coccinelle: Add script to find cases of missing locks

This script finds cases of missing locks in the code.
There is some possibilty of false positives in cases
where a particular function is supposed to exit with
the lock held or there is any preceding function call
that releases the lock.

Suggested-by: Julia Lawall <[email protected]>
Signed-off-by: Himanshu Jha <[email protected]>

Author: himanshujha199640

scripts/coccinelle/mini_lock.cocci

@@ -0,0 +1,102 @@
+/// Find missing unlocks.  This semantic match considers the specific case
+/// where the unlock is missing from an if branch, and there is a lock
+/// before the if and an unlock after the if.  False positives are due to
+/// cases where the if branch represents a case where the function is
+/// supposed to exit with the lock held, or where there is some preceding
+/// function call that releases the lock.
+///
+// Confidence: Moderate
+// Copyright: (C) 2010-2012 Nicolas Palix.  GPLv2.
+// Copyright: (C) 2010-2012 Julia Lawall, INRIA/LIP6.  GPLv2.
+// Copyright: (C) 2010-2012 Gilles Muller, INRIA/LiP6.  GPLv2.
+// URL: http://coccinelle.lip6.fr/
+
+virtual context
+virtual org
+virtual report
+
+@prelocked depends on !(file in "ext")@
+position p1,p;
+expression E1;
+@@
+
+(
+irq_lock@p1
+|
+k_mutex_lock@p1
+|
+k_sem_take@p1
+|
+k_spin_lock@p1
+) (E1@p,...);
+
+@looped depends on !(file in "ext")@
+position r;
+@@
+
+for(...;...;...) { <+... return@r ...; ...+> }
+
+@balanced exists@
+position p1 != prelocked.p1;
+position prelocked.p;
+position pif;
+identifier lock,unlock;
+expression x <= prelocked.E1;
+expression E,prelocked.E1;
+expression E2;
+@@
+
+if (E) {
+ ... when != E1
+ lock(E1@p,...)
+ ... when any
+}
+... when != E1
+    when != \(x = E2\|&x\)
+if@pif (E) {
+ ... when != E1
+ unlock@p1(E1,...)
+ ... when any
+}
+
+@err depends on !(file in "ext") exists@
+expression E1;
+position prelocked.p,balanced.pif;
+position up != prelocked.p1;
+position r!=looped.r;
+identifier lock,unlock;
+statement S1,S2;
+@@
+
+*lock(E1@p,...);
+... when != E1
+    when any
+    when != if@pif (...) S1
+if (...) {
+  ... when != E1
+      when != if@pif (...) S2
+*  return@r ...;
+}
+... when != E1
+    when any
+*unlock@up(E1,...);
+
+@script:python depends on org@
+p << prelocked.p1;
+lock << err.lock;
+unlock << err.unlock;
+p2 << err.r;
+@@
+
+cocci.print_main(lock,p)
+cocci.print_secs(unlock,p2)
+
+@script:python depends on report@
+p << prelocked.p1;
+lock << err.lock;
+unlock << err.unlock;
+p2 << err.r;
+@@
+
+msg = "preceding lock on line %s" % (p[0].line)
+coccilib.report.print_report(p2[0],msg)