linux-kernel - Re: [PATCH v5 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2)

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Date:	Thu, 21 Jan 2016 22:29:13 +0100 (CET)
From:	Jiri Kosina <jikos@...nel.org>
To:	Torsten Duwe <duwe@....de>
cc:	Michael Ellerman <mpe@...erman.id.au>,
	Petr Mladek <pmladek@...e.com>,
	Denis Kirjanov <kda@...ux-powerpc.org>,
	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	live-patching@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v5 0/9] ftrace with regs + live patching for ppc64 LE
 (ABI v2)

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.

Thanks,

-- 
Jiri Kosina
SUSE Labs