a true scratch register. This change and future re-allocations will
eventually result in code that we can unwind to to get the preserved
registers of the process. This of course means that we cannot trash
them while saving the process context.
While re-allocating, remove the register aliases. Abstraction is in
this case disadvanteous.
have f16-f31 as part of the context. The PCB has been reorganized to
better match how we save and restore the (preserved) registers. This
commit also moves the context restoriation to its own function (named
pcb_restore), as we did with pcb_save.
Only minimal effort has been put in writing optimal assembly. The
expectation is that there will be more rounds of changes.
from all low-level bus space support functions. There's no need
to actually force the read/write to be accepted by the platform
before we can do anything else. We still have the mf instruction
there, which forces ordering. This too is not required given the
semantices of the bus space I/O functions, but it's not at all
clear to me if there are any poorly written device drivers that
depend on the strict ordering by the processor. The motto here is
to take small steps...
o Properly set the pointer to the counter for each interrupt and
update the intrnames table.
o Remove Alpha cruft from intrcnt.h.
o Create INTRNAME_LEN as the single entity that defines the width
of the names in the intrnames table (incl. terminatinf '\0').
This guarantees that loads and stores emitted before the fence are
made visible before the IPI becomes pended.
Remove the mf.a instruction after initiating the IPI. There's no
guarantee that the IPI becomes pended prior to subsequent reads or
writes. Even if there was a guarantee, it would mostly be without
any benefit.
handling clean and functional as 5.x evolves. This allows some of the
nasty bandaids in the 5.x codepaths to be unwound.
Encapsulate 4.x signal handling under COMPAT_FREEBSD4 (there is an
anti-foot-shooting measure in place, 5.x folks need this for a while) and
finish encapsulating the older stuff under COMPAT_43. Since the ancient
stuff is required on alpha (longjmp(3) passes a 'struct osigcontext *'
to the current sigreturn(2), instead of the 'ucontext_t *' that sigreturn
is supposed to take), add a compile time check to prevent foot shooting
there too. Add uniform COMPAT_43 stubs for ia64/sparc64/powerpc.
Tested on: i386, alpha, ia64. Compiled on sparc64 (a few days ago).
Approved by: re
so that there is ony one copy of it. Fix that one copy
so that KSEs with no mailbox in a KSE program are not a cause
of page faults (this can legitmatly happen).
Submitted by: (parts) davidxu
pointer to a dumperinfo instead of di. A brainfart, surely. This
bug went unnoticed for all this time because the pointer is only
used by buf_write() when it can write a completely filled buffer
to the dump device. This depends on the number of memory chunks
that needs to be dumped. This has apparently been low enough that
it has never happened up until this point.
for defining vectors. As a result, each vector will be a global
function with unwind directives to notify the unwinder that we're
in an interrupt handler. In the debugger this will show up something
like:
Debugger(0xe000000000a211d8, 0xe000000000748960) at Debugger+0x31
panic(0xe000000000a36858, 0xe0000000021d32d0, 0xe000000000ae42e8, ...
trap(0x14, 0x100000, 0xe0000000021d32d0, 0x0, 0xa0000000002095f0, ...
ivt_Data_TLB(0x14, 0x100000, 0xe0000000021d32d0) at ivt_Data_TLB+0x1f0
This is for the not-quite-ready signal/fpu abi stuff. It may not see
the light of day, but I'm certainly not going to be able to validate it
when getting shot in the foot due to syscall number conflicts.
execve_secure() system call, which permits a process to pass in a label
for a label change during exec. This permits SELinux to change the
label for the resulting exec without a race following a manual label
change on the process. Because this interface uses our general purpose
MAC label abstraction, we call it execve_mac(), and wrap our port of
SELinux's execve_secure() around it with appropriate sid mappings.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories
by using the linker hooks. Since these hooks are called for the
kernel as well, we don't need to deal with that with a special
SYSINIT. The initialization implicitly performed on the first
update of the unwind information is made explicit with a SYSINIT.
We now don't need the _ia64_unwind_{start|end} symbols.
The primary reason for this is to allow MD code to process machine
specific attributes, segments or sections in the ELF file and
update machine specific state accordingly. An immediate use of this
is in the ia64 port where unwind information is updated to allow
debugging and tracing in/across modules. Note that this commit
does not add the functionality to the ia64 port. See revision 1.9
of ia64/ia64/elf_machdep.c.
Validated on: alpha, i386, ia64
ACL configuration changes, this shouldn't result in different code paths
for file systems not explicitly configured for ACLs by the system
administrator. For UFS1, administrators must still recompile their
kernel to add support for extended attributes; for UFS2, it's sufficient
to enable ACLs using tunefs or at mount-time (tunefs preferred for
reliability reasons). UFS2, for a variety of reasons, including
performance and reliability, is the preferred file system for use with
ACLs.
Approved by: re
were improperly relocated due to faulty logic in lookup_fdesc()
in elf_machdep.c. The symbol index (symidx) was bogusly used for
load modules other than the one the relocation applied to. This
resulted in bogus bindings and consequently runtime failures.
The fix is to use the symbol index only for the module being
relocated and to use the symbol name for look-ups in the
modules in the dependent list. As such, we need a function to
return the symbol name given the linker file and symbol index.
the predicate registers. Even though the ITLB and DTLB interrupts
happen often enough, this bug didn't do much harm. The reason
is that the interrupt handlers only modify p1 and since this is
a preserved (callee-saved) register it is hardly used in code
generated by the compiler. Compilers use scratch registers by
default. Changing the interrupt handlers to use p6 (ie a scratch
register) proved that the bug was in fact fatal.
o Replace KSTACK_PAGES with pages on panic() in pmap_new_thread(),
o Fix style bugs in adjacent code,
o Use NULL instead of 0 for pointers,
o Save the virtual kstack address if we create an alternate
kstack because 1) we can derive the physical (RR7) address
from it and 2) we need the virtual address for contigfree()
in pmap_dispose_thread(). Thus td_altkstack saves
td_md.md_kstackvirt.
as a trivial function that only calls ia64_tpa() and hence requires
the prototype of ia64_tpa(), but by defining pmap_kextract as
ia64_tpa. This solves the inclusion ordering issue in ddb/db_watch.c
NB: But it will enable it in all kernels not having options "NO_GEOM"
Put the GEOM related options into the intended order.
Add "options NO_GEOM" to all kernel configs apart from NOTES.
