Commit Graph

1915 Commits

Author SHA1 Message Date
Marius Strobl
546e977edb Now that we have a working OF_printf() since r230631 and a OF_panic()
helper since r230632, use these for output and panicing during the
early cycles and move cninit() until after the static per-CPU data
has been set up. This solves a couple of issue regarding the non-
availability of the static per-CPU data:
- panic() not working and only making things worse when called,
- having to supply a special DELAY() implementation to the low-level
  console drivers,
- curthread accesses of mutex(9) usage in low-level console drivers
  that aren't conditional due to compiler optimizations (basically,
  this is the problem described in r227537 but in this case for
  keyboards attached via uart(4)). [1]

PR:	164123 [1]
2012-01-27 23:21:54 +00:00
Marius Strobl
a500e985ad - Now that we have a working OF_printf() since r230631, use it for
implementing a simple OF_panic() that may be used during the early
  cycles when panic() isn't available, yet.
- Mark cpu_{exit,shutdown}() as __dead2 as appropriate.
2012-01-27 22:35:53 +00:00
Marius Strobl
21bbe2ac13 For machines where the kernel address space is unrestricted increase
VM_KMEM_SIZE_SCALE to 2, awaiting more insight from alc@. As it turns
out, the VM apparently has problems with machines that have large holes
in the physical address space, causing the kmem_suballoc() call in
kmeminit() to fail with a VM_KMEM_SIZE_SCALE of 1. Using a value of 2
allows these, namely Blade 1500 with 2GB of RAM, to boot.

PR:	164227
2012-01-27 22:25:46 +00:00
Marius Strobl
733ce5d25e Mark cpu_{halt,reset}() as __dead2 as appropriate. 2012-01-27 22:04:43 +00:00
David Schultz
2ee7b1d4ae Add C11 macros describing subnormal numbers to float.h.
Reviewed by:	bde
2012-01-23 06:36:41 +00:00
Kenneth D. Merry
130f4520cb Add the CAM Target Layer (CTL).
CTL is a disk and processor device emulation subsystem originally written
for Copan Systems under Linux starting in 2003.  It has been shipping in
Copan (now SGI) products since 2005.

It was ported to FreeBSD in 2008, and thanks to an agreement between SGI
(who acquired Copan's assets in 2010) and Spectra Logic in 2010, CTL is
available under a BSD-style license.  The intent behind the agreement was
that Spectra would work to get CTL into the FreeBSD tree.

Some CTL features:

 - Disk and processor device emulation.
 - Tagged queueing
 - SCSI task attribute support (ordered, head of queue, simple tags)
 - SCSI implicit command ordering support.  (e.g. if a read follows a mode
   select, the read will be blocked until the mode select completes.)
 - Full task management support (abort, LUN reset, target reset, etc.)
 - Support for multiple ports
 - Support for multiple simultaneous initiators
 - Support for multiple simultaneous backing stores
 - Persistent reservation support
 - Mode sense/select support
 - Error injection support
 - High Availability support (1)
 - All I/O handled in-kernel, no userland context switch overhead.

(1) HA Support is just an API stub, and needs much more to be fully
    functional.

ctl.c:			The core of CTL.  Command handlers and processing,
			character driver, and HA support are here.

ctl.h:			Basic function declarations and data structures.

ctl_backend.c,
ctl_backend.h:		The basic CTL backend API.

ctl_backend_block.c,
ctl_backend_block.h:	The block and file backend.  This allows for using
			a disk or a file as the backing store for a LUN.
			Multiple threads are started to do I/O to the
			backing device, primarily because the VFS API
			requires that to get any concurrency.

ctl_backend_ramdisk.c:	A "fake" ramdisk backend.  It only allocates a
			small amount of memory to act as a source and sink
			for reads and writes from an initiator.  Therefore
			it cannot be used for any real data, but it can be
			used to test for throughput.  It can also be used
			to test initiators' support for extremely large LUNs.

ctl_cmd_table.c:	This is a table with all 256 possible SCSI opcodes,
			and command handler functions defined for supported
			opcodes.

ctl_debug.h:		Debugging support.

ctl_error.c,
ctl_error.h:		CTL-specific wrappers around the CAM sense building
			functions.

ctl_frontend.c,
ctl_frontend.h:		These files define the basic CTL frontend port API.

