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 features and options
  10 which are provided by Coccinelle version 1.0.0-rc11 and above.
  11 Using earlier versions will fail as the option names used by
  12 the Coccinelle files and coccicheck have been updated.
  13
  14 Coccinelle is available through the package manager
  15 of many distributions, e.g. :
  16
  17  - Debian
  18  - Fedora
  19  - Ubuntu
  20  - OpenSUSE
  21  - Arch Linux
  22  - NetBSD
  23  - FreeBSD
  24
  25
  26 You can get the latest version released from the Coccinelle homepage at
  27 http://coccinelle.lip6.fr/
  28
  29 Information and tips about Coccinelle are also provided on the wiki
  30 pages at http://cocci.ekstranet.diku.dk/wiki/doku.php
  31
  32 Once you have it, run the following command:
  33
  34         ./configure
  35         make
  36
  37 as a regular user, and install it with
  38
  39         sudo make install
  40
  41  Using Coccinelle on the Linux kernel
  42 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  43
  44 A Coccinelle-specific target is defined in the top level
  45 Makefile. This target is named 'coccicheck' and calls the 'coccicheck'
  46 front-end in the 'scripts' directory.
  47
  48 Four basic modes are defined: patch, report, context, and org. The mode to
  49 use is specified by setting the MODE variable with 'MODE=<mode>'.
  50
  51 'patch' proposes a fix, when possible.
  52
  53 'report' generates a list in the following format:
  54   file:line:column-column: message
  55
  56 'context' highlights lines of interest and their context in a
  57 diff-like style.Lines of interest are indicated with '-'.
  58
  59 'org' generates a report in the Org mode format of Emacs.
  60
  61 Note that not all semantic patches implement all modes. For easy use
  62 of Coccinelle, the default mode is "report".
  63
  64 Two other modes provide some common combinations of these modes.
  65
  66 'chain' tries the previous modes in the order above until one succeeds.
  67
  68 'rep+ctxt' runs successively the report mode and the context mode.
  69            It should be used with the C option (described later)
  70            which checks the code on a file basis.
  71
  72 Examples:
  73         To make a report for every semantic patch, run the following command:
  74
  75                 make coccicheck MODE=report
  76
  77         To produce patches, run:
  78
  79                 make coccicheck MODE=patch
  80
  81
  82 The coccicheck target applies every semantic patch available in the
  83 sub-directories of 'scripts/coccinelle' to the entire Linux kernel.
  84
  85 For each semantic patch, a commit message is proposed.  It gives a
  86 description of the problem being checked by the semantic patch, and
  87 includes a reference to Coccinelle.
  88
  89 As any static code analyzer, Coccinelle produces false
  90 positives. Thus, reports must be carefully checked, and patches
  91 reviewed.
  92
  93 To enable verbose messages set the V= variable, for example:
  94
  95    make coccicheck MODE=report V=1
  96
  97  Coccinelle parallelization
  98 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  99
 100 By default, coccicheck tries to run as parallel as possible. To change
 101 the parallelism, set the J= variable. For example, to run across 4 CPUs:
 102
 103    make coccicheck MODE=report J=4
 104
 105 As of Coccinelle 1.0.2 Coccinelle uses Ocaml parmap for parallelization,
 106 if support for this is detected you will benefit from parmap parallelization.
 107
 108 When parmap is enabled coccicheck will enable dynamic load balancing by using
 109 '--chunksize 1' argument, this ensures we keep feeding threads with work
 110 one by one, so that we avoid the situation where most work gets done by only
 111 a few threads. With dynamic load balancing, if a thread finishes early we keep
 112 feeding it more work.
 113
 114 When parmap is enabled, if an error occurs in Coccinelle, this error
 115 value is propagated back, the return value of the 'make coccicheck'
 116 captures this return value.
 117
 118  Using Coccinelle with a single semantic patch
 119 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 120
 121 The optional make variable COCCI can be used to check a single
 122 semantic patch. In that case, the variable must be initialized with
 123 the name of the semantic patch to apply.