In some order of controlled fashion, the NO_GEOM options will be
removed, architecture by architecture in the coming days.
There are currently three known issues which may force people to
need the NO_GEOM option:
boot0cfg/fdisk:
Tries to update the MBR while it is being used to control
slices. GEOM does not allow this as a direct operation.
SCSI floppy drives:
Appearantly the scsi-da driver return "EBUSY" if no media
is inserted. This is wrong, it should return ENXIO.
PC98:
It is unclear if GEOM correctly recognizes all variants of
PC98 disklabels. (Help Wanted! I have neither docs nor HW)
These issues are all being worked.
Sponsored by: DARPA & NAI Labs.
is partly based on the Alpha system which duplicates the clock to
each cpu, instead of doing a clock roundrobin like on i386. This means
we get hz * ncpu clocks per second and so we have to seperate clock
sampling from actual 'do the work' clock processing. The BSP runs the
complete processing, the rest just sample state etc.
Using the on-cpu interval timer is not ideal as it will drift. There
is more to be done here, we should use an external clock source.
expand to __attribute__((packed)) and __attribute__((aligned(x)))
respectively. Replace the handful of gcc-ism's that use
__attribute__((aligned(16))) etc around the kernel with __aligned(16).
There are over 400 __attribute__((packed)) to deal with, that can come
later. I just want to use __packed in new code rather than add more
gcc-ism's.
and predictable way, and I apologize if I have gotten it wrong anywhere,
getting prior review on a patch like this is not feasible, considering
the number of people involved and hardware availability etc.)
If struct disklabel is the messenger: kill the messenger.
Inside struct disk we had a struct disklabel which disk drivers used to
communicate certain metrics to the disklayer above (GEOM or the disk
mini-layer). This commit changes this communication to use four
explicit fields instead.
Amongst the benefits is that the fields do not get overwritten by
wrong or bogus on-disk disklabels.
Once that is clear, <sys/disk.h> which is included in the drivers
no longer need to pull <sys/disklabel.h> and <sys/diskslice.h> in,
the few places that needs them, have gotten explicit #includes for
them.
The disklabel inside struct disk is now only for internal use in
the disk mini-layer, so instead of embedding it, we malloc it as
we need it.
This concludes (modulus any mistakes) the series of disklabel related
commits.
I belive it all amounts to a NOP for all the rest of you :-)
Sponsored by: DARPA & NAI Labs.
function were put in i386/i386/machdep.c from where it has been
cut and pasted to other architectures with only minor corruption.
Disklabel is really a MI format in many ways, at least it certainly
is when you operate on struct disklabel.
Put bounds_check_with_label() back in subr_disklabel.c where it belongs.
Sponsored by: DARPA & NAI Labs.
MD function is just a wrapper around db_stack_trace_cmd() that prints out
a backtrace of curthread. Currently, this function is only implemented
on i386 and alpha (and the alpha version isn't quite tested yet, will do
that in a bit). Other changes:
- For i386, fix a bug in the raw frame address case. The eip we extract
from the passed in frame address does not match the frame we received.
Thus, instead of printing a bogus frame with the wrong eip, go ahead
and advance frame down to the same frame as the eip we are using.
- For alpha, attempt to add a way of doing a raw trace for alpha. Instead
of passing a frame address in 'addr', pass in a pointer to a structure
containing PC and KSP and use those to start the backtrace. The alpha
db_print_backtrace() uses asm to read in the current PC and KSP values
into such a request.
Tested on: i386
Requested by: many
under way to move the remnants of the a.out toolchain to ports. As the
comment in src/Makefile said, this stuff is deprecated and one should not
expect this to remain beyond 4.0-REL. It has already lasted WAY beyond
that.
Notable exceptions:
gcc - I have not touched the a.out generation stuff there.
ldd/ldconfig - still have some code to interface with a.out rtld.
old as/ld/etc - I have not removed these yet, pending their move to ports.
some includes - necessary for ldd/ldconfig for now.
Tested on: i386 (extensively), alpha
next step is to allow > 1 to be allocated per process. This would give
multi-processor threads. (when the rest of the infrastructure is
in place)
While doing this I noticed libkvm and sys/kern/kern_proc.c:fill_kinfo_proc
are diverging more than they should.. corrective action needed soon.
to userland in the signal handler that were not being iflled out before, but
should and can be.
This part of sendsig could be slightly refactored to use an MI interface, or
ideally, *sendsig*() would have an API change to accept a siginfo_t, which
would be filled out by an MI function in the level above sendsig, and said MI
function would make a small call into MD code to fill out the MD parts (some
of which may be bogus, such as the si_addr stuff in some places). This would
eventually make it possible for parts of the kernel sending signals to set up
a siginfo with meaningful information.
Reviewed by: mux
MFC after: 2 weeks
sysentvec. Initialized all fields of all sysentvecs, which will allow
them to be used instead of constants in more places. Provided stack
fixup routines for emulations that previously used the default.
in the original hardwired sysctl implementation.
The buf size calculator still overflows an integer on machines with large
KVA (eg: ia64) where the number of pages does not fit into an int. Use
'long' there.
Change Maxmem and physmem and related variables to 'long', mostly for
completeness. Machines are not likely to overflow 'int' pages in the
near term, but then again, 640K ought to be enough for anybody. This
comes for free on 32 bit machines, so why not?
These types are unlikely to ever become very MD. They include:
clockid_t, ct_rune_t, fflags_t, intrmask_t, mbstate_t, off_t, pid_t,
rune_t, socklen_t, timer_t, wchar_t, and wint_t.
While moving them, make a few adjustments (submitted by bde):
o __ct_rune_t needs to be precisely `int', not necessarily __int32_t,
since the arg type of the ctype functions is int.
o __rune_t, __wchar_t and __wint_t inherit this via a typedef of
__ct_rune_t.
o Some minor wording changes in the comment blocks for ct_rune_t and
mbstate_t.
Submitted by: bde (partially)
called <machine/_types.h>.
o <machine/ansi.h> will continue to live so it can define MD clock
macros, which are only MD because of gratuitous differences between
architectures.
o Change all headers to make use of this. This mainly involves
changing:
#ifdef _BSD_FOO_T_
typedef _BSD_FOO_T_ foo_t;
#undef _BSD_FOO_T_
#endif
to:
#ifndef _FOO_T_DECLARED
typedef __foo_t foo_t;
#define _FOO_T_DECLARED
#endif
Concept by: bde
Reviewed by: jake, obrien
make a series of modifications to the credential arguments relating
to file read and write operations to cliarfy which credential is
used for what:
- Change fo_read() and fo_write() to accept "active_cred" instead of
"cred", and change the semantics of consumers of fo_read() and
fo_write() to pass the active credential of the thread requesting
an operation rather than the cached file cred. The cached file
cred is still available in fo_read() and fo_write() consumers
via fp->f_cred. These changes largely in sys_generic.c.
