Root/Documentation/coccinelle.txt

1Copyright 2010 Nicolas Palix <npalix@diku.dk>
2Copyright 2010 Julia Lawall <julia@diku.dk>
3Copyright 2010 Gilles Muller <Gilles.Muller@lip6.fr>
4
5
6 Getting Coccinelle
7~~~~~~~~~~~~~~~~~~~~
8
9The semantic patches included in the kernel use the 'virtual rule'
10feature which was introduced in Coccinelle version 0.1.11.
11
12Coccinelle (>=0.2.0) is available through the package manager
13of many distributions, e.g. :
14
15 - Debian (>=squeeze)
16 - Fedora (>=13)
17 - Ubuntu (>=10.04 Lucid Lynx)
18 - OpenSUSE
19 - Arch Linux
20 - NetBSD
21 - FreeBSD
22
23
24You can get the latest version released from the Coccinelle homepage at
25http://coccinelle.lip6.fr/
26
27Information and tips about Coccinelle are also provided on the wiki
28pages at http://cocci.ekstranet.diku.dk/wiki/doku.php
29
30Once you have it, run the following command:
31
32         ./configure
33        make
34
35as a regular user, and install it with
36
37        sudo make install
38
39The semantic patches in the kernel will work best with Coccinelle version
400.2.4 or later. Using earlier versions may incur some parse errors in the
41semantic patch code, but any results that are obtained should still be
42correct.
43
44 Using Coccinelle on the Linux kernel
45~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
46
47A Coccinelle-specific target is defined in the top level
48Makefile. This target is named 'coccicheck' and calls the 'coccicheck'
49front-end in the 'scripts' directory.
50
51Four modes are defined: patch, report, context, and org. The mode to
52use is specified by setting the MODE variable with 'MODE=<mode>'.
53
54'patch' proposes a fix, when possible.
55
56'report' generates a list in the following format:
57  file:line:column-column: message
58
59'context' highlights lines of interest and their context in a
60diff-like style.Lines of interest are indicated with '-'.
61
62'org' generates a report in the Org mode format of Emacs.
63
64Note that not all semantic patches implement all modes. For easy use
65of Coccinelle, the default mode is "chain" which tries the previous
66modes in the order above until one succeeds.
67
68To make a report for every semantic patch, run the following command:
69
70    make coccicheck MODE=report
71
72NB: The 'report' mode is the default one.
73
74To produce patches, run:
75
76    make coccicheck MODE=patch
77
78
79The coccicheck target applies every semantic patch available in the
80sub-directories of 'scripts/coccinelle' to the entire Linux kernel.
81
82For each semantic patch, a commit message is proposed. It gives a
83description of the problem being checked by the semantic patch, and
84includes a reference to Coccinelle.
85
86As any static code analyzer, Coccinelle produces false
87positives. Thus, reports must be carefully checked, and patches
88reviewed.
89
90
91 Using Coccinelle with a single semantic patch
92~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
93
94The optional make variable COCCI can be used to check a single
95semantic patch. In that case, the variable must be initialized with
96the name of the semantic patch to apply.
97
98For instance:
99
100    make coccicheck COCCI=<my_SP.cocci> MODE=patch
101or
102    make coccicheck COCCI=<my_SP.cocci> MODE=report
103
104
105 Using Coccinelle on (modified) files
106~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
107
108To apply Coccinelle on a file basis, instead of a directory basis, the
109following command may be used:
110
111    make C=1 CHECK="scripts/coccicheck"
112
113To check only newly edited code, use the value 2 for the C flag, i.e.
114
115    make C=2 CHECK="scripts/coccicheck"
116
117This runs every semantic patch in scripts/coccinelle by default. The
118COCCI variable may additionally be used to only apply a single
119semantic patch as shown in the previous section.
120
121The "chain" mode is the default. You can select another one with the
122MODE variable explained above.
123
124In this mode, there is no information about semantic patches
125displayed, and no commit message proposed.
126
127
128 Proposing new semantic patches
129~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
130
131New semantic patches can be proposed and submitted by kernel
132developers. For sake of clarity, they should be organized in the
133sub-directories of 'scripts/coccinelle/'.
134
135
136 Detailed description of the 'report' mode
137~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
138
139'report' generates a list in the following format:
140  file:line:column-column: message
141
142Example:
143
144Running
145
146    make coccicheck MODE=report COCCI=scripts/coccinelle/api/err_cast.cocci
147
148will execute the following part of the SmPL script.