 124
 125 For instance:
 126
 127         make coccicheck COCCI=<my_SP.cocci> MODE=patch
 128 or
 129         make coccicheck COCCI=<my_SP.cocci> MODE=report
 130
 131
 132  Controlling Which Files are Processed by Coccinelle
 133 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 134 By default the entire kernel source tree is checked.
 135
 136 To apply Coccinelle to a specific directory, M= can be used.
 137 For example, to check drivers/net/wireless/ one may write:
 138
 139     make coccicheck M=drivers/net/wireless/
 140
 141 To apply Coccinelle on a file basis, instead of a directory basis, the
 142 following command may be used:
 143
 144     make C=1 CHECK="scripts/coccicheck"
 145
 146 To check only newly edited code, use the value 2 for the C flag, i.e.
 147
 148     make C=2 CHECK="scripts/coccicheck"
 149
 150 In these modes, which works on a file basis, there is no information
 151 about semantic patches displayed, and no commit message proposed.
 152
 153 This runs every semantic patch in scripts/coccinelle by default. The
 154 COCCI variable may additionally be used to only apply a single
 155 semantic patch as shown in the previous section.
 156
 157 The "report" mode is the default. You can select another one with the
 158 MODE variable explained above.
 159
 160  Debugging Coccinelle SmPL patches
 161 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 162
 163 Using coccicheck is best as it provides in the spatch command line
 164 include options matching the options used when we compile the kernel.
 165 You can learn what these options are by using V=1, you could then
 166 manually run Coccinelle with debug options added.
 167
 168 Alternatively you can debug running Coccinelle against SmPL patches
 169 by asking for stderr to be redirected to stderr, by default stderr
 170 is redirected to /dev/null, if you'd like to capture stderr you
 171 can specify the DEBUG_FILE="file.txt" option to coccicheck. For
 172 instance:
 173
 174     rm -f cocci.err
 175     make coccicheck COCCI=scripts/coccinelle/free/kfree.cocci MODE=report DEBUG_FILE=cocci.err
 176     cat cocci.err
 177
 178 You can use SPFLAGS to add debugging flags, for instance you may want to
 179 add both --profile --show-trying to SPFLAGS when debugging. For instance
 180 you may want to use:
 181
 182     rm -f err.log
 183     export COCCI=scripts/coccinelle/misc/irqf_oneshot.cocci
 184     make coccicheck DEBUG_FILE="err.log" MODE=report SPFLAGS="--profile --show-trying" M=./drivers/mfd/arizona-irq.c
 185
 186 err.log will now have the profiling information, while stdout will
 187 provide some progress information as Coccinelle moves forward with
 188 work.
 189
 190 DEBUG_FILE support is only supported when using coccinelle >= 1.2.
 191
 192  .cocciconfig support
 193 ~~~~~~~~~~~~~~~~~~~~~~
 194
 195 Coccinelle supports reading .cocciconfig for default Coccinelle options that
 196 should be used every time spatch is spawned, the order of precedence for
 197 variables for .cocciconfig is as follows:
 198
 199   o Your current user's home directory is processed first
 200   o Your directory from which spatch is called is processed next
 201   o The directory provided with the --dir option is processed last, if used
 202
 203 Since coccicheck runs through make, it naturally runs from the kernel
 204 proper dir, as such the second rule above would be implied for picking up a
 205 .cocciconfig when using 'make coccicheck'.
 206
 207 'make coccicheck' also supports using M= targets.If you do not supply
 208 any M= target, it is assumed you want to target the entire kernel.
 209 The kernel coccicheck script has:
 210
 211     if [ "$KBUILD_EXTMOD" = "" ] ; then
 212         OPTIONS="--dir $srctree $COCCIINCLUDE"
 213     else
 214         OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
 215     fi
 216
 217 KBUILD_EXTMOD is set when an explicit target with M= is used. For both cases
 218 the spatch --dir argument is used, as such third rule applies when whether M=
 219 is used or not, and when M= is used the target directory can have its own
 220 .cocciconfig file. When M= is not passed as an argument to coccicheck the
 221 target directory is the same as the directory from where spatch was called.
 222
 223 If not using the kernel's coccicheck target, keep the above precedence
 224 order logic of .cocciconfig reading. If using the kernel's coccicheck target,
 225 override any of the kernel's .coccicheck's settings using SPFLAGS.
