[25/26] pch_gbe: constify local structures

For structure types defined in the same file or local header files, find
top-level static structure declarations that have the following
properties:
1. Never reassigned.
2. Address never taken
3. Not passed to a top-level macro call
4. No pointer or array-typed field passed to a function or stored in a
variable.
Declare structures having all of these properties as const.

Done using Coccinelle.
Based on a suggestion by Joe Perches <joe@perches.com>.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>

---
The semantic patch seems too long for a commit log, but is in the cover
letter.

 drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Julia, I went over the networking driver patches in this series and
I have to say that I'd rather see these changes be more durable
and self-checking.

By this I mean that I want you to also make the driver private pointer
that holds these structures be const too.

Then if there are really any assignments to the objects being marked
const, it will show immediately.

Thank you.

On Sun, 11 Sep 2016, David Miller wrote:

>
> Julia, I went over the networking driver patches in this series and
> I have to say that I'd rather see these changes be more durable
> and self-checking.
>
> By this I mean that I want you to also make the driver private pointer
> that holds these structures be const too.

Sorry, I'm not sure what you are asking for.  In these cases, we often end
up with something like:

static const struct foo = { ... };

and then later

xxx.ops = foo;

So foo is protected, but its lifetime of interest is quite short.  But we
can't set the ops field of the type of xxx to be const either, because it
is obviously not - the code above modifies it.  Everything would be fine
if ops were of pointer type but not structure type, but that is not the
case in this patch series, because the semantic patch disallows &foo.
There is the __ro_after_init annotation that might help in some cases, but
I have often seen these assignments in probe functions that are not
__init.  Kees Cook mentioned some code that could be inserted before and
after an assignment to make a field temporarily writeable, but I haven't
looked into that possibility yet.

Have I misunderstood something?

thanks,
julia

> Then if there are really any assignments to the objects being marked
> const, it will show immediately.
>
> Thank you.
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On Sun, 11 Sep 2016, Julia Lawall wrote:

> For structure types defined in the same file or local header files, find
> top-level static structure declarations that have the following
> properties:
> 1. Never reassigned.
> 2. Address never taken
> 3. Not passed to a top-level macro call
> 4. No pointer or array-typed field passed to a function or stored in a
> variable.
> Declare structures having all of these properties as const.

Actually, this patch should be dropped.  Coccinelle did not recognize
kernel_ulong_t as a type, so it interpreted

(kernel_ulong_t)&pch_gbe_minnow_privdata

as a bit and operation.

julia

> Done using Coccinelle.
> Based on a suggestion by Joe Perches <joe@perches.com>.
>
> Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
>
> ---
> The semantic patch seems too long for a commit log, but is in the cover
> letter.
>
>  drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c b/drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c
> index 3cd87a4..6f33258 100644
> --- a/drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c
> +++ b/drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c
> @@ -2729,7 +2729,7 @@ static int pch_gbe_minnow_platform_init(struct pci_dev *pdev)
>  	return ret;
>  }
>
> -static struct pch_gbe_privdata pch_gbe_minnow_privdata = {
> +static const struct pch_gbe_privdata pch_gbe_minnow_privdata = {
>  	.phy_tx_clk_delay = true,
>  	.phy_disable_hibernate = true,
>  	.platform_init = pch_gbe_minnow_platform_init,
>
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From: Julia Lawall <julia.lawall@lip6.fr>
Date: Mon, 12 Sep 2016 11:07:15 +0200 (CEST)

> So foo is protected, but its lifetime of interest is quite short.  But we
> can't set the ops field of the type of xxx to be const either, because it
> is obviously not - the code above modifies it.

You can definitely make it a pointer to a const thing.

Just like "netdev_ops" in struct net_device is const.