Re: [PATCH] lib: __builtin_object_size should accept void *

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Nov 24, 2016 at 08:16:24AM +0800, Christopher Li wrote:
> A similar patch has been applied:
> 
> Chris
> 
> commit f2bf519e1da89779380fd781c0eb28aae415979d
> Author: Lance Richardson <lrichard@redhat.com>
> Date:   Wed Sep 21 10:13:58 2016 -0400
> 
>     sparse: update __builtin_object_size() prototype
> 
>     Sparse emits a large number of warnings for the linux kernel source
>     tree of the form:
>         ./arch/x86/include/asm/uaccess.h:735:18: \
>             warning: incorrect type in argument 1 (different modifiers)
>         ./arch/x86/include/asm/uaccess.h:735:18:    expected void *<noident>
>         ./arch/x86/include/asm/uaccess.h:735:18:    got void const *from
> 
>     Fix by making the first parameter to __builtin_object_size()
>     type "const void *" instead of "void *", which is consistent with GCC
>     behavior (the prototype for this builtin in GCC documentation is evidently
>     incorrect).
> 
>     Signed-off-by: Lance Richardson <lrichard@redhat.com>
>     Acked-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
>     Signed-off-by: Christopher Li <sparse@chrisli.org>

Doesn't seem to be pushed yet - at least I don't see it in master
on git://git.kernel.org/pub/scm/devel/sparse/sparse.git


> diff --git a/lib.c b/lib.c
> index d5b56b0..2d66aa0 100644
> --- a/lib.c
> +++ b/lib.c
> @@ -888,7 +888,7 @@ void declare_builtin_functions(void)
>         add_pre_buffer("extern long double __builtin_nanl(const char *);\n");
> 
>         /* And some __FORTIFY_SOURCE ones.. */
> -       add_pre_buffer ("extern __SIZE_TYPE__
> __builtin_object_size(void *, int);\n");
> +       add_pre_buffer ("extern __SIZE_TYPE__
> __builtin_object_size(const void *, int);\n");
>         add_pre_buffer ("extern void * __builtin___memcpy_chk(void *,
> const void *, __SIZE_TYPE__, __SIZE_TYPE__);\n");
>         add_pre_buffer ("extern void * __builtin___memmove_chk(void *,
> const void *, __SIZE_TYPE__, __SIZE_TYPE__);\n");
>         add_pre_buffer ("extern void * __builtin___mempcpy_chk(void *,
> const void *, __SIZE_TYPE__, __SIZE_TYPE__);\n");
> 
> 
> 
> On Thu, Nov 24, 2016 at 4:24 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > I'm seeing these warnings with current Linux:
> > ./arch/x86/include/asm/uaccess.h:705:18: warning: incorrect type in argument 1 (different modifiers)
> > ./arch/x86/include/asm/uaccess.h:705:18:    expected void *<noident>
> > ./arch/x86/include/asm/uaccess.h:705:18:    got void const *from
> >
> > Because of this code:
> >
> > static __always_inline unsigned long __must_check
> > copy_to_user(void __user *to, const void *from, unsigned long n)
> > {
> >         int sz = __compiletime_object_size(from);
> >
> > ...
> > }
> >
> > where we have
> >
> > # define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
> >
> > to fix, mark the argument as const void *.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >
> > Sorry if this has already been reported/fixed.
> >
> >  lib.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/lib.c b/lib.c
> > index d5b56b0..2d66aa0 100644
> > --- a/lib.c
> > +++ b/lib.c
> > @@ -888,7 +888,7 @@ void declare_builtin_functions(void)
> >         add_pre_buffer("extern long double __builtin_nanl(const char *);\n");
> >
> >         /* And some __FORTIFY_SOURCE ones.. */
> > -       add_pre_buffer ("extern __SIZE_TYPE__ __builtin_object_size(void *, int);\n");
> > +       add_pre_buffer ("extern __SIZE_TYPE__ __builtin_object_size(const void *, int);\n");
> >         add_pre_buffer ("extern void * __builtin___memcpy_chk(void *, const void *, __SIZE_TYPE__, __SIZE_TYPE__);\n");
> >         add_pre_buffer ("extern void * __builtin___memmove_chk(void *, const void *, __SIZE_TYPE__, __SIZE_TYPE__);\n");
> >         add_pre_buffer ("extern void * __builtin___mempcpy_chk(void *, const void *, __SIZE_TYPE__, __SIZE_TYPE__);\n");
> > --
> > MST
> > --
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