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SubjectRe: [PATCH] nvdimm: constify device_type structures
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On Tue, 2017-01-24 at 18:40 -0800, Dan Williams wrote:
> On Tue, Jan 24, 2017 at 6:37 PM, Joe Perches <joe@perches.com> wrote:
> > On Wed, 2017-01-25 at 00:54 +0530, Bhumika Goyal wrote:
> > > Declare device_type structure as const as it is only stored in the
> > > type field of a device structure. This field is of type const, so add
> > > const to declaration of device_type structure.
> > >
> > > File size before:
> > > text data bss dec hex filename
> > > 19278 3199 16 22493 57dd nvdimm/namespace_devs.o
> > >
> > > File size after:
> > > text data bss dec hex filename
> > > 19929 3160 16 23105 5a41 nvdimm/namespace_devs.o
> >
> > Fine, but are you sure about the sizes?
> >
> > It seems odd the text went up 651 bytes
> > while the data went down just 39 bytes.
> >
>
> Right, the size data wasn't why I applied it. It was the general rule
> of "make function pointer data read-only whenever possible to
> eliminate a kernel attack vector".

Exactly the correct reason it's a fine patch and one
that should be applied.

> Bhumika, you might want to mention
> this as the motivating reason to apply the patch if you do more of
> these changes.

Regardless, the object sizes are still odd.

The config should be mentioned because actually,
the commonly compiles sizes reported are not correct.

with an x86-64 defconfig I get:

$ size drivers/nvdimm/namespace_devs.o*
   text    data     bss     dec     hex filename
  14615     519      16   15150    3b2e drivers/nvdimm/namespace_devs.o.new
  14439     695      16   15150    3b2e drivers/nvdimm/namespace_devs.o.old

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