Based on kernel version 4.8. Page generated on 2016-10-06 23:19 EST.
1 Copyright 2004 Linus Torvalds 2 Copyright 2004 Pavel Machek <pavel@ucw.cz> 3 Copyright 2006 Bob Copeland <me@bobcopeland.com> 4 5 Using 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 17 which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is 18 there because sparse will complain about casting to/from a bitwise type, 19 but in this case we really _do_ want to force the conversion). And because 20 the enum values are all the same type, now "enum pm_request" will be that 21 type too. 22 23 And with gcc, all the __bitwise/__force stuff goes away, and it all ends 24 up looking just like integers to gcc. 25 26 Quite frankly, you don't need the enum there. The above all really just 27 boils down to one special "int __bitwise" type. 28 29 So 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 36 and you now have all the infrastructure needed for strict typechecking. 37 38 One small note: the constant integer "0" is special. You can use a 39 constant zero as a bitwise integer type without sparse ever complaining. 40 This is because "bitwise" (as the name implies) was designed for making 41 sure that bitwise types don't get mixed up (little-endian vs big-endian 42 vs cpu-endian vs whatever), and there the constant "0" really _is_ 43 special. 44 45 __bitwise__ - to be used for relatively compact stuff (gfp_t, etc.) that 46 is mostly warning-free and is supposed to stay that way. Warnings will 47 be generated without __CHECK_ENDIAN__. 48 49 __bitwise - noisy stuff; in particular, __le*/__be* are that. We really 50 don't want to drown in noise unless we'd explicitly asked for it. 51 52 Using sparse for lock checking 53 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 54 55 The following macros are undefined for gcc and defined during a sparse 56 run to use the "context" tracking feature of sparse, applied to 57 locking. These annotations tell sparse when a lock is held, with 58 regard 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 66 If the function enters and exits without the lock held, acquiring and 67 releasing the lock inside the function in a balanced way, no 68 annotation is needed. The tree annotations above are for cases where 69 sparse would otherwise report a context imbalance. 70 71 Getting sparse 72 ~~~~~~~~~~~~~~ 73 74 You can get latest released versions from the Sparse homepage at 75 https://sparse.wiki.kernel.org/index.php/Main_Page 76 77 Alternatively, you can get snapshots of the latest development version 78 of sparse using git to clone.. 79 80 git://git.kernel.org/pub/scm/devel/sparse/sparse.git 81 82 DaveJ has hourly generated tarballs of the git tree available at.. 83 84 http://www.codemonkey.org.uk/projects/git-snapshots/sparse/ 85 86 87 Once you have it, just do 88 89 make 90 make install 91 92 as a regular user, and it will install sparse in your ~/bin directory. 93 94 Using sparse 95 ~~~~~~~~~~~~ 96 97 Do a kernel make with "make C=1" to run sparse on all the C files that get 98 recompiled, or use "make C=2" to run sparse on the files whether they need to 99 be recompiled or not. The latter is a fast way to check the whole tree if you 100 have already built it. 101 102 The optional make variable CF can be used to pass arguments to sparse. The 103 build system passes -Wbitwise to sparse automatically. To perform endianness 104 checks, you may define __CHECK_ENDIAN__: 105 106 make C=2 CF="-D__CHECK_ENDIAN__" 107 108 These checks are disabled by default as they generate a host of warnings.