large (1G) memory machine configurations. I was able to run 'dbench 32'
on a 32MB system without bring the machine to a grinding halt.
* buffer cache hash table now dynamically allocated. This will
have no effect on memory consumption for smaller systems and
will help scale the buffer cache for larger systems.
* minor enhancement to pmap_clearbit(). I noticed that
all the calls to it used constant arguments. Making
it an inline allows the constants to propogate to
deeper inlines and should produce better code.
* removal of inherent vfs_ioopt support through the emplacement
of appropriate #ifdef's, with John's permission. If we do not
find a use for it by the end of the year we will remove it entirely.
* removal of getnewbufloops* counters & sysctl's - no longer
necessary for debugging, getnewbuf() is now optimal.
* buffer hash table functions removed from sys/buf.h and localized
to vfs_bio.c
* VFS_BIO_NEED_DIRTYFLUSH flag and support code added
( bwillwrite() ), allowing processes to block when too many dirty
buffers are present in the system.
* removal of a softdep test in bdwrite() that is no longer necessary
now that bdwrite() no longer attempts to flush dirty buffers.
* slight optimization added to bqrelse() - there is no reason
to test for available buffer space on B_DELWRI buffers.
* addition of reverse-scanning code to vfs_bio_awrite().
vfs_bio_awrite() will attempt to locate clusterable areas
in both the forward and reverse direction relative to the
offset of the buffer passed to it. This will probably not
make much of a difference now, but I believe we will start
to rely on it heavily in the future if we decide to shift
some of the burden of the clustering closer to the actual
I/O initiation.
* Removal of the newbufcnt and lastnewbuf counters that Kirk
added. They do not fix any race conditions that haven't already
been fixed by the gbincore() test done after the only call
to getnewbuf(). getnewbuf() is a static, so there is no chance
of it being misused by other modules. ( Unless Kirk can think
of a specific thing that this code fixes. I went through it
very carefully and didn't see anything ).
* removal of VOP_ISLOCKED() check in flushbufqueues(). I do not
think this check is necessary, the buffer should flush properly
whether the vnode is locked or not. ( yes? ).
* removal of extra arguments passed to getnewbuf() that are not
necessary.
* missed cluster_wbuild() that had to be a cluster_wbuild_wb() in
vfs_cluster.c
* vn_write() now calls bwillwrite() *PRIOR* to locking the vnode,
which should greatly aid flushing operations in heavy load
situations - both the pageout and update daemons will be able
to operate more efficiently.
* removal of b_usecount. We may add it back in later but for now
it is useless. Prior implementations of the buffer cache never
had enough buffers for it to be useful, and current implementations
which make more buffers available might not benefit relative to
the amount of sophistication required to implement a b_usecount.
Straight LRU should work just as well, especially when most things
are VMIO backed. I expect that (even though John will not like
this assumption) directories will become VMIO backed some point soon.
Submitted by: Matthew Dillon <dillon@backplane.com>
Reviewed by: Kirk McKusick <mckusick@mckusick.com>
than a review, this was a nice puzzle.
This is supposed to be binary and source compatible with older
applications that access the old FreeBSD-style three arguments to a
signal handler.
Except those applications that access hidden signal handler arguments
bejond the documented third one. If you have applications that do,
please let me know so that we take the opportunity to provide the
functionality they need in a documented manner.
Also except application that use 'struct sigframe' directly. You need
to recompile gdb and doscmd. `make world` is recommended.
Example program that demonstrates how SA_SIGINFO and old-style FreeBSD
handlers (with their three args) may be used in the same process is at
http://www3.cons.org/tmp/fbsd-siginfo.c
Programs that use the old FreeBSD-style three arguments are easy to
change to SA_SIGINFO (although they don't need to, since the old style
will still work):
Old args to signal handler:
void handler_sn(int sig, int code, struct sigcontext *scp)
New args:
void handler_si(int sig, siginfo_t *si, void *third)
where:
old:code == new:second->si_code
old:scp == &(new:si->si_scp) /* Passed by value! */
The latter is also pointed to by new:third, but accessing via
si->si_scp is preferred because it is type-save.
FreeBSD implementation notes:
- This is just the framework to make the interface POSIX compatible.
For now, no additional functionality is provided. This is supposed
to happen now, starting with floating point values.
- We don't use 'sigcontext_t.si_value' for now (POSIX meant it for
realtime-related values).
- Documentation will be updated when new functionality is added and
the exact arguments passed are determined. The comments in
sys/signal.h are meant to be useful.
Reviewed by: BDE
into uipc_mbuf.c. This reduces three sets of identical tunable code to
one set, and puts the initialisation with the mbuf code proper.
Make NMBUFs tunable as well.
Move the nmbclusters sysctl here as well.
Move the initialisation of maxsockets from param.c to uipc_socket2.c,
next to its corresponding sysctl.
Use the new tunable macros for the kern.vm.kmem.size tunable (this should have
been in a separate commit, whoops).
print_AMD_info(), L2 internal cache is shown, as are AMD's special CPUID
infos:
CPU: AMD-K6(tm) 3D processor (350.81-MHz 586-class CPU)
Origin = "AuthenticAMD" Id = 0x58c Stepping=12
Features=0x8021bf<FPU,VME,DE,PSE,TSC,MSR,MCE,CX8,PGE,MMX>
AMD Features=0x808029bf<FPU,VME,DE,PSE,TSC,MSR,MCE,CX8,SYSCALL,PGE,MMX,3DNow!>
PR: kern/12512
Submitted by: Louis A. Mamakos <louie@TransSys.COM>
we will never use more memory than this value (if specified), but will always
check memory for validity up to this amount.
Get rid of the speculative_mprobe option; the memory amount can now be
specified by hw.physmem.
QUEUE_AGE, QUEUE_LRU, and QUEUE_EMPTY we instead have QUEUE_CLEAN,
QUEUE_DIRTY, QUEUE_EMPTY, and QUEUE_EMPTYKVA. With this patch clean
and dirty buffers have been separated. Empty buffers with KVM
assignments have been separated from truely empty buffers. getnewbuf()
has been rewritten and now operates in a 100% optimal fashion. That is,
it is able to find precisely the right kind of buffer it needs to
allocate a new buffer, defragment KVM, or to free-up an existing buffer
when the buffer cache is full (which is a steady-state situation for
the buffer cache).
