12:54 ` Michael Ellerman
2016-01-21 15:06 ` Torsten Duwe
2016-01-21 15:12 ` Torsten Duwe
2016-01-21 21:29 ` Jiri Kosina
2016-01-21 21:56 ` Torsten Duwe [this message]
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