For each implementation of fo_read() and fo_write(), update cred
usage to reflect this change and maintain current semantics:
- badfo_readwrite() unchanged
- kqueue_read/write() unchanged
pipe_read/write() now authorize MAC using active_cred rather
than td->td_ucred
- soo_read/write() unchanged
- vn_read/write() now authorize MAC using active_cred but
VOP_READ/WRITE() with fp->f_cred
Modify vn_rdwr() to accept two credential arguments instead of a
single credential: active_cred and file_cred. Use active_cred
for MAC authorization, and select a credential for use in
VOP_READ/WRITE() based on whether file_cred is NULL or not. If
file_cred is provided, authorize the VOP using that cred,
otherwise the active credential, matching current semantics.
Modify current vn_rdwr() consumers to pass a file_cred if used
in the context of a struct file, and to always pass active_cred.
When vn_rdwr() is used without a file_cred, pass NOCRED.
These changes should maintain current semantics for read/write,
but avoid a redundant passing of fp->f_cred, as well as making
it more clear what the origin of each credential is in file
descriptor read/write operations.
Follow-up commits will make similar changes to other file descriptor
operations, and modify the MAC framework to pass both credentials
to MAC policy modules so they can implement either semantic for
revocation.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
<stdint.h>. Previously, parts were defined in <machine/ansi.h> and
<machine/limits.h>. This resulted in two problems:
(1) Defining macros in <machine/ansi.h> gets in the way of that
header only defining types.
(2) Defining C99 limits in <machine/limits.h> adds pollution to
<limits.h>.
handler in the kernel at the same time. Also, allow for the
exec_new_vmspace() code to build a different sized vmspace depending on
the executable environment. This is a big help for execing i386 binaries
on ia64. The ELF exec code grows the ability to map partial pages when
there is a page size difference, eg: emulating 4K pages on 8K or 16K
hardware pages.
Flesh out the i386 emulation support for ia64. At this point, the only
binary that I know of that fails is cvsup, because the cvsup runtime
tries to execute code in pages not marked executable.
Obtained from: dfr (mostly, many tweaks from me).
on the Itanium2 system I have when we use up *all* of the initial 256MB
direct mapped region before we are ready to dynamically expand it.
The machine that I have has 4 cpus and a very big hole in the middle.
This makes the bogus '(last_address - first_address) / PAGE_SIZE'
calculations especially dangerous and caused many millions of initial
PV/PTE's to be preallocated.
choosethread() in MI C code instead of doing it in in assembly in all the
various cpu_switch() functions. This fixes problems on ia64 and sparc64.
Reviewed by: julian, peter, benno
Tested on: i386, alpha, sparc64
hardly MD, since all our platforms share the same macro. It's not
really compiler dependent either, but this helps in reducing
<machine/ansi.h> to only type definitions.
threaded VM pagezero kthread outside of Giant. For some platforms, this
is really easy since it can just use the direct mapped region. For others,
IPI sending is involved or there are other issues, so grab Giant when
needed.
We still have preemption issues to deal with, but Alan Cox has an
interesting suggestion on how to minimize the problem on x86.
Use Luigi's hack for preserving the (lack of) priority.
Turn the idle zeroing back on since it can now actually do something useful
outside of Giant in many cases.
pmap_swapin_proc/pmap_swapout_proc functions from the MD pmap code
and use a single equivalent MI version. There are other cleanups
needed still.
While here, use the UMA zone hooks to keep a cache of preinitialized
proc structures handy, just like the thread system does. This eliminates
one dependency on 'struct proc' being persistent even after being freed.
There are some comments about things that can be factored out into
ctor/dtor functions if it is worth it. For now they are mostly just
doing statistics to get a feel of how it is working.
we just have to deal with the kstack when told to. We do not have a
UMA-managed cache for the proc struct and its associated upage yet. So,
go back to the old lazy mechanism. Note that if UMA destroys pages that
used to contain proc structures, we'll lose the corresponding upage
forever. (zones never did this - once a page was allocated, it stayed
attached to the proc zone forever)
The ability to schedule multiple threads per process
(one one cpu) by making ALL system calls optionally asynchronous.
to come: ia64 and power-pc patches, patches for gdb, test program (in tools)
Reviewed by: Almost everyone who counts
(at various times, peter, jhb, matt, alfred, mini, bernd,
and a cast of thousands)
NOTE: this is still Beta code, and contains lots of debugging stuff.
expect slight instability in signals..
obtained, when all other scheduling activity is suspended. This is needed
on sparc64 to deactivate the vmspace of the exiting process on all cpus.
Otherwise if another unrelated process gets the exact same vmspace structure
allocated to it (same address), its address space will not be activated
properly. This seems to fix some spontaneous signal 11 problems with smp
on sparc64.
implementations can provide a base zero ffs function if they wish.
This changes
#define RQB_FFS(mask) (ffs64(mask))
foo = RQB_FFS(mask) - 1;
to
#define RQB_FFS(mask) (ffs64(mask) - 1)
foo = RQB_FFS(mask);
On some platforms we can get the "- 1" for free, eg: those that use the
C code for ffs64().
Reviewed by: jake (in principle)
- ktrace no longer requires Giant so do ktrace syscall events before and
after acquiring and releasing Giant, respectively.
- For i386, ia32 syscalls on ia64, powerpc, and sparc64, get rid of the
goto bad hack and instead use the model on ia64 and alpha were we
skip the actual syscall invocation if error != 0. This fixes a bug
where if we the copyin() of the arguments failed for a syscall that
was not marked MP safe, we would try to release Giant when we had
not acquired it.
struct uuid defined in <sys/uuid.h>.
Use uuid/UUID instead of guid/GUID to emphasize that the
identifiers are DCE version 1 identifiers and also to avoid
inconsistencies as much a possible.
combining too much conditions and as such ended up with the
kernel map instead of the corresponding process map. While
here, remove code to allow access to the stackgap and restyle
slightly to improve readability.
