linux-kernel - Re: [PATCH 1/2] Allow constructor name selection by architecture.

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Date:	Thu, 18 Apr 2013 13:39:31 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	"George G. Davis" <gdavis@...sta.com>
Cc:	Sam Ravnborg <sam@...nborg.org>,
	Vincent Sanders <vincent.sanders@...labora.co.uk>,
	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
	Vincent Sanders <vince@...labora.co.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] Allow constructor name selection by architecture.

Looks to me like this has died again.  Unless Sam responds shortly,
I'm going to ask for this to be put into the patch system and I'll
just apply it for 3.10 and be done with it.

On Mon, Apr 01, 2013 at 06:21:51PM -0400, George G. Davis wrote:
> On Mon, Apr 1, 2013 at 5:58 PM, Sam Ravnborg <sam@...nborg.org> wrote:
> > On Mon, Apr 01, 2013 at 05:47:38PM -0400, George G. Davis wrote:
> >> On Jun 6, 2012, at 6:12 AM, Russell King - ARM Linux wrote:
> >> > On Tue, May 29, 2012 at 10:06:14AM +0100, Russell King - ARM Linux wrote:
> >> >> On Mon, May 28, 2012 at 10:30:05PM +0200, Sam Ravnborg wrote:
> >> >>> On Mon, May 28, 2012 at 07:33:37PM +0100, Vincent Sanders wrote:
> >> >>>> From: Vincent Sanders <vince@...labora.co.uk>
> >> >>>>
> >> >>>> The constructor symbol name is different between platforms. Allow this
> >> >>>> to be selected by configuration and set suitable default values.
> >> >>>>
> >> >>>> Signed-off-by: Vincent Sanders <vincent.sanders@...labora.co.uk>
> >> >>>> ---
> >> >>>> include/asm-generic/vmlinux.lds.h |    6 +++---
> >> >>>> init/Kconfig                      |    6 ++++++
> >> >>>> kernel/module.c                   |    2 +-
> >> >>>> 3 files changed, 10 insertions(+), 4 deletions(-)
> >> >>>>
> >> >>>> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> >> >>>> index 8aeadf6..fd34808 100644
> >> >>>> --- a/include/asm-generic/vmlinux.lds.h
> >> >>>> +++ b/include/asm-generic/vmlinux.lds.h
> >> >>>> @@ -471,9 +471,9 @@
> >> >>>>  }
> >> >>>>
> >> >>>> #ifdef CONFIG_CONSTRUCTORS
> >> >>>> -#define KERNEL_CTORS()  . = ALIGN(8);                      \
> >> >>>> -                        VMLINUX_SYMBOL(__ctors_start) = .; \
> >> >>>> -                        *(.ctors)                          \
> >> >>>> +#define KERNEL_CTORS()  . = ALIGN(8);                                   \
> >> >>>> +                        VMLINUX_SYMBOL(__ctors_start) = .;              \
> >> >>>> +                        *(CONFIG_CONSTRUCTORS_NAME)                     \
> >> >>>>                  VMLINUX_SYMBOL(__ctors_end) = .;
> >> >>>
> >> >>> What is wrong with adding both "standard" names for ctors uncnditionally?
> >> >>> Like this:
> >> >>>>                  *(.ctors)                          \
> >> >>>> +                        *(.init_array)                     \
> >> >>
> >> >> That doesn't get rid of CONFIG_CONSTRUCTORS_NAME, because it's needed
> >> >> in the module code.  Do you have a suggestion to solve that as well?
> >> >
> >> > Ping.
> >>
> >> Pinging this back to life.  I'd like to see GCOV for ARM eABI finally make it upstream.
> >> So, any objections to this?  Should it be resubmitted?
> >
> > Why is CONFIG_CONSTRUCTORS_NAME needed in module code?
> 
> Because ARM eABI uses the .init_array section for C++ constructors,
> rather than .ctors.
> So the patch defined CONFIG_CONSTRUCTORS_NAME to set the correct section name
> for ARM eABI while leaving non-ARM-eABI as before, .ctors.  Here are the changes
> from the patch for reference:
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index 6cfd71d..52181a1 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -20,6 +20,12 @@ config CONSTRUCTORS
>         bool
>         depends on !UML
> 
> +config CONSTRUCTORS_NAME
> +       string
> +       depends on CONSTRUCTORS
> +       default ".init_array" if ARM && AEABI
> +       default ".ctors"
> +
>  config HAVE_IRQ_WORK
>         bool
> 
> diff --git a/kernel/module.c b/kernel/module.c
> index 78ac6ec..e5fad5e 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2600,7 +2600,7 @@ static void find_module_sections(struct module
> *mod, struct load_info *info)
>         mod->unused_gpl_crcs = section_addr(info, "__kcrctab_unused_gpl");
>  #endif
>  #ifdef CONFIG_CONSTRUCTORS
> -       mod->ctors = section_objs(info, ".ctors",
> +       mod->ctors = section_objs(info, CONFIG_CONSTRUCTORS_NAME,
>                                   sizeof(*mod->ctors), &mod->num_ctors);
>  #endif
> 
> W/o the above, GCOV does not work on ARM eABI for kernel modules.
> Meanwhile, it still works as before for non-ARM-eABI kernel modules.
> 
> Thanks!
> 
> --
> Regards,
> George
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