Copyright 2010 Nicolas Palix Copyright 2010 Julia Lawall Copyright 2010 Gilles Muller 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='. '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= MODE=patch or make coccicheck 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. @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) 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. @ depends on !context && patch && !org && !report @ expression x; @@ - ERR_PTR(PTR_ERR(x)) + ERR_CAST(x) 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. @ depends on context && !patch && !org && !report@ expression x; @@ * ERR_PTR(PTR_ERR(x)) 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. @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) 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]]