Copyright 2010 Nicolas Palix <npalix@diku.dk>
  Copyright 2010 Julia Lawall <julia@diku.dk>
  Copyright 2010 Gilles Muller <Gilles.Muller@lip6.fr>
  
  
   Getting Coccinelle
  ~~~~~~~~~~~~~~~~~~~~

  The semantic patches included in the kernel use features and options
  which are provided by Coccinelle version 1.0.0-rc11 and above.
  Using earlier versions will fail as the option names used by
  the Coccinelle files and coccicheck have been updated.

  Coccinelle is available through the package manager

  of many distributions, e.g. :

   - Debian
   - Fedora
   - Ubuntu

   - OpenSUSE
   - Arch Linux
   - NetBSD
   - FreeBSD
  
  
  You can get the latest version released from the Coccinelle homepage at
  http://coccinelle.lip6.fr/

  Information and tips about Coccinelle are also provided on the wiki
  pages at http://cocci.ekstranet.diku.dk/wiki/doku.php

  Once you have it, run the following command:
  
       	./configure
          make
  
  as a regular user, and install it with
  
          sudo make install

   Supplemental documentation
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  For supplemental documentation refer to the wiki:
  
  https://bottest.wiki.kernel.org/coccicheck
  
  The wiki documentation always refers to the linux-next version of the script.

   Using Coccinelle on the Linux kernel
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  A Coccinelle-specific target is defined in the top level
  Makefile. This target is named 'coccicheck' and calls the 'coccicheck'
  front-end in the 'scripts' directory.

  Four basic modes are defined: patch, report, context, and org. The mode to

  use is specified by setting the MODE variable with 'MODE=<mode>'.

  'patch' proposes a fix, when possible.

  'report' generates a list in the following format:
    file:line:column-column: message

  'context' highlights lines of interest and their context in a
  diff-like style.Lines of interest are indicated with '-'.
  
  'org' generates a report in the Org mode format of Emacs.

  Note that not all semantic patches implement all modes. For easy use

  of Coccinelle, the default mode is "report".

  Two other modes provide some common combinations of these modes.

  'chain' tries the previous modes in the order above until one succeeds.

  'rep+ctxt' runs successively the report mode and the context mode.
  	   It should be used with the C option (described later)
  	   which checks the code on a file basis.

  Examples:
  	To make a report for every semantic patch, run the following command:

  		make coccicheck MODE=report
  
  	To produce patches, run:
  
  		make coccicheck MODE=patch

  
  
  The coccicheck target applies every semantic patch available in the

  sub-directories of 'scripts/coccinelle' to the entire Linux kernel.

  For each semantic patch, a commit message is proposed.  It gives a

  description of the problem being checked by the semantic patch, and
  includes a reference to Coccinelle.
  
  As any static code analyzer, Coccinelle produces false
  positives. Thus, reports must be carefully checked, and patches
  reviewed.

  To enable verbose messages set the V= variable, for example:
  
     make coccicheck MODE=report V=1

   Coccinelle parallelization
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

  By default, coccicheck tries to run as parallel as possible. To change
  the parallelism, set the J= variable. For example, to run across 4 CPUs:
  
     make coccicheck MODE=report J=4

  As of Coccinelle 1.0.2 Coccinelle uses Ocaml parmap for parallelization,
  if support for this is detected you will benefit from parmap parallelization.
  
  When parmap is enabled coccicheck will enable dynamic load balancing by using
  '--chunksize 1' argument, this ensures we keep feeding threads with work
  one by one, so that we avoid the situation where most work gets done by only
  a few threads. With dynamic load balancing, if a thread finishes early we keep
  feeding it more work.
  
  When parmap is enabled, if an error occurs in Coccinelle, this error
  value is propagated back, the return value of the 'make coccicheck'
  captures this return value.

  
   Using Coccinelle with a single semantic patch
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  The optional make variable COCCI can be used to check a single
  semantic patch. In that case, the variable must be initialized with
  the name of the semantic patch to apply.
  
  For instance:
  
  	make coccicheck COCCI=<my_SP.cocci> MODE=patch
  or
  	make coccicheck COCCI=<my_SP.cocci> MODE=report

   Controlling Which Files are Processed by Coccinelle
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  By default the entire kernel source tree is checked.
  
  To apply Coccinelle to a specific directory, M= can be used.
  For example, to check drivers/net/wireless/ one may write:

      make coccicheck M=drivers/net/wireless/

  To apply Coccinelle on a file basis, instead of a directory basis, the
  following command may be used:
  
      make C=1 CHECK="scripts/coccicheck"
  
  To check only newly edited code, use the value 2 for the C flag, i.e.
  
      make C=2 CHECK="scripts/coccicheck"

  In these modes, which works on a file basis, there is no information
  about semantic patches displayed, and no commit message proposed.

  This runs every semantic patch in scripts/coccinelle by default. The
  COCCI variable may additionally be used to only apply a single
  semantic patch as shown in the previous section.

  The "report" mode is the default. You can select another one with the

  MODE variable explained above.

   Debugging Coccinelle SmPL patches
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  Using coccicheck is best as it provides in the spatch command line
  include options matching the options used when we compile the kernel.
  You can learn what these options are by using V=1, you could then
  manually run Coccinelle with debug options added.
  
  Alternatively you can debug running Coccinelle against SmPL patches
  by asking for stderr to be redirected to stderr, by default stderr
  is redirected to /dev/null, if you'd like to capture stderr you
  can specify the DEBUG_FILE="file.txt" option to coccicheck. For
  instance:
  
      rm -f cocci.err
      make coccicheck COCCI=scripts/coccinelle/free/kfree.cocci MODE=report DEBUG_FILE=cocci.err
      cat cocci.err

  You can use SPFLAGS to add debugging flags, for instance you may want to
  add both --profile --show-trying to SPFLAGS when debugging. For instance
  you may want to use:
  
      rm -f err.log
      export COCCI=scripts/coccinelle/misc/irqf_oneshot.cocci
      make coccicheck DEBUG_FILE="err.log" MODE=report SPFLAGS="--profile --show-trying" M=./drivers/mfd/arizona-irq.c
  
  err.log will now have the profiling information, while stdout will
  provide some progress information as Coccinelle moves forward with
  work.

  DEBUG_FILE support is only supported when using coccinelle >= 1.2.

   .cocciconfig support
  ~~~~~~~~~~~~~~~~~~~~~~
  
