Documentation/coccinelle.txt

   1 Copyright 2010 Nicolas Palix <npalix@diku.dk>
   2 Copyright 2010 Julia Lawall <julia@diku.dk>
   3 Copyright 2010 Gilles Muller <Gilles.Muller@lip6.fr>
   4
   5
   6  Getting Coccinelle
   7 ~~~~~~~~~~~~~~~~~~~~
   8
   9 The semantic patches included in the kernel use the 'virtual rule'
  10 feature which was introduced in Coccinelle version 0.1.11.
  11
  12 Coccinelle (>=0.2.0) is available through the package manager
  13 of 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
  24 You can get the latest version released from the Coccinelle homepage at
  25 http://coccinelle.lip6.fr/
  26
  27 Information and tips about Coccinelle are also provided on the wiki
  28 pages at http://cocci.ekstranet.diku.dk/wiki/doku.php
  29
  30 Once you have it, run the following command:
  31
  32         ./configure
  33         make
  34
  35 as a regular user, and install it with
  36
  37         sudo make install
  38
  39 The semantic patches in the kernel will work best with Coccinelle version
  40 0.2.4 or later.  Using earlier versions may incur some parse errors in the
  41 semantic patch code, but any results that are obtained should still be
  42 correct.
  43
  44  Using Coccinelle on the Linux kernel
  45 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  46
  47 A Coccinelle-specific target is defined in the top level
  48 Makefile. This target is named 'coccicheck' and calls the 'coccicheck'
  49 front-end in the 'scripts' directory.
  50
  51 Four modes are defined: patch, report, context, and org. The mode to
  52 use 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
  60 diff-like style.Lines of interest are indicated with '-'.
  61
  62 'org' generates a report in the Org mode format of Emacs.
  63
  64 Note that not all semantic patches implement all modes. For easy use
  65 of Coccinelle, the default mode is "chain" which tries the previous
  66 modes in the order above until one succeeds.
  67
  68 To make a report for every semantic patch, run the following command:
  69
  70         make coccicheck MODE=report
  71
  72 NB: The 'report' mode is the default one.
  73
  74 To produce patches, run:
  75
  76         make coccicheck MODE=patch
  77
  78
  79 The coccicheck target applies every semantic patch available in the
  80 sub-directories of 'scripts/coccinelle' to the entire Linux kernel.
  81
  82 For each semantic patch, a commit message is proposed.  It gives a
  83 description of the problem being checked by the semantic patch, and
  84 includes a reference to Coccinelle.
  85
  86 As any static code analyzer, Coccinelle produces false
  87 positives. Thus, reports must be carefully checked, and patches
  88 reviewed.
  89
  90 To enable verbose messages set the V= variable, for example:
  91
  92    make coccicheck MODE=report V=1
  93
  94
  95  Using Coccinelle with a single semantic patch
  96 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  97
  98 The optional make variable COCCI can be used to check a single
  99 semantic patch. In that case, the variable must be initialized with
 100 the name of the semantic patch to apply.
 101
 102 For instance:
 103
 104         make coccicheck COCCI=<my_SP.cocci> MODE=patch
 105 or
 106         make coccicheck COCCI=<my_SP.cocci> MODE=report
 107
 108
 109  Controlling Which Files are Processed by Coccinelle
 110 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 111 By default the entire kernel source tree is checked.
 112
 113 To apply Coccinelle to a specific directory, M= can be used.
 114 For example, to check drivers/net/wireless/ one may write:
 115
 116     make coccicheck M=drivers/net/wireless/
 117
 118 To apply Coccinelle on a file basis, instead of a directory basis, the
 119 following command may be used:
 120
 121     make C=1 CHECK="scripts/coccicheck"
 122
 123 To check only newly edited code, use the value 2 for the C flag, i.e.
 124
 125     make C=2 CHECK="scripts/coccicheck"
 126
 127 This runs every semantic patch in scripts/coccinelle by default. The
 128 COCCI variable may additionally be used to only apply a single
 129 semantic patch as shown in the previous section.
 130
 131 The "chain" mode is the default. You can select another one with the
 132 MODE variable explained above.
 133
 134 In this mode, there is no information about semantic patches
 135 displayed, and no commit message proposed.
 136
 137
 138  Proposing new semantic patches
 139 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 140
 141 New semantic patches can be proposed and submitted by kernel
 142 developers. For sake of clarity, they should be organized in the
 143 sub-directories of 'scripts/coccinelle/'.
 144
 145
 146  Detailed description of the 'report' mode
 147 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 148
 149 'report' generates a list in the following format:
 150   file:line:column-column: message
 151
 152 Example:
 153
 154 Running
 155
 156         make coccicheck MODE=report COCCI=scripts/coccinelle/api/err_cast.cocci
 157
 158 will execute the following part of the SmPL script.
