[RFC PATCH] coccinelle: misc: add uninitialized_var.cocci script

[Denis Efremov <efremov@linux.com>]

Commit 63a0895d960a ("compiler: Remove uninitialized_var() macro") and
commit 4b19bec97c88 ("docs: deprecated.rst: Add uninitialized_var()")
removed uninitialized_var() and deprecated it.

The purpose of this script is to prevent new occurrences of open-coded
variants of uninitialized_var().

Cc: Kees Cook <keescook@chromium.org>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Denis Efremov <efremov@linux.com>
---
List of warnings:
./lib/glob.c:48:31-39: WARNING: this kind of initialization is deprecated
./tools/testing/selftests/vm/userfaultfd.c:349:15-22: WARNING: this kind of initialization is deprecated
./drivers/block/drbd/drbd_vli.h:330:5-9: WARNING: this kind of initialization is deprecated
./drivers/char/hw_random/intel-rng.c:333:15-18: WARNING: this kind of initialization is deprecated
./drivers/gpu/drm/nouveau/nvkm/subdev/instmem/nv50.c:316:7-10: WARNING: this kind of initialization is deprecated
./arch/x86/include/asm/paravirt_types.h:455:15-20: WARNING: this kind of initialization is deprecated
./arch/x86/include/asm/paravirt_types.h:455:30-35: WARNING: this kind of initialization is deprecated
./arch/x86/include/asm/paravirt_types.h:455:45-50: WARNING: this kind of initialization is deprecated
./arch/x86/include/asm/paravirt_types.h:475:15-20: WARNING: this kind of initialization is deprecated
./arch/x86/include/asm/paravirt_types.h:475:30-35: WARNING: this kind of initialization is deprecated
./arch/x86/include/asm/paravirt_types.h:476:2-7: WARNING: this kind of initialization isdeprecated
./arch/x86/include/asm/paravirt_types.h:476:17-22: WARNING: this kind of initialization is deprecated
./arch/x86/include/asm/paravirt_types.h:476:32-37: WARNING: this kind of initialization is deprecated

 .../coccinelle/misc/uninitialized_var.cocci   | 51 +++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 scripts/coccinelle/misc/uninitialized_var.cocci

diff --git a/scripts/coccinelle/misc/uninitialized_var.cocci b/scripts/coccinelle/misc/uninitialized_var.cocci
new file mode 100644
index 000000000000..e4787bc6ab9c
--- /dev/null
+++ b/scripts/coccinelle/misc/uninitialized_var.cocci
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0-only
+///
+/// uninitialized_var() and its open-coded variations are
+/// deprecated. For details, see:
+/// Documentation/process/deprecated.rst
+///
+// Confidence: High
+// Copyright: (C) 2020 Denis Efremov ISPRAS
+// Options: --no-includes --include-headers
+//
+
+virtual context
+virtual report
+virtual org
+
+@r@
+identifier var;
+type T;
+position p;
+@@
+
+(
+* T var@p = var;
+|
+* T var@p = *(&(var));
+//|
+// TODO: Actually, I'm not sure about this pattern.
+// Looks like it's used in wireless drivers to determine
+// whether data belongs to the driver or not.
+// Here are all matches:
+// https://elixir.bootlin.com/linux/latest/source/net/mac802154/util.c#L14
+// https://elixir.bootlin.com/linux/latest/source/drivers/staging/wlan-ng/cfg80211.c#L48
+// https://elixir.bootlin.com/linux/latest/source/drivers/net/wireless/intersil/orinoco/cfg.c#L21
+// https://elixir.bootlin.com/linux/latest/source/net/mac80211/util.c#L37
+// https://elixir.bootlin.com/linux/latest/source/drivers/net/wireless/rndis_wlan.c#L544
+// * T *var@p = &var;
+)
+
+@script:python depends on report@
+p << r.p;
+@@
+
+coccilib.report.print_report(p[0],
+  "WARNING: this kind of initialization is deprecated")
+
+@script:python depends on org@
+p << r.p;
+@@
+
+coccilib.org.print_todo(p[0],
+  "WARNING: this kind of initialization is deprecated")
-- 
2.26.2