Buffer flushing has been reorganized. Previously buffers were flushed
in the context of whatever process hit the conditions forcing buffer
flushing to occur. This resulted in processes blocking on conditions
unrelated to what they were doing. This also resulted in inappropriate
VFS stacking chains due to multiple processes getting stuck trying to
flush dirty buffers or due to a single process getting into a situation
where it might attempt to flush buffers recursively - a situation that
was only partially fixed in prior commits. We have added a new daemon
called the buf_daemon which is responsible for flushing dirty buffers
when the number of dirty buffers exceeds the vfs.hidirtybuffers limit.
This daemon attempts to dynamically adjust the rate at which dirty buffers
are flushed such that getnewbuf() calls (almost) never block.
The number of nbufs and amount of buffer space is now scaled past the
8MB limit that was previously imposed for systems with over 64MB of
memory, and the vfs.{lo,hi}dirtybuffers limits have been relaxed
somewhat. The number of physical buffers has been increased with the
intention that we will manage physical I/O differently in the future.
reassignbuf previously attempted to keep the dirtyblkhd list sorted which
could result in non-deterministic operation under certain conditions,
such as when a large number of dirty buffers are being managed. This
algorithm has been changed. reassignbuf now keeps buffers locally sorted
if it can do so cheaply, and otherwise gives up and adds buffers to
the head of the dirtyblkhd list. The new algorithm is deterministic but
not perfect. The new algorithm greatly reduces problems that previously
occured when write_behind was turned off in the system.
The P_FLSINPROG proc->p_flag bit has been replaced by the more descriptive
P_BUFEXHAUST bit. This bit allows processes working with filesystem
buffers to use available emergency reserves. Normal processes do not set
this bit and are not allowed to dig into emergency reserves. The purpose
of this bit is to avoid low-memory deadlocks.
A small race condition was fixed in getpbuf() in vm/vm_pager.c.
Submitted by: Matthew Dillon <dillon@apollo.backplane.com>
Reviewed by: Kirk McKusick <mckusick@mckusick.com>
behavior slightly.
If machine/bus.h is included, but neither bus_memio.h nor bus_pio.h
are included, then behave as if both were included.
This won't change existing drivers, all of which include one or more
of bus_{p,mem}io.h, but will allow drivers from other systems to come
over with fewer changes. I freely admit that this might not be
optimal for some drivers, but those drivers can be optimized for
FreeBSD after the initial bringup happens.
Without the change, there is a bug that preclude drivers from
compiling with strange warning/errors.
I've been running this here for a while now w/o ill effects.
Reviewed by: gibbs
Not objected to by: bde, arch@ list.
- The kernel environment variable 'hw.physmem' can be used to set the
amount of physical memory space, based at 0, that FreeBSD will use.
Any memory detected over this limit is ignored. Documentation for
this is available under 'help set tunables' in the loader.
- In the case where system memory size can't be accurately determined,
hw.physmem is used as a best-guess memory size, but speculative
probing will be used to determine actual memory size if any of the
guesses or hints are 16M or more.
- If RB_VERBOSE, we list the memory regions as we test them.
- The compile-time option MAXMEM supplies a default value for
'hw.physmem'.
specified in the kernel config file - but setting options MAXMEM works
exactly the same. Userconfig overrides of this have not worked for
ages.
Also, change the getenv for the loader override to hw.physmem based on a
prior suggestion from Mike Smith. I think he still wants to change this
some, but this shouldn't get in his way. This is a forced setting of
the memory size, not a "cap". We probably should have a plain 'maxmem'
variable as well which does do a cap, without loosing the bios memory
configuration data.
memory size. If somebody wants to change the name, fine - I used this
since it's consistant with the config variable it replaces.
This is intended to replace the npx0 msize hack (which no longer works).
SYSINIT_KT() etc (which is a static, compile-time procedure), use a
NetBSD-style kthread_create() interface. kproc_start is still available
as a SYSINIT() hook. This allowed simplification of chunks of the
sysinit code in the process. This kthread_create() is our old kproc_start
internals, with the SYSINIT_KT fork hooks grafted in and tweaked to work
the same as the NetBSD one.
One thing I'd like to do shortly is get rid of nfsiod as a user initiated
process. It makes sense for the nfs client code to create them on the
fly as needed up to a user settable limit. This means that nfsiod
doesn't need to be in /sbin and is always "available". This is a fair bit
easier to do outside of the SYSINIT_KT() framework.
1. Rise is recognized in identdcpu.c.
2. The TSC is not written to. A workaround for the CPU bug is being
applied to clock.c (the bug being that the mP6 has TSC enabled
in its CPUID-capabilities, but it only supports reading it. If we
try to write to it (MSR 16), a GPF occurs.) The new behavior is that
FreeBSD will _not_ zero the TSC. Instead, we do a bit of 64-bit
arithmetic.
Reviewed by: msmith
Obtained from: unfurl & msmith
sure that i686_mem was only used when
1. CPUID had MTRR set (this was there before)
2. the CPU was GenuineIntel (not there)
3. the CPU is a 686 (also not there)
This should prevent any problems with CPUs that set MTRR but aren't
compatibile with Intel's interface (none that I know of yet.)
automatically hacks on the active copy of the IDT if f00f_hack()
has changed it. This also allows simplifications in setidt().
This fixes breakage of FP exception handling by rev.1.55 of
sys/kernel.h. FP exceptions were sent to npx.c's probe handlers
because npx.c "restored" the old handlers to the wrong copy of the
IDT. The SYSINIT for f00f_hack() was purposely run quite late to
avoid problems like this, but it is bogusly associated with the
SYSINIT for proc0 so it was moved with the latter.
Problem reported and fix tested by: Martin Cracauer <cracauer@cons.org>
The cdevsw_add() function now finds the major number(s) in the
struct cdevsw passed to it. cdevsw_add_generic() is no longer
needed, cdevsw_add() does the same thing.
cdevsw_add() will print an message if the d_maj field looks bogus.
Remove nblkdev and nchrdev variables. Most places they were used
bogusly. Instead check a dev_t for validity by seeing if devsw()
or bdevsw() returns NULL.
Move bdevsw() and devsw() functions to kern/kern_conf.c
Bump __FreeBSD_version to 400006
This commit removes:
72 bogus makedev() calls
26 bogus SYSINIT functions
if_xe.c bogusly accessed cdevsw[], author/maintainer please fix.
I4b and vinum not changed. Patches emailed to authors. LINT
probably broken until they catch up.
Reformat and initialize correctly all "struct cdevsw".
Initialize the d_maj and d_bmaj fields.
