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Diffstat (limited to 'kernel/Documentation/coccinelle.txt')
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diff --git a/kernel/Documentation/coccinelle.txt b/kernel/Documentation/coccinelle.txt new file mode 100644 index 000000000..7f773d51f --- /dev/null +++ b/kernel/Documentation/coccinelle.txt @@ -0,0 +1,324 @@ +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 + + 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 + +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 + + + 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. + + Additional flags +~~~~~~~~~~~~~~~~~~ + +Additional flags can be passed to spatch through the SPFLAGS +variable. + + make SPFLAGS=--use-glimpse coccicheck + make SPFLAGS=--use-idutils 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. + + 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]] |