From: Jonathan Corbet Date: Sun, 7 Aug 2016 21:09:14 +0000 (-0600) Subject: docs: sphinxify sparse.txt and move to dev-tools X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=d228af5bcb60fda50f8b3a100c0539c4994df040;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git docs: sphinxify sparse.txt and move to dev-tools Fold the sparse document into the development tools set; no changes to the text itself beyond formatting. Signed-off-by: Jonathan Corbet --- diff --git a/Documentation/dev-tools/sparse.rst b/Documentation/dev-tools/sparse.rst new file mode 100644 index 000000000000..8c250e8a2105 --- /dev/null +++ b/Documentation/dev-tools/sparse.rst @@ -0,0 +1,117 @@ +.. Copyright 2004 Linus Torvalds +.. Copyright 2004 Pavel Machek +.. Copyright 2006 Bob Copeland + +Sparse +====== + +Sparse is a semantic checker for C programs; it can be used to find a +number of potential problems with kernel code. See +https://lwn.net/Articles/689907/ for an overview of sparse; this document +contains some kernel-specific sparse information. + + +Using sparse for typechecking +----------------------------- + +"__bitwise" is a type attribute, so you have to do something like this:: + + typedef int __bitwise pm_request_t; + + enum pm_request { + PM_SUSPEND = (__force pm_request_t) 1, + PM_RESUME = (__force pm_request_t) 2 + }; + +which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is +there because sparse will complain about casting to/from a bitwise type, +but in this case we really _do_ want to force the conversion). And because +the enum values are all the same type, now "enum pm_request" will be that +type too. + +And with gcc, all the "__bitwise"/"__force stuff" goes away, and it all +ends up looking just like integers to gcc. + +Quite frankly, you don't need the enum there. The above all really just +boils down to one special "int __bitwise" type. + +So the simpler way is to just do:: + + typedef int __bitwise pm_request_t; + + #define PM_SUSPEND ((__force pm_request_t) 1) + #define PM_RESUME ((__force pm_request_t) 2) + +and you now have all the infrastructure needed for strict typechecking. + +One small note: the constant integer "0" is special. You can use a +constant zero as a bitwise integer type without sparse ever complaining. +This is because "bitwise" (as the name implies) was designed for making +sure that bitwise types don't get mixed up (little-endian vs big-endian +vs cpu-endian vs whatever), and there the constant "0" really _is_ +special. + +__bitwise__ - to be used for relatively compact stuff (gfp_t, etc.) that +is mostly warning-free and is supposed to stay that way. Warnings will +be generated without __CHECK_ENDIAN__. + +__bitwise - noisy stuff; in particular, __le*/__be* are that. We really +don't want to drown in noise unless we'd explicitly asked for it. + +Using sparse for lock checking +------------------------------ + +The following macros are undefined for gcc and defined during a sparse +run to use the "context" tracking feature of sparse, applied to +locking. These annotations tell sparse when a lock is held, with +regard to the annotated function's entry and exit. + +__must_hold - The specified lock is held on function entry and exit. + +__acquires - The specified lock is held on function exit, but not entry. + +__releases - The specified lock is held on function entry, but not exit. + +If the function enters and exits without the lock held, acquiring and +releasing the lock inside the function in a balanced way, no +annotation is needed. The tree annotations above are for cases where +sparse would otherwise report a context imbalance. + +Getting sparse +-------------- + +You can get latest released versions from the Sparse homepage at +https://sparse.wiki.kernel.org/index.php/Main_Page + +Alternatively, you can get snapshots of the latest development version +of sparse using git to clone:: + + git://git.kernel.org/pub/scm/devel/sparse/sparse.git + +DaveJ has hourly generated tarballs of the git tree available at:: + + http://www.codemonkey.org.uk/projects/git-snapshots/sparse/ + + +Once you have it, just do:: + + make + make install + +as a regular user, and it will install sparse in your ~/bin directory. + +Using sparse +------------ + +Do a kernel make with "make C=1" to run sparse on all the C files that get +recompiled, or use "make C=2" to run sparse on the files whether they need to +be recompiled or not. The latter is a fast way to check the whole tree if you +have already built it. + +The optional make variable CF can be used to pass arguments to sparse. The +build system passes -Wbitwise to sparse automatically. To perform endianness +checks, you may define __CHECK_ENDIAN__:: + + make C=2 CF="-D__CHECK_ENDIAN__" + +These checks are disabled by default as they generate a host of warnings. diff --git a/Documentation/dev-tools/tools.rst b/Documentation/dev-tools/tools.rst index ae0c58c784db..d4bbda319e79 100644 --- a/Documentation/dev-tools/tools.rst +++ b/Documentation/dev-tools/tools.rst @@ -15,3 +15,4 @@ whole; patches welcome! :maxdepth: 2 coccinelle + sparse diff --git a/Documentation/sparse.txt b/Documentation/sparse.txt deleted file mode 100644 index eceab1308a8c..000000000000 --- a/Documentation/sparse.txt +++ /dev/null @@ -1,108 +0,0 @@ -Copyright 2004 Linus Torvalds -Copyright 2004 Pavel Machek -Copyright 2006 Bob Copeland - -Using sparse for typechecking -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -"__bitwise" is a type attribute, so you have to do something like this: - - typedef int __bitwise pm_request_t; - - enum pm_request { - PM_SUSPEND = (__force pm_request_t) 1, - PM_RESUME = (__force pm_request_t) 2 - }; - -which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is -there because sparse will complain about casting to/from a bitwise type, -but in this case we really _do_ want to force the conversion). And because -the enum values are all the same type, now "enum pm_request" will be that -type too. - -And with gcc, all the __bitwise/__force stuff goes away, and it all ends -up looking just like integers to gcc. - -Quite frankly, you don't need the enum there. The above all really just -boils down to one special "int __bitwise" type. - -So the simpler way is to just do - - typedef int __bitwise pm_request_t; - - #define PM_SUSPEND ((__force pm_request_t) 1) - #define PM_RESUME ((__force pm_request_t) 2) - -and you now have all the infrastructure needed for strict typechecking. - -One small note: the constant integer "0" is special. You can use a -constant zero as a bitwise integer type without sparse ever complaining. -This is because "bitwise" (as the name implies) was designed for making -sure that bitwise types don't get mixed up (little-endian vs big-endian -vs cpu-endian vs whatever), and there the constant "0" really _is_ -special. - -__bitwise__ - to be used for relatively compact stuff (gfp_t, etc.) that -is mostly warning-free and is supposed to stay that way. Warnings will -be generated without __CHECK_ENDIAN__. - -__bitwise - noisy stuff; in particular, __le*/__be* are that. We really -don't want to drown in noise unless we'd explicitly asked for it. - -Using sparse for lock checking -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -The following macros are undefined for gcc and defined during a sparse -run to use the "context" tracking feature of sparse, applied to -locking. These annotations tell sparse when a lock is held, with -regard to the annotated function's entry and exit. - -__must_hold - The specified lock is held on function entry and exit. - -__acquires - The specified lock is held on function exit, but not entry. - -__releases - The specified lock is held on function entry, but not exit. - -If the function enters and exits without the lock held, acquiring and -releasing the lock inside the function in a balanced way, no -annotation is needed. The tree annotations above are for cases where -sparse would otherwise report a context imbalance. - -Getting sparse -~~~~~~~~~~~~~~ - -You can get latest released versions from the Sparse homepage at -https://sparse.wiki.kernel.org/index.php/Main_Page - -Alternatively, you can get snapshots of the latest development version -of sparse using git to clone.. - - git://git.kernel.org/pub/scm/devel/sparse/sparse.git - -DaveJ has hourly generated tarballs of the git tree available at.. - - http://www.codemonkey.org.uk/projects/git-snapshots/sparse/ - - -Once you have it, just do - - make - make install - -as a regular user, and it will install sparse in your ~/bin directory. - -Using sparse -~~~~~~~~~~~~ - -Do a kernel make with "make C=1" to run sparse on all the C files that get -recompiled, or use "make C=2" to run sparse on the files whether they need to -be recompiled or not. The latter is a fast way to check the whole tree if you -have already built it. - -The optional make variable CF can be used to pass arguments to sparse. The -build system passes -Wbitwise to sparse automatically. To perform endianness -checks, you may define __CHECK_ENDIAN__: - - make C=2 CF="-D__CHECK_ENDIAN__" - -These checks are disabled by default as they generate a host of warnings.