[PATCH v2] coccinelle: semantic code search for missing of_node_put

[Wen Yang]

There are functions which increment a reference counter for a device node.
These functions belong to a programming interface for the management
of information from device trees.
The counter must be decremented after the last usage of a device node.
We find these functions by using the following SmPL:

<SmPL>
@initialize:ocaml@
@@

let relevant_str = "use of_node_put() on it when done"

let contains s1 s2 =
    let re = Str.regexp_string s2
    in
        try ignore (Str.search_forward re s1 0); true
        with Not_found -> false

let relevant_functions = ref []

let add_function f c =
    if not (List.mem f !relevant_functions)
    then
      begin
        let s = String.concat " "
          (
            (List.map String.lowercase_ascii
              (List.filter
                (function x ->
                  Str.string_match
                  (Str.regexp "[a-zA-Z_\\(\\)][-a-zA-Z0-9_\\(\\)]*$")
                x 0) (Str.split (Str.regexp "[ .;\t\n]+") c)))) in
             if contains s relevant_str
             then
               Printf.printf "Found relevant function: %s\n" f;
               relevant_functions := f :: !relevant_functions;
      end

@r@
identifier fn;
comments c;
type T = struct device_node *;
@@

T@c fn(...) {
...
}

@script:ocaml@
f << r.fn;
c << r.c;
@@

let (cb,cm,ca) = List.hd c in
let c = String.concat " " cb in
add_function f c
</SmPL>

And this patch also looks for places where an of_node_put()
call is on some paths but not on others.

Suggested-by: Julia Lawall <Julia.Lawall@xxxxxxx>
Signed-off-by: Wen Yang <wen.yang99@xxxxxxxxxx>
Cc: Julia Lawall <Julia.Lawall@xxxxxxx>
Cc: Gilles Muller <Gilles.Muller@xxxxxxx>
Cc: Nicolas Palix <nicolas.palix@xxxxxxx>
Cc: Michal Marek <michal.lkml@xxxxxxxxxxx>
Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Cc: Markus Elfring <Markus.Elfring@xxxxxx>
Cc: cocci@xxxxxxxxxxxxxxx
---
v2: improve the commit description and delete duplicate code.

 scripts/coccinelle/free/of_node_put.cocci | 143 ++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 scripts/coccinelle/free/of_node_put.cocci

diff --git a/scripts/coccinelle/free/of_node_put.cocci b/scripts/coccinelle/free/of_node_put.cocci
new file mode 100644
index 0000000..81a9f54
--- /dev/null
+++ b/scripts/coccinelle/free/of_node_put.cocci
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+/// Find missing of_node_put
+///
+// Confidence: Moderate
+// Copyright: (C) 2018-2019 Wen Yang, ZTE.
+// Comments:
+// Options: --no-includes --include-headers
+
+virtual report
+virtual org
+
+@initialize:python@
+@@
+
+seen = set()
+
+def add_if_not_present (p1, p2):
+    if (p1, p2) not in seen:
+        seen.add((p1, p2))
+        return True
+    return False
+
+def display_report(p1, p2):
+    if add_if_not_present(p1[0].line, p2[0].line):
+       coccilib.report.print_report(p2[0],
+                                    "ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line "
+                                    + p1[0].line
+                                    + ", but without a corresponding object release within this function.")
+
+def display_org(p1, p2):
+    cocci.print_main("acquired a node pointer with refcount incremented", p1)
+    cocci.print_secs("needed of_node_put", p2)
+
+@r1 exists@
+local idexpression struct device_node *x;
+expression e, e1;
+position p1, p2;
+statement S;
+type T;
+@@
+
+x = @p1\(of_find_all_nodes\|
+         of_get_cpu_node\|
+         of_get_parent\|
+         of_get_next_parent\|
+         of_get_next_child\|
+         of_get_next_cpu_node\|
+         of_get_compatible_child\|
+         of_get_child_by_name\|
+         of_find_node_opts_by_path\|
+         of_find_node_by_name\|
+         of_find_node_by_type\|
+         of_find_compatible_node\|
+         of_find_node_with_property\|
+         of_find_matching_node_and_match\|
+         of_find_node_by_phandle\|
+         of_parse_phandle\|
+         of_find_next_cache_node\|
+         of_get_next_available_child\)(...);
+...
+if (x == NULL || ...) S
+... when != e = (T)x
+    when != true x == NULL
+    when != of_node_put(x)
+    when != of_get_next_parent(x)
+    when != of_find_matching_node(x, ...)
+    when != if (x) { ... return x; }
+    when != v4l2_async_notifier_add_fwnode_subdev(<...x...>)
+    when != e1 = of_fwnode_handle(x)
+(
+if (x) { ... when forall
+         of_node_put(x) ... }
+|
+return x;
+|
+return of_fwnode_handle(x);
+|
+return@p2 ...;
+)
+
+@script:python depends on report && r1@
+p1 << r1.p1;
+p2 << r1.p2;
+@@
+
+display_report(p1, p2)
+
+@script:python depends on org && r1@
+p1 << r1.p1;
+p2 << r1.p2;
+@@
+
+display_org(p1, p2)
+
+@r2 exists@
+local idexpression struct device_node *x;
+expression e, e1;
+position p1, p2;
+identifier f;
+statement S;
+type T;
+@@
+
+(
+x = f@p1(...);
+... when != e = (T)x
+    when != true x == NULL
+    when != of_node_put(x)
+    when != of_get_next_parent(x)
+    when != of_find_matching_node(x, ...)
+    when != if (x) { ... return x; }
+    when != v4l2_async_notifier_add_fwnode_subdev(<...x...>)
+    when != e1 = of_fwnode_handle(x)
+(
+if (x) { ... when forall
+         of_node_put(x) ... }
+|
+return x;
+|
+return of_fwnode_handle(x);
+|
+return@p2 ...;
+)
+&
+x = f(...)
+...
+if (<+...x...+>) S
+...
+of_node_put(x);
+)
+@script:python depends on report && r2@
+p1 << r2.p1;
+p2 << r2.p2;
+@@
+
+display_report(p1, p2)
+
+@script:python depends on org && r2@
+p1 << r2.p1;
+p2 << r2.p2;
+@@
+
+display_org(p1, p2)
-- 
2.9.5