linux-kernel - Re: [Devel] Re: [PATCH] ACPICA: fix UBSAN warning using __builtin

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Date:   Thu, 11 Jun 2020 10:06:19 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     "Kaneda, Erik" <erik.kaneda@...el.com>
Cc:     Jung-uk Kim <jkim@...ebsd.org>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "glider@...gle.com" <glider@...gle.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "pcc@...gle.com" <pcc@...gle.com>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "will@...nel.org" <will@...nel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "devel@...ica.org" <devel@...ica.org>
Subject: Re: [Devel] Re: [PATCH] ACPICA: fix UBSAN warning using __builtin_offsetof

On Thu, Jun 11, 2020 at 9:45 AM Kaneda, Erik <erik.kaneda@...el.com> wrote:
>
> > From: Jung-uk Kim <jkim@...eBSD.org>
> >
> > Actually, I think we should let platform-specific acfoo.h decide what to
> > do here, i.e.,
>
> That's a better solution. For Linux, it would look something like this:
>
> --- a/include/acpi/actypes.h
> +++ b/include/acpi/actypes.h
> @@ -508,10 +508,15 @@ typedef u64 acpi_integer;
>
>  #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_PHYSADDR_TO_PTR(i)         ACPI_TO_POINTER(i)
>  #define ACPI_PTR_TO_PHYSADDR(i)         ACPI_TO_INTEGER(i)
>
> +/* Platforms may want to define their own ACPI_OFFSET */
> +
> +#ifndef ACPI_OFFSET
> +#define ACPI_OFFSET(d, f)               ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0)
> +#endif
> +
>  /* Optimizations for 4-character (32-bit) acpi_name manipulation */
>
>  #ifndef ACPI_MISALIGNMENT_NOT_SUPPORTED
> diff --git a/include/acpi/platform/aclinux.h b/include/acpi/platform/aclinux.h
> index 987e2af7c335..5d1ca6015fce 100644
> --- a/include/acpi/platform/aclinux.h
> +++ b/include/acpi/platform/aclinux.h
> @@ -71,6 +71,11 @@
>  #undef ACPI_DEBUG_DEFAULT
>  #define ACPI_DEBUG_DEFAULT          (ACPI_LV_INFO | ACPI_LV_REPAIR)
>
> +/* Use gcc's builtin offset instead of the default */
> +
> +#undef ACPI_OFFSET
> +#define ACPI_OFFSET(a,b)            __builtin_offsetof(a,b)
> +
>  #ifndef CONFIG_ACPI
>

Looks good at first glance.  Wouldn't actypes.h need to include
platform/acenv.h first though?  Otherwise you put some header
inclusion order dependency on folks who include actypes.h to first
include acenv.h otherwise we're not getting the definition in terms of
__builtin_offsetof.

-- 
Thanks,
~Nick Desaulniers