This fix specifically fixes the procfs failure we're having
when reading the process map (cat /proc/curproc/map)
As a minor positive side-effect, code at -O0 is more optimal. As a
minor negative side-effect, certain boundary cases yield no better
code than non-boundary cases. For example, atomic_set_acq_32(p, 0)
does a useless logical OR with value 0. This was previously elimina-
ted as part of if/while optimizations. Non-boundary cases yield
identical code at -O1 and -O2.
- Don't include ia64_cpu.h and cpu.h
- Guard definitions by _NO_NAMESPACE_POLLUTION
- Move definition of KERNBASE to vmparam.h
o Move definitions of IA64_RR_{BASE|MASK} to vmparam.h
o Move definitions of IA64_PHYS_TO_RR{6|7} to vmparam.h
o While here, remove some left-over Alpha references.
function to return the total number of CPUs and not the highest
CPU id.
o Define mp_maxid based on the minimum of the actual number of
CPUs in the system and MAXCPU.
o In cpu_mp_add, when the CPU id of the CPU we're trying to add
is larger than mp_maxid, don't add the CPU. Formerly this was
based on MAXCPU. Don't count CPUs when we add them. We already
know how many CPUs exist.
o Replace MAXCPU with mp_maxid when used in loops that iterate
over the id space. This avoids a couple of useless iterations.
o In cpu_mp_unleash, use the number of CPUs to determine if we
need to launch the CPUs.
o Remove mp_hardware as it's not used anymore.
o Move the IPI vector array from mp_machdep.c to sal.c. We use
the array as a centralized place to collect vector assignments.
Note that we still assign vectors to SMP specific IPIs in
non-SMP configurations. Rename the array from mp_ipi_vector to
ipi_vector.
o Add IPI_MCA_RENDEZ and IPI_MCA_CMCV. These are used by MCA.
Note that IPI_MCA_CMCV is not SMP specific.
o Initialize the ipi_vector array so that we place the IPIs in
sensible priority classes. The classes are relative to where
the AP wake-up vector is located to guarantee that it's the
highest priority (external) interrupt. Class assignment is
as follows:
class IPI notes
x AP wake-up (normally x=15)
x-1 MCA rendezvous
x-2 AST, Rendezvous, stop
x-3 CMCV, test
o Create pcb_save as the backend for savectx and cpu_switch.
o While here, use explicit bundling for pcb_save and optimize
for compactness (~87% density).
o Not part of the commit is a backend pcb_restore. restorectx()
still jumps halfway into cpu_switch().
pmap_ensure_rid(). This can happen because the function is
called for both user and kernel addresses, while the rid array
only has room for user addresses. This bug got exposed by rev
1.58 of ia64/ia64/pmap.c and rev 1.8 of ia64/include/pmap.h.
only for exceptions.
While adding this to exception_save and exception_restore, it was hard
to find a good place to put the instructions. The code sequence was
sufficiently arbitrarily ordered that the density was low (roughly 67%).
No explicit bundling was used.
Thus, I rewrote the functions to optimize for density (close to 80% now),
and added explicit bundles and nop instructions. The immediate operand
on the nop instruction has been incremented with each instance, to make
debugging a bit easier when looking at recurring patterns. Redundant
stops have been removed as much as possible. Future optimizations can
focus more on performance. A well-placed lfetch can make all the
difference here!
Also, the FRAME_Fxx defines in frame.h were mostly bogus. FRAME_F10 to
FRAME_F15 were copied from FRAME_F9 and still had the same index. We
don't use them yet, so nothing was broken.
i386/ia64/alpha - catch up to sparc64/ppc:
- replace pmap_kernel() with refs to kernel_pmap
- change kernel_pmap pointer to (&kernel_pmap_store)
(this is a speedup since ld can set these at compile/link time)
all platforms (as suggested by jake):
- gc unused pmap_reference
- gc unused pmap_destroy
- gc unused struct pmap.pm_count
(we never used pm_count - we track address space sharing at the vmspace)
collected at boot and made available through sysctl(8). At the
moment, the following MIB names are created:
hw.mca.count - The number of error records collected.
hw.mca.first - The lowest sequence number present.
hw.mca.last - The highest sequence number present.
hw.mca.<X> - The error record with sequence number <X>.
Using sysctl(8) allows us to easily detect and analyze the records,
which is very helpful during development of MCA but can also be used
in production as a way to collect machine health statistics.
the symbol index defined by the relocation. The elf_lookup() support
function is to be used by elf_reloc() when symbol lookups need to be
done. The elf_lookup() function operates on the symbol index and
will do a symbol name based lookup when such is required, otherwise
it uses the symbol index directly. This solves the problem seen on
ia64 where the symbol hash table does not contain local symbols and
a symbol name based lookup would fail for those symbols.
Don't pass the symbol name to elf_reloc(), as it isn't used any more.
check handling. In its current form, it only determines the largest
amount of state information it can get from SAL and allocates a region
7 memory block for it.
The next steps involve:
o get and log any unconsumed (NVM stored) error records across
reboots,
o register an OS_MCA handler and enable machine checks.
the SMP case. While on the subject, remove unnecessary stops. I don't
know if this resolves the memory corruption I'm seeing, but it does
have the potential. We'll see...
both Elf_Rel and Elf_Rela types of relocation, so handle them both
even though we only have Rel_Rela ATM. We don't handle 32-bit and
big-endian variants yet. Support for that is not trivial enough to
implement it without any evidence that we ever need it in the near
future.
For the FPTR relocations, we currently use the fptr_storage used by
_reloc() is locore.s. This is in no way a real solution, but for now
provides the service we need to get the basics going.
A static recursive function lookup_fdesc() is used to find the address
of a function in a way that keeps track of the load module so that
we can get the correct GP value if we need to construct an OPD (ie
there's no OPD yet for the function.
For simplicity, we create an OPD for the IPLT relocations as well and
simply fill the user provided function descriptor from the OPD. Since
the the official descriptors are unique, this has no bad side effects.
Note that we ignore the addend for FPTR relocations, but use the
addend for IPLT relocations as an offset to the function address.
This commit allows us to load and relocate modules and modules appear
to work correctly, although we probably need to make sure that we set
GP correctly in all cases when we have inter-module calls. This
especially applies to assembly coded functions that have cross module
calls.
here mostly mirror the changes made in
boot/efi/libefi/arch/ia64/start.S rev 1.5
Significant difference: We don't handle the IPLT relocation here.
