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SubjectRe: [PATCH v2] coccinelle: misc: add flexible_array.cocci script


On Mon, 10 Aug 2020, Denis Efremov wrote:

> Commit 68e4cd17e218 ("docs: deprecated.rst: Add zero-length and one-element
> arrays") marks one-element and zero-length arrays as deprecated. Kernel
> code should always use "flexible array members" instead.
>
> The script warns about one-element and zero-length arrays in structs.
>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
> Signed-off-by: Denis Efremov <efremov@linux.com>
> ---
> 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.
>
> On the current master branch, the rule generates:
> - context: https://gist.github.com/evdenis/e2b4323491f9eff35376372df07f723c
> - patch: https://gist.github.com/evdenis/46081da9d68ecefd07edc3769cebcf32
>
> 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..bf6dcda1783e
> --- /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 exists@

exists is not necessary here. There are not multiple control-flow paths
through a structure declaration.

> +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"
> +coccilib.report.print_report(p[0], msg)
> +
> +@script: python depends on org@
> +p << r.p;
> +@@
> +
> +msg = "WARNING: use flexible-array member instead"
> +coccilib.org.print_todo(p, msg)

This should be coccilib.org.print_todo(p[0], msg)

julia

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