The d_reset field was not removed, although it is never used.
I used a program to do most of this, so all the files now use the
same consistent format. Please keep it that way.
Vinum and i4b not modified, patches emailed to respective authors.
The old version only worked right when the time was read strictly
more often than every 1/HZ seconds, but we only guarantee reading
it every (1/HZ + epsilon) seconds. Part of rev.1.126-1.127 attempted
to fix this but didn't succeed. Detect counter rollover using the
heuristic from the old version of microtime() with additional
complications for supporting calls from fast interrupt handlers.
This works provided i8254 interrupts are not delayed by more than
1/(2*HZ) seconds.
This needs more comments, and cleanups for the SMP case, and more
testing of the SMP case before it is merged into RELENG_3.
Tested by: jhay
on systems with no FFS.
- Remove all references to mfs from cpu_rootconf(). mfs_init is
called prior to cpu_rootconf(), so it can set mountrootfsname to mfs
and (more imporantly) set rootdev using the (bogus in Bruce's opinion)
special major number of 255.
* Re-work the resource allocation code to use helper functions in subr_bus.c.
* Add simple isa interface for manipulating the resource ranges which can be
allocated and remove the code from isa_write_ivar() which was previously
used for this purpose.
ADMtek AL981 "Comet" chipset. The AL981 is yet another DEC tulip clone,
except with simpler receive filter options. The AL981 has a built-in
transceiver, power management support, wake on LAN and flow control.
This chip performs extremely well; it's on par with the ASIX chipset
in terms of speed, which is pretty good (it can do 11.5MB/sec with TCP
easily).
I would have committed this driver sooner, except I ran into one problem
with the AL981 that required a workaround. When the chip is transmitting
at full speed, it will sometimes wedge if you queue a series of packets
that wrap from the end of the transmit descriptor list back to the
beginning. I can't explain why this happens, and none of the other tulip
clones behave this way. The workaround this is to just watch for the end
of the transmit ring and make sure that al_start() breaks out of its
packet queuing loop and waiting until the current batch of transmissions
completes before wrapping back to the start of the ring. Fortunately, this
does not significantly impact transmit performance.
This is one of those things that takes weeks of analysis just to come
up with two or three lines of code changes.
Implement priorities.
GENERIC, LINT, files:
Remove remarks about ordering of device names.
GENERIC, LINT:
Sort the devices alphabetically in LINT and GENERIC.
though, on systems (386 mostly) that still have a seperate fpu, but it
might be possible to find systems where the FPU coprocessor is wired to
a different IRQ pin.
instances to a parent bus.
* Define a new method BUS_ADD_CHILD which can be called from DEVICE_IDENTIFY
to add new instances.
* Add a generic implementation of DEVICE_PROBE which calls DEVICE_IDENTIFY
for each driver attached to the parent's devclass.
* Move the hint-based isa probe from the isa driver to a new isahint driver
which can be shared between i386 and alpha.
udev_t in the kernel but still called dev_t in userland.
Provide functions to manipulate both types:
major() umajor()
minor() uminor()
makedev() umakedev()
dev2udev() udev2dev()
For now they're functions, they will become in-line functions
after one of the next two steps in this process.
Return major/minor/makedev to macro-hood for userland.
Register a name in cdevsw[] for the "filedescriptor" driver.
In the kernel the udev_t appears in places where we have the
major/minor number combination, (ie: a potential device: we
may not have the driver nor the device), like in inodes, vattr,
cdevsw registration and so on, whereas the dev_t appears where
we carry around a reference to a actual device.
In the future the cdevsw and the aliased-from vnode will be hung
directly from the dev_t, along with up to two softc pointers for
the device driver and a few houskeeping bits. This will essentially
replace the current "alias" check code (same buck, bigger bang).
A little stunt has been provided to try to catch places where the
wrong type is being used (dev_t vs udev_t), if you see something
not working, #undef DEVT_FASCIST in kern/kern_conf.c and see if
it makes a difference. If it does, please try to track it down
(many hands make light work) or at least try to reproduce it
as simply as possible, and describe how to do that.
Without DEVT_FASCIST I belive this patch is a no-op.
Stylistic/posixoid comments about the userland view of the <sys/*.h>
files welcome now, from userland they now contain the end result.
Next planned step: make all dev_t's refer to the same devsw[] which
means convert BLK's to CHR's at the perimeter of the vnodes and
other places where they enter the game (bootdev, mknod, sysctl).
Fixed profiling of elf kernels. Made high resolution profiling compile
for elf kernels (it is broken for all kernels due to lack of egcs support).
Renaming of many assembler labels is avoided by declaring by declaring
the labels that need to be visible to gprof as having type "function"
and depending on the elf version of gprof being zealous about discarding
the others. A few type declarations are still missing, mainly for SMP.
PR: 9413
Submitted by: Assar Westerlund <assar@sics.se> (initial parts)
implicitly LOCK'ed instruction), so there shouldn't be any harm in making
it volatile pointer compatable for one of the users of it. It seems to
generate the same code regardless.
upset about it (and generate things like __main() calls that are reserved
for main()). Renaming was phk's suggestion, but I'd already thought about
it too. (phk liked my suggested name tada() but I decided against it :-)
Reviewed by: phk
config kernel mumble mumble
line has been obsoleted and removed and with it went all knowledge of
devices on the part of config.
You can still configure a root device (which is used if you give
the "-r" flag) but now with an option:
options ROOTDEVNAME=\"da0s2e\"
The string is parsed by the same code as at the "boot -a" prompt.
At the same time, make the "boot -a" prompt both more able and more
informative.
ALPHA/PC98 people: You will have to adapt a few simple changes
(defining rootdev and dumpdev somewhere else) before config works
for you again, sorry, but it's all in the name of progress.
I'm not too happy about the result either, but at least it has less
chance of backfiring.
This particular feature could be called "a mess" without offending
anybody.
and ISA DMA channels (ie: on most PCI systems, they are not.. they are
on the ISA side of the PCI-ISA bridge and could be duplicated if there
were multiple PCI-ISA bridges, say in a laptop docking station), while
the APIC resources would be global on SMP systems.
Also, revert a previous change, change some printfs back to panics.
that big a deal just yet and isn't worth a whole line on the boot screen.
This could change later in the face of multi-ISA-bus (eg: laptop docking
stations with two independent ISA busses) and SMP/APIC systems. The Alpha
already has multiple interrupt destinations to deal with.
new isa drivers with sensitive flags. If the resource_find() code
is meant to "find" the wildcard sensitive flag for a driver even though
a unit is supplied, this can be simplified.