For barebones KLD support, we make the fptr_storage global.
environment needed at boot time to a dynamic subsystem when VM is
up. The dynamic kernel environment is protected by an sx lock.
This adds some new functions to manipulate the kernel environment :
freeenv(), setenv(), unsetenv() and testenv(). freeenv() has to be
called after every getenv() when you have finished using the string.
testenv() only tests if an environment variable is present, and
doesn't require a freeenv() call. setenv() and unsetenv() are self
explanatory.
The kenv(2) syscall exports these new functionalities to userland,
mainly for kenv(1).
Reviewed by: peter
and pmap_copy_page(). This gets rid of a couple more physical addresses
in upper layers, with the eventual aim of supporting PAE and dealing with
the physical addressing mostly within pmap. (We will need either 64 bit
physical addresses or page indexes, possibly both depending on the
circumstances. Leaving this to pmap itself gives more flexibilitly.)
Reviewed by: jake
Tested on: i386, ia64 and (I believe) sparc64. (my alpha was hosed)
o Use chunk instead of region when we talk about a memory range.
Region can be confused with region register and we already
call it chunk in machdep.c
o Update the twiddle every 16MB
without a few patches for the rest of the kernel to allow the image
activator to override exec_copyout_strings and setregs.
None of the syscall argument translation has been done. Possibly, this
translation layer can be shared with any platform that wants to support
running ILP32 binaries on an LP64 host (e.g. sparc32 binaries?)
to be sure that it is always correct and this was not true for the first
call to cpu_switch. When thread0 resumed later, it ended up calling
pmap_install with a null pmap, which is bad.
_BYTE_ORDER. These are far more useful than their non-underscored
equivalents as these can be used in restricted namespace environments.
Mark the non-underscored variants as deprecated.
the program headers. As a result of this, dumplo was advanced too
much causing the end of the dump and most notably the trailing
dump header to be written beyond the end of the the dump medium.
most cases NULL is passed, but in some cases such as network driver locks
(which use the MTX_NETWORK_LOCK macro) and UMA zone locks, a name is used.
Tested on: i386, alpha, sparc64
In the i386 case, options BOOTP requires options NFS_ROOT as well as
options NFSCLIENT. With *both* the NFS options, a bootpc_init()
prototype is brought in by nfsclient/nfsdiskless.h.
In the ia64 case, it just doesn't work and my change just pushes it
further away from working.
Suggested to be wrong by: bde
they aren't in the usual path of execution for syscalls and traps.
The main complication for this is that we have to set flags to control
ast() everywhere that changes the signal mask.
Avoid locking in userret() in most of the remaining cases.
Submitted by: luoqi (first part only, long ago, reorganized by me)
Reminded by: dillon
in dump byte order (=network byte order). Swap blocksize and dumptime
to avoid extraneous padding on 64-bit architectures. Use CTASSERT
instead of runtime checks to make sure the header is 512 bytes large.
Various style(9) fixes.
Reviewed by: phk, bde, mike
emitted the total number of pages it still had to dump prior to
dumping a block of up to 16 pages. For a 128MB region this would
result in 8M number of printf()s. Barf!
The problem in general is that memory typically has one really
big region and a number of "scattered" smaller regions. Some may
even be just a few pages. The twiddle works best for now, but
it doesn't really give a good progress indication for the large
regions. Those are the cases where you definitely want good PI
to avoid having the user turn into a twiddle :-)
various machdep.c's to being declared in kern_mutex.c.
- Add a new function mutex_init() used to perform early initialization
needed for mutexes such as setting up thread0's contested lock list
and initializing MI mutexes. Change the various MD startup routines
to call this function instead of duplicating all the code themselves.
Tested on: alpha, i386
constructs an ELF image, consisting of the ELF header, for
each memory region a program header, followed by the memory
contents for each region. It does blocked I/O for the headers
as they are typically smaller than DEV_BSIZE.
and cpu_critical_exit() and moves associated critical prototypes into their
own header file, <arch>/<arch>/critical.h, which is only included by the
three MI source files that need it.
Backout and re-apply improperly comitted syntactical cleanups made to files
that were still under active development. Backout improperly comitted program
structure changes that moved localized declarations to the top of two
procedures. Partially re-apply one of the program structure changes to
move 'mask' into an intermediate block rather then in three separate
sub-blocks to make the code more readable. Re-integrate bug fixes that Jake
made to the sparc64 code.
Note: In general, developers should not gratuitously move declarations out
of sub-blocks. They are where they are for reasons of structure, grouping,
readability, compiler-localizability, and to avoid developer-introduced bugs
similar to several found in recent years in the VFS and VM code.
Reviewed by: jake
general cleanup of the API. The entire API now consists of two functions
similar to the pre-KSE API. The suser() function takes a thread pointer
as its only argument. The td_ucred member of this thread must be valid
so the only valid thread pointers are curthread and a few kernel threads
such as thread0. The suser_cred() function takes a pointer to a struct
ucred as its first argument and an integer flag as its second argument.
The flag is currently only used for the PRISON_ROOT flag.
Discussed on: smp@
bootinfo block in register r8. In locore.s we save the address
in the global variable 'pa_bootinfo'. In machdep.c we compare
this value against the hardwired address, but don't depend on its
validity yet (ie: we still expect the bootinfo block to be at the
hardwired address). After a small amount of time, we'll flip the
switch and depend on the loader to pass us the address. From that
moment on the loader is free to put it anywhere it likes, provided
the machine itself likes it as well.
Add some verbosity to aid in the transition. We emit a message if
the loader didn't pass the address and we also emit a message if
there's no bootinfo block at the hardwired address.
While in locore.s, reduce the number of redundant serialization
instructions. A srlz.i is a proper superset of a srlz.d and thus
is a valid replacement. Also slightly reorder the movl instructions
to improve bundle density.
back into the calling MD code. The MD code must ensure no races between
checking the astpening flag and returning to usermode.
Submitted by: peter (ia64 bits)
Tested on: alpha (peter, jeff), i386, ia64 (peter), sparc64
with this flag. Remove the dup_list and dup_ok code from subr_witness. Now
we just check for the flag instead of doing string compares.
Also, switch the process lock, process group lock, and uma per cpu locks over
to this interface. The original mechanism did not work well for uma because
per cpu lock names are unique to each zone.