ctl_frontend_cam_sim.c:	This is a CTL frontend port that is also a CAM SIM.
			This frontend allows for using CTL without any
			target-capable hardware.  So any LUNs you create in
			CTL are visible in CAM via this port.

ctl_frontend_internal.c,
ctl_frontend_internal.h:
			This is a frontend port written for Copan to do
			some system-specific tasks that required sending
			commands into CTL from inside the kernel.  This
			isn't entirely relevant to FreeBSD in general,
			but can perhaps be repurposed.

ctl_ha.h:		This is a stubbed-out High Availability API.  Much
			more is needed for full HA support.  See the
			comments in the header and the description of what
			is needed in the README.ctl.txt file for more
			details.

ctl_io.h:		This defines most of the core CTL I/O structures.
			union ctl_io is conceptually very similar to CAM's
			union ccb.

ctl_ioctl.h:		This defines all ioctls available through the CTL
			character device, and the data structures needed
			for those ioctls.

ctl_mem_pool.c,
ctl_mem_pool.h:		Generic memory pool implementation used by the
			internal frontend.

ctl_private.h:		Private data structres (e.g. CTL softc) and
			function prototypes.  This also includes the SCSI
			vendor and product names used by CTL.

ctl_scsi_all.c,
ctl_scsi_all.h:		CTL wrappers around CAM sense printing functions.

ctl_ser_table.c:	Command serialization table.  This defines what
			happens when one type of command is followed by
			another type of command.

ctl_util.c,
ctl_util.h:		CTL utility functions, primarily designed to be
			used from userland.  See ctladm for the primary
			consumer of these functions.  These include CDB
			building functions.

scsi_ctl.c:		CAM target peripheral driver and CTL frontend port.
			This is the path into CTL for commands from
			target-capable hardware/SIMs.

README.ctl.txt:		CTL code features, roadmap, to-do list.

usr.sbin/Makefile:	Add ctladm.

ctladm/Makefile,
ctladm/ctladm.8,
ctladm/ctladm.c,
ctladm/ctladm.h,
ctladm/util.c:		ctladm(8) is the CTL management utility.
			It fills a role similar to camcontrol(8).
			It allow configuring LUNs, issuing commands,
			injecting errors and various other control
			functions.

usr.bin/Makefile:	Add ctlstat.

ctlstat/Makefile
ctlstat/ctlstat.8,
ctlstat/ctlstat.c:	ctlstat(8) fills a role similar to iostat(8).
			It reports I/O statistics for CTL.

sys/conf/files:		Add CTL files.

sys/conf/NOTES:		Add device ctl.

sys/cam/scsi_all.h:	To conform to more recent specs, the inquiry CDB
			length field is now 2 bytes long.

			Add several mode page definitions for CTL.

sys/cam/scsi_all.c:	Handle the new 2 byte inquiry length.

sys/dev/ciss/ciss.c,
sys/dev/ata/atapi-cam.c,
sys/cam/scsi/scsi_targ_bh.c,
scsi_target/scsi_cmds.c,
mlxcontrol/interface.c:	Update for 2 byte inquiry length field.

scsi_da.h:		Add versions of the format and rigid disk pages
			that are in a more reasonable format for CTL.

amd64/conf/GENERIC,
i386/conf/GENERIC,
ia64/conf/GENERIC,
sparc64/conf/GENERIC:	Add device ctl.

i386/conf/PAE:		The CTL frontend SIM at least does not compile
			cleanly on PAE.

Sponsored by:	Copan Systems, SGI and Spectra Logic
MFC after:	1 month
2012-01-12 00:34:33 +00:00
Robert Watson
009d2032af Add "options CAPABILITY_MODE" and "options CAPABILITIES" to GENERIC kernel
configurations for various architectures in FreeBSD 10.x.  This allows
basic Capsicum functionality to be used in the default FreeBSD
configuration on non-embedded architectures; process descriptors are not
yet enabled by default.

