linux-kernel - Re: [PATCH] ACPI: avoid NULL pointer arithmetic

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Message-ID: <CAJZ5v0jDKK6ecsubVDv_=EUF3goiiDW28tvbKF9cesMphgKaug@mail.gmail.com>
Date:   Thu, 30 Sep 2021 20:52:59 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Len Brown <lenb@...nel.org>, Robert Moore <robert.moore@...el.com>,
        Arnd Bergmann <arnd@...db.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Erik Kaneda <erik.kaneda@...el.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "open list:ACPI COMPONENT ARCHITECTURE (ACPICA)" <devel@...ica.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] ACPI: avoid NULL pointer arithmetic

On Wed, Sep 29, 2021 at 8:47 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Mon, Sep 27, 2021 at 2:13 PM Arnd Bergmann <arnd@...nel.org> wrote:
> >
> > From: Arnd Bergmann <arnd@...db.de>
> >
> > There are some very old macros for doing an open-coded offsetof() and
> > cast between pointer and integer in ACPI headers. clang-14 now complains
> > about these:
> >
> > drivers/acpi/acpica/tbfadt.c:86:3: error: performing pointer subtraction with a null pointer has undefined behavior [-Werror,-Wnull-pointer-subtraction]
> >          ACPI_FADT_OFFSET(pm_timer_block),
> >          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > include/acpi/actbl.h:376:47: note: expanded from macro 'ACPI_FADT_OFFSET'
> >  #define ACPI_FADT_OFFSET(f)             (u16) ACPI_OFFSET (struct acpi_table_fadt, f)
> >                                               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > include/acpi/actypes.h:511:41: note: expanded from macro 'ACPI_OFFSET'
> >  #define ACPI_OFFSET(d, f)               ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0)
> >                                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > include/acpi/actypes.h:505:79: note: expanded from macro 'ACPI_PTR_DIFF'
> >  #define ACPI_PTR_DIFF(a, b)             ((acpi_size) (ACPI_CAST_PTR (u8, (a)) - ACPI_CAST_PTR (u8, (b))))
> >                                                                               ^ ~~~~~~~~~~~~~~~~~~~~~~~
> > Convert them to the modern equivalents.
> >
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > ---
> >  include/acpi/actypes.h | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h
> > index 92c71dfce0d5..285bc7b73de3 100644
> > --- a/include/acpi/actypes.h
> > +++ b/include/acpi/actypes.h
> > @@ -507,8 +507,8 @@ typedef u64 acpi_integer;
> >  /* Pointer/Integer type conversions */
> >
> >  #define ACPI_TO_POINTER(i)              ACPI_CAST_PTR (void, (acpi_size) (i))
> > -#define ACPI_TO_INTEGER(p)              ACPI_PTR_DIFF (p, (void *) 0)
> > -#define ACPI_OFFSET(d, f)               ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0)
> > +#define ACPI_TO_INTEGER(p)              ((uintptr_t)(p))
> > +#define ACPI_OFFSET(d, f)               offsetof(d, f)
> >  #define ACPI_PHYSADDR_TO_PTR(i)         ACPI_TO_POINTER(i)
> >  #define ACPI_PTR_TO_PHYSADDR(i)         ACPI_TO_INTEGER(i)
> >
> > --
>
> Queued up as 5.16 material, converted into an upstream ACPICA pull
> request and submitted, thanks!

And reverted from there, because it introduced build issues.

Can we use alternative definitions that don't depend on uintptr_t and
offsetof()?