Approved by: jhb
disablement assumptions in kern_fork.c by adding another API call,
cpu_critical_fork_exit(). Cleanup the td_savecrit field by moving it
from MI to MD. Temporarily move cpu_critical*() from <arch>/include/cpufunc.h
to <arch>/<arch>/critical.c (stage-2 will clean this up).
Implement interrupt deferral for i386 that allows interrupts to remain
enabled inside critical sections. This also fixes an IPI interlock bug,
and requires uses of icu_lock to be enclosed in a true interrupt disablement.
This is the stage-1 commit. Stage-2 will occur after stage-1 has stabilized,
and will move cpu_critical*() into its own header file(s) + other things.
This commit may break non-i386 architectures in trivial ways. This should
be temporary.
Reviewed by: core
Approved by: core
Instead of caching the ucred reference, just go ahead and eat the
decerement and increment of the refcount. Now that Giant is pushed down
into crfree(), we no longer have to get Giant in the common case. In the
case when we are actually free'ing the ucred, we would normally free it on
the next kernel entry, so the cost there is not new, just in a different
place. This also removse td_cache_ucred from struct thread. This is
still only done #ifdef DIAGNOSTIC.
Tested on: i386, alpha
a bit before handing it over to the OS. I occasionally have 11
segments with several 8K or so fragments depending on nvram settings and
what I have done under loader(8) before booting. This needs to be
revisited.
a language feature that I do not know about. gcc is complaining about
a left shift >= sizeof type, even when shifting a (cast) 64 bit type left
by 43 bits.
lose if a process is preempted while pmap is temporarily switched to
another pmap.
* For SMP, drop the high-fp state when a thread is switched away from
so that if another cpu resumes that thread, it doesn't have to play
games with IPI to get ahold of the correct register values.
* Don't call ast() from interrupt() - if we switch, then we will miss
writing cr.eoi which will prevent the current cpu from receiving
interrupts until the current thread is resumed. The call to ast()
happens magically in exception_restore where it is safe.
* Add DDB 'show irq' command to examine interrupt hardware state.
* Use ptc.g instead of ptc.l so that TLB shootdowns are broadcast to the
coherence domain.
* Use smp_rendezvous for pmap_invalidate_all to ensure it happens on all
cpus.
* Dike out a DIAGNOSTIC printf which didn't compile.
* Protect the internals of pmap_install with cpu_critical_enter/exit.
o In i386's <machine/endian.h>, macros have some advantages over
inlines, so change some inlines to macros.
o In i386's <machine/endian.h>, ungarbage collect word_swap_int()
(previously __uint16_swap_uint32), it has some uses on i386's with
PDP endianness.
Submitted by: bde
o Move a comment up in <machine/endian.h> that was accidentially moved
down a few revisions ago.
o Reenable userland's use of optimized inline-asm versions of
byteorder(3) functions.
o Fix ordering of prototypes vs. redefinition of byteorder(3)
functions, so that the non-GCC (libc asm) case has proper
prototypes.
o Add proper prototypes for byteorder(3) functions in <sys/param.h>.
o Prevent redundant duplicate prototypes by making use of the
_BYTEORDER_PROTOTYPED define.
o Move the bswap16(), bswap32(), bswap64() C functions into MD space
for platforms in which asm versions don't exist. This significantly
reduces the complexity of some things at the cost of duplicate code.
Reviewed by: bde
* Move the section which manipulates ia64_pal_base to after cninit() so
that we don't risk printing anything before we have a console.
* Don't call ia64_probe_sapics() for a SKI build. This should really
be dependant on ACPICA being present or something.
In order to determine what to page out, the vm_daemon checks
reference bits on all pages belonging to all processes. Unfortunately,
the algorithm used reacted badly with shared pages; each shared page
would be checked once per process sharing it; this caused an O(N^2)
growth of tlb invalidations. The algorithm has been changed so that
each page will be checked only 16 times.
Prior to this change, a fork/sleepbomb of 1300 processes could cause
the vm_daemon to take over 60 seconds to complete, effectively
freezing the system for that time period. With this change
in place, the vm_daemon completes in less than a second. Any system
with hundreds of processes sharing pages should benefit from this change.
Note that the vm_daemon is only run when the system is under extreme
memory pressure. It is likely that many people with loaded systems saw
no symptoms of this problem until they reached the point where swapping
began.
Special thanks go to dillon, peter, and Chuck Cranor, who helped me
get up to speed with vm internals.
PR: 33542, 20393
Reviewed by: dillon
MFC after: 1 week
device drivers for bus system with other endinesses than the CPU (using
interfaces compatible to NetBSD):
- bwap16() and bswap32(). These have optimized implementations on some
architectures; for those that don't, there exist generic implementations.
- macros to convert from a certain byte order to host byte order and vice
versa, using a naming scheme like le16toh(), htole16().
These are implemented using the bswap functions.
- stream bus space access functions, which do not perform a byte order
conversion (while the normal access functions would if the bus endianess
differs from the CPU endianess).
htons(), htonl(), ntohs() and ntohl() are implemented using the new
functions above for kernel usage. None of the above interfaces is currently
exported to user land.
Make use of the new functions in a few places where local implementations
of the same functionality existed.
Reviewed by: mike, bde
Tested on alpha by: mike
While in userland, keep the thread's ucred reference in a shadow
field so that the usual place to store it is NULL.
If DIAGNOSTIC is not set, the thread ucred is kept valid until the next
kernel entry, at which time it is checked against the process cred
and possibly corrected. Produces a BIG speedup in
kernels with INVARIANTS set. (A previous commit corrected it
for the non INVARIANTS case already)
Reviewed by: dillon@freebsd.org
deprecated in favor of the POSIX-defined lowercase variants.
o Change all occurrences of NTOHL() and associated marcros in the
source tree to use the lowercase function variants.
o Add missing license bits to sparc64's <machine/endian.h>.
Approved by: jake
o Clean up <machine/endian.h> files.
o Remove unused __uint16_swap_uint32() from i386's <machine/endian.h>.
o Remove prototypes for non-existent bswapXX() functions.
o Include <machine/endian.h> in <arpa/inet.h> to define the
POSIX-required ntohl() family of functions.
o Do similar things to expose the ntohl() family in libstand, <netinet/in.h>,
and <sys/param.h>.
o Prepend underscores to the ntohl() family to help deal with
complexities associated with having MD (asm and inline) versions, and
having to prevent exposure of these functions in other headers that
happen to make use of endian-specific defines.
o Create weak aliases to the canonical function name to help deal with
third-party software forgetting to include an appropriate header.
o Remove some now unneeded pollution from <sys/types.h>.
o Add missing <arpa/inet.h> includes in userland.