MFC after:	3 months
Sponsored by:	Google, Inc
2011-12-29 22:48:36 +00:00
Alan Cox
3b03ca3bbe Eliminate vestiges of page coloring. 2011-12-15 05:07:16 +00:00
Ed Schouten
53627e400f Replace __signed by signed.
The signed keyword is an integral part of the C syntax. There's no need
to use __signed.
2011-12-13 13:38:03 +00:00
Marius Strobl
66b82ed179 Revert r225889 a bit. While it's correct that in total store order there's
no need to additionally add CPU memory barriers to the acquire variants of
atomic(9), these are documented to also include compiler memory barriers.
So add the latter, which were previously included by using membar(), back.
2011-12-03 13:51:57 +00:00
Jayachandran C.
07042bef45 Fix OF_finddevice error return value in case of FDT.
According to the open firmware standard, finddevice call has to return
a phandle with value of -1 in case of error.

This commit is to:
- Fix the FDT implementation of this interface (ofw_fdt_finddevice) to
  return (phandle_t)-1 in case of error, instead of 0 as it does now.
- Fix up the callers of OF_finddevice() to compare the return value with
  -1 instead of 0 to check for errors.
- Since phandle_t is unsigned, the return value of OF_finddevice should
  be checked with '== -1' rather than '<= 0' or '> 0', fix up these cases
  as well.

Reported by:	nwhitehorn

Reviewed by:	raj
Approved by:	raj, nwhitehorn
2011-12-02 15:24:39 +00:00
Marius Strobl
c7bba74954 Update comment. 2011-11-27 15:49:46 +00:00
Marius Strobl
abef0e6700 For sparc64 also adjust the geometry of da(4) driven disks to not overflow
the 16-bit cylinders field of the VTOC8 disk label (at around 502GB). The
geometry chosen for disks above that limit allows to use disks up to 2TB,
which is the limit of the extended VTOC8 format. The geometry used for
disks smaller than the 16-bit cylinders limit stays the same as used by
cam_calc_geometry(9) for extended translation.
Thanks to Hans-Joerg Sirtl for providing hardware for testing this change.

MFC after:	3 days
2011-11-27 15:43:40 +00:00
Marius Strobl
1fa2664f97 Move to SCHED_ULE by default. Since r226057 SCHED_ULE and sparc64 are
compatible with each other and since r227539 the last issue seen when
using SCHED_ULE is fixed. At least on UP and 2-way machines SCHED_4BSD
still performs better than SCHED_ULE, however, the optimizations done
in r225889 pretty much compensate that so there's at least no net
regression.
Thanks go to Peter Jeremy for extensive testing.
2011-11-25 17:40:01 +00:00
Marius Strobl
7266520baf Increase the CDMA sync timeout for Schizo bridges to 15 seconds as used by
OpenSolaris. One second turned out to be not enough for certain loads while
10 seconds were sufficient.
Reported by: Peter Jeremy

MFC after:	3 days
2011-11-24 23:48:22 +00:00
Marius Strobl
848e30ff51 s,KOBJMETHOD_END,DEVMETHOD_END,g in order to fully hide the explicit mention
of kobj(9) from device drivers.
2011-11-22 21:55:40 +00:00
Marius Strobl
4b7ec27007 - There's no need to overwrite the default device method with the default
one. Interestingly, these are actually the default for quite some time
  (bus_generic_driver_added(9) since r52045 and bus_generic_print_child(9)
  since r52045) but even recently added device drivers do this unnecessarily.
  Discussed with: jhb, marcel
- While at it, use DEVMETHOD_END.
  Discussed with: jhb
- Also while at it, use __FBSDID.
2011-11-22 21:28:20 +00:00
Pawel Jakub Dawidek
1859c4740e Fix make universe. 2011-11-16 18:42:43 +00:00
Marius Strobl
1249ba5fc6 Define curthread as an inline function that loads the thread pointer
directly from g7, the pcpu pointer. This guarantees correct behavior
when the thread migrates to a different CPU.
Commit message stolen from r205431. Additional testing by Peter Jeremy.

MFC after:	3 days
2011-11-15 20:17:18 +00:00
Attilio Rao
ed1f6dc235 Introduce the option VFS_ALLOW_NONMPSAFE and turn it on by default on
all the architectures.
The option allows to mount non-MPSAFE filesystem. Without it, the
kernel will refuse to mount a non-MPSAFE filesytem.

This patch is part of the effort of killing non-MPSAFE filesystems
from the tree.

No MFC is expected for this patch.

