- Send the systrace_args files for all the compat ABIs to /dev/null for
now. Right now makesyscalls.sh generates a file with a hardcoded
function name, so it wouldn't work for any of the ABIs anyway. Probably
the function name should be configurable via a 'systracename' variable
and the functions should be stored in a function pointer in the sysvec
structure.
line switch. Other files which may make the same mistake (according to
fxr.watson.org) but aren't fixed in this commit (people with more clue
about those files should fix this):
- i386/xbox/xbox.c
- arm/arm/elf_trampoline.c
- arm/arm/mem.c
Noticed by: cognet
- TLS - complete
- pid/tid mangling - complete
- thread area - complete
- futexes - complete with issues
- clone() extension - complete with some possible minor issues
- mq*/timer*/clock* stuff - complete but untested and the mq* stuff is
disabled when not build as part of the kernel with native FreeBSD mq*
support (module support for this will come later)
Tested with:
- linux-firefox - works, tested
- linux-opera - works, tested
- linux-realplay - doesnt work, issue with futexes
- linux-skype - doesnt work, issue with futexes
- linux-rt2-demo - works, tested
- linux-acroread - doesnt work, unknown reason (coredump) and sometimes
issue with futexes
- various unix utilities in linux-base-gentoo3 and linux-base-fc4:
everything tried worked
On amd64 not everything is supported like on i386, the catchup is planned for
later when the remaining bugs in the new functions are fixed.
To test this new stuff, you have to run
sysctl compat.linux.osrelease=2.6.16
to switch back use
sysctl compat.linux.osrelease=2.4.2
Don't switch while running a linux program, strange things may or may not
happen.
Sponsored by: Google SoC 2006
Submitted by: rdivacky
Some suggestions/help by: jhb, kib, manu@NetBSD.org, netchild
compat.linux.osrelease is changed to "2.6.16" or similar).
On amd64 not everything is supported like on i386, the catchup is planned for
later when the remaining bugs in the new functions are fixed.
Sponsored by: Google SoC 2006
Submitted by: rdivacky
aren't mapped via pmap_enter() (KVA). We will eventually support PAT bits
on user pages, but those will require some sort of MI caching mode stored
in the vm_page.
Reviewed by: alc
WB (write-back) on x86 via control bits in PTEs and PDEs (including making
use of the PAT MSR). Changes include:
- A new pmap_mapdev_attr() function for amd64 and i386 which takes an
additional parameter (relative to pmap_mapdev()) specifying the cache
mode for this mapping. Note that on amd64 only WB mappings are done with
the direct map, all other modes result in a private mapping.
- pmap_mapdev() on i386 and amd64 now defaults to using UC (uncached)
mappings rather than WB. Previously we relied on the BIOS setting up
MTRR's to enforce memio regions being treated as UC. This might make
hw.cbb_start_memory unnecessary in some cases now for example.
- A new pmap_mapbios()/pmap_unmapbios() API has been added to allow places
that used pmap_mapdev() to map non-device memory (such as ACPI tables)
to do so using WB as before.
- A new pmap_change_attr() function for amd64 and i386 that changes the
caching mode for a range of KVA.
Reviewed by: alc
Originally, I had adopted sparc64's name, pmap_clear_write(), for the
function that is now pmap_remove_write(). However, this function is more
like pmap_remove_all() than like pmap_clear_modify() or
pmap_clear_reference(), hence, the name change.
The higher-level rationale behind this change is described in
src/sys/amd64/amd64/pmap.c revision 1.567. The short version is that I'm
trying to clean up and fix our support for execute access.
Reviewed by: marcel@ (ia64)
and pc98 MD files. Remove nodevice and nooption lines specific
to sio(4) from ia64, powerpc and sparc64 NOTES. There were no
such lines for arm yet.
sio(4) is usable on less than half the platforms, not counting
a future mips platform. Its presence in MI files is therefore
increasingly becoming a burden.
mark system calls as being MPSAFE:
- Stop conditionally acquiring Giant around system call invocations.
- Remove all of the 'M' prefixes from the master system call files.
- Remove support for the 'M' prefix from the script that generates the
syscall-related files from the master system call files.
- Don't explicitly set SYF_MPSAFE when registering nfssvc.
implementations and adjust some of the checks while I'm here:
- Add a new check to make sure we don't return from a syscall in a critical
section.