Made a new (inline) function devsw(dev_t dev) and substituted it.
Changed to the BDEV variant to this format as well: bdevsw(dev_t dev)
DEVFS will eventually benefit from this change too.
Virtualize bdevsw[] from cdevsw. bdevsw() is now an (inline)
function.
Join CDEV_MODULE and BDEV_MODULE to DEV_MODULE (please pay attention
to the order of the cmaj/bmaj arguments!)
Join CDEV_DRIVER_MODULE and BDEV_DRIVER_MODULE to DEV_DRIVER_MODULE
(ditto!)
(Next step will be to convert all bdev dev_t's to cdev dev_t's
before they get to do any damage^H^H^H^H^H^Hwork in the kernel.)
Mark the GDB port in the config file with flags 0x80. Currently
only the sio driver checks these flags and sets up a GDB port,
but adding similar code to other serial drivers would be easy.
For backward compatibility, if an sio port is marked as the console
and no port is marked as the gdb port, the GDB port will be mapped
to the console port. This hack should go away at some point.
for elf kernels (it is broken for all kernels due to lack of egcs support).
Renaming of many assembler labels is avoided by declaring by declaring
the labels that need to be visible to gprof as having type "function"
and depending on the elf version of gprof being zealous about discarding
the others. A few type declarations are still missing, mainly for SMP.
PR: 9413
Submitted by: Assar Westerlund <assar@sics.se> (initial parts)
handler. This fixes pnp interrupts and would have fixed pccard interrupts
but a workaround has been applied there.
This the sound driver problems which people have reported with new-bus.
range attributes after they have been extracted from the master.
Hook up the i686 MP code to do this for each AP.
Be more careful about printing the default memory type for the i686.
Suggestions from: luoqi
- %fs register is added to trapframe and saved/restored upon kernel entry/exit.
- Per-cpu pages are no longer mapped at the same virtual address.
- Each cpu now has a separate gdt selector table. A new segment selector
is added to point to per-cpu pages, per-cpu global variables are now
accessed through this new selector (%fs). The selectors in gdt table are
rearranged for cache line optimization.
- fask_vfork is now on as default for both UP and SMP.
- Some aio code cleanup.
Reviewed by: Alan Cox <alc@cs.rice.edu>
John Dyson <dyson@iquest.net>
Julian Elischer <julian@whistel.com>
Bruce Evans <bde@zeta.org.au>
David Greenman <dg@root.com>
1:
s/suser/suser_xxx/
2:
Add new function: suser(struct proc *), prototyped in <sys/proc.h>.
3:
s/suser_xxx(\([a-zA-Z0-9_]*\)->p_ucred, \&\1->p_acflag)/suser(\1)/
The remaining suser_xxx() calls will be scrutinized and dealt with
later.
There may be some unneeded #include <sys/cred.h>, but they are left
as an exercise for Bruce.
More changes to the suser() API will come along with the "jail" code.
Conditionally compile 386-specific code.
pmap_enter:
Eliminate unnecessary TLB shootdowns.
pmap_zero_page and pmap_zero_page_area:
Use invltlb_1pg instead of duplicating the code.
conversion from short to unsigned long which is an argument of
bus_alloc_resource. Since the value -1 is used to indicate no port
reousece, id_port need to be signed (suggested by Doug Rabson and
Peter Wemm.)
Interrupts under the new scheme are managed by the i386 nexus with the
awareness of the resource manager. There is further room for optimizing
the interfaces still. All the users of register_intr()/intr_create()
should be gone, with the exception of pcic and i386/isa/clock.c.
Use pmap_TLB_invalidate instead of invltlb_1pg to eliminate
unnecessary IPIs.
pmap_remove, pmap_protect and pmap_remove_pages:
Use pmap_TLB_invalidate_all instead of invltlb to eliminate
unnecessary IPIs.
pmap_copy:
Use cpu_invltlb instead of invltlb when updating APTDpde.
pmap_changebit:
Rather than deleting the unused "set bit" option (which may be
useful later), make pmap_changebit an inline that is used
by the new pmap_clearbit procedure.
Collectively, the first three changes reduce the number of TLB shootdown
IPIs by 1/3 for a kernel compile.
attached to the nexus. With one exception, this (for example) allows
you to do wierd things like kldload the eisa bus on the fly and then
drivers, and have it auto probe the eisa bus when the drivers come online.
The one exception being pci, it only adds the pcib after the presence of
the pci bus is detected and that's #if'ed code.
A side effect of this is that isa and eisa will be attached to the nexus
directly rather than the PCI->ISA or PCI->EISA bridges. I'm not sure if
this is good or bad at this point, but it seems to be closer to the way
things are for the i386 family... This is likely to be followed up.
This also fixes compilation without a PCI bus configured and will allow
eisa to work without PCI too.
had a quirk that made a shim rather hard to implement properly and it was
just easier to convert the drivers in one go. The changes to the
buslogic driver go beyond just this - the whole driver was new-bus'ed
including pci and isa. I have only tested the EISA part of this so far.
Submitted by: Doug Rabson <dfr@nlsystems.com>
i386 platform boots, it is no longer ISA-centric, and is fully dynamic.
Most old drivers compile and run without modification via 'compatability
shims' to enable a smoother transition. eisa, isapnp and pccard* are
not yet using the new resource manager. Once fully converted, all drivers
will be loadable, including PCI and ISA.
(Some other changes appear to have snuck in, including a port of Soren's
ATA driver to the Alpha. Soren, back this out if you need to.)
This is a checkpoint of work-in-progress, but is quite functional.
The bulk of the work was done over the last few years by Doug Rabson and
Garrett Wollman.
Approved by: core
only worked for configurations with "swap on generic".
usr.sbin/config/config.y:
- ignore all "swap [on] device ...' specifications except for
warning about them. They haven't done anything related to swap
for almost 4 years, and were previously silently ignored,
except for "swap on generic" which stopped swap${KERNEL}.c
from being generated. Code to support swapping is now deader
than before.
usr.sbin/config/mkswapconf.c:
- don't generate a dummy setconf() function in swap${KERNEL}.c.
sys/i386/conf/files.i386:
- swapgeneric.c is now standard. It should be merged into autoconf.c
so that it doesn't conflict with swap${KERNEL}.c for kernels named
"generic".
sys/i386/i386/autoconf.c:
- don't call setroot() for mfs roots. Since setroot() doesn't do anything
harmful, this was just a waste of time, except possibly for booting with
-a it may have helped prevent an undesireable call to setconf() by
finding a bogus rootdev.