  Coccinelle supports reading .cocciconfig for default Coccinelle options that
  should be used every time spatch is spawned, the order of precedence for
  variables for .cocciconfig is as follows:
  
    o Your current user's home directory is processed first
    o Your directory from which spatch is called is processed next
    o The directory provided with the --dir option is processed last, if used
  
  Since coccicheck runs through make, it naturally runs from the kernel
  proper dir, as such the second rule above would be implied for picking up a
  .cocciconfig when using 'make coccicheck'.
  
  'make coccicheck' also supports using M= targets.If you do not supply
  any M= target, it is assumed you want to target the entire kernel.
  The kernel coccicheck script has:
  
      if [ "$KBUILD_EXTMOD" = "" ] ; then
          OPTIONS="--dir $srctree $COCCIINCLUDE"
      else
          OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
      fi
  
  KBUILD_EXTMOD is set when an explicit target with M= is used. For both cases
  the spatch --dir argument is used, as such third rule applies when whether M=
  is used or not, and when M= is used the target directory can have its own
  .cocciconfig file. When M= is not passed as an argument to coccicheck the
  target directory is the same as the directory from where spatch was called.
  
  If not using the kernel's coccicheck target, keep the above precedence
  order logic of .cocciconfig reading. If using the kernel's coccicheck target,
  override any of the kernel's .coccicheck's settings using SPFLAGS.
  