- Add a new explicit check before userret() to make sure we don't return
with any locks held. The advantage here is that we can include the
syscall number and name in syscall() whereas that info is not available
in userret().
- Drop the mtx_assert()'s of sched_lock and Giant. They are replaced by
the more general checks just added.
MFC after: 2 weeks
map was obtained from the SMAP. SMAP is trustworthy, and the memory
extending feature is a band-aid for older systems where FreeBSD's methods
of detecting memory were not always trustworthy. This fixes the issue
where using hw.physmem could result in the ACPI tables getting trashed
breaking ACPI.
MFC after: 3 days
Tested on: i386
Giant VFS locking in that function.
- Remove bogus code to handle the case where namei() returns success but a
NULL vnode pointer.
- Note that this code duplicates exec_check_permissions() and annotate
where it differs.
- Hold the vnode lock longer to protect the write to set VV_TEXT in
v_vflag.
- Mark linux_uselib() MPSAFE.
Reviewed by: rwatson
system's machine-dependent and machine-independent layers. Once
pmap_clear_write() is implemented on all of our supported
architectures, I intend to replace all calls to pmap_page_protect() by
calls to pmap_clear_write(). Why? Both the use and implementation of
pmap_page_protect() in our virtual memory system has subtle errors,
specifically, the management of execute permission is broken on some
architectures. The "prot" argument to pmap_page_protect() should
behave differently from the "prot" argument to other pmap functions.
Instead of meaning, "give the specified access rights to all of the
physical page's mappings," it means "don't take away the specified
access rights from all of the physical page's mappings, but do take
away the ones that aren't specified." However, owing to our i386
legacy, i.e., no support for no-execute rights, all but one invocation
of pmap_page_protect() specifies VM_PROT_READ only, when the intent
is, in fact, to remove only write permission. Consequently, a
faithful implementation of pmap_page_protect(), e.g., ia64, would
remove execute permission as well as write permission. On the other
hand, some architectures that support execute permission have
basically ignored whether or not VM_PROT_EXECUTE is passed to
pmap_page_protect(), e.g., amd64 and sparc64. This change represents
the first step in replacing pmap_page_protect() by the less subtle
pmap_clear_write() that is already implemented on amd64, i386, and
sparc64.
Discussed with: grehan@ and marcel@
pmap_clear_ptes() is already convoluted. This will worsen with the
implementation of superpages. Eliminate it and add pmap_clear_write().
There are no functional changes. Checked by: md5
pmap_remove_all() before rather than after the pmap is unlocked. At
present, the page queues lock provides sufficient sychronization. In the
future, the page queues lock may not always be held when free_pv_entry() is
called.
Make three simplifications to pmap_ts_referenced():
Eliminate an initialized but otherwise unused variable.
Eliminate an unnecessary test.
Exit the loop in a shorter way.
install custom pager functions didn't actually happen in practice (they
all just used the simple pager and passed in a local quit pointer). So,
just hardcode the simple pager as the only pager and make it set a global
db_pager_quit flag that db commands can check when the user hits 'q' (or a
suitable variant) at the pager prompt. Also, now that it's easy to do so,
enable paging by default for all ddb commands. Any command that wishes to
honor the quit flag can do so by checking db_pager_quit. Note that the
pager can also be effectively disabled by setting $lines to 0.
Other fixes:
- 'show idt' on i386 and pc98 now actually checks the quit flag and
terminates early.
- 'show intr' now actually checks the quit flag and terminates early.
ibcs2_getdents(), ibcs2_read(), ogetdirentries(), svr4_sys_getdents(),
and svr4_sys_getdents64() similar to that in getdirentries().
- Mark ibcs2_getdents(), ibcs2_read(), linux_getdents(), linux_getdents64(),
linux_readdir(), ogetdirentries(), svr4_sys_getdents(), and
svr4_sys_getdents64() MPSAFE.
that the 'data' pointer is already setup to point to a valid KVM buffer
or contains the copied-in data from userland as appropriate (ioctl(2)
still does this). kern_ioctl() takes care of looking up a file pointer,
implementing FIONCLEX and FIOCLEX, and calling fi_ioctl().