- honor -a for ffs roots. -a now overrides all other ways of specifying
the root device. Previously, -r had precedence over -a, and the -a
handling was usually a no-op.
- don't honor -a for non-ffs roots, since it would currently just get in
the way of a clean panic.
sys/i386/i386/swapgeneric.c:
- don't declare things that are now always declared in swap${KERNEL}.c.
Don't decide things that are now decided in autoconf.c. Code to
support the "generic" case is now dead instead of useless.
perform a cleanup/unifdef sweep over it to tidy things up. The atapi
code is permanently attached to the wd driver and is always probed.
I will add an extra option bit in the flags to disable an atapi probe on
either the master or slave if needed, if people want this.
Remember, this driver is destined to die some time. It's possible that
it will loose all atapi support down the track and only be used for
dumb non-ATA disks and all ata/atapi devices will be handled by the new
ata system.
ATAPI, ATAPI_STATIC and CMD640 are no longer options, all are implicit.
Previously discussed with: sos
Split out ioctl handler a little more cleanly, add memory
range attribute handling for both kernel and user-space
consumers.
pmap.c
Remove obsolete P6 MTRR-related code.
i686_mem.c
Map generic memory-range attribute interface to the P6 MTRR
model.
1. Switch to pmap_TLB_invalidate from invltlb, eliminating a full TLB
flush where a single-page flush suffices. (Also, this eliminates some
unnecessary IPIs.)
2. Use "loadandclear" to update the pte, eliminating a race condition
on SMPs.
Change #2 should be committed to -STABLE.
unallocated parts of the last page when the file ended on a frag
but not a page boundary.
Delimitted by tags PRE_MATT_MMAP_EOF and POST_MATT_MMAP_EOF,
in files alpha/alpha/pmap.c i386/i386/pmap.c nfs/nfs_bio.c vm/pmap.h
vm/vm_page.c vm/vm_page.h vm/vnode_pager.c miscfs/specfs/spec_vnops.c
ufs/ufs/ufs_readwrite.c kern/vfs_bio.c
Submitted by: Matt Dillon <dillon@freebsd.org>
Reviewed by: Alan Cox <alc@freebsd.org>
the address of the ps_strings structure to the process via %ebx.
For other kinds of binaries, %ebx is still zeroed as before.
Submitted by: Thomas Stephens <tas@stephens.org>
Reviewed by: jdp
In particular, replace the unused field pmap::pm_flag by pmap::pm_active,
which is a bit mask representing which processors have the pmap activated.
(Thus, it is a simple Boolean on UPs.)
Also, eliminate an unnecessary memory reference from cpu_switch()
in swtch.s.
Assisted by: John S. Dyson <dyson@iquest.net>
Tested by: Luoqi Chen <luoqi@watermarkgroup.com>,
Poul-Henning Kamp <phk@critter.freebsd.dk>
of private_tss, and there's no need to use a bit array. Also fixes
the problem of using `je' after btrl, since cmpl sets ZF.
Noticed by: Luoqi, on -current
Use the pmap_kenter/pmap_kremove inline functions
instead of duplicating them.
pmap_remove_all:
Eliminate an unused (but initialized) variable.
pmap_ts_reference:
Change the implementation. The new implementation is much smaller
and simpler, but functionally identical. (Reviewed by
"John S. Dyson" <dyson@iquest.net>.)
bootblocks in order to boot the kernel after this! Also note that this
change breaks BSDI BSD/OS compatibility.
Also increased default NKPT to 17 so that FreeBSD can boot on machines
with >=2GB of RAM. Booting on machines with exactly 4GB requires other
patches, not included.
to manage their own memory. Tested on my machine (make buildworld).
I've made analogous changes on the alpha, but don't have a machine
to test.
Not-objected-to by: dg, gibbs
numbers as chars or use bogus casts in an attempt to unmisrepresnt
them. In top, don't assume that 0xff is the only negative cpu
number when cpu numbers are (mis)represented.
a TLB invalidation optimization that won't work given the
limitations of our current SMP support.
This patch should be applied to -stable ASAP.
Thanks to John Capo <jc@irbs.com>,
Steve Kargl <sgk@troutmask.apl.washington.edu>, and
Chuck Robey <chuckr@mat.net>
for testing.
not per-process. Keep it in `switchtime' consistently.
It is now clear that the timestamp is always valid in fork_trampoline()
except when the child is running on a previously idle cpu, which
can only happen if there are multiple cpus, so don't check or set
the timestamp in fork_trampoline except in the (i386) SMP case.
Just remove the alpha code for setting it unconditionally, since
there is no SMP case for alpha and the code had rotted.
Parts reviewed by: dfr, phk
is the preparation step for moving pmap storage out of vmspace proper.
Reviewed by: Alan Cox <alc@cs.rice.edu>
Matthew Dillion <dillon@apollo.backplane.com>
put it, just like on the Alpha. It was wrong to load it at the
fixed address 0x08000000. That should only be done if the dynamic
linker is an executable (not a shared object) with a specific load
address encoded in the object file itself.
This fixes the recent breakage in the Linux emulator.
This makes it possible to change the sysctl tree at runtime.
* Change KLD to find and register any sysctl nodes contained in the loaded
file and to unregister them when the file is unloaded.
Reviewed by: Archie Cobbs <archie@whistle.com>,
Peter Wemm <peter@netplex.com.au> (well they looked at it anyway)
programs, including msdos, set PSL_NT in probes for old cpu types,
although PSL_NT doesn't do anything useful in vm86 or real mode.
PSL_NT is even less useful in the signal handlers. It just causes
T_TSSFLT faults on return from syscalls made by the handlers.
These faults are fixed up lazily so that Xsyscall() doesn't have
to be slowed down to prevent them. The fault handler recently
started complaining about these faults occurring "with interrupts
disabled". It should not have, but the complaints pointed to this
bug.
PR: 9211
when the process starts, and having it nonzero causes statically-linked
Linux binaries to fail.
PR: i386/10015
Submitted by: Marcel Moolenaar <marcel@scc.nl>
PQ_FREE. There is little operational difference other then the kernel
being a few kilobytes smaller and the code being more readable.
* vm_page_select_free() has been *greatly* simplified.
