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 Controlling Which Files are Processed by Coccinelle
106~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
107By default the entire kernel source tree is checked.
108
109To apply Coccinelle to a specific directory, M= can be used.
110For example, to check drivers/net/wireless/ one may write:
111
112    make coccicheck M=drivers/net/wireless/
113    
114To apply Coccinelle on a file basis, instead of a directory basis, the
115following command may be used:
116
117    make C=1 CHECK="scripts/coccicheck"
118
119To check only newly edited code, use the value 2 for the C flag, i.e.
120
121    make C=2 CHECK="scripts/coccicheck"
122
123This runs every semantic patch in scripts/coccinelle by default. The
124COCCI variable may additionally be used to only apply a single
125semantic patch as shown in the previous section.
126
127The "chain" mode is the default. You can select another one with the
128MODE variable explained above.
129
130In this mode, there is no information about semantic patches
131displayed, and no commit message proposed.
132
133
134 Proposing new semantic patches
135~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
136
137New semantic patches can be proposed and submitted by kernel
138developers. For sake of clarity, they should be organized in the
139sub-directories of 'scripts/coccinelle/'.
140
141
142 Detailed description of the 'report' mode
143~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
144
145'report' generates a list in the following format:
146  file:line:column-column: message
147
148Example:
149
150Running
151
152    make coccicheck MODE=report COCCI=scripts/coccinelle/api/err_cast.cocci
153
154will execute the following part of the SmPL script.
155
156<smpl>
157@r depends on !context && !patch && (org || report)@
158expression x;
159position p;
160@@
161
162 ERR_PTR@p(PTR_ERR(x))
163
164@script:python depends on report@
165p << r.p;
166x << r.x;
167@@
168
169msg="ERR_CAST can be used with %s" % (x)
170coccilib.report.print_report(p[0], msg)
171</smpl>
172
173This SmPL excerpt generates entries on the standard output, as
174illustrated below:
175
176/home/user/linux/crypto/ctr.c:188:9-16: ERR_CAST can be used with alg
177/home/user/linux/crypto/authenc.c:619:9-16: ERR_CAST can be used with auth
178/home/user/linux/crypto/xts.c:227:9-16: ERR_CAST can be used with alg
179
180
181 Detailed description of the 'patch' mode
182~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
183
184When the 'patch' mode is available, it proposes a fix for each problem
185identified.
186
187Example:
188
189Running
190    make coccicheck MODE=patch COCCI=scripts/coccinelle/api/err_cast.cocci
191
192will execute the following part of the SmPL script.
193
194<smpl>
195@ depends on !context && patch && !org && !report @
196expression x;
197@@
198
199- ERR_PTR(PTR_ERR(x))
200+ ERR_CAST(x)
201</smpl>
202
203This SmPL excerpt generates patch hunks on the standard output, as
204illustrated below:
205
206diff -u -p a/crypto/ctr.c b/crypto/ctr.c
207--- a/crypto/ctr.c 2010-05-26 10:49:38.000000000 +0200
208+++ b/crypto/ctr.c 2010-06-03 23:44:49.000000000 +0200
209@@ -185,7 +185,7 @@ static struct crypto_instance *crypto_ct
210     alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
211                   CRYPTO_ALG_TYPE_MASK);
212     if (IS_ERR(alg))
213- return ERR_PTR(PTR_ERR(alg));
214+ return ERR_CAST(alg);
215 
216     /* Block size must be >= 4 bytes. */
217     err = -EINVAL;
218
219 Detailed description of the 'context' mode
220~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
221
222'context' highlights lines of interest and their context
223in a diff-like style.
224
225NOTE: The diff-like output generated is NOT an applicable patch. The
226      intent of the 'context' mode is to highlight the important lines
227      (annotated with minus, '-') and gives some surrounding context
228      lines around. This output can be used with the diff mode of
229      Emacs to review the code.
230
231Example:
232
233Running
234    make coccicheck MODE=context COCCI=scripts/coccinelle/api/err_cast.cocci
235
236will execute the following part of the SmPL script.
237
238<smpl>
239@ depends on context && !patch && !org && !report@
240expression x;
241@@
242
243* ERR_PTR(PTR_ERR(x))
244</smpl>
245
246This SmPL excerpt generates diff hunks on the standard output, as
247illustrated below:
248
249diff -u -p /home/user/linux/crypto/ctr.c /tmp/nothing
250--- /home/user/linux/crypto/ctr.c 2010-05-26 10:49:38.000000000 +0200
251+++ /tmp/nothing
252@@ -185,7 +185,6 @@ static struct crypto_instance *crypto_ct
253     alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
254                   CRYPTO_ALG_TYPE_MASK);
255     if (IS_ERR(alg))
256- return ERR_PTR(PTR_ERR(alg));
257 
258     /* Block size must be >= 4 bytes. */
259     err = -EINVAL;
260
261 Detailed description of the 'org' mode
262~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
263
264'org' generates a report in the Org mode format of Emacs.
265
266Example:
267
268Running
269    make coccicheck MODE=org COCCI=scripts/coccinelle/api/err_cast.cocci
270
271will execute the following part of the SmPL script.
272
273<smpl>
274@r depends on !context && !patch && (org || report)@
275expression x;
276position p;
277@@
278
279 ERR_PTR@p(PTR_ERR(x))
280
281@script:python depends on org@
282p << r.p;
283x << r.x;
284@@
285
286msg="ERR_CAST can be used with %s" % (x)
287msg_safe=msg.replace("[","@(").replace("]",")")
288coccilib.org.print_todo(p[0], msg_safe)
289</smpl>
290
291This SmPL excerpt generates Org entries on the standard output, as
292illustrated below:
293
294* TODO [[view:/home/user/linux/crypto/ctr.c::face=ovl-face1::linb=188::colb=9::cole=16][ERR_CAST can be used with alg]]
295* TODO [[view:/home/user/linux/crypto/authenc.c::face=ovl-face1::linb=619::colb=9::cole=16][ERR_CAST can be used with auth]]
296* TODO [[view:/home/user/linux/crypto/xts.c::face=ovl-face1::linb=227::colb=9::cole=16][ERR_CAST can be used with alg]]
297

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