- Use kern_ioctl() to implement xenix_rdchk() instead of using the stackgap
and mark xenix_rdchk() MPSAFE.
ibcs2_[gs]etgroups() rather than using the stackgap. This also makes
ibcs2_[gs]etgroups() MPSAFE. Also, it cleans up one bit of weirdness in
the old setgroups() where it allocated an entire credential just so it had
a place to copy the group list into. Now setgroups just allocates a
NGROUPS_MAX array on the stack that it copies into and then passes to
kern_setgroups().
ABI as FreeBSD's poll(2) is ABI compatible. The ibcs2_poll() function
attempted to implement poll(2) using a wrapper around select(2). Besides
being somewhat ugly, it also had at least one bug in that instead of
allocating complete fdset's on the stack via the stackgap it just allocated
pointers to fdsets.
OpenBSD. This driver seems to give a small performance increase, and
should lead to better maintainability in the future.
The nForce Ethernet-specific hack in sys/i386/xbox/xbox.c is still
required, judging from dev/nfe/if_nfe.c. The condition it hacks will
almost certainly only occur on XBOX-es anyway, so it is best left there.
Approved by: imp (mentor)
to a copied-in copy of the 'union semun' and a uioseg to indicate which
memory space the 'buf' pointer of the union points to. This is then used
in linux_semctl() and svr4_sys_semctl() to eliminate use of the stackgap.
- Mark linux_ipc() and svr4_sys_semsys() MPSAFE.
from going away. mount(2) is now MPSAFE.
- Expand the scope of Giant some in unmount(2) to protect the mp structure
(or rather, to handle concurrent unmount races) from going away.
umount(2) is now MPSAFE, as well as linux_umount() and linux_oldumount().
- nmount(2) and linux_mount() were already MPSAFE.
pmap_copy() if the mapping is VM_INHERIT_SHARE. Suppose the mapping
is also wired. vmspace_fork() clears the wiring attributes in the vm
map entry but pmap_copy() copies the PG_W attribute in the PTE. I
don't think this is catastrophic. It blocks pmap_remove_pages() from
destroying the mapping and corrupts the pmap's wiring count.
This revision fixes the problem by changing pmap_copy() to clear the
PG_W attribute.
Reviewed by: tegge@
This driver was ported from OpenBSD by Shigeaki Tagashira
<shigeaki@se.hiroshima-u.ac.jp> and posted at
http://www.se.hiroshima-u.ac.jp/~shigeaki/software/freebsd-nfe.html
It was additionally cleaned up by me.
It is still a work-in-progress and thus is purposefully not in GENERIC.
And it conflicts with nve(4), so only one should be loaded.
in 1999, and there are changes to the sysctl names compared to PR,
according to that discussion. The description is in sys/conf/NOTES.
Lines in the GENERIC files are added in commented-out form.
I'll attach the test script I've used to PR.
PR: kern/14584
Submitted by: babkin
VM_ALLOC_NORMAL instead of VM_ALLOC_SYSTEM when try is TRUE. In other
words, when get_pv_entry() is permitted to fail, it no longer tries as
hard to allocate a page.
Change pmap_enter_quick_locked() to fail rather than wait if it is
unable to allocate a page table page. This prevents a race between
pmap_enter_object() and the page daemon. Specifically, an inactive
page that is a successor to the page that was given to
pmap_enter_quick_locked() might become a cache page while
pmap_enter_quick_locked() waits and later pmap_enter_object() maps
the cache page violating the invariant that cache pages are never
mapped. Similarly, change
pmap_enter_quick_locked() to call pmap_try_insert_pv_entry() rather
than pmap_insert_entry(). Generally speaking,
pmap_enter_quick_locked() is used to create speculative mappings. So,
it should not try hard to allocate memory if free memory is scarce.
Add an assertion that the object containing m_start is locked in
pmap_enter_object(). Remove a similar assertion from
pmap_enter_quick_locked() because that function no longer accesses the
containing object.
Remove a stale comment.
Reviewed by: ups@
syscalls. This way there will be a log message printed to the console
(this time for real).
Note: UNIMPL should be used for syscalls we do not implement ever, e.g.
syscalls to load linux kernel modules.
Submitted by: rdivacky
Sponsored by: Goole SoC 2006
P4 IDs: 99600, 99602
when we're about to call kdb_trap() because the latter MI
function can disable interrupts by itself now.