Tested on: alpha, i386
Reviewed by: bde, jake, tmm
patch from a year ago: give file flags their own type. This does not
(yet) change the type used by system calls or library functions.
The underlying type was chosen to match what is returned by stat().
slower, and may be impeding adoption of -CURRENT by developers. We
recommend turning on WITNESS by default on crash boxes, and when doing
locking development. It will probably get turned on by default for a week
or two following any major locking commits, also.
Approved by: all and sundry (jhb, phk, ...)
this is a low-functionality change that changes the kernel to access the main
thread of a process via the linked list of threads rather than
assuming that it is embedded in the process. It IS still embeded there
but remove all teh code that assumes that in preparation for the next commit
which will actually move it out.
Reviewed by: peter@freebsd.org, gallatin@cs.duke.edu, benno rice,
some arches and the syscall table is machine-independent. It was
(bogusly) conditional on COMPAT_43, so this usually makes no difference.
ia64: in addition:
- replace the bogus cloned comment before osigreturn() by a correct one.
osigreturn() is just a stub fo ia64's.
- fix the formatting of cloned comment before sigreturn().
- fix the return code. use nosys() instead of returning ENOSYS to get
the same semantics as if the syscall is not in the syscall table.
Generating SIGSYS is actually correct here.
- fix style bugs.
powerpc: copy the cleaned up ia64 stub. This mainly fixes a bogus comment.
sparc64: copy the cleaned up the ia64 stub, since there was no stub before.
db_machdep.h to fix the link failure (multiple definitions)
caused by disabling the emission of common symbols. As a result,
there were no definitions at all. While here, remove useless
declarations.
mutex releases to not require flags for the cases when preemption is
not allowed:
The purpose of the MTX_NOSWITCH and SWI_NOSWITCH flags is to prevent
switching to a higher priority thread on mutex releease and swi schedule,
respectively when that switch is not safe. Now that the critical section
API maintains a per-thread nesting count, the kernel can easily check
whether or not it should switch without relying on flags from the
programmer. This fixes a few bugs in that all current callers of
swi_sched() used SWI_NOSWITCH, when in fact, only the ones called from
fast interrupt handlers and the swi_sched of softclock needed this flag.
Note that to ensure that swi_sched()'s in clock and fast interrupt
handlers do not switch, these handlers have to be explicitly wrapped
in critical_enter/exit pairs. Presently, just wrapping the handlers is
sufficient, but in the future with the fully preemptive kernel, the
interrupt must be EOI'd before critical_exit() is called. (critical_exit()
can switch due to a deferred preemption in a fully preemptive kernel.)
I've tested the changes to the interrupt code on i386 and alpha. I have
not tested ia64, but the interrupt code is almost identical to the alpha
code, so I expect it will work fine. PowerPC and ARM do not yet have
interrupt code in the tree so they shouldn't be broken. Sparc64 is
broken, but that's been ok'd by jake and tmm who will be fixing the
interrupt code for sparc64 shortly.
Reviewed by: peter
Tested on: i386, alpha
o Do not use a special struct to keep track of CPUs we found;
instead, use struct pcpu. This handles all the magic WRT
thread creation (yay!).
o Respect MAXCPU.
o Use the vhpt_base and vhpt_size values to initialize the AP.
o Style fixes.
Note that this commit temporarily breaks SMP configurations.
Previously APs didn't do anything, but they now enter the
scheduler. They hold sched_lock for more than 5 secs though
and cause a panic. That's what I call progress :-)
ia64_pal_base instead of scanning the EFI tables. This way
AP startup code can more easily use the function.
o Initialize ia64_pal_base in ia64_init(). When the PAL code
doesn't need explicit mapping or no PAL code has been found,
ia64_pal_base will be 0.
o Remove some unused global variables.
o Also in ia64_init(), allocate only 1 page for struct pcpu
and remove some Alpha leftovers.
o Initialize pc_pcb in cpu_pcpu_init().
- The MD functions critical_enter/exit are renamed to start with a cpu_
prefix.
- MI wrapper functions critical_enter/exit maintain a per-thread nesting
count and a per-thread critical section saved state set when entering
a critical section while at nesting level 0 and restored when exiting
to nesting level 0. This moves the saved state out of spin mutexes so
that interlocking spin mutexes works properly.
- Most low-level MD code that used critical_enter/exit now use
cpu_critical_enter/exit. MI code such as device drivers and spin
mutexes use the MI wrappers. Note that since the MI wrappers store
the state in the current thread, they do not have any return values or
arguments.
- mtx_intr_enable() is replaced with a constant CRITICAL_FORK which is
assigned to curthread->td_savecrit during fork_exit().
Tested on: i386, alpha
- The MI portions of struct globaldata have been consolidated into a MI
struct pcpu. The MD per-CPU data are specified via a macro defined in
machine/pcpu.h. A macro was chosen over a struct mdpcpu so that the
interface would be cleaner (PCPU_GET(my_md_field) vs.
PCPU_GET(md.md_my_md_field)).
- All references to globaldata are changed to pcpu instead. In a UP kernel,
this data was stored as global variables which is where the original name
came from. In an SMP world this data is per-CPU and ideally private to each
CPU outside of the context of debuggers. This also included combining
machine/globaldata.h and machine/globals.h into machine/pcpu.h.
- The pointer to the thread using the FPU on i386 was renamed from
npxthread to fpcurthread to be identical with other architectures.
- Make the show pcpu ddb command MI with a MD callout to display MD
fields.
- The globaldata_register() function was renamed to pcpu_init() and now
init's MI fields of a struct pcpu in addition to registering it with
the internal array and list.
- A pcpu_destroy() function was added to remove a struct pcpu from the
internal array and list.
Tested on: alpha, i386
Reviewed by: peter, jake
o Hide nonstandard functions and types in <netinet/in.h> when
_POSIX_SOURCE is defined.
o Add some missing types (required by POSIX.1-200x) to <netinet/in.h>.
o Restore vendor ID from Rev 1.1 in <netinet/in.h> and make use of new
__FBSDID() macro.
o Fix some miscellaneous issues in <arpa/inet.h>.
o Correct final argument for the inet_ntop() function (POSIX.1-200x).
o Get rid of the namespace pollution from <sys/types.h> in
<arpa/inet.h>.