  We help Coccinelle when used against Linux with a set of sensible defaults
  options for Linux with our own Linux .cocciconfig. This hints to coccinelle
  git can be used for 'git grep' queries over coccigrep. A timeout of 200
  seconds should suffice for now.
  
  The options picked up by coccinelle when reading a .cocciconfig do not appear
  as arguments to spatch processes running on your system, to confirm what
  options will be used by Coccinelle run:
  
        spatch --print-options-only
  
  You can override with your own preferred index option by using SPFLAGS. Take
  note that when there are conflicting options Coccinelle takes precedence for
  the last options passed. Using .cocciconfig is possible to use idutils, however
  given the order of precedence followed by Coccinelle, since the kernel now
  carries its own .cocciconfig, you will need to use SPFLAGS to use idutils if
  desired. See below section "Additional flags" for more details on how to use
  idutils.

   Additional flags
  ~~~~~~~~~~~~~~~~~~
  
  Additional flags can be passed to spatch through the SPFLAGS

  variable. This works as Coccinelle respects the last flags
  given to it when options are in conflict.

      make SPFLAGS=--use-glimpse coccicheck

  
  Coccinelle supports idutils as well but requires coccinelle >= 1.0.6.
  When no ID file is specified coccinelle assumes your ID database file
  is in the file .id-utils.index on the top level of the kernel, coccinelle
  carries a script scripts/idutils_index.sh which creates the database with
  
      mkid -i C --output .id-utils.index
  
  If you have another database filename you can also just symlink with this
  name.

      make SPFLAGS=--use-idutils coccicheck

  Alternatively you can specify the database filename explicitly, for
  instance:
  
      make SPFLAGS="--use-idutils /full-path/to/ID" coccicheck

  See spatch --help to learn more about spatch options.

  Note that the '--use-glimpse' and '--use-idutils' options
  require external tools for indexing the code. None of them is
  thus active by default. However, by indexing the code with
  one of these tools, and according to the cocci file used,
  spatch could proceed the entire code base more quickly.

   SmPL patch specific options
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  SmPL patches can have their own requirements for options passed
  to Coccinelle. SmPL patch specific options can be provided by
  providing them at the top of the SmPL patch, for instance:
  
  // Options: --no-includes --include-headers
  
   SmPL patch Coccinelle requirements
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  As Coccinelle features get added some more advanced SmPL patches
  may require newer versions of Coccinelle. If an SmPL patch requires
  at least a version of Coccinelle, this can be specified as follows,
  as an example if requiring at least Coccinelle >= 1.0.5:
  
  // Requires: 1.0.5

   Proposing new semantic patches
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  New semantic patches can be proposed and submitted by kernel
  developers. For sake of clarity, they should be organized in the

  sub-directories of 'scripts/coccinelle/'.

  
  
   Detailed description of the 'report' mode
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  'report' generates a list in the following format:
    file:line:column-column: message
  
  Example:
  
  Running

  	make coccicheck MODE=report COCCI=scripts/coccinelle/api/err_cast.cocci

  
  will execute the following part of the SmPL script.
  
  <smpl>
  @r depends on !context && !patch && (org || report)@
  expression x;
  position p;
  @@
  
   ERR_PTR@p(PTR_ERR(x))
  
  @script:python depends on report@
  p << r.p;
  x << r.x;
  @@
  
  msg="ERR_CAST can be used with %s" % (x)