 159
 160 <smpl>
 161 @r depends on !context && !patch && (org || report)@
 162 expression x;
 163 position p;
 164 @@
 165
 166  ERR_PTR@p(PTR_ERR(x))
 167
 168 @script:python depends on report@
 169 p << r.p;
 170 x << r.x;
 171 @@
 172
 173 msg="ERR_CAST can be used with %s" % (x)
 174 coccilib.report.print_report(p[0], msg)
 175 </smpl>
 176
 177 This SmPL excerpt generates entries on the standard output, as
 178 illustrated below:
 179
 180 /home/user/linux/crypto/ctr.c:188:9-16: ERR_CAST can be used with alg
 181 /home/user/linux/crypto/authenc.c:619:9-16: ERR_CAST can be used with auth
 182 /home/user/linux/crypto/xts.c:227:9-16: ERR_CAST can be used with alg
 183
 184
 185  Detailed description of the 'patch' mode
 186 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 187
 188 When the 'patch' mode is available, it proposes a fix for each problem
 189 identified.
 190
 191 Example:
 192
 193 Running
 194         make coccicheck MODE=patch COCCI=scripts/coccinelle/api/err_cast.cocci
 195
 196 will execute the following part of the SmPL script.
 197
 198 <smpl>
 199 @ depends on !context && patch && !org && !report @
 200 expression x;
 201 @@
 202
 203 - ERR_PTR(PTR_ERR(x))
 204 + ERR_CAST(x)
 205 </smpl>
 206
 207 This SmPL excerpt generates patch hunks on the standard output, as
 208 illustrated below:
 209
 210 diff -u -p a/crypto/ctr.c b/crypto/ctr.c
 211 --- a/crypto/ctr.c 2010-05-26 10:49:38.000000000 +0200
 212 +++ b/crypto/ctr.c 2010-06-03 23:44:49.000000000 +0200
 213 @@ -185,7 +185,7 @@ static struct crypto_instance *crypto_ct
 214         alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
 215                                   CRYPTO_ALG_TYPE_MASK);
 216         if (IS_ERR(alg))
 217 -               return ERR_PTR(PTR_ERR(alg));
 218 +               return ERR_CAST(alg);
 219
 220         /* Block size must be >= 4 bytes. */
 221         err = -EINVAL;
 222
 223  Detailed description of the 'context' mode
 224 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 225
 226 'context' highlights lines of interest and their context
 227 in a diff-like style.
 228
 229 NOTE: The diff-like output generated is NOT an applicable patch. The
 230       intent of the 'context' mode is to highlight the important lines
 231       (annotated with minus, '-') and gives some surrounding context
 232       lines around. This output can be used with the diff mode of
 233       Emacs to review the code.
 234
 235 Example:
 236
 237 Running
 238         make coccicheck MODE=context COCCI=scripts/coccinelle/api/err_cast.cocci
 239
 240 will execute the following part of the SmPL script.
 241
 242 <smpl>
 243 @ depends on context && !patch && !org && !report@
 244 expression x;
 245 @@
 246
 247 * ERR_PTR(PTR_ERR(x))
 248 </smpl>
 249
 250 This SmPL excerpt generates diff hunks on the standard output, as
 251 illustrated below:
 252
 253 diff -u -p /home/user/linux/crypto/ctr.c /tmp/nothing
 254 --- /home/user/linux/crypto/ctr.c       2010-05-26 10:49:38.000000000 +0200
 255 +++ /tmp/nothing
 256 @@ -185,7 +185,6 @@ static struct crypto_instance *crypto_ct
 257         alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
 258                                   CRYPTO_ALG_TYPE_MASK);
 259         if (IS_ERR(alg))
 260 -               return ERR_PTR(PTR_ERR(alg));
 261
 262         /* Block size must be >= 4 bytes. */
 263         err = -EINVAL;
 264
 265  Detailed description of the 'org' mode
 266 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 267
 268 'org' generates a report in the Org mode format of Emacs.
 269
 270 Example:
 271
 272 Running
 273         make coccicheck MODE=org COCCI=scripts/coccinelle/api/err_cast.cocci
 274
 275 will execute the following part of the SmPL script.
 276
 277 <smpl>
 278 @r depends on !context && !patch && (org || report)@
 279 expression x;
 280 position p;
 281 @@
 282
 283  ERR_PTR@p(PTR_ERR(x))
 284
 285 @script:python depends on org@
 286 p << r.p;
 287 x << r.x;
 288 @@
 289
 290 msg="ERR_CAST can be used with %s" % (x)
 291 msg_safe=msg.replace("[","@(").replace("]",")")
 292 coccilib.org.print_todo(p[0], msg_safe)
 293 </smpl>
 294
 295 This SmPL excerpt generates Org entries on the standard output, as
 296 illustrated below:
 297
 298 * TODO [[view:/home/user/linux/crypto/ctr.c::face=ovl-face1::linb=188::colb=9::cole=16][ERR_CAST can be used with alg]]
 299 * TODO [[view:/home/user/linux/crypto/authenc.c::face=ovl-face1::linb=619::colb=9::cole=16][ERR_CAST can be used with auth]]
 300 * TODO [[view:/home/user/linux/crypto/xts.c::face=ovl-face1::linb=227::colb=9::cole=16][ERR_CAST can be used with alg]]