Re: [PATCH] coccinelle: api: add kvmalloc script

Re: [PATCH] coccinelle: api: add kvmalloc script

[Julia Lawall]

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On Mon, 3 Aug 2020, Markus Elfring wrote:

> …
> > +++ b/scripts/coccinelle/api/kvmalloc.cocci
> …
> > +@opportunity depends on !patch@
> > +expression E, E1, size;
> > +position p;
> > +@@
> > +
> > +(
> …
> > +|
> > +* E = \(kmalloc\|kzalloc\|kcalloc\|kmalloc_node\|kzalloc_node\|
> > +*       kmalloc_array\|kmalloc_array_node\|kcalloc_node\)(..., size, ...)
> > +  ... when != E = E1
> > +      when != size = E1
> > +      when any
> > +* if (\(!E\|E == NULL\))@p {

Actually, you shouldn't need both E == NULL and !E.  E == NULL should be
sufficient.

julia

> …
>
> I suggest to extend the SmPL code exclusion specification so that
> pointer dereferences will be filtered out before the shown null pointer detection.
>
>
> > +@depends on patch@
> > +expression E, E1, flags, size, node;
> > +identifier x;
> > +type T;
> > +@@
> > +
> > +(
> > +- if (\(size <= E1\|size < E1\|size == E1\|size > E1\))
>
> This condition check is repeated a few times.
> Thus I imagine that the usage of another metavariable with a SmPL constraint
> can eventually be helpful.
>
> +binary operator bo = {<=, <, ==, >};
> …
> +-if (size bo E1)
>
>
>
> > +-    E = kmalloc(size, flags);
> > +- else
> > +-    E = vmalloc(size);
>
> Will it be interesting to support also the use of conditional operators
> by another part of a SmPL disjunction?
>
> -E = (…) ? kmalloc(size, flags) : vmalloc(size);
>
>
> > ++ E = kvmalloc(size, flags);
> > +|
> > +- E = kmalloc(size, flags | __GFP_NOWARN);
> > +- if (\(!E\|E == NULL\))
> > +-   E = vmalloc(size);
> > ++ E = kvmalloc(size, flags);
>
> This source code replacement line is repeated. Thus I imagine
> that it would be nice if such SmPL code duplication could be avoided
> by the application of another SmPL disjunction.
> Unfortunately, the software “Coccinelle 1.0.8-00146-g04f36d53” presents
> the error message “15: no available token to attach to” then.
> Would you like to adjust anything in this area?
>
> Regards,
> Markus
>

[PATCH] coccinelle: api: add kvmalloc script

[Denis Efremov]

Suggest kvmalloc instead of opencoded kmalloc && vmalloc condition.

Signed-off-by: Denis Efremov <efremov@linux.com>
---

If coccinelle fails with "Segmentation fault" during analysis, then
one needs to increase stack limit, e.g. ulimit -s 32767.

Current, I've sent only one patch for this rule and will send the rest
after the merge window. https://lkml.org/lkml/2020/7/31/986

 scripts/coccinelle/api/kvmalloc.cocci | 127 ++++++++++++++++++++++++++
 1 file changed, 127 insertions(+)
 create mode 100644 scripts/coccinelle/api/kvmalloc.cocci

