MFC: r317982

- Also outside of the KOBJOPLOOKUP macro - which in turn is used by
the code auto-generated for *.m - kobj_lookup_method(9) is useful;
for example in back-ends or base class device drivers in order to
determine whether a default method has been overridden. Thus, allow
for the kobj_method_t pointer argument - used by KOBJOPLOOKUP in
order to update the cache entry - of kobj_lookup_method(9), to be
NULL. Actually, that pointer is redundant as it's just set to the
same kobj_method_t that the kobj_lookup_method(9) function returns
in the first place, but probably it serves to reduce the number of
instructions generated for KOBJOPLOOKUP.
- For the same reason, move updating kobj_lookup_{hits,misses} (if
KOBJ_STATS is defined) from kobj_lookup_method(9) to KOBJOPLOOKUP.
As a side-effect, this gets rid of the convoluted approach of always
incrementing kobj_lookup_hits in KOBJOPLOOKUP and then in case of
a cache miss, decrementing it in kobj_lookup_method(9) again.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

As it turns out, r186347 actually is insufficient to avoid the use of the
curthread-accessing part of mtx_{,un}lock(9) when using a r210623-style
curthread implementation on sparc64, crashing the kernel in its early
cycles as PCPU isn't set up, yet (and can't be set up as OFW is one of the
things we need for that, which leads to a chicken-and-egg problem). What
happens is that due to the fact that the idea of r210623 actually is to
allow the compiler to cache invocations of curthread, it factors out
obtaining curthread needed for both mtx_lock(9) and mtx_unlock(9) to
before the branch based on kobj_mutex_inited when compiling the kernel
without the debugging options. So change kobj_class_compile_static(9)
to just never acquire kobj_mtx, effectively restricting it to its
documented use, and add a kobj_init_static(9) for initializing objects
using a class compiled with the former and that also avoids using mutex(9)
(and malloc(9)). Also assert in both of these functions that they are
used in their intended way only.
While at it, inline kobj_register_method() and kobj_unregister_method()
as there wasn't much point for factoring them out in the first place
and so that a reader of the code has to figure out the locking for
fewer functions missing a KOBJ_ASSERT.
Tested on powerpc{,64} by andreast.

Reviewed by: nwhitehorn (earlier version), jhb
MFC after: 3 days

Simplify the code emitted by makeobjops.awk slightly.

Just place the default kobj_method inside the kobjop_desc structure.
There's no need to give these kobj_methods their own symbol. This shaves
off 10 KB of a GENERIC kernel binary.

Make kobj_methods constant.

These structures hold no information that is modified during runtime. By
marking this constant, we see approximately 600 symbols become
read-only (amd64 GENERIC). While there, also mark the kobj_method
structures generated by makeobjops.awk static. They are only referenced
by the kobjop_desc structures within the same file.

Before:

$ ls -l kernel
-rwxr-xr-x 1 ed wheel 15937309 Nov 8 16:29 kernel*
$ size kernel
text data bss dec hex filename
12260854 1358468 2848832 16468154 fb48ba kernel
$ nm kernel | fgrep -c ' r '
8240

After:

$ ls -l kernel
-rwxr-xr-x 1 ed wheel 15922469 Nov 8 16:25 kernel*
$ size kernel
text data bss dec hex filename
12302869 1302660 2848704 16454233 fb1259 kernel
$ nm kernel | fgrep -c ' r '
8838

sysctl(9) cleanup checkpoint: amd64 GENERIC builds cleanly.

Commit the kernel changes.

Use NULL in preference to 0 in pointer contexts.

Modularize the Open Firmware client interface to allow run-time switching
of OFW access semantics, in order to allow future support for real-mode
OF access and flattened device frees. OF client interface modules are
implemented using KOBJ, in a similar way to the PPC PMAP modules.

Because we need Open Firmware to be available before mutexes can be used on
sparc64, changes are also included to allow KOBJ to be used very early in
the boot process by only using the mutex once we know it has been initialized.

Reviewed by: marius, grehan

Increment kobj_lookup_misses on a miss rather than decrementing it.
Otherwise, the miss count is actually -kobj_lookup_misses. Mostly a
pedantic change as KOBJ_STATS isn't on by default.

Export a routine, kobj_machdep_init(), that allows platforms
to use the kobj subsystem as soon at mutex_init() has been called
instead of having to wait for the SI_SUB_LOCK sysinit.

Reviewed by: dfr

* Add multiple inheritance to kobj. Each class can have zero or more base
classes and if a method is not found in a given class, its base classes
are searched (in the order they were declared). This search is recursive,
i.e. a method may be define in a base class of a base class.
* Change the kobj method lookup algorithm to one which is SMP-safe. This
relies only on the constraint that an observer of a sequence of writes
of pointer-sized values will see exactly one of those values, not a
mixture of two or more values. This assumption holds for all processors
which FreeBSD supports.
* Add locking to kobj class initialisation.
* Add a simpler form of 'inheritance' for devclasses. Each devclass can
have a parent devclass. Searches for drivers continue up the chain of
devclasses until either a matching driver is found or a devclass is
reached which has no parent. This can allow, for instance, pci drivers
to match cardbus devices (assuming that cardbus declares pci as its
parent devclass).
* Increment __FreeBSD_version.

This preserves the driver API entirely except for one minor feature used
by the ISA compatibility shims. A workaround for ISA compatibility will
be committed separately. The kobj and newbus ABI has changed - all modules
must be recompiled.

add a read-only sysctl to display the number of entries in the fixed size
kobj global method table; also kassert that the table has not overflowed
when defining a new method.

there are indications that the table is being overflowed in certain
situations as we gain more kobj consumers- this will allow us to check
whether kobj is at fault. symptoms would be incorrect methods being called.

Use __FBSDID().

Convert hit and miss counters to unsigned values. Surely negative values
for either does not make sense.

PR: (one small part of) 19720

Convert more malloc+bzero to malloc+M_ZERO.

Submitted by: josh@zipperup.org
Submitted by: Robert Drehmel <robd@gmx.net>

Add kobj_class_compile_static() to allow classes to be initialised
statically (i.e. without calling malloc). This allows kobj to be used
very early in the boot sequence.

* Move the driver_t::refs field to kobj_t to replace kobj_t::instances.
* Back out a couple of workarounds for the confusion between
kobj_t::instances and driver_t::refs.

* Factor out the object system from new-bus so that it can be used by
non-device code.
* Re-implement the method dispatch to improve efficiency. The new system
takes about 40ns for a method dispatch on a 300Mhz PII which is only
10ns slower than a direct function call on the same hardware.

This changes the new-bus ABI slightly so make sure you re-compile any
driver modules which you use.