Re: [Cocci] linux-kernel janitorial RFP: Mark static arrays as const

[Mansour Moufid <mansourmoufid@gmail.com>]

On Tue, Mar 2, 2021 at 4:22 PM Joe Perches <joe@perches.com> wrote:
>
> Here is a possible opportunity to reduce data usage in the kernel.
>
> $ git grep -P -n '^static\s+(?!const|struct)(?:\w+\s+){1,3}\w+\s*\[\s*\]' drivers/ | \
>   grep -v __initdata | \
>   wc -l
> 3250
>
> Meaning there are ~3000 declarations of arrays with what appears to be
> file static const content that are not marked const.
>
> So there are many static arrays that could be marked const to move the
> compiled object code from data to text minimizing the total amount of
> exposed r/w data.
>
> However, I do not know of a mechanism using coccinelle to determine
> whether or not any of these static declarations are ever modified.

I thought it would be a fun exercise but it got tedious quick.

I don't know how to ignore an attribute like __initdata.

Feel free to refine it:


@@
type t;
identifier x;
@@
(
    static const struct { ... } x[];
|
    static
+   const
    struct { ... } x[];
|
    static const struct s *x[];
|
    static
+   const
    struct s *x[];
|
    static const struct s x[];
|
    static
+   const
    struct s x[];
|
    static const t *x[];
|
    static
+   const
    t *x[];
|
    static const t x[];
|
    static
+   const
    t x[];
)

@@
type t;
identifier s, x, y, z;
assignment operator xx;
@@
(
    static const struct { ... } x[] = { ... };
|
    static
+   const
    struct { ... } x[] = { ... };
|
    static const struct s *x[] = { ... };
|
    static
+   const
    struct s *x[] = { ... };
|
    static const struct s x[] = { ... };
|
    static
+   const
    struct s x[] = { ... };
|
    static const t *x[] = { ... };
|
    static
+   const
    t *x[] = { ... };
|
    static const t x[] = { ... };
|
    static
+   const
    t x[] = { ... };
)
    ... when != x.y xx ...
        when != x[...] xx ...
        when != z = x
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