Tested by:	gianni
Reviewed by:	kib
2011-11-08 10:18:07 +00:00
Ed Schouten
6472ac3d8a Mark all SYSCTL_NODEs static that have no corresponding SYSCTL_DECLs.
The SYSCTL_NODE macro defines a list that stores all child-elements of
that node. If there's no SYSCTL_DECL macro anywhere else, there's no
reason why it shouldn't be static.
2011-11-07 15:43:11 +00:00
Ed Schouten
d745c852be Mark MALLOC_DEFINEs static that have no corresponding MALLOC_DECLAREs.
This means that their use is restricted to a single C file.
2011-11-07 06:44:47 +00:00
Marius Strobl
a9ab459b31 Add a PCI front-end to esp(4) allowing it to support AMD Am53C974 and
replace amd(4) with the former in the amd64, i386 and pc98 GENERIC kernel
configuration files. Besides duplicating functionality, amd(4), which
previously also supported the AMD Am53C974, unlike esp(4) is no longer
maintained and has accumulated enough bit rot over time to always cause
a panic during boot as long as at least one target is attached to it
(see PR 124667).

PR:		124667
Obtained from:	NetBSD (based on)
MFC after:	3 days
2011-11-01 21:26:57 +00:00
Marius Strobl
fb1b34b313 Actually, limit to 32-bit DMA for the transfer buffers as the address is
written into a 32-bit register.
2011-10-30 21:42:35 +00:00
Marius Strobl
f1ffe65cc5 Correct the DMA constraints, the LSI64854 isn't limited to 32-bit DMA. 2011-10-30 21:19:13 +00:00
Marius Strobl
5e141ae05f - Use device_t rather than the NetBSDish struct device.
- Move esp_devclass to ncr53c9x.c in order to allow different bus front-ends
  to use it.
- Use KOBJMETHOD_END.
- Remove the gl_clear_latched_intr hook as it's not needed for any of the
  chips nor the front-ends supported in FreeBSD and likely never will be.
- Correct the DMA constraints used in the SBus front-end, the LSI64854 isn't
  limited to 32-bit DMA.
- The ESP200 also only supports up to 64k transfers.
- Don't let the DMA and SBus front-end supply a maximum transfer size larger
  than MAXPHYS as that's the maximum the upper layers use and we otherwise
  just waste resources unnecessarily.
- Initialize the ECB callout and don't zero the handle when returning ECBs
  to the free list so that ncr53c9x_callout() actually is called with the
  driver lock held.
- On detach the driver lock should be held across cam_sim_free() according
  to isp(4) and a panic received.
- Check the return value of NCRDMA_SETUP(), i.e. bus_dmamap_load(9), and try
  to handle failures gracefully.
- In ncr53c9x_action() replace N calls to xpt_done() in a switch with just
  one at the end.
- On XPT_PATH_INQ report "NCR" rather than "Sun" as the vendor as the former
  is somewhat more correct as well as the maximum supported transfer size via
  maxio in order to take advantage of controllers that that can handle more
  than DFLTPHYS.
- Print the number of MESSAGE (EXTENDED) rejected.
- Fix the path encoded in the multiple inclusion protection of ncr53c9xvar.h.
- Correct the DMA constraints used in the LSI64854 core to not exceed the
  maximum supported transfer size and include the boundary so we don't need
  to check on every setup of a DMA transfer.
- Let the bus DMA map callbacks do nothing in case of an error.
- Correctly handle > 64k transfers for FAS366 in the LSI64854. A new feature
  flag NCR_F_LARGEXFER was introduced so we just need to check for this one
  and not for individual controllers supporting large transfers in several
  places.
- Let the LSI64854 core load transfer buffers using BUS_DMA_NOWAIT as the
  NCR53C9x core can't handle EINPROGRESS. Due to lack of bounce buffers
  support, sparc64 doesn't actually use EINPROGRESS and likely never will,
  as an example for writing additional front-ends for the NCR53C9x core it
  makes sense to set BUS_DMA_NOWAIT anyway though.
- Some minor cleanup.
2011-10-30 21:17:42 +00:00
Ken Smith
6168545a11 Adjust the debugger options slightly. This should help me do the right
thing when changing the debugging options as part of head becoming a new
stable branch.  It may also help people who for one reason or another want
to run head but don't want it slowed down by the debugging support.

Reviewed by:	kib
2011-10-27 13:07:49 +00:00
David Schultz
a50079b7ff People porting FreeBSD to new architectures ought not have to
implement a deprecated FPU control interface in addition to the
standard one.  To make this clearer, further deprecate ieeefp.h
by not declaring the function prototypes except on architectures
that implement them already.

