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Date: Mon, 9 Nov 2015 08:42:53 +0300
From: Dan Carpenter <dan.carpenter@...cle.com>
To: Julia Lawall <julia.lawall@...6.fr>, Joe Perches <joe@...ches.com>
Cc: kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
Kees Cook <keescook@...omium.org>, kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH] video: constify geode ops structures
On Sun, Nov 08, 2015 at 10:24:49PM +0000, Julia Lawall wrote:
> On Mon, 9 Nov 2015, Dan Carpenter wrote:
>
> > Cool. So, in grsec they use a GCC plugin to make these const
> > automatically since they only contain function pointers. There about
> > 100 struct types marked as __no_const. Kees would like to adopt the
> > grsec pluggin approach I expect. Do you have an idea how many structs
> > only contain function pointers or how many consts we would have to add
> > to get the same effect without the plugin?
>
> My list has 373 type names. In the list there are counts for good
> (already const) and bad (not const). The sum of the bad values is 2467.
> The list is below.
>
> julia
Fantastic! Thanks. We could autogenerate the list of type names and
make checkpatch.pl complain if we declared those types as non const.
I ran this command to find which functions grsec marks as __no_const.
egrep '(^ struct |^@@|__no_const;)' grsecurity-3.1-4.2.5-201511021814.patch | grep __no_const -B1 | grep -v __no_const | grep -v '^--' | cut -d @ -f 5- | cut -b 9- | cut -d ' ' -f 1
There are 60 structs declared as __no_const. For some structs they
declare a no_const version and use it as needed. Like this:
typedef struct net_device_ops __no_const net_device_ops_no_const;
grep __no_const grsecurity-3.1-4.2.5-201511021814.patch | grep typedef | cut -d ' ' -f 3
There are 32 of those.
Then I compared to see if their structs were on your list. For some
reason there quite a few one their list which are not on yours. Out
of the first 10 about half weren't on your list. cpu_cache_fns,
outer_cache_fns, psci_operations, smp_operations, omap_hwmod_soc_ops,
smp_ops_t. These are mostly different arches?
Also bit_table has in int has well as a function pointers but it is on
their list. I'm not sure why. Maybe they are marking structs const
that I don't know about.
The other trick that they do is they define structs as __do_const if
they want them to be const by default, which is pretty neat. This feels
like it should be a standard GCC feature. In the meantime we could
mark things as __do_const and print a sparse warning if it was declared
as not const.
I have attached the list of __no_const structs.
regards,
dan carpenter
View attachment "no_const" of type "text/plain" (1404 bytes)
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