# RE: \[Devel\] Re: \[PATCH\] ACPICA: fix UBSAN warning using \_\_builtin\_offsetof

- From: Kaneda, Erik \<hidden\>
- Date: 2020-06-16 21:39:38 
- List: linux-arm-kernel
- Page: https://ratatoskr.run/linux-arm-kernel/2020/06/6001653
- Thread: https://ratatoskr.run/linux-arm-kernel/2020/05/5973580/t.md

```text


> -----Original Message-----
> From: Nick Desaulniers <ndesaulniers@google.com>
> Sent: Thursday, June 11, 2020 10:06 AM
> To: Kaneda, Erik <redacted>
> Cc: Jung-uk Kim <redacted>; Wysocki, Rafael J
> [ref]; Ard Biesheuvel [ref];
> dvyukov@google.com; glider@google.com; linux-arm-
> kernel@lists.infradead.org; linux-kernel@vger.kernel.org;
> lorenzo.pieralisi@arm.com; mark.rutland@arm.com; pcc@google.com;
> rjw@rjwysocki.net; will@kernel.org; stable@vger.kernel.org; linux-
> acpi@vger.kernel.org; devel@acpica.org
> Subject: Re: [Devel] Re: [PATCH] ACPICA: fix UBSAN warning using
> __builtin_offsetof
> 
> On Thu, Jun 11, 2020 at 9:45 AM Kaneda, Erik [ref]
> wrote:
> >
> > > From: Jung-uk Kim <redacted>
> > >
> > > 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
> >
> 
Hi,

Sorry about the delayed response.

> 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.

Actypes.h is intended for ACPICA use. For files using ACPI_OFFSET, they include headers like acpi.h that ends up including aclinux.h before including actypes.h. For those using ACPI_OFFSET, precedence will be given to the definition in aclinux.h before falling back to the definition in actypes.

Erik

> 
> --
> Thanks,
> ~Nick Desaulniers
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