Copyright 2010 Nicolas Palix Copyright 2010 Julia Lawall Copyright 2010 Gilles Muller Getting Coccinelle ~~~~~~~~~~~~~~~~~~~~ The semantic patches included in the kernel use the 'virtual rule' feature which was introduced in Coccinelle version 0.1.11. Coccinelle (>=0.2.0) is available through the package manager of many distributions, e.g. : - Debian (>=squeeze) - Fedora (>=13) - Ubuntu (>=10.04 Lucid Lynx) - OpenSUSE - Arch Linux - NetBSD - FreeBSD You can get the latest version released from the Coccinelle homepage at http://coccinelle.lip6.fr/ 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 modes are defined: report, patch, context, and org. The mode to use is specified by setting the MODE variable with 'MODE='. 'report' generates a list in the following format: file:line:column-column: message 'patch' proposes a fix, when possible. '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. To make a report for every semantic patch, run the following command: make coccicheck MODE=report NB: The 'report' mode is the default one. To produce patches, run: make coccicheck MODE=patch The coccicheck target applies every semantic patch available in the subdirectories of 'scripts/coccinelle' to the entire Linux kernel. For each semantic patch, a changelog 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. 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 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 subdirectories 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/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/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/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/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]]