* The PQ_ZERO page queue and supporting structures have been removed
* vm_page_zero_idle() revamped (see below)
PG_ZERO setting and clearing has been migrated from vm_page_alloc()
to vm_page_free[_zero]() and will eventually be guarenteed to remain
tracked throughout a page's life ( if it isn't already ).
When a page is freed, PG_ZERO pages are appended to the appropriate
tailq in the PQ_FREE queue while non-PG_ZERO pages are prepended.
When locating a new free page, PG_ZERO selection operates from within
vm_page_list_find() ( get page from end of queue instead of beginning
of queue ) and then only occurs in the nominal critical path case. If
the nominal case misses, both normal and zero-page allocation devolves
into the same _vm_page_list_find() select code without any specific
zero-page optimizations.
Additionally, vm_page_zero_idle() has been revamped. Hysteresis has been
added and zero-page tracking adjusted to conform with the other changes.
Currently hysteresis is set at 1/3 (lo) and 1/2 (hi) the number of free
pages. We may wish to increase both parameters as time permits. The
hysteresis is designed to avoid silly zeroing in borderline allocation/free
situations.
to an architecture-specific value defined in <machine/elf.h>. This
solves problems on large-memory systems that have a high value for
MAXDSIZ.
The load address is controlled by a new macro ELF_RTLD_ADDR(vmspace).
On the i386 it is hard-wired to 0x08000000, which is the standard
SVR4 location for the dynamic linker.
On the Alpha, the dynamic linker is loaded MAXDSIZ bytes beyond
the start of the program's data segment. This is the same place
a userland mmap(0, ...) call would put it, so it ends up just below
all the shared libraries. The rationale behind the calculation is
that it allows room for the data segment to grow to its maximum
possible size.
These changes have been tested on the i386 for several months
without problems. They have been tested on the Alpha as well,
though not for nearly as long. I would like to merge the changes
into 3.1 within a week if no problems have surfaced as a result of
them.
panic during boot on machines with >=2GB of RAM. Also changed some
incorrect printf conversion specifiers from %d to %u (signed to unsigned).
This fixes bugs when printing the amount of memory on machines with >=2GB
of RAM.
/dev/urandom takes about 38 seconds on a P5/133. It is useful
to be able to kill such reads almost immediately. Processes
doing such reads are now scheduled so their denial of service
is no worse than that of processes looping in user mode.
Sun implemented iBCS2 compatibility on Solaris >= 2.6: The emulator
runs in user-mode, patching the LDT so that client programs making
syscalls through the old iBCS2 call gate get handled by the emulator
process. Unemulated syscalls therefore need their own call-gate that
bypasses the emulator. Sun chose LDT entry 4 to implement this, which
is what we've been using as LUDATA_SEL, so we need to change LUDATA_SEL
if we want to run Solaris executables.
Discussed with: Mike Smith
changes to the VM system to support the new swapper, VM bug
fixes, several VM optimizations, and some additional revamping of the
VM code. The specific bug fixes will be documented with additional
forced commits. This commit is somewhat rough in regards to code
cleanup issues.
Reviewed by: "John S. Dyson" <root@dyson.iquest.net>, "David Greenman" <dg@root.com>
keyboard and video card drivers.
Because of the changes, you are required to update your kernel
configuration file now!
The files in sys/dev/syscons are still i386-specific (but less so than
before), and won't compile for alpha and PC98 yet.
syscons still directly accesses the video card registers here and
there; this will be rectified in the later stages.
was tested for month or two in production).
Noticed by: Stephen McKay
Stephen also suggested to remove the complication at all. I don't do it as
it would be backout of a large part of 1.190 (from 1998/03/16)...
on the ASIX AX88140A chip. Update /sys/conf/files, RELNOTES.TXT,
/sys/i388/i386/userconfig.c, sysinstall/devices.c, GENERIC and LINT
accordingly.
For now, the only board that I know of that uses this chip is the
Alfa Inc. GFC2204. (Its predecessor, the GFC2202, was a DEC tulip card.)
Thanks again to Ulf for obtaining the board for me. If anyone runs
across another, please feel free to update the man page and/or the
release notes. (The same applies for the other drivers.)
FreeBSD should now have support for all of the DEC tulip workalike
chipsets currently on the market (Macronix, Lite-On, Winbond, ASIX).
And unless I'm mistaken, it should also have support for all PCI fast
ethernet chipsets in general (except maybe the SMC FEAST chip, which
nobody seems to ever use, including SMC). Now if only we could convince
3Com, Intel or whoever to cough up some documentation for gigabit
ethernet hardware.
Also updated RELNOTEX.TXT to mention that the SVEC PN102TX is supported
by the Macronix driver (assuming you actually have an SVEC PN102TX with
a Macronix chip on it; I tried to order a PN102TX once and got a box
labeled 'Hawking Technology PN102TX' that had a VIA Rhine board inside
it).
versions of gcc and broken for current versions of egcs.
Cleaned up the asm statement for do_cpuid() a little.
Submitted by: "John S. Dyson" <dyson@iquest.net> but rewritten by me
On a system with a large amount of ram (e.g. 2G), allocation of per-page
data structures (512K physical pages) could easily bust the initial kernel
page table (36M), and growth of kernel page table requires kptobj.
from sc, vt and sio drivers. Use instead a linker_set to collect them.
Staticize ??cngetc(), ??cnputc(), etc functions in sc and vt drivers.
We must still have siocngetc() and siocnputc() as globals because they
are directly referred to by i386-gdbstub.c :-(
Oked by: bde
downward growing stacks more general.
Add (but don't activate) code to use the new stack facility
when running threads, (specifically the linux threads support).
This allows people to use both linux compiled linuxthreads, and also the
native FreeBSD linux-threads port.
The code is conditional on VM_STACK. Not using this will
produce the old heavily tested system.
Submitted by: Richard Seaman <dick@tar.com>
There's something that's been bugging me for a while, so I decided to fix it.
FreeBSD now will DTRT WRT DDB and DDB_UNATTENDED (!debugger_on_panic), at least
in my opinion. The behavior change is such that:
1. Nothing changes when debugger_on_panic != 0.
2. When DDB_UNATTENDED (!debugger_on_panic), if a panic occurs, the
machine will reboot. Also, if a trap occurs, the machine will
panic and reboot, unlike how it broke to DDB before. HOWEVER,
a trap inside DDB will not cause a panic, allowing full use
of DDB without having to worry about the machine being stuck
at a DDB prompt if something goes wrong during the day.