diff --git a/scripts/coccinelle/api/kvmalloc.cocci b/scripts/coccinelle/api/kvmalloc.cocci
new file mode 100644
index 000000000000..76d6aeab7c09
--- /dev/null
+++ b/scripts/coccinelle/api/kvmalloc.cocci
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0-only
+///
+/// Find conditions in code for kmalloc/vmalloc calls.
+/// Suggest to use kvmalloc instead.
+///
+// Confidence: High
+// Copyright: (C) 2020 Denis Efremov ISPRAS
+// Options: --no-includes --include-headers
+//
+
+virtual patch
+virtual report
+virtual org
+virtual context
+
+@opportunity depends on !patch@
+expression E, E1, size;
+position p;
+@@
+
+(
+* if (\(size <= E1\|size < E1\|size == E1\|size > E1\) || ...)@p {
+    ...
+*    E = \(kmalloc\|kzalloc\|kcalloc\|kmalloc_node\|kzalloc_node\|
+*          kmalloc_array\|kmalloc_array_node\|kcalloc_node\)(..., size, ...)
+    ...
+  } else {
+    ...
+*    E = \(vmalloc\|vzalloc\|vmalloc_node\|vzalloc_node\)(..., size, ...)
+    ...
+  }
+|
+* E = \(kmalloc\|kzalloc\|kcalloc\|kmalloc_node\|kzalloc_node\|
+*       kmalloc_array\|kmalloc_array_node\|kcalloc_node\)(..., size, ...)
+  ... when != E = E1
+      when != size = E1
+      when any
+* if (\(!E\|E == NULL\))@p {
+    ...
+*   E = \(vmalloc\|vzalloc\|vmalloc_node\|vzalloc_node\)(..., size, ...)
+    ...
+  }
+)
+
+@depends on patch@
+expression E, E1, flags, size, node;
+identifier x;
+type T;
+@@
+
+(
+- if (\(size <= E1\|size < E1\|size == E1\|size > E1\))
+-    E = kmalloc(size, flags);
+- else
+-    E = vmalloc(size);
++ E = kvmalloc(size, flags);
+|
+- E = kmalloc(size, flags | __GFP_NOWARN);
+- if (\(!E\|E == NULL\))
+-   E = vmalloc(size);
++ E = kvmalloc(size, flags);
+|
+- T x = kmalloc(size, flags | __GFP_NOWARN);
+- if (\(!x\|x == NULL\))
+-   x = vmalloc(size);
++ T x = kvmalloc(size, flags);
+|
+- if (\(size <= E1\|size < E1\|size == E1\|size > E1\))
+-    E = kzalloc(size, flags);
+- else
+-    E = vzalloc(size);
++ E = kvzalloc(size, flags);
+|
+- E = kzalloc(size, flags | __GFP_NOWARN);
+- if (\(!E\|E == NULL\))
+-   E = vzalloc(size);
++ E = kvzalloc(size, flags);
+|
+- T x = kzalloc(size, flags | __GFP_NOWARN);
+- if (\(!x\|x == NULL\))
+-   x = vzalloc(size);
++ T x = kvzalloc(size, flags);
+|
+- if (\(size <= E1\|size < E1\|size == E1\|size > E1\))
+-    E = kmalloc_node(size, flags, node);
+- else
+-    E = vmalloc_node(size, node);
++ E = kvmalloc_node(size, flags, node);
+|
+- E = kmalloc_node(size, flags | __GFP_NOWARN, node);
+- if (\(!E\|E == NULL\))
+-   E = vmalloc_node(size, node);
++ E = kvmalloc_node(size, flags, node);
+|
+- T x = kmalloc_node(size, flags | __GFP_NOWARN, node);
+- if (\(!x\|x == NULL\))
+-   x = vmalloc_node(size, node);
++ T x = kvmalloc_node(size, flags, node);
+|
+- if (\(size <= E1\|size < E1\|size == E1\|size > E1\))
+-    E = kvzalloc_node(size, flags, node);
+- else
+-    E = vzalloc_node(size, node);
++ E = kvzalloc_node(size, flags, node);
+|
+- E = kvzalloc_node(size, flags | __GFP_NOWARN, node);
+- if (\(!E\|E == NULL\))
+-   E = vzalloc_node(size, node);
++ E = kvzalloc_node(size, flags, node);
+|
+- T x = kvzalloc_node(size, flags | __GFP_NOWARN, node);
+- if (\(!x\|x == NULL\))
+-   x = vzalloc_node(size, node);
++ T x = kvzalloc_node(size, flags, node);
+)
+
+@script: python depends on report@
+p << opportunity.p;
+@@
+
+coccilib.report.print_report(p[0], "WARNING: opportunity for kvmalloc")
+
+@script: python depends on org@
+p << opportunity.p;
+@@
+
+coccilib.org.print_todo(p[0], "WARNING: opportunity for kvmalloc")
-- 
2.26.2