1Copyright 2004 Linus Torvalds 2Copyright 2004 Pavel Machek <pavel@ucw.cz> 3Copyright 2006 Bob Copeland <me@bobcopeland.com> 4 5Using sparse for typechecking 6~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7 8"__bitwise" is a type attribute, so you have to do something like this: 9 10 typedef int __bitwise pm_request_t; 11 12 enum pm_request { 13 PM_SUSPEND = (__force pm_request_t) 1, 14 PM_RESUME = (__force pm_request_t) 2 15 }; 16 17which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is 18there because sparse will complain about casting to/from a bitwise type, 19but in this case we really _do_ want to force the conversion). And because 20the enum values are all the same type, now "enum pm_request" will be that 21type too. 22 23And with gcc, all the __bitwise/__force stuff goes away, and it all ends 24up looking just like integers to gcc. 25 26Quite frankly, you don't need the enum there. The above all really just 27boils down to one special "int __bitwise" type. 28 29So the simpler way is to just do 30 31 typedef int __bitwise pm_request_t; 32 33 #define PM_SUSPEND ((__force pm_request_t) 1) 34 #define PM_RESUME ((__force pm_request_t) 2) 35 36and you now have all the infrastructure needed for strict typechecking. 37 38One small note: the constant integer "0" is special. You can use a 39constant zero as a bitwise integer type without sparse ever complaining. 40This is because "bitwise" (as the name implies) was designed for making 41sure that bitwise types don't get mixed up (little-endian vs big-endian 42vs cpu-endian vs whatever), and there the constant "0" really _is_ 43special. 44 45__bitwise__ - to be used for relatively compact stuff (gfp_t, etc.) that 46is mostly warning-free and is supposed to stay that way. Warnings will 47be generated without __CHECK_ENDIAN__. 48 49__bitwise - noisy stuff; in particular, __le*/__be* are that. We really 50don't want to drown in noise unless we'd explicitly asked for it. 51 52Using sparse for lock checking 53~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 54 55The following macros are undefined for gcc and defined during a sparse 56run to use the "context" tracking feature of sparse, applied to 57locking. These annotations tell sparse when a lock is held, with 58regard to the annotated function's entry and exit. 59 60__must_hold - The specified lock is held on function entry and exit. 61 62__acquires - The specified lock is held on function exit, but not entry. 63 64__releases - The specified lock is held on function entry, but not exit. 65 66If the function enters and exits without the lock held, acquiring and 67releasing the lock inside the function in a balanced way, no 68annotation is needed. The tree annotations above are for cases where 69sparse would otherwise report a context imbalance. 70 71Getting sparse 72~~~~~~~~~~~~~~ 73 74You can get latest released versions from the Sparse homepage at 75https://sparse.wiki.kernel.org/index.php/Main_Page 76 77Alternatively, you can get snapshots of the latest development version 78of sparse using git to clone.. 79 80 git://git.kernel.org/pub/scm/devel/sparse/sparse.git 81 82DaveJ has hourly generated tarballs of the git tree available at.. 83 84 http://www.codemonkey.org.uk/projects/git-snapshots/sparse/ 85 86 87Once you have it, just do 88 89 make 90 make install 91 92as a regular user, and it will install sparse in your ~/bin directory. 93 94Using sparse 95~~~~~~~~~~~~ 96 97Do a kernel make with "make C=1" to run sparse on all the C files that get 98recompiled, or use "make C=2" to run sparse on the files whether they need to 99be recompiled or not. The latter is a fast way to check the whole tree if you 100have already built it. 101 102The optional make variable CF can be used to pass arguments to sparse. The 103build system passes -Wbitwise to sparse automatically. To perform endianness 104checks, you may define __CHECK_ENDIAN__: 105 106 make C=2 CF="-D__CHECK_ENDIAN__" 107 108These checks are disabled by default as they generate a host of warnings. 109