ksyms: Lock the object while setting NOSPLIT.

[markj]

Summary

Alan pointed out that the object resides in the global object list, so
formally we should lock it to synchronize with a scan of the list.

[alc]

I think that we should consider adding a vm_object_allocate_flags().

[kib]

Although unlocked manipulations of the flags were removed AFAIR.

[markj]

I realized after submitting this that really we should be using OBJT_PHYS here. The object's contents are not pageable.

[markj]

Convert to OBJT_PHYS and stop setting NOSPLIT entirely.

[alc]

sys/dev/ksyms/ksyms.c

44

Is this still needed?

[markj]

Remove unneeded include.

[alc]

In D22229#485773, @kib wrote:

Although unlocked manipulations of the flags were removed AFAIR.

Yes, I believe so. However, in recent weeks, I recall seeing at least two attempts to reintroduce unlocked manipulations, counting this as one of them. I think that a vm_object_allocate_flags() would eliminate the temptation to do so.