linux-kernel - Re: [PATCH 01/12] powerpc/module: Only try to generate the ftrace

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Message-ID: <20160225130839.GC21932@lst.de>
Date:	Thu, 25 Feb 2016 14:08:39 +0100
From:	Torsten Duwe <duwe@....de>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	linuxppc-dev@...abs.org, bsingharora@...il.com,
	linux-kernel@...r.kernel.org, rostedt@...dmis.org,
	kamalesh@...ux.vnet.ibm.com, pmladek@...e.com, jeyu@...hat.com,
	jkosina@...e.cz, live-patching@...r.kernel.org, mbenes@...e.cz
Subject: Re: [PATCH 01/12] powerpc/module: Only try to generate the
	ftrace_caller() stub once

On Thu, Feb 25, 2016 at 01:28:24AM +1100, Michael Ellerman wrote:
> Currently we generate the module stub for ftrace_caller() at the bottom
> of apply_relocate_add(). However apply_relocate_add() is potentially
> called more than once per module, which means we will try to generate
> the ftrace_caller() stub multiple times.
> 
> Although the current code deals with that correctly, ie. it only
> generates a stub the first time, it would be clearer to only try to
> generate the stub once.
> 
> Note also on first reading it may appear that we generate a different
> stub for each section that requires relocation, but that is not the
> case. The code in stub_for_addr() that searches for an existing stub
> uses sechdrs[me->arch.stubs_section], ie. the single stub section for
> this module.
> 
> A cleaner approach is to only generate the ftrace_caller() stub once,
> from module_finalize(). An additional benefit is we can clean the ifdefs
> up a little.
> 
> Finally we must propagate the const'ness of some of the pointers passed
> to module_finalize(), but that is also an improvement.
> 
> Signed-off-by: Michael Ellerman <mpe@...erman.id.au>

Reviewed-by: Torsten Duwe <duwe@...e.de>

	Torsten