Re: [PATCH v3] coccinelle: misc: add flexible_array.cocci script

[Julia Lawall]

On Mon, 21 Sep 2020, Denis Efremov wrote:

> One-element and zero-length arrays are deprecated [1]. Kernel
> code should always use "flexible array members" instead, except
> for existing uapi definitions.
>
> The script warns about one-element and zero-length arrays in structs.
>
> [1] commit 68e4cd17e218 ("docs: deprecated.rst: Add zero-length and
>     one-element arrays")
>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
> Signed-off-by: Denis Efremov <efremov@xxxxxxxxx>

Applied, thanks.


> ---
> Changes in v2:
>  - all uapi headers are now filtered-out. Unfortunately, coccinelle
>    doesn't provide structure names in Location.current_element.
>    For structures the field is always "something_else". Thus, there is
>    no easy way to create a list of existing structures in uapi headers
>    and suppress the warning only for them, but not for the newly added
>    uapi structures.
>  - The pattern doesn't require 2+ fields in a structure/union anymore.
>    Now it also checks single field structures/unions.
>  - The pattern simplified and now uses disjuction in array elements
>    (Thanks, Markus)
>  - Unions are removed from patch mode
>  - one-element arrays are removed from patch mode. Correct patch may
>    involve turning the array to a simple field instead of a flexible
>    array.
> Changes in v3:
>  - exists removed from "depends on patch"
>  - position argument fixed in org mode
>  - link to the online documentation added to the warning message
>
>  scripts/coccinelle/misc/flexible_array.cocci | 88 ++++++++++++++++++++
>  1 file changed, 88 insertions(+)
>  create mode 100644 scripts/coccinelle/misc/flexible_array.cocci
>
> diff --git a/scripts/coccinelle/misc/flexible_array.cocci b/scripts/coccinelle/misc/flexible_array.cocci
> new file mode 100644
> index 000000000000..947fbaff82a9
> --- /dev/null
> +++ b/scripts/coccinelle/misc/flexible_array.cocci
> @@ -0,0 +1,88 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +///
> +/// Zero-length and one-element arrays are deprecated, see
> +/// Documentation/process/deprecated.rst
> +/// Flexible-array members should be used instead.
> +///
> +//
> +// Confidence: High
> +// Copyright: (C) 2020 Denis Efremov ISPRAS.
> +// Comments:
> +// Options: --no-includes --include-headers
> +
> +virtual context
> +virtual report
> +virtual org
> +virtual patch
> +
> +@initialize:python@
> +@@
> +def relevant(positions):
> +    for p in positions:
> +        if "uapi" in p.file:
> +             return False
> +    return True
> +
> +@r depends on !patch@
> +identifier name, array;
> +type T;
> +position p : script:python() { relevant(p) };
> +@@
> +
> +(
> +  struct name {
> +    ...
> +*   T array@p[\(0\|1\)];
> +  };
> +|
> +  struct {
> +    ...
> +*   T array@p[\(0\|1\)];
> +  };
> +|
> +  union name {
> +    ...
> +*   T array@p[\(0\|1\)];
> +  };
> +|
> +  union {
> +    ...
> +*   T array@p[\(0\|1\)];
> +  };
> +)
> +
> +@depends on patch@
> +identifier name, array;
> +type T;
> +position p : script:python() { relevant(p) };
> +@@
> +
> +(
> +  struct name {
> +    ...
> +    T array@p[
> +-       0
> +    ];
> +  };
> +|
> +  struct {
> +    ...
> +    T array@p[
> +-       0
> +    ];
> +  };
> +)
> +
> +@script: python depends on report@
> +p << r.p;
> +@@
> +
> +msg = "WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays)"
> +coccilib.report.print_report(p[0], msg)
> +
> +@script: python depends on org@
> +p << r.p;
> +@@
> +
> +msg = "WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays)"
> +coccilib.org.print_todo(p[0], msg)
> --
> 2.26.2
>
>