Pointed out by: bde
X-MFC remark: depends on kern/subr_kdb.c#1.18
Sponsored by: RiNet (Cronyx Plus LLC)
when the bit 22 is set to 1, CPUID with EAX=0 returns a maximum
value in EAX[7..0] of 3, when set to 0(default), CPUID with EAX=0
returns the number corresponding to the maximum standard function
supported. On my machine, BIOS sets the bit to 1 to make it to be
compatible with old OS, this causes dual-core Pentium-D (two
physical cores) to be identified as hyperthreading (two logical
cores) by function mp_topology().
the return address on the stack and only then "dereferences" %pc.
Therefore, in the case of a call to an invalid address, we arrive
to the trap handler with the invalid value in tf_eip. This used
to prevent db_backtrace() from assigning the most recent and interesting
frame on the stack to the right spot in the right function, from
which the invalid call was attempted.
Try to detect and work around that by recovering the return address
from the stack.
The work-around requires the fault address be passed to db_backtrace().
Smuggle it as tf_err.
MFC after: 1 month
Sponsored by: RiNet (Cronyx Plus LLC)
Now GCC likes to stick a "mov %eax, %FOO" instruction before
"addl $BAR, %esp" if the function just called returns an int,
which is a very common case in the kernel.
Sponsored by: RiNet (Cronyx Plus LLC)
an explicit comment that it's needed for the linuxolator. This is not the
case anymore. For all other architectures there was only a "KEEP THIS".
I'm (and other people too) running a COMPAT_43-less kernel since it's not
necessary anymore for the linuxolator. Roman is running such a kernel for a
for longer time. No problems so far. And I doubt other (newer than ia32
or alpha) architectures really depend on it.
This may result in a small performance increase for some workloads.
If the removal of COMPAT_43 results in a not working program, please
recompile it and all dependencies and try again before reporting a
problem.
The only place where COMPAT_43 is needed (as in: does not compile without
it) is in the (outdated/not usable since too old) svr4 code.
Note: this does not remove the COMPAT_43TTY option.
Nagging by: rdivacky
There is a race with the current locking scheme and removing
it should have no measurable performance impact.
This fixes page faults leading to panics in pmap_enter_quick_locked()
on amd64/i386.
Reviewed by: alc,jhb,peter,ps
Update of syscall.master:
o Adding of several new dummy syscalls (268-310)
o Synchronization of amd64 syscall.master with i386 one
o Auditing added to amd64 syscall.master
o Change auditing type for lstat syscall (bugfix). [1]
P4-Changes: 98672, 98674
Noticed by: rwatson [1]
Sponsored by: Google SoC 2006
Submitted by: rdivacky
I picked it up again. The scheduler is forked from ULE, but the
algorithm to detect an interactive process is almost completely
different with ULE, it comes from Linux paper "Understanding the
Linux 2.6.8.1 CPU Scheduler", although I still use same word
"score" as a priority boost in ULE scheduler.
Briefly, the scheduler has following characteristic:
1. Timesharing process's nice value is seriously respected,
timeslice and interaction detecting algorithm are based
on nice value.
2. per-cpu scheduling queue and load balancing.
3. O(1) scheduling.
4. Some cpu affinity code in wakeup path.
5. Support POSIX SCHED_FIFO and SCHED_RR.
Unlike scheduler 4BSD and ULE which using fuzzy RQ_PPQ, the scheduler
uses 256 priority queues. Unlike ULE which using pull and push, the
scheduelr uses pull method, the main reason is to let relative idle
cpu do the work, but current the whole scheduler is protected by the
big sched_lock, so the benefit is not visible, it really can be worse
than nothing because all other cpu are locked out when we are doing
balancing work, which the 4BSD scheduelr does not have this problem.
The scheduler does not support hyperthreading very well, in fact,
the scheduler does not make the difference between physical CPU and
logical CPU, this should be improved in feature. The scheduler has
priority inversion problem on MP machine, it is not good for
realtime scheduling, it can cause realtime process starving.
As a result, it seems the MySQL super-smack runs better on my
Pentium-D machine when using libthr, despite on UP or SMP kernel.
for CBUS-PNP cards there) by default, as there are no amd64 and sparc64
machines with ISA slots and which therefore could make use of this code
known to exist. For sparc64 this additionally allows to get rid of the
compat shims for in{b,w,l}()/out{b,w,l}() etc and the associated hacks.
