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--- coccicheck [2015/10/22 13:34]
Luis R. Rodriguez
+++ coccicheck [2016/06/22 00:04]
Luis R. Rodriguez
@@ Line 3: / Line 3: @@
 ===== coccicheck =====
-'''coccicheck''' is one of the targets of the Linux kernel, this page documents how you can use it, what it provides and how to help extend it. '''coccicheck''' provides a series of semantic patches written in Semantic Patch Language (SmPL) and make use of the [[http://coccinelle.lip6.fr/|Coccinelle engine]] to interpret and complete these tests. These tests can help you vet for correctness and avoid certain bugs which have been able to be expressed semantically. If you're a maintainer please note you are encouraged to be using coccicheck with M=your/maintained-code-path so you can make use of the learned SmPL patches to avoid bugs in your maintained code. How maintainers can use this is explained below.
+'''coccicheck''' is one of the targets of the Linux kernel, this page documents how you can use it, what it provides and how to help extend it. '''coccicheck''' provides a series of semantic patches written in Semantic Patch Language (SmPL) and make use of the [[http://coccinelle.lip6.fr/|Coccinelle engine]] to interpret and complete these tests. These tests can help you vet for correctness and avoid certain bugs which have been able to be expressed semantically.
-SmPL patches exist for these different types of categories, documented below.
+If you're a developer you are encouraged to vet for your patch using cocciecheck to ensure you are not introducing issues which are known semantically. If you're a maintainer you are encouraged to be using coccicheck with M=your/maintained-code-path so you can make use of the learned SmPL patches to avoid bugs in your maintained code. How maintainers can use this is explained below. Automatic code bot setups which test patches for inlusion upstream are encouraged to consider using 'make coccicheck' as well.
+SmPL patches exist for a few different types of categories, documented below.
 ==== Confidence ====
@@ Line 13: / Line 15: @@
 ==== Modes ====
-There are three different modes you can use to use the semantic patches:
+There are four different modes you can use to use the semantic patches:
-  * report - lets you generate a report - this is the '''default''' mode if one is not specified
-  * org - xxx
   * patch - lets you fix the issues found
+  * report - lets you generate a report - this is the '''default''' mode if one is not specified
+  * 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
-You specify the mode want to operate
+You specify the mode want to operate. 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.
 ==== Run tests ====
@@ Line 28: / Line 37: @@
 make coccicheck MODE=report
 </code>
+To produce patches for the entire kernel, run:
+<code bash>
+make coccicheck MODE=patch
+</code>
+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.
+==== Maintainer work ====
 If you are a maintainer you may want to use M=your/maintained-path/ to limit the scope to only the files you maintain. For instance the following will generate a report for all files in drivers/net/ only.
@@ Line 40: / Line 61: @@
 <code bash>
-export COCCI=scripts/coccinelle/locks/double_lock.cocci
+make coccicheck COCCI=scripts/coccinelle/locks/double_lock.cocci MODE=report
-make coccicheck MODE=report
 </code>
-===== Types of tests ====
+or
+<code bash>
+make coccicheck COCCI=scripts/coccinelle/locks/double_lock.cocci MODE=patch
+</code>
+===== 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:
+<code bash>
+make coccicheck MODE=report M=drivers/net/wireless/
+</code>
+To apply Coccinelle on a file basis, instead of a directory basis, the following command may be used:
+<code bash>
+make C=1 CHECK="scripts/coccicheck"
+</code>
+To check only newly edited code, use the value 2 for the C flag, i.e.
+<code bash>
+make C=2 CHECK="scripts/coccicheck"
+</code>
+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.
+<code bash>
+make SPFLAGS=--use-idutils coccicheck
+</code>
+See spatch --help to learn more about spatch options.
+===== 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/'.
+===== Types of tests =====
 Below we document each type of test category which as been devised.
@@ Line 95: / Line 161: @@
 Average developers can and should use coccicheck as well but care should be taken to ensure the '''Confidence''' tag is reviewed and proper dilligence is done before sending any reports / fixes to kernel maintainers.
+It seems the zero day bot test infrastructure also makes use of 'make coccicheck' --- this section needs to be extended to document in what capacity this is done, how often, etc.
+===== How often are these tests run =====
+The point of merging these SmPL patches upstream was to enable develoeprs and maintainers vet for code themselves. Ideally developers would run 'make coccicheck M=path/to-their-code/' prior to submitting a patch upstream, and maintainers would use it regularly, perhaps after applying new patches, to avoid introducing new issues.
+Time permitting Julia will also run these tests on her own when possible as linux-next moves on. There is no specific regular interval in which these tests are run. The zero day bot tests infrasctructure also seems to use 'make coccicheck' -- but this section should be extended to document this.

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