Currently i386 and amd64 implement the ieeefp.h interface for
compatibility, and for fp[gs]etprec(), which doesn't exist on
most other hardware.  Powerpc, sparc64, and ia64 partially implement
it and probably shouldn't, and other architectures don't implement it
at all.
2011-10-21 06:41:46 +00:00
Ken Smith
7042aba738 Add a warning about why sbp(4) is commented out so that curious folks
are forewarned they might wind up with a hole in their foot if they
decide to give it a try.

Suggested by:	dougb
2011-10-19 21:55:20 +00:00
Ken Smith
4c0ba9b742 Comment out the sbp(4) driver for architectures that support it.
As part of the 8.0-RELEASE cycle this was done in stable/8 (r199112)
but was left alone in head so people could work on fixing an issue that
caused boot failure on some motherboards.  Apparently nobody has worked
on it and we are getting reports of boot failure with the 9.0 test builds.
So this time I'll comment out the driver in head (still hoping someone
will work on it) and MFC to stable/9.

Submitted by:	Alberto Villa <avilla at FreeBSD dot org>
2011-10-18 13:45:16 +00:00
Dag-Erling Smørgrav
a417d4a46b Trace attempts to call restricted MD syscalls. 2011-10-18 07:39:27 +00:00
Marius Strobl
2b6ae84b63 Merge from NetBSD:
- Remove clause 3 and 4 from TNF licenses.
- Fix memset usage.
- Various cleanup.
- Kill caddr_t.
2011-10-15 09:29:43 +00:00
Konstantin Belousov
6bfe4c78c8 Remove unused define.
MFC after:	1 month
2011-10-07 16:09:44 +00:00
Marius Strobl
c95589317d - Use atomic operations rather than sched_lock for safely assigning pm_active
and pc_pmap for SMP. This is key to allowing adding support for SCHED_ULE.
  Thanks go to Peter Jeremy for additional testing.
- Add support for SCHED_ULE to cpu_switch().

