Alexander Leidinger

Just another weblog

Sep
29

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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One Response to “Ker­nel fea­tures patch­set (from GSoC 2010)”

  1. Įvairios naujienos | FreeBSD.lt Says:

    […] bran­duo­lio pataisa, kuri buvo sukurta GSOC 2010 metu ir leis iš “user­land” sužinoti branduolio […]