From: Denis Efremov <efremov@linux.com>
To: Julia Lawall <julia.lawall@inria.fr>
Cc: Kees Cook <keescook@chromium.org>,
"Gustavo A . R . Silva" <gustavoars@kernel.org>,
cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org
Subject: [Cocci] [RFC PATCH] coccinelle: misc: add flexible_array.cocci script
Date: Fri, 7 Aug 2020 01:03:42 +0300 [thread overview]
Message-ID: <20200806220342.25426-1-efremov@linux.com> (raw)
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>
---
Currently, it's just a draft. I've placed a number of questions in the
script and marked them as TODO. Kees, Gustavo, if you could help me with
my questions I think that this rule will be enough to close:
https://github.com/KSPP/linux/issues/76
BTW, I it's possible to not warn about files in uapi folder if
this is relevant. Do I need to do it in the script?
scripts/coccinelle/misc/flexible_array.cocci | 158 +++++++++++++++++++
1 file changed, 158 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..1e7165c79e60
--- /dev/null
+++ b/scripts/coccinelle/misc/flexible_array.cocci
@@ -0,0 +1,158 @@
+// 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
+
+@r depends on !patch@
+identifier name, size, array;
+// TODO: We can additionally restrict size and array to:
+// identifier size =~ ".*(num|len|count|size|ncpus).*";
+// identifier array !~ ".*(pad|reserved).*";
+// Do we need it?
+type TS, TA;
+position p;
+@@
+
+(
+ // This will also match: typedef struct name { ...
+ // However nested structs are not matched, i.e.:
+ // struct name1 { struct name2 { int s; int a[0]; } st; int i; }
+ // will not be matched. Do we need to handle it?
+ struct name {
+ ... // TODO: Maybe simple ... is enough? It will match structs with a
+ TS size; // single field, e.g.
+ ... // https://elixir.bootlin.com/linux/v5.8/source/arch/arm/include/uapi/asm/setup.h#L127
+(
+* TA array@p[0];
+|
+ // TODO: It seems that there are exception cases for array[1], e.g.
+ // https://elixir.bootlin.com/linux/v5.8/source/arch/powerpc/boot/rs6000.h#L152
+ // https://elixir.bootlin.com/linux/v5.8/source/include/uapi/linux/cdrom.h#L292
+ // https://elixir.bootlin.com/linux/v5.8/source/drivers/net/wireless/ath/ath6kl/usb.c#L108
+ // We could either drop array[1] checking from this rule or
+ // restrict array name with regexp and add, for example, an "allowlist"
+ // with struct names where we allow this code pattern.
+ // TODO: How to handle: u8 data[1][MAXLEN_PSTR6]; ?
+* TA array@p[1];
+)
+ };
+|
+ struct {
+ ...
+ TS size;
+ ...
+(
+* TA array@p[0];
+|
+* TA array@p[1];
+)
+ };
+|
+ // TODO: do we need to handle unions?
+ union name {
+ ...
+ TS size;
+ ...
+(
+* TA array@p[0];
+|
+* TA array@p[1];
+)
+ };
+|
+ union {
+ ...
+ TS size;
+ ...
+(
+* TA array@p[0];
+|
+* TA array@p[1];
+)
+ };
+)
+
+// FIXME: Patch mode doesn't work as expected.
+// Coccinelle handles formatting incorrectly.
+// Patch mode in this rule should be disabled until
+// proper formatting will be supported.
+@depends on patch exists@
+identifier name, size, array;
+type TS, TA;
+@@
+
+(
+ struct name {
+ ...
+ TS size;
+ ...
+(
+- TA array[0];
+|
+- TA array[1];
+)
++ TA array[];
+ };
+|
+ struct {
+ ...
+ TS size;
+ ...
+(
+- TA array[0];
+|
+- TA array[1];
+)
++ TA array[];
+ };
+|
+ union name {
+ ...
+ TS size;
+ ...
+(
+- TA array[0];
+|
+- TA array[1];
+)
++ TA array[];
+ };
+|
+ union {
+ ...
+ TS size;
+ ...
+(
+- TA array[0];
+|
+- TA array[1];
+)
++ TA array[];
+ };
+)
+
+@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)
--
2.26.2
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next reply other threads:[~2020-08-06 22:04 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-06 22:03 Denis Efremov [this message]
2020-08-07 16:18 ` [Cocci] [RFC PATCH] coccinelle: misc: add flexible_array.cocci script Gustavo A. R. Silva
2020-08-09 21:26 ` [Cocci] [PATCH v2] " Denis Efremov
2020-09-12 14:43 ` Julia Lawall
2020-09-13 6:15 ` Denis Efremov
2020-09-21 17:49 ` [Cocci] [PATCH v3] " Denis Efremov
2020-10-03 20:09 ` Julia Lawall
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