 226
 227 We help Coccinelle when used against Linux with a set of sensible defaults
 228 options for Linux with our own Linux .cocciconfig. This hints to coccinelle
 229 git can be used for 'git grep' queries over coccigrep. A timeout of 200
 230 seconds should suffice for now.
 231
 232 The options picked up by coccinelle when reading a .cocciconfig do not appear
 233 as arguments to spatch processes running on your system, to confirm what
 234 options will be used by Coccinelle run:
 235
 236       spatch --print-options-only
 237
 238 You can override with your own preferred index option by using SPFLAGS. Take
 239 note that when there are conflicting options Coccinelle takes precedence for
 240 the last options passed. Using .cocciconfig is possible to use idutils, however
 241 given the order of precedence followed by Coccinelle, since the kernel now
 242 carries its own .cocciconfig, you will need to use SPFLAGS to use idutils if
 243 desired. See below section "Additional flags" for more details on how to use
 244 idutils.
 245
 246  Additional flags
 247 ~~~~~~~~~~~~~~~~~~
 248
 249 Additional flags can be passed to spatch through the SPFLAGS
 250 variable. This works as Coccinelle respects the last flags
 251 given to it when options are in conflict.
 252
 253     make SPFLAGS=--use-glimpse coccicheck
 254
 255 Coccinelle supports idutils as well but requires coccinelle >= 1.0.6.
 256 When no ID file is specified coccinelle assumes your ID database file
 257 is in the file .id-utils.index on the top level of the kernel, coccinelle
 258 carries a script scripts/idutils_index.sh which creates the database with
 259
 260     mkid -i C --output .id-utils.index
 261
 262 If you have another database filename you can also just symlink with this
 263 name.
 264
 265     make SPFLAGS=--use-idutils coccicheck
 266
 267 Alternatively you can specify the database filename explicitly, for
 268 instance:
 269
 270     make SPFLAGS="--use-idutils /full-path/to/ID" coccicheck
 271
 272 See spatch --help to learn more about spatch options.
 273
 274 Note that the '--use-glimpse' and '--use-idutils' options
 275 require external tools for indexing the code. None of them is
 276 thus active by default. However, by indexing the code with
 277 one of these tools, and according to the cocci file used,
 278 spatch could proceed the entire code base more quickly.
 279
 280  Proposing new semantic patches
 281 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 282
 283 New semantic patches can be proposed and submitted by kernel
 284 developers. For sake of clarity, they should be organized in the
 285 sub-directories of 'scripts/coccinelle/'.
 286
 287
 288  Detailed description of the 'report' mode
 289 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 290
 291 'report' generates a list in the following format:
 292   file:line:column-column: message
 293
 294 Example:
 295
 296 Running
 297
 298         make coccicheck MODE=report COCCI=scripts/coccinelle/api/err_cast.cocci
 299
 300 will execute the following part of the SmPL script.
 301
 302 <smpl>
 303 @r depends on !context && !patch && (org || report)@
 304 expression x;
 305 position p;
 306 @@
 307
 308  ERR_PTR@p(PTR_ERR(x))
 309
 310 @script:python depends on report@
 311 p << r.p;
 312 x << r.x;
 313 @@
 314
 315 msg="ERR_CAST can be used with %s" % (x)
 316 coccilib.report.print_report(p[0], msg)
 317 </smpl>
 318
 319 This SmPL excerpt generates entries on the standard output, as
 320 illustrated below:
 321
 322 /home/user/linux/crypto/ctr.c:188:9-16: ERR_CAST can be used with alg
 323 /home/user/linux/crypto/authenc.c:619:9-16: ERR_CAST can be used with auth
 324 /home/user/linux/crypto/xts.c:227:9-16: ERR_CAST can be used with alg
 325
 326
 327  Detailed description of the 'patch' mode
 328 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 329
 330 When the 'patch' mode is available, it proposes a fix for each problem
 331 identified.
 332
 333 Example:
 334
 335 Running
 336         make coccicheck MODE=patch COCCI=scripts/coccinelle/api/err_cast.cocci
 337
 338 will execute the following part of the SmPL script.
