Coccinelle: add atomic_as_refcounter script

atomic_as_refcounter.cocci script allows detecting
cases when refcount_t type and API should be used
instead of atomic_t.
Signed-off-by: NElena Reshetova <elena.reshetova@intel.com>
Acked-by: NJulia Lawall <julia.lawall@lip6.fr>
Reviewed-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

scripts/coccinelle/api/atomic_as_refcounter.cocci

+// Check if refcount_t type and API should be used
+// instead of atomic_t type when dealing with refcounters
+//
+// Copyright (c) 2016-2017, Elena Reshetova, Intel Corporation
+//
+// Confidence: Moderate
+// URL: http://coccinelle.lip6.fr/
+// Options: --include-headers --very-quiet
+
+virtual report
+
+@r1 exists@
+identifier a, x;
+position p1, p2;
+identifier fname =~ ".*free.*";
+identifier fname2 =~ ".*destroy.*";
+identifier fname3 =~ ".*del.*";
+identifier fname4 =~ ".*queue_work.*";
+identifier fname5 =~ ".*schedule_work.*";
+identifier fname6 =~ ".*call_rcu.*";
+
+@@
+
+(
+ atomic_dec_and_test@p1(&(a)->x)
+|
+ atomic_dec_and_lock@p1(&(a)->x, ...)
+|
+ atomic_long_dec_and_lock@p1(&(a)->x, ...)
+|
+ atomic_long_dec_and_test@p1(&(a)->x)
+|
+ atomic64_dec_and_test@p1(&(a)->x)
+|
+ local_dec_and_test@p1(&(a)->x)
+)
+...
+(
+ fname@p2(a, ...);
+|
+ fname2@p2(...);
+|
+ fname3@p2(...);
+|
+ fname4@p2(...);
+|
+ fname5@p2(...);
+|
+ fname6@p2(...);
+)
+
+
+@script:python depends on report@
+p1 << r1.p1;
+p2 << r1.p2;
+@@
+msg = "atomic_dec_and_test variation before object free at line %s."
+coccilib.report.print_report(p1[0], msg % (p2[0].line))
+
+@r4 exists@
+identifier a, x, y;
+position p1, p2;
+identifier fname =~ ".*free.*";
+
+@@
+
+(
+ atomic_dec_and_test@p1(&(a)->x)
+|
+ atomic_dec_and_lock@p1(&(a)->x, ...)
+|
+ atomic_long_dec_and_lock@p1(&(a)->x, ...)
+|
+ atomic_long_dec_and_test@p1(&(a)->x)
+|
+ atomic64_dec_and_test@p1(&(a)->x)
+|
+ local_dec_and_test@p1(&(a)->x)
+)
+...
+y=a
+...
+fname@p2(y, ...);
+
+
+@script:python depends on report@
+p1 << r4.p1;
+p2 << r4.p2;
+@@
+msg = "atomic_dec_and_test variation before object free at line %s."
+coccilib.report.print_report(p1[0], msg % (p2[0].line))
+
+@r2 exists@
+identifier a, x;
+position p1;
+@@
+
+(
+atomic_add_unless(&(a)->x,-1,1)@p1
+|
+atomic_long_add_unless(&(a)->x,-1,1)@p1
+|
+atomic64_add_unless(&(a)->x,-1,1)@p1
+)
+
+@script:python depends on report@
+p1 << r2.p1;
+@@
+msg = "atomic_add_unless"
+coccilib.report.print_report(p1[0], msg)
+
+@r3 exists@
+identifier x;
+position p1;
+@@
+
+(
+x = atomic_add_return@p1(-1, ...);
+|
+x = atomic_long_add_return@p1(-1, ...);
+|
+x = atomic64_add_return@p1(-1, ...);
+)
+
+@script:python depends on report@
+p1 << r3.p1;
+@@
+msg = "x = atomic_add_return(-1, ...)"
+coccilib.report.print_report(p1[0], msg)