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diff --git a/Documentation/coccinelle.txt b/Documentation/coccinelle.txt new file mode 100644 index 0000000..ba3315d --- /dev/null +++ b/Documentation/coccinelle.txt @@ -0,0 +1,258 @@ +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 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 Karmic Koala) + - 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=<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=<my_SP.cocci> MODE=patch +or + make coccicheck COCCI=<my_SP.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. + +<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/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/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/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]] |