Automagic SYSCTLs

mdf at mdf at
Sun Jan 16 00:12:46 UTC 2011

I started out with a plan to import a patch from Isilon that adds
type-safety to the existing SYSCTLs for scalar variables in the
kernel.  After the discussion on the svn mailing list here
I now have a prototype patch for SYSCTL_ADD_SCALAR that could replace
most uses of SYSCTL_ADD_{INT, UINT, LONG, ULONG, QUAD} and is suitable
for the SYSCTL_ADD_FOO that are used on 16 and 8 bit members (without
type checking) today.

The gist is that the handler knows the sizeof the variable in the
kernel and uses this to copy out.  For the case of a long, there's
some goop for SCTL_MASK32.  For the case of 8 and 16 bit variables,
they are still copied in and out as 32-bit quantities.

Let me know if this seems like the right or wrong direction in which
to move.  I haven't tackled the static sysctls as the code I have does
some run-time evaluation because the code is easier to write that way.
 One possibility is to change the sysctl_oid struct or at least add a
SIGNED flag; this would also have the advantage of making it possible
to clean up the CTLTYPE_[U]INT issue where there is no real difference
between the two CTLTYPEs.


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