Reviewed by: fenner
Partially submitted by: bde
pointless and would be inadequate for SMP systems. We will rely on the
VM system's locks to serialise this for now.
* Change pmap_remove() so that if the range being removed is larger than
the number of pages mapped by the pmap, we iterate over the currently
mapped pages instead of over the virtual address range. This should
make a difference when removing large virtual address ranges from an
address space.
Protect against an infinite loop when prefaulting pages. This can
happen when the vm system maps past the end of an object or tries
to map a zero length object, the pmap layer misses the fact that
offsets wrap into negative numbers and we get stuck.
Make flushing dirty pages work correctly on filesystems that
unexpectedly do not complete writes even with sync I/O requests.
This should help the behavior of mmaped files when using
softupdates (and perhaps in other circumstances also.)
reading cr.ivr, as well as writing to cr.eoi.
o use global variables to pass information to os_boot_rendez
so that it doesn't have to jump through hoops to find it
out. This avoids traps on the AP without it even being
initialized. This fixes SMP configurations.
o Move the probing of the MADT to the end of cpu_startup,
instead of at the start of cpu_mp_probe. We need to probe
the MADT for non-SMP configurations as well. This fixes
uniprocessor configurations.
o Serialize AP wake-up by waiting for the AP. We need to do
this since we use global variables to for the AP to use.
As a side-effect, we can use printf() more easily to see
what's going on.
It doesn't help us catch overflowing vector entries at compile time.
Instead use the .org directive. The last entry in the IVT doesn't
strictly need to be limited to 256 bytes, but doing so allows the
the VHPT to be placed immediately following the IVT without wasting
any space due to alignment.
* Re-organise RID allocation so that we don't accidentally give a RID
to two different processes. Also randomise the order to try to reduce
collisions in VHPT and TLB. Don't allocate RIDs for regions which are
unused.
* Allocate space for VHPT based on the size of physical memory. More
tuning is needed here.
* Add sysctl instrumentation for VHPT - see sysctl vm.stats.vhpt
* Fix a bug in pmap_prefault() which prevented it from actually adding
pages to the pmap.
* Remove ancient dead debugging code.
* Add DDB commands for examining translation registers and region
registers.
The first change fixes the 'free/cache page %p was dirty' panic which I
have been seeing when the system is put under moderate load. It also
fixes the negative RSS values in ps which have been confusing me for a
while.
With this set of changes the ia64 port is reliable enough to build its
own kernels, even with a 20-way parallel build. Next stop buildworld.
actually the address of the function descriptor. The fdesc has both
the address of the function and it's corresponding gp value. Now
that we have a gp value, use it instead of passing 0.
o Make <stdint.h> a symbolic link to <sys/stdint.h>.
o Move most of <sys/inttypes.h> into <sys/stdint.h>, as per C99.
o Remove <sys/inttypes.h>.
o Adjust includes in sys/types.h and boot/efi/include/ia64/efibind.h
to reflect new location of integer types in <sys/stdint.h>.
o Remove previously symbolicly linked <inttypes.h>, instead create a
new file.
o Add MD headers <machine/_inttypes.h> from NetBSD.
o Include <sys/stdint.h> in <inttypes.h>, as required by C99; and
include <machine/_inttypes.h> in <inttypes.h>, to fill in the
remaining requirements for <inttypes.h>.
o Add additional integer types in <machine/ansi.h> and
<machine/limits.h> which are included via <sys/stdint.h>.
Partially obtain from: NetBSD
Tested on: alpha, i386
Discussed on: freebsd-standards@bostonradio.org
Reviewed by: bde, fenner, obrien, wollman
When we truncate the msgbuf size because the last chunk is too small,
correctly terminate the phys_avail[] array - the VM system tests
the *end* for zero, not the start. This leads the VM startup to
attempt to recreate a duplicate set of pages for all physical memory.
XXX the msgbuf handling is suspiciously different on i386 vs
alpha/ia64...
* Implement a fairly simplistic parser for unwinding stack frames.
* Use unwind records for DDB's 'trace' command. Also add support for
tracing past exceptions to the context which generated the exception.
The stack unwind code requires a toolchain based on binutils-2.11.2 or
later and gcc-3.0.1 or later.
starts at offset 8; not 6. Hence the structure is 12 bytes and
not 10 bytes. Adjust the definition so that the ProcessorEnabled
flag is moved from bit 15 to bit 31 in the Flags field.
The definition now matches ACPI 2.0 Errata 1.5.
do it as a side-effect of probing for MP hardware. This allows
us to scan for local SAPICs early (especially before MBUF
initialization).
o Fix the Local SAPIC structure so that matches the Local SAPIC
table entry. Now that the Local SAPIC info is the same as the
Local APIC info, stop dumping the Local APIC entries.
o For every Local SAPIC entry in the MADT that's not disabled,
let the SMP code know about it. They represent actual CPUs.
o Register the OS_BOOT_RENDEZ entry point and provide a (bogus)
implementation for the entry point.
o Provide a mapping for internal IPI numbers to ExtINT vectors.
o In a MP system, announce the CPUs and start them by sending
IPI_AP_WAKEUP to each of them. Not that it makes a difference
at this time :-)
o Miscellaneous style fixes and other adjustments.
This emulates APM device node interface APIs (mainly ioctl) and
provides APM services for the applications. The goal is to support
most of APM applications without any changes.
Implemented ioctls in this commit are:
- APMIO_SUSPEND (mapped ACPI S3 as default but changable by sysctl)
- APMIO_STANDBY (mapped ACPI S1 as default but changable by sysctl)
- APMIO_GETINFO and APMIO_GETINFO_OLD
- APMIO_GETPWSTATUS
With above, many APM applications which get batteries, ac-line
info. and transition the system into suspend/standby mode (such as
wmapm, xbatt) should work with ACPI enabled kernel (if ACPI works well :-)
Reviewed by: arch@, audit@ and some guys
userland. The per thread ucred reference is immutable and thus needs no
locks to be read. However, until all the proc locking associated with
writes to p_ucred are completed, it is still not safe to use the per-thread
reference.
Tested on: x86 (SMP), alpha, sparc64
pcb_onfault is not set) or arrange to restart at the location in
pcb_onfault.
This ought to help the stability of a system under moderate load. It
certainly stops DDB from hanging the kernel when it tries to access a
non-present page.