Committed from:	201110DevSummit
2011-10-06 11:01:31 +00:00
Marius Strobl
2ab9ab1ffe Actually enable NEW_PCIB by default, missed in r225931. 2011-10-02 23:31:14 +00:00
Marius Strobl
bda8e754a1 Make sparc64 compatible with NEW_PCIB and enable it:
- Implement bus_adjust_resource() methods as far as necessary and in non-PCI
  bridge drivers as far as feasible without rototilling them.
- As NEW_PCIB does a layering violation by activating resources at layers
  above pci(4) without previously bubbling up their allocation there, move
  the assignment of bus tags and handles from the bus_alloc_resource() to
  the bus_activate_resource() methods like at least the other NEW_PCIB
  enabled architectures do. This is somewhat unfortunate as previously
  sparc64 (ab)used resource activation to indicate whether SYS_RES_MEMORY
  resources should be mapped into KVA, which is only necessary if their
  going to be accessed via the pointer returned from rman_get_virtual() but
  not for bus_space(9) as the later always uses physical access on sparc64.
  Besides wasting KVA if we always map in SYS_RES_MEMORY resources, a driver
  also may deliberately not map them in if the firmware already has done so,
  possibly in a special way. So in order to still allow a driver to decide
  whether a SYS_RES_MEMORY resource should be mapped into KVA we let it
  indicate that by calling bus_space_map(9) with BUS_SPACE_MAP_LINEAR as
  actually documented in the bus_space(9) page. This is implemented by
  allocating a separate bus tag per SYS_RES_MEMORY resource and passing the
  resource via the previously unused bus tag cookie so we later on can call
  rman_set_virtual() in sparc64_bus_mem_map(). As a side effect this now
  also allows to actually indicate that a SYS_RES_MEMORY resource should be
  mapped in as cacheable and/or read-only via BUS_SPACE_MAP_CACHEABLE and
  BUS_SPACE_MAP_READONLY respectively.
- Do some minor cleanup like taking advantage of rman_init_from_resource(),
  factor out the common part of bus tag allocation into a newly added
  sparc64_alloc_bus_tag(), hook up some missing newbus methods and replace
  some homegrown versions with the generic counterparts etc.
- While at it, let apb_attach() (which can't use the generic NEW_PCIB code
  as APB bridges just don't have the base and limit registers implemented)
  regarding the config space registers cached in pcib_softc and the SYSCTL
  reporting nodes set up.
2011-10-02 23:22:38 +00:00
Marius Strobl
1866626239 Remove obsolete macros. 2011-10-01 13:33:14 +00:00
Marius Strobl
6319597402 Nuke SUN4U #ifdef's which with the demise of sun4v no longer serve any
purpose.
2011-10-01 13:16:01 +00:00
Marius Strobl
1ef3f048e0 Also allocate space for the PIL counters. Given that no machine actually
uses IV_MAX interrupt vectors this wasn't a problem in practice though.
2011-10-01 13:11:29 +00:00
Marius Strobl
64020d8477 Re-reading the Schizo errata suggests that it's actually tolerable to
also use the streaming buffer of pre version 5/revision 2.3 hardware as
long as we stay away from context flushes (which iommu(4) so far doesn't
take advantage of). OpenSolaris does the same.
2011-10-01 00:31:30 +00:00
Marius Strobl
0224e43d7c - Add protective parentheses to macros as far as possible.
- Move {r,w,}mb() to the top of this file where they live on most of the
  other architectures.
2011-10-01 00:22:24 +00:00
Marius Strobl
fafda37b15 In total store which we use for running the kernel and all of the userland
atomic operations behave as if the were followed by a memory barrier so
there's no need to include ones in the acquire variants of atomic(9).
Removing these results a small performance improvement, specifically this
is sufficient to compensate the performance loss seen in the worldstone
benchmark seen when using SCHED_ULE instead of SCHED_4BSD.
This change is inspired by Linux even more radically doing the equivalent
thing some time ago.
Thanks go to Peter Jeremy for additional testing.
2011-10-01 00:11:03 +00:00
Marius Strobl
9a91e2aa2e Add a comment about why contrary to what once would think running all of
userland with total store order actually is appropriate.
2011-09-30 20:23:18 +00:00
Marius Strobl
ade68e910d Use the extended integer condition code when comparing 64-bit values. Given
that ATOMIC_INC_LONG currently is unused this happened to not be fatal.
2011-09-30 20:13:51 +00:00
Marius Strobl
6fd7e2b7c6 - Right-justify backslashes as suggested by style(9).
- Rename ATOMIC_INC_ULONG to ATOMIC_INC_LONG in order to be consistent with
  the names of the other macros in this file an adjust accordingly.
2011-09-30 20:06:23 +00:00
Konstantin Belousov
578113aaa3 Remove locking of the vm page queues from several pmaps, which only
protected the dirty mask updates. The dirty mask updates are handled
by atomics after the r225840.

Submitted by:	alc
Tested by:	flo (sparc64)
MFC after:	2 weeks
2011-09-28 15:01:20 +00:00
Attilio Rao
e984e612a7 It is safe to initialize locks even on early boot (and it is the same
thing all the other architectures already do) thus just initialize
kernel_pmap in pmap_bootstrap().

Reported by:	alc
Reviewed by:	alc, marius
Tested by:	flo, marius
Approved by:	re (kib)
MFC after:	1 week
2011-09-19 18:29:15 +00:00
Kip Macy
8451d0dd78 In order to maximize the re-usability of kernel code in user space this
patch modifies makesyscalls.sh to prefix all of the non-compatibility
calls (e.g. not linux_, freebsd32_) with sys_ and updates the kernel
entry points and all places in the code that use them. It also
fixes an additional name space collision between the kernel function
psignal and the libc function of the same name by renaming the kernel
psignal kern_psignal(). By introducing this change now we will ease future
MFCs that change syscalls.

Reviewed by:	rwatson
Approved by:	re (bz)
2011-09-16 13:58:51 +00:00
Christian Brueffer
b48f7c4c8d Fix a zyd(4) comment typo that was copy+pasted into most kernel config files.
PR:		160276
Submitted by:	MATSUMIYA Ryo <matsumiya@mma.club.uec.ac.jp>
Approved by:	re (kib)
MFC after:	1 week
2011-09-11 17:39:51 +00:00
Konstantin Belousov
26ccf4f10f Inline the syscallenter() and syscallret(). This reduces the time measured
by the syscall entry speed microbenchmarks by ~10% on amd64.

Submitted by:	jhb
Approved by:	re (bz)
MFC after:	2 weeks
2011-09-11 16:05:09 +00:00