Patches for this behavior follow my signature, and it would
be a boon to anyone (like me) who uses DDB_UNATTENDED, but
actually wants the machine to panic on a trap (otherwise,
what's the use, if the machine causes a fatal trap rather than
a true panic, of debugger_on_panic?). The changes cause no
adverse behavior, but do involve two symbols becoming global
Submitted by: Brian Feldman <green@unixhelp.org>
CPU_WT_ALLOC does not work correctly for K6-2s of model 8+ and
probably K6-3s (when they appear on the market soon). In addition,
print_AMD_info() incorrectly printfs write allocation's size. I've
fixed them, so they now Do The Right Thing, and added a
"NO_MEMORY_HOLE" option to easily allow 15-16mb range handling for us
K6 and K6-2 users.
Submitted by: Brian Feldman <green@unixhelp.org>
adjusted related casts to match (only in the kernel in this commit).
The pointer was only wanted in one place in kern_exec.c. Applications
should use the kern.ps_strings sysctl instead of PS_STRINGS, so they
shouldn't notice this change.
for possible buffer overflow problems. Replaced most sprintf()'s
with snprintf(); for others cases, added terminating NUL bytes where
appropriate, replaced constants like "16" with sizeof(), etc.
These changes include several bug fixes, but most changes are for
maintainability's sake. Any instance where it wasn't "immediately
obvious" that a buffer overflow could not occur was made safer.
Reviewed by: Bruce Evans <bde@zeta.org.au>
Reviewed by: Matthew Dillon <dillon@apollo.backplane.com>
Reviewed by: Mike Spengler <mks@networkcs.com>
PCI fast ethernet adapters, plus man pages.
if_pn.c: Netgear FA310TX model D1, LinkSys LNE100TX, Matrox FastNIC 10/100,
various other PNIC devices
if_mx.c: NDC Communications SOHOware SFA100 (Macronix 98713A), various
other boards based on the Macronix 98713, 98713A, 98715, 98715A
and 98725 chips
if_vr.c: D-Link DFE530-TX, other boards based on the VIA Rhine and
Rhine II chips (note: the D-Link and certain other cards
that actually use a Rhine II chip still return the PCI
device ID of the Rhine I. I don't know why, and it doesn't
really matter since the driver treats both chips the same
anyway.)
if_wb.c: Trendware TE100-PCIE and various other cards based on the
Winbond W89C840F chip (the Trendware card is identical to
the sample boards Winbond sent me, so who knows how many
clones there are running around)
All drivers include support for ifmedia, BPF and hardware multicast
filtering.
Also updated GENERIC, LINT, RELNOTES.TXT, userconfig and
sysinstall device list.
I also have a driver for the ASIX AX88140A in the works.
problem is worked around by using an interrupt gate for the page
fault handler. This code was originally made for NetBSD/pc98 by
Naofumi Honda <honda@kururu.math.sci.hokudai.ac.jp> and has already
been in PC98 tree. Because of this bug, trap_fatal cannot show
correct page fault address if %cr2 is obtained in this function.
Therefore, trap_fatal uses the value from trap() function.
- The trap handler always enables interruption when buggy application
or kernel code has disabled interrupts and then trapped. This code
was prepared by Bruce Evans <bde@FreeBSD.org>.
Submitted by: Bruce Evans <bde@FreeBSD.org>
Naofumi Honda <honda@kururu.math.sci.hokudai.ac.jp>
truncated to 32 bits.
* Change the calling convention of the device mmap entry point to
pass a vm_offset_t instead of an int for the offset allowing
devices with a larger memory map than (1<<32) to be supported
on the alpha (/dev/mem is one such).
These changes are required to allow the X server to mmap the various
I/O regions used for device port and memory access on the alpha.
for in a loaded module of type "userconfig_script". The RB_CONFIG
flag will always result in the user being left inside userconfig at
the end of the script's execution, regardless of 'quit' commands in
the script. If the RB_CONFIG flag is not specified, the user will
never be left inside userconfig, even if the script does not have an
explicit exit command.
Add the INTRO_USERCONFIG option. This option forces the userconfig 'intro'
screen (after a script has optionally been executed). There is no longer
a need to queue an 'intro' command.
installed.
Remove cpu_power_down, and replace it with an entry at the end of the
SHUTDOWN_FINAL queue in the only place it's used (APM).
Submitted by: Some ideas from Bruce Walter <walter@fortean.com>
{ port_name = "IO_TIMER", port_number = 1 } and only worked because
it was reassembled to "IO_TIMER1". Trailing digits always work, but
this is too magic to depend on.
Don't quote port names that don't have a digit in them.
RealTek 8129/8139 chipset like I've been threatening. Update kernel
configs, userconfig.c, relnotes and sysinstall. No man page yet;
comming soon.
I consider this driver stable enough that I want to give it some
exposure in -current.
This is the bulk of the support for doing kld modules. Two linker_sets
were replaced by SYSINIT()'s. VFS's and exec handlers are self registered.
kld is now a superset of lkm. I have converted most of them, they will
follow as a seperate commit as samples.
This all still works as a static a.out kernel using LKM's.
1) The vnode pager wasn't properly tracking the file size due to
"size" being page rounded in some cases and not in others.
This sometimes resulted in corrupted files. First noticed by
Terry Lambert.
Fixed by changing the "size" pager_alloc parameter to be a 64bit
byte value (as opposed to a 32bit page index) and changing the
pagers and their callers to deal with this properly.
2) Fixed a bogus type cast in round_page() and trunc_page() that
caused some 64bit offsets and sizes to be scrambled. Removing
the cast required adding casts at a few dozen callers.
There may be problems with other bogus casts in close-by
macros. A quick check seemed to indicate that those were okay,
however.
specified. This makes haveseen_isadev() useful for searching for a
free resource. This increases the bitrot in the pci RESOURCE_CHECK
code.
Fixed the pre-attach conflict message. The flag for distinguishing
pre-attach conflict checks from pre-probe ones was never set.
trying to do it in locore. We also walk through the module table
and relocate any MODINFO_ADDR pointers so that they become KVM relative
rather than physical addresses. This means that hacks for adding
0xf0000000 in places like MFS go away.
Enable optimization for nobounce_dmamap clients by setting the map
held by the client to NULL. This allows the macros in bus.h to check
against a constant to avoid function calls.
Don't attempt to 'free()' contigmalloced pages in bus_dmamem_free().
We currently leak these pages, which is not ideal, but is better than
a panic. The leak will be fixed when contigmalloc is merged into the
bus dma framework after 3.0R.