  coccilib.report.print_report(p[0], msg)
  </smpl>
  
  This SmPL excerpt generates entries on the standard output, as
  illustrated below:
  
  /home/user/linux/crypto/ctr.c:188:9-16: ERR_CAST can be used with alg
  /home/user/linux/crypto/authenc.c:619:9-16: ERR_CAST can be used with auth
  /home/user/linux/crypto/xts.c:227:9-16: ERR_CAST can be used with alg
  
  
   Detailed description of the 'patch' mode
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  When the 'patch' mode is available, it proposes a fix for each problem
  identified.
  
  Example:
  
  Running

  	make coccicheck MODE=patch COCCI=scripts/coccinelle/api/err_cast.cocci

  
  will execute the following part of the SmPL script.
  
  <smpl>
  @ depends on !context && patch && !org && !report @
  expression x;
  @@
  
  - ERR_PTR(PTR_ERR(x))
  + ERR_CAST(x)
  </smpl>
  
  This SmPL excerpt generates patch hunks on the standard output, as
  illustrated below:
  
  diff -u -p a/crypto/ctr.c b/crypto/ctr.c
  --- a/crypto/ctr.c 2010-05-26 10:49:38.000000000 +0200
  +++ b/crypto/ctr.c 2010-06-03 23:44:49.000000000 +0200
  @@ -185,7 +185,7 @@ static struct crypto_instance *crypto_ct
   	alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
   				  CRYPTO_ALG_TYPE_MASK);
   	if (IS_ERR(alg))
  -		return ERR_PTR(PTR_ERR(alg));
  +		return ERR_CAST(alg);
   
   	/* Block size must be >= 4 bytes. */
   	err = -EINVAL;
  
   Detailed description of the 'context' mode
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  'context' highlights lines of interest and their context
  in a diff-like style.
  
  NOTE: The diff-like output generated is NOT an applicable patch. The
        intent of the 'context' mode is to highlight the important lines
        (annotated with minus, '-') and gives some surrounding context
        lines around. This output can be used with the diff mode of
        Emacs to review the code.
  
  Example:
  
  Running

  	make coccicheck MODE=context COCCI=scripts/coccinelle/api/err_cast.cocci

  
  will execute the following part of the SmPL script.
  
  <smpl>
  @ depends on context && !patch && !org && !report@
  expression x;
  @@
  
  * ERR_PTR(PTR_ERR(x))
  </smpl>
  
  This SmPL excerpt generates diff hunks on the standard output, as
  illustrated below:
  
  diff -u -p /home/user/linux/crypto/ctr.c /tmp/nothing
  --- /home/user/linux/crypto/ctr.c	2010-05-26 10:49:38.000000000 +0200
  +++ /tmp/nothing
  @@ -185,7 +185,6 @@ static struct crypto_instance *crypto_ct
   	alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
   				  CRYPTO_ALG_TYPE_MASK);
   	if (IS_ERR(alg))
  -		return ERR_PTR(PTR_ERR(alg));
   
   	/* Block size must be >= 4 bytes. */
   	err = -EINVAL;
  
   Detailed description of the 'org' mode
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  'org' generates a report in the Org mode format of Emacs.
  
  Example:
  
  Running

  	make coccicheck MODE=org COCCI=scripts/coccinelle/api/err_cast.cocci

  
  will execute the following part of the SmPL script.
  
  <smpl>
  @r depends on !context && !patch && (org || report)@
  expression x;
  position p;
  @@
  
   ERR_PTR@p(PTR_ERR(x))
  
  @script:python depends on org@
  p << r.p;
  x << r.x;
  @@
  
  msg="ERR_CAST can be used with %s" % (x)
  msg_safe=msg.replace("[","@(").replace("]",")")
  coccilib.org.print_todo(p[0], msg_safe)
  </smpl>
  
  This SmPL excerpt generates Org entries on the standard output, as
  illustrated below:
  
  * TODO [[view:/home/user/linux/crypto/ctr.c::face=ovl-face1::linb=188::colb=9::cole=16][ERR_CAST can be used with alg]]
  * TODO [[view:/home/user/linux/crypto/authenc.c::face=ovl-face1::linb=619::colb=9::cole=16][ERR_CAST can be used with auth]]
  * TODO [[view:/home/user/linux/crypto/xts.c::face=ovl-face1::linb=227::colb=9::cole=16][ERR_CAST can be used with alg]]