149
150<smpl>
151@r depends on !context && !patch && (org || report)@
152expression x;
153position p;
154@@
155
156 ERR_PTR@p(PTR_ERR(x))
157
158@script:python depends on report@
159p << r.p;
160x << r.x;
161@@
162
163msg="ERR_CAST can be used with %s" % (x)
164coccilib.report.print_report(p[0], msg)
165</smpl>
166
167This SmPL excerpt generates entries on the standard output, as
168illustrated below:
169
170/home/user/linux/crypto/ctr.c:188:9-16: ERR_CAST can be used with alg
171/home/user/linux/crypto/authenc.c:619:9-16: ERR_CAST can be used with auth
172/home/user/linux/crypto/xts.c:227:9-16: ERR_CAST can be used with alg
173
174
175 Detailed description of the 'patch' mode
176~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
177
178When the 'patch' mode is available, it proposes a fix for each problem
179identified.
180
181Example:
182
183Running
184    make coccicheck MODE=patch COCCI=scripts/coccinelle/api/err_cast.cocci
185
186will execute the following part of the SmPL script.
187
188<smpl>
189@ depends on !context && patch && !org && !report @
190expression x;
191@@
192
193- ERR_PTR(PTR_ERR(x))
194+ ERR_CAST(x)
195</smpl>
196
197This SmPL excerpt generates patch hunks on the standard output, as
198illustrated below:
199
200diff -u -p a/crypto/ctr.c b/crypto/ctr.c
201--- a/crypto/ctr.c 2010-05-26 10:49:38.000000000 +0200
202+++ b/crypto/ctr.c 2010-06-03 23:44:49.000000000 +0200
203@@ -185,7 +185,7 @@ static struct crypto_instance *crypto_ct
204     alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
205                   CRYPTO_ALG_TYPE_MASK);
206     if (IS_ERR(alg))
207- return ERR_PTR(PTR_ERR(alg));
208+ return ERR_CAST(alg);
209 
210     /* Block size must be >= 4 bytes. */
211     err = -EINVAL;
212
213 Detailed description of the 'context' mode
214~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
215
216'context' highlights lines of interest and their context
217in a diff-like style.
218
219NOTE: The diff-like output generated is NOT an applicable patch. The
220      intent of the 'context' mode is to highlight the important lines
221      (annotated with minus, '-') and gives some surrounding context
222      lines around. This output can be used with the diff mode of
223      Emacs to review the code.
224
225Example:
226
227Running
228    make coccicheck MODE=context COCCI=scripts/coccinelle/api/err_cast.cocci
229
230will execute the following part of the SmPL script.
231
232<smpl>
233@ depends on context && !patch && !org && !report@
234expression x;
235@@
236
237* ERR_PTR(PTR_ERR(x))
238</smpl>
239
240This SmPL excerpt generates diff hunks on the standard output, as
241illustrated below:
242
243diff -u -p /home/user/linux/crypto/ctr.c /tmp/nothing
244--- /home/user/linux/crypto/ctr.c 2010-05-26 10:49:38.000000000 +0200
245+++ /tmp/nothing
246@@ -185,7 +185,6 @@ static struct crypto_instance *crypto_ct
247     alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
248                   CRYPTO_ALG_TYPE_MASK);
249     if (IS_ERR(alg))
250- return ERR_PTR(PTR_ERR(alg));
251 
252     /* Block size must be >= 4 bytes. */
253     err = -EINVAL;
254
255 Detailed description of the 'org' mode
256~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
257
258'org' generates a report in the Org mode format of Emacs.
259
260Example:
261
262Running
263    make coccicheck MODE=org COCCI=scripts/coccinelle/api/err_cast.cocci
264
265will execute the following part of the SmPL script.
266
267<smpl>
268@r depends on !context && !patch && (org || report)@
269expression x;
270position p;
271@@
272
273 ERR_PTR@p(PTR_ERR(x))
274
275@script:python depends on org@
276p << r.p;
277x << r.x;
278@@
279
280msg="ERR_CAST can be used with %s" % (x)
281msg_safe=msg.replace("[","@(").replace("]",")")
282coccilib.org.print_todo(p[0], msg_safe)
283</smpl>
284
285This SmPL excerpt generates Org entries on the standard output, as
286illustrated below:
287
288* TODO [[view:/home/user/linux/crypto/ctr.c::face=ovl-face1::linb=188::colb=9::cole=16][ERR_CAST can be used with alg]]
289* TODO [[view:/home/user/linux/crypto/authenc.c::face=ovl-face1::linb=619::colb=9::cole=16][ERR_CAST can be used with auth]]
290* TODO [[view:/home/user/linux/crypto/xts.c::face=ovl-face1::linb=227::colb=9::cole=16][ERR_CAST can be used with alg]]
291

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