OK'ed by: imp, peter
the arm to compile without all the extras that don't appear, at least
not in the flavors of ARM I deal with. This helps us save about 100k.
If I've botched the available devices on a platform, please let me
know and I'll correct ASAP.
not be necessary but might be helpful and at least reduce fragmentation.
* Add an assert to detect if the wakecode ever grows too big. We include
1 KB for stack, which should be more than enough also.
* Remove unnecessary initialization of static variables.
* Add comments and a bootverbose print giving the page phys address.
to 4. There is no need to be more strict at assembly time since we copy
the code anyway to a private page.
* Clear the direction flag and eflags. Probably not necessary but it won't
hurt to be safe.
* Add prefixes to all instructions to prevent any assembler mistakes.
* Remove zeroing of eax - edi. We use those registers immediately after
to transfer values to protected mode so this was pointless.
* Update comments to reflect info found during code review.
* Add hw.acpi.resume_beep tunable and sysctl, default to 0. Beeps the PC
speaker soon after waking to diagnose whether the wakeup code is even
getting run before other drivers possibly hang the system. To stop the beep,
cause another beep (i.e. keyboard bell). Submitted by takawata@, I changed
the frequency to be lower.
* Use 4096 instead of 4 byte alignment. Might be useful although doesn't
seem to be necessary.
* Remove a useless assignment to acpi_reset_video. It was overwritten by
the default sysctl value anyway.
Eliminate unnecessary, recursive acquisitions and releases of the page
queues lock by free_pv_entry() and pmap_remove_pages().
Reduce the scope of the page queues lock in pmap_remove_pages().
that it just warns the user with a printf when it misaligns a piece
of memory that was requested through a busdma tag.
Some drivers (such as mpt, and probably others) were asking for alignments
that could not be satisfied, but as far as driver operation was concerned,
that did not matter. In the theory that other drivers will fall into
this same category, we agreed that panicing or making the allocation
fail will cause more hardship than is necessary. The printf should
be sufficient motivation to get the driver glitch fixed.
POSIX (susv3) requires this, but it is unclear what should be inherited,
duplicating whole 387 stack for new thread seems to be unnecessary and
dangerous. Revert to previous code, force a new thread to be started with
clean FP state.
the high 16 bits is non-zero, fxrstor instruction will generate GP fault,
resulting kernel crash, this bug can be triggered by setcontext and
ptrace(PT_SETXMMREGS).
other timeouts could not happen while suspending, including timeouts
for things like msleep. This caused the system to hang on suspend
when the cbb was enabled, since its suspend path powered down the
socket which used a timeout to wait for it to be done.
APM now creates a thread when it is enabled, and deletes the thread
when it is disabled. This thread takes the place of the timeout by
doing its polling every ~.9s. When the thread is disabled, it will
wakeup early, otherwise it times out and polls the varius things the
old timeout polled (APM events, suspend delays, etc).
This makes my Sony VAIO 505TS suspend/resume correctly when APM is
enabled (ACPI is black listed on my 505TS).
This will likely fix other problems with the suspend path where
drivers would sleep with msleep and/or do other timeouts. Maybe
there's some special case code that would use DELAY while suspending
and msleep otherwise that can be revisited and removed.
This was also tested by glebius@, who pointed out that in the patch I
sent him, I'd forgotten apm_saver.c
MFC After: 3 weeks
lnc(4) on PC98 and i386. The ISA front-end supports the same non-PNP
network cards as lnc(4) did and additionally a couple of PNP ones.
Like lnc(4), the C-bus front-end of le(4) only supports C-NET(98)S
and is untested due to lack of such hardware, but given that's it's
based on the respective lnc(4) and not too different from the ISA
front-end it should be highly likely to work.
- Remove the descriptions of le(4), which where converted from lnc(4),
from sys/i386/conf/NOTES and sys/pc98/conf/NOTES as there's a common
one in sys/conf/NOTES.
entry to the PCI NICs section so it's in the same spot in all GENERIC
config files.
- Add a note to the description of pcn(4) informing that is has precedence
over le(4).
Remove an unnecessary check of the table's bus clock. CPUs that
support this feature export only the high/low settings via the MSR,
packed into 32 bits.
