linux-kernel - Re: [PATCH] drivers/irqchip: Remove function callback casts

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Message-ID: <20200524160626.GA30346@ubuntu>
Date:   Sun, 24 May 2020 18:06:26 +0200
From:   Oscar Carter <oscar.carter@....com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Oscar Carter <oscar.carter@....com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/irqchip: Remove function callback casts

Hi Marc,

On Sun, May 24, 2020 at 12:46:34PM +0100, Marc Zyngier wrote:
> On Sun, 24 May 2020 10:09:10 +0200
> Oscar Carter <oscar.carter@....com> wrote:
>
> Hi Oscar,
>
> Thanks for this. Comments below.
>
> > In an effort to enable -Wcast-function-type in the top-level Makefile to
> > support Control Flow Integrity builds, remove all the function callback
> > casts.
> >
> > To do this, modify the IRQCHIP_ACPI_DECLARE macro initializing the
> > acpi_probe_entry struct directly instead of use the existent macro
> > ACPI_DECLARE_PROBE_ENTRY.
> >
> > In this new initialization use the probe_subtbl field instead of the
> > probe_table field use in the ACPI_DECLARE_PROBE_ENTRY macro.
>
> Please add *why* this is a valid transformation (probe_table and
> probe_subtbl are part of a union).

Ok, I will add a more detailed explanation.

> > Signed-off-by: Oscar Carter <oscar.carter@....com>
> > ---
> >  include/linux/irqchip.h | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/irqchip.h b/include/linux/irqchip.h
> > index 950e4b2458f0..1f464fd10df0 100644
> > --- a/include/linux/irqchip.h
> > +++ b/include/linux/irqchip.h
> > @@ -39,8 +39,14 @@
> >   * @fn: initialization function
> >   */
> >  #define IRQCHIP_ACPI_DECLARE(name, subtable, validate, data, fn)	\
> > -	ACPI_DECLARE_PROBE_ENTRY(irqchip, name, ACPI_SIG_MADT, 		\
> > -				 subtable, validate, data, fn)
> > +	static const struct acpi_probe_entry __acpi_probe_##name	\
> > +		__used __section(__irqchip_acpi_probe_table) = {	\
> > +			.id = ACPI_SIG_MADT,				\
> > +			.type = subtable,				\
> > +			.subtable_valid = validate,			\
> > +			.probe_subtbl = (acpi_tbl_entry_handler)fn,	\
> > +			.driver_data = data,				\
> > +		}
> >
>
> I'd rather you add an ACPI_DECLARE_SUBTABLE_PROBE_ENTRY to acpi.h, and
> use that here so that we can keep the ACPI gunk in a single place.

Ok, I will do the changes you suggested and I will resend a new version.
Later, I will also send a series to clean up the checkpatch warnings and
errors for the acpi.h header.

> >  #ifdef CONFIG_IRQCHIP
> >  void irqchip_init(void);
> > --
> > 2.20.1
> >
> >
>
> Thanks,
>
> 	M.
> --
> Jazz is not dead. It just smells funny...

Thanks,
Oscar Carter