coccinelle: check for casting malloc output

Casting the (void *) output of memory allocation functions before
assignment like in

	sata->cmd_hdr_tbl_offset = (void *)malloc(length + align);

is useless.

Adopt the Linux kernel script
scripts/coccinelle/api/alloc/alloc_cast.cocci.

Now 'make coccicheck' generates warnings like:

./drivers/ata/fsl_sata.c:143:29-33:
WARNING: casting value returned by memory allocation function
to (void *) is useless.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

scripts/coccinelle/api/alloc/alloc_cast.cocci

@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/// Remove casting the values returned by memory allocation functions
+/// like kmalloc, kzalloc, kmem_cache_alloc, kmem_cache_zalloc etc.
+///
+//# This makes an effort to find cases of casting of values returned by
+//# malloc, calloc, kmalloc, kmalloc_array, kmalloc_node and removes
+//# the casting as it is not required. The result in the patch case may
+//# need some reformatting.
+//
+// Confidence: High
+// Copyright: (C) 2014 Himangi Saraogi
+// Copyright: (C) 2017 Himanshu Jha
+// Comments:
+// Options: --no-includes --include-headers
+//
+
+virtual context
+virtual patch
+virtual org
+virtual report
+
+@initialize:python@
+@@
+import re
+pattern = '__'
+m = re.compile(pattern)
+
+@r1 depends on context || patch@
+type T;
+@@
+
+  (T *)
+  \(malloc\|calloc\|kmalloc\|kmalloc_array\|kmalloc_node\)(...)
+
+//----------------------------------------------------------
+//  For context mode
+//----------------------------------------------------------
+
+@script:python depends on context@
+t << r1.T;
+@@
+
+if m.search(t) != None:
+        cocci.include_match(False)
+
+@depends on context && r1@
+type r1.T;
+@@
+
+* (T *)
+  \(malloc\|calloc\|kmalloc\|kmalloc_array\|kmalloc_node\)(...)
+
+//----------------------------------------------------------
+//  For patch mode
+//----------------------------------------------------------
+
+@script:python depends on patch@
+t << r1.T;
+@@
+
+if m.search(t) != None:
+        cocci.include_match(False)
+
+@depends on patch && r1@
+type r1.T;
+@@
+
+- (T *)
+  \(malloc\|calloc\|kmalloc\|kmalloc_array\|kmalloc_node\)(...)
+
+//----------------------------------------------------------
+//  For org and report mode
+//----------------------------------------------------------
+
+@r2 depends on org || report@
+type T;
+position p;
+@@
+
+ (T@p *)
+  \(malloc\|calloc\|kmalloc\|kmalloc_array\|kmalloc_node\)(...)
+
+@script:python depends on org@
+p << r2.p;
+t << r2.T;
+@@
+
+if m.search(t) != None:
+	cocci.include_match(False)
+else:
+	coccilib.org.print_safe_todo(p[0], t)
+
+@script:python depends on report@
+p << r2.p;
+t << r2.T;
+@@
+
+if m.search(t) != None:
+	cocci.include_match(False)
+else:
+	msg="WARNING: casting value returned by memory allocation function to (%s *) is useless." % (t)
+	coccilib.report.print_report(p[0], msg)