Addi­tion­al FEATURE macros on the way

It seems I have a bit of free time now to take care about some FreeB­SD relat­ed things.

As part of this I already com­mit­ted the UFS/FFS relat­ed FEATURE macros which where devel­oped by kibab@ dur­ing the Google Sum­mer of Code 2010. The net­work/ALTQ relat­ed FEATURE macros are in the hands of bz@, he already reviewed them and wants to com­mit them (with some changes) as part of his improve­ments of parts of the net­work relat­ed code.

The GEOM relat­ed FEATURE macros I just send some min­utes ago to geom@ for review. All the rest went out to hackers@ for review. The rest in this case is relat­ed to AUDIT, CAM, IPC, KTR, MAC, NFS, NTP, PMC, SYSV and a few oth­er things.

If every­thing is com­mit­ted, it should look a bit like this if queried from user­land (not all fea­tures are shown, those are just the ones which are enabled in the ker­nel in one of my machines):

kern.features.scbus: 1
kern.features.geom_vol: 1
kern.features.geom_part_bsd: 1
kern.features.geom_part_ebr_compat: 1
kern.features.geom_part_ebr: 1
kern.features.geom_part_mbr: 1
kern.features.kposix_priority_scheduling: 1
kern.features.kdtrace_hooks: 1
kern.features.ktrace: 1
kern.features.invariant_support: 1
kern.features.compat_freebsd7: 1
kern.features.compat_freebsd6: 1
kern.features.pps_sync: 1
kern.features.stack: 1
kern.features.sysv_msg: 1
kern.features.sysv_sem: 1
kern.features.sysv_shm: 1
kern.features.posix_shm: 1
kern.features.ffs_snapshot: 1
kern.features.softupdates: 1
kern.features.ufs_acl: 1

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Ker­nel fea­tures patch­set (from GSoC 2010)

I am play­ing around with the patch­set “my” stu­dent gen­er­at­ed dur­ing this years GSoC (the code for all projects is avail­able from Google). In short, it gives you the pos­si­bil­i­ty to query from user­land, which option­al ker­nel fea­tures are avail­able. I have let him most­ly do those fea­tures, which are not so easy to detect from user­land, or where the detec­tion could trig­ger an autoload of a ker­nel mod­ule.

I let the out­put speak for him­self, first the out­put before his patch­set:

kern.features.compat_freebsd7: 1
kern.features.compat_freebsd6: 1
kern.features.posix_shm: 1

And now with his patch­set:

kern.features.compat_freebsd6: 1
kern.features.compat_freebsd7: 1
kern.features.ffs_snapshot: 1
kern.features.geom_label: 1
kern.features.geom_mirror: 1
kern.features.geom_part_bsd: 1
kern.features.geom_part_ebr: 1
kern.features.geom_part_ebr_compat: 1
kern.features.geom_part_mbr: 1
kern.features.geom_vol: 1
kern.features.invariant_support: 1
kern.features.kdtrace_hooks: 1
kern.features.kposix_priority_scheduling: 1
kern.features.ktrace: 1
kern.features.nfsclient: 1
kern.features.nfsserver: 1
kern.features.posix_shm: 1
kern.features.pps_sync: 1
kern.features.quota: 1
kern.features.scbus: 1
kern.features.softupdates: 1
kern.features.stack: 1
kern.features.sysv_msg: 1
kern.features.sysv_sem: 1
kern.features.sysv_shm: 1
kern.features.ufs_acl: 1

With his patch­es we have a total of 84 ker­nel fea­tures which can be queried (obvi­ous­ly I do not have all option­al options enabled in the ker­nel which pro­duces this out­put). All of the fea­tures also have a descrip­tion, and it is easy to add more fea­tures. As an exam­ple I present what is nec­es­sary to pro­duce the kern.features.stack out­put:

./kern/subr_stack.c:FEATURE(stack, “Sup­port for cap­tur­ing ker­nel stack”);

There is also a lit­tle user­land appli­ca­tion (and a library inter­face) which allows to query sev­er­al fea­tures from scripts/applications with the pos­si­bil­i­ty to pre­tend a fea­ture is not there (the require­ment for this was for ports; pre­tend­ing a fea­ture is there if it is not was ruled out because such run-time detec­tion is only nec­es­sary for things which have to run soon and pre­tend­ing some fea­ture is there while it is not will cause big prob­lems). Unfor­tu­nate­ly the man page for the appli­ca­tion is not yet ready, but I’m sure you can fig­ure out how to use it.

The names of the fea­tures and the descrip­tion fol­lows an easy scheme, what is writ­ten down in NOTES is used as a name and a descrip­tion for the fea­ture (an excep­tion is geom_part_X, there we decid­ed to use a com­mon theme (“GEOM par­ti­tion­ing class for XXX”) which is dis­tinct from the cor­re­spond­ing geom_X class). If you have com­plains about what is used in a spe­cif­ic fea­ture, do not com­plain to him: change it in NOTES and the fea­ture will fol­low.

If you have ques­tions, sug­ges­tions, or some oth­er inter­est to con­tact him, his FreeB­SD address is kibab@. Feel free to encour­age him to go ahead with the next steps (fin­ish­ing the man page, split­ting up the patch­es into sen­si­ble pieces and pre­sent­ing them on appro­pri­ate mail­inglists for review). 🙂

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