 339
 340 <smpl>
 341 @ depends on !context && patch && !org && !report @
 342 expression x;
 343 @@
 344
 345 - ERR_PTR(PTR_ERR(x))
 346 + ERR_CAST(x)
 347 </smpl>
 348
 349 This SmPL excerpt generates patch hunks on the standard output, as
 350 illustrated below:
 351
 352 diff -u -p a/crypto/ctr.c b/crypto/ctr.c
 353 --- a/crypto/ctr.c 2010-05-26 10:49:38.000000000 +0200
 354 +++ b/crypto/ctr.c 2010-06-03 23:44:49.000000000 +0200
 355 @@ -185,7 +185,7 @@ static struct crypto_instance *crypto_ct
 356         alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
 357                                   CRYPTO_ALG_TYPE_MASK);
 358         if (IS_ERR(alg))
 359 -               return ERR_PTR(PTR_ERR(alg));
 360 +               return ERR_CAST(alg);
 361
 362         /* Block size must be >= 4 bytes. */
 363         err = -EINVAL;
 364
 365  Detailed description of the 'context' mode
 366 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 367
 368 'context' highlights lines of interest and their context
 369 in a diff-like style.
 370
 371 NOTE: The diff-like output generated is NOT an applicable patch. The
 372       intent of the 'context' mode is to highlight the important lines
 373       (annotated with minus, '-') and gives some surrounding context
 374       lines around. This output can be used with the diff mode of
 375       Emacs to review the code.
 376
 377 Example:
 378
 379 Running
 380         make coccicheck MODE=context COCCI=scripts/coccinelle/api/err_cast.cocci
 381
 382 will execute the following part of the SmPL script.
 383
 384 <smpl>
 385 @ depends on context && !patch && !org && !report@
 386 expression x;
 387 @@
 388
 389 * ERR_PTR(PTR_ERR(x))
 390 </smpl>
 391
 392 This SmPL excerpt generates diff hunks on the standard output, as
 393 illustrated below:
 394
 395 diff -u -p /home/user/linux/crypto/ctr.c /tmp/nothing
 396 --- /home/user/linux/crypto/ctr.c       2010-05-26 10:49:38.000000000 +0200
 397 +++ /tmp/nothing
 398 @@ -185,7 +185,6 @@ static struct crypto_instance *crypto_ct
 399         alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
 400                                   CRYPTO_ALG_TYPE_MASK);
 401         if (IS_ERR(alg))
 402 -               return ERR_PTR(PTR_ERR(alg));
 403
 404         /* Block size must be >= 4 bytes. */
 405         err = -EINVAL;
 406
 407  Detailed description of the 'org' mode
 408 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 409
 410 'org' generates a report in the Org mode format of Emacs.
 411
 412 Example:
 413
 414 Running
 415         make coccicheck MODE=org COCCI=scripts/coccinelle/api/err_cast.cocci
 416
 417 will execute the following part of the SmPL script.
 418
 419 <smpl>
 420 @r depends on !context && !patch && (org || report)@
 421 expression x;
 422 position p;
 423 @@
 424
 425  ERR_PTR@p(PTR_ERR(x))
 426
 427 @script:python depends on org@
 428 p << r.p;
 429 x << r.x;
 430 @@
 431
 432 msg="ERR_CAST can be used with %s" % (x)
 433 msg_safe=msg.replace("[","@(").replace("]",")")
 434 coccilib.org.print_todo(p[0], msg_safe)
 435 </smpl>
 436
 437 This SmPL excerpt generates Org entries on the standard output, as
 438 illustrated below:
 439
 440 * TODO [[view:/home/user/linux/crypto/ctr.c::face=ovl-face1::linb=188::colb=9::cole=16][ERR_CAST can be used with alg]]
 441 * TODO [[view:/home/user/linux/crypto/authenc.c::face=ovl-face1::linb=619::colb=9::cole=16][ERR_CAST can be used with auth]]
 442 * TODO [[view:/home/user/linux/crypto/xts.c::face=ovl-face1::linb=227::colb=9::cole=16][ERR_CAST can be used with alg]]