The code was originaly contributed by Kelly Yancey
<kbyanc@freedomnet.com> in PR i386/6269 and revised by Akio Morita
<amorita@meadow.scphys.kyoto-u.ac.jp> and me. Test was performed by
Akio Morita and Toshiomi Moriki <moriki@db.is.kyushu-u.ac.jp>.
- Fix stylistic bug in identcpu.c.
- Update copyright in initcpu.c
- Fix typo in LINT.
PR: 6269 and 6270
fix the 50% idle problem that the ELF /sbin/init triggered. The problem
appeared when the last context switch before a fork() call was due to
the kernel faulting in user pages via normal page faults (e.g. copyin).
Reviewed by: Peter Wemm <peter@netplex.com.au>
The last consumer of this code (the old SCSI system) has left us and
the CAM code does it's own bouncing. The isa dma system has been
doing it's own bouncing for a while too.
Reviewed by: core
went backwards when interrupts were masked for more than one i8254
interrupt period. It sometimes went backwards when the i8254 counter
was reprogrammed. Neither of these should happen in normal operation.
Update the i8254 timecounter support variables atomically. Calling
timecounter functions from fast interrupt handlers may actually work
in all cases now.
Convert autoconf hooks from old SCSI system to CAM.
busdma_machdep.c:
bus_dmamap_free() should expect the nobounce map, not a NULL one.
mountroot.c:
swapgeneric.c:
da and od changes.
symbols.raw:
Nuke the old disk stat symbols.
userconfig.c:
Disable the SCSI listing code until it can be converted to CAM.
and set_regs() but for the floating point register state. The code
is stolen from procfs_machdep.c, and moved out of there into
machdep.c.
These functions are needed for generating ELF core dumps.
the relevant characteristics of the native machine, for building
and checking Elf_Ehdr structures.
Add structures to represent ELF "note" headers. Add defines for the
note types used in ELF core files.
as "machdep.msgbuf". It's needed in case of using stripped kernels, where
normal dmesg (which has to use kvm) doesn't work.
The buffer is unwound, meaning that the data will be linear, possibly
with some leading NULLs.
Reviewed by: Jordan K. Hubbard <jkh@freebsd.org>
the executable file, so it will work for both a.out and ELF format
files. I have split the object format specific code into separate
source files. It's cleaner than it was before, but it's still
pretty crufty.
Don't cheat on your make world for this update. A lot of things
have to be rebuilt for it to work, including the compiler and all
of the profiled libraries.
and use this when masking/unmasking interrupts.
Maintain a mapping from (iopaic number, int pin) tuple to irq number,
and use this when configuring devices and programming the ioapics.
Previous code assumed that irq number was equal to int pin number, and
that the ioapic number was 0.
Don't let an AP enter _cpu_switch before all local apics are initialized.
- moved definition of MACHINE_ARCH from cpu.h to parm.h as alpha.
- Added definitions of _MACHINE and _MACHINE_ARCH.
- Added hw.ispc98. The hw.ispc98 is 1 in PC98 kernel and is 0 in
IBM-PC kernel.
Discussed with: John Birrell <jb@FreeBSD.ORG>
Add some overflow checks to read/write (from bde).
Change all modifications to vm_page::flags, vm_page::busy, vm_object::flags
and vm_object::paging_in_progress to use operations which are not
interruptable.
Reviewed by: Bruce Evans <bde@zeta.org.au>
in a SMP system. Unexpected things could happen if each cpu
has a different ldt setting and one cpu tries to use value
of currentldt set by another cpu.
The fix is to move currentldt to the per-cpu area. It includes
patches I filed in PR i386/6219 which are also user ldt related.
PR: i386/7591, i386/6219
Submitted by: Luoqi Chen <luoqi@watermarkgroup.com>
stability now. ALso modify /sys/conf/files, /sys/i386/conf/GENERIC
and /sys/i386/conf/LINT to add entries for the XL driver. Deactivate
support for the XL adapters in the vortex driver. LAstly, add a man
page.
(Also added an MLINKS entry for the ThunderLAN man page which I forgot
previously.)
applications. Here's how it works.
The kernel should include <machine/elf.h> to get the definitions
for the native architecture. It can reference the various ELF
structures with generic names like Elf_Sym, Elf_Shdr, etc. A define
__ELF_WORD_SIZE is also available with the value 32 or 64 as
appropriate for the native architecture.
Generic applications should include <elf.h>, which is just a wrapper
for <machine/elf.h>.
Applications such as object file dumpers that need to deal with
foreign ELF files can include <sys/elf32.h> and/or <sys/elf64.h>.
Both can be included from the same source file if desired. The
structure names must be referenced using wordsize-specific names
like Elf32_Sym, Elf64_Shdr, etc.
I haven't change the alpha stuff, but I haven't broken it either.
Cast pointers to (vm_offset_t) instead of to (u_long) (as before) or to
(uintptr_t)(void *) (as would be more correct). Don't cast vm_offset_t's
to (u_long) just to do arithmetic on them.
mp_machdep.c:
Cast pointers to (uintptr_t) instead of to (u_long). Don't forget
to cast pointers to (void *) first or to recover from integral
possible integral promotions, although this is too much work for
machine-dependent code.
vm code generally avoids warnings for pointer vs long size mismatches
by using vm_offset_t to represent pointers; pmap.c often uses plain
`unsigned int' instead of vm_offset_t and didn't use u_long elsewhere,
but this style was messed up by code apparently imported from mp_machdep.c.
instead of at compile time using ifdefs.
Use _swi_null instead of dummycamisr. CAM and dpt should call
register_swi() instead of hacking on ihandlers[] directly.
instead of 0) was "restored" after handling a trap that occurred while
returning to user mode. This bug was most noticeable for VM86 and is
still detected and fixed up (on return from the next exception) in doreti
if VM86 is configured.
fork_trampoline() if switchtime is valid. This fixes not accounting
for the time between the previous context switch and and the current
time (when the forked child starts up here) in most cases - the time
is now counted in the child's runtime. I think it actually fixes
all cases, and switchtime is always valid here, since there must have
been a context switch just before the forked child starts up. Some
code should be removed if this is correct. The check that switchtime
is valid sometimes gives a false negative because the check isn't
correct until the after the first context switch after the system
has been up for >= 1 second.
potentially re-use the stack page.
Cosmetic cleanup of the code to de-obfuscate it and make it easier
to follow. There should be no functional changes in this commit.