Hardware from: Centaur Technologies
MFC after: 1 week
Add back in a scheme to emulate old type major/minor numbers via hooks into
stat, linprocfs to return major/minors that Linux app's expect. Currently
only /dev/null is always registered. Drivers can register via the Linux
type shim similar to the ioctl shim but by using
linux_device_register_handler/linux_device_unregister_handler functions.
The structure is:
struct linux_device_handler {
char *bsd_driver_name;
char *linux_driver_name;
char *bsd_device_name;
char *linux_device_name;
int linux_major;
int linux_minor;
int linux_char_device;
};
Linprocfs uses this to display the major number of the driver. The
soon to be available linsysfs will use it to fill in the driver name.
Linux_stat uses it to translate the major/minor into Linux type values.
Note major numbers are dynamically assigned via passing in a -1 for
the major number so we don't need to keep track of them.
This is somewhat needed due to us switching to our devfs. MegaCli
will not run until I add in the linsysfs and mfi Linux compat changes.
Sponsored by: IronPort Systems
conformance with the mbuf and uio load routines. ENOMEM can only happen
with BUS_DMA_NOWAIT is passed in, thus the deferals are disabled. I don't
like doing this, but fixing this fixes assumptions in other important drivers,
which is a net benefit for now.
to the unused kva in the pv memory block to thread a freelist through.
This allows us to free pages that used to be used for pv entry chunks
since we can now track holes in the kva memory block.
Idea from: ups
o Properly use rman(9) to manage resources. This eliminates the
need to puc-specific hacks to rman. It also allows devinfo(8)
to be used to find out the specific assignment of resources to
serial/parallel ports.
o Compress the PCI device "database" by optimizing for the common
case and to use a procedural interface to handle the exceptions.
The procedural interface also generalizes the need to setup the
hardware (program chipsets, program clock frequencies).
o Eliminate the need for PUC_FASTINTR. Serdev devices are fast by
default and non-serdev devices are handled by the bus.
o Use the serdev I/F to collect interrupt status and to handle
interrupts across ports in priority order.
o Sync the PCI device configuration to include devices found in
NetBSD and not yet merged to FreeBSD.
o Add support for Quatech 2, 4 and 8 port UARTs.
o Add support for a couple dozen Timedia serial cards as found
in Linux.
Remove the code to dyanmically change the pv_entry limits. Go back
to a single fixed kva reservation for pv entries, like was done
before when using the uma zone. Go back to never freeing pages
back to the free pool after they are no longer used, just like
before.
This stops the lock order reversal due to aquiring the kernel map
lock while pmap was locked.
This fixes the recursive panic if invariants are enabled.
The problem was that allocating/freeing kva causes vm_map_entry
nodes to be allocated/freed. That can recurse back into pmap as
new pages are hooked up to kvm and hence all the problem.
Allocating/freeing kva indirectly allocate/frees memory.
So, by going back to a single fixed size kva block and an index,
we avoid the recursion panics and the LOR.
The problem is that now with a linear block of kva, we have no
mechanism to track holes once pages are freed. UMA has the same
problem when using custom object for a zone and a fixed reservation
of kva. Simple solutions like having a bitmap would work, but would
be very inefficient when there are hundreds of thousands of bits
in the map. A first-free pointer is similarly flawed because pages
can be freed at random and the first-free pointer would be rewinding
huge amounts. If we could allocate memory for tree strucures or
an external freelist, that would work. Except we cannot allocate/free
memory here because we cannot allocate/free address space to use
it in. Anyway, my change here reverts back to the UMA behavior of
not freeing pages for now, thereby avoiding holes in the map.
ups@ had a truely evil idea that I'll investigate. It should allow
freeing unused pages again by giving us a no-cost way to track the
holes in the kva block. But in the meantime, this should get people
booting with witness and/or invariants again.
Footnote: amd64 doesn't have this problem because of the direct map
access method. I'd done all my witness/invariants testing there. I'd
never considered that the harmless-looking kmem_alloc/kmem_free calls
would cause such a problem and it didn't show up on the boot test.
entry (PTE) have the same meaning. The exception to this rule is the
eighth bit (0x080). It is the PS bit in a PDE and the PAT bit in a
PTE. This change avoids the possibility that pmap_enter() confuses a
PAT bit with a PS bit, avoiding a panic().
Eliminate a diagnostic printf() from the i386 pmap_enter() that serves
no current purpose, i.e., I've seen no bug reports in the last two
years that are helped by this printf().
Reviewed by: jhb
