MFC rarm: correct kernelstack allocation size

This appears to be a copy-pasto from previous lines that propagated to v6
over the years. Indeed, nothing references kernelstack beyond
USPACE_SVC_STACK_TOP and it would be odd if anything did.

MFC r340995

Prevent kernel stack disclosure in signal delivery

On arm64 and riscv platforms, sendsig() failed to zero the signal
frame before copying it out to userspace. Zero it.

On arm, I believe all the contents of the frame were initialized,
so there was no disclosure. However, explicitly zero the whole frame
because that fact could inadvertently change in the future,
it's more clear to the reader, and I could be wrong in the first place.

Security: similar to FreeBSD-EN-18:12.mem and CVE-2018-17155
Sponsored by: Dell EMC Isilon

MFC r328467:

Implement mitigation for Spectre version 2 attacks on ARMv7.

Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

MFC r329989, r330044

r329989:
Add support for booting into kdb on arm platforms when the RB_KDB is set
(using "boot -d" at the loader propmt or setting boot_ddb in loader.conf).

Submitted by: Thomas Skibo <thomasskibo@yahoo.com>
Differential Revision: https://reviews.freebsd.org/D14428

r330044:
Add a hw.model sysctl oid for armv6/7 which reports the CPU model, similar
to what other arches (all except riscv and armv4/5) do.

Submitted by: Hyun Hwang <hyun@caffeinated.codes>
Differential Revision: https://reviews.freebsd.org/D14465

MFC r317055,r317056 (glebius): Include sys/vmmeter.h as included

r317055: All these files need sys/vmmeter.h, but now they got it implicitly
included via sys/pcpu.h.

r317056: Typo!

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

MFC r327048-r327050

r327048:
Restore the ability to use EARLY_PRINTF support during most of initarm().

The real kernel page tables are set up much earlier in initarm() now than
they were when early printf support was first added, and they end up undoing
the mapping made in locore.S for early printf support. This re-adds the
mapping after switching to the new/real kernel page tables, making early
printf work again right after switching to them.

r327049:
Allow pmap_kremove() to remove 1MB section mappings as well as 4K pages.
This will allow it to undo temporary device mappings such as those made
with pmap_preboot_map_attr().

Reviewed by: cognet

r327050:
If a temporary mapping is made to support EARLY_PRINTF, undo that mapping
after cninit() runs, otherwise we leave a bogus device-memory mapping in
userspace VA in the kernel pmap forever.

Pointed out by: cognet

MFC r326137:

Ensure we check the program state set in the trap frame on arm and arm64.
This value may be set by userspace so we need to check it before using it.
If this is not done correctly on exception return the kernel may continue
in kernel mode with all registers set to a userspace controlled value. Fix
this by moving the check into set_mcontext, and also add the missing
sanitisation from the arm64 set_regs.

Discussed with: security-officer@
Sponsored by: DARPA, AFRL

MFC 323581,323582,323583: Add ptrace operations for VFP registers.

323581:
Only mess with VFP state on the CPU for curthread for get/set_vfpcontext.

Future changes will use these functions to fetch and store VFP state for
threads other than curthread.

323582:
Add ptrace operations to fetch and store VFP registers.

323583:
Export get/set_vfpcontext from machdep.c.

Should have been part of the previous commit to add ptrace operations
for VFP registers.

MFC r324660:

Save VFP state in getcontext(3) on ARM. This is a last followup of r315974,
which fixes userland part of VFP save/restore problems described in PR
217611.

MFC r315900,r315973,r315974:

r315900:
Cleanup structures related to VFP and/or mcontext_t. - in mcontext_t,
rename newer used 'union __vfp' to equaly sized 'mc_spare'.
Space allocated by 'union __vfp' is too small and cannot hold full VFP
context.
- move structures defined in fp.h to more appropriate headers. - remove
all unused VFP structures.
r315973:
Save VFP state on fork(). Update the copy of VFP state in PCB before it is
cloned for new process.
r315974:
Preserve VFP state across signal delivery.

MFC r303261,r315059:

r303261:
Add more UEFI/e820 memory types from latest specifications.
r315059:
Split overbloated machep.c to multiple files and do basic cleanup of these
fragments.

MFC r306704,r308406:

r306704:
ARM: Remove next bunch of unused cpu_functions from ARMv6.
r308406:
Only include sys/boot.h if LINUX_BOOT_ABI is defined

MFC r305942:
Consolidate four efi_next_descriptor() definitions.

MFC r304285:
Implement userspace gettimeofday(2) with HPET timecounter.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Include machine/acle-compat.h in cdefs.h on arm if the compiler doesn't
have ACLE support built in. The ACLE (ARM C Language Extensions) defines
a set of standardized symbols which indicate the architecture version and
features available. ACLE support is built in to modern compilers (both
clang and gcc), but absent from gcc prior to 4.4.

ARM (the company) provides the acle-compat.h header file to define the
right symbols for older versions of gcc. Basically, acle-compat.h does
for arm about the same thing cdefs.h does for freebsd: defines
standardized macros that work no matter which compiler you use. If ARM
hadn't provided this file we would have ended up with a big #ifdef __arm__
section in cdefs.h with our own compatibility shims.

Remove #include <machine/acle-compat.h> from the zillion other places (an
ever-growing list) that it appears. Since style(9) requires sys/types.h
or sys/param.h early in the include list, and both of those lead to
including cdefs.h, only a couple special cases still need to include
acle-compat.h directly.

Loves it: imp

Use the new(-ish) CP15_SCTLR macro to generate system control reg accesses
where possible. In the places that doesn't work (multi-line inline asm,
and places where the old armv4 cpufuncs mechanism is used), annotate the
accesses with a comment that includes SCTLR. Now a grep -i sctlr can find
all the system control register manipulations.

No functional changes.

sys/arm: Minor spelling fixes.

Only affects comments: no functional change.

Add a MULTIDELAY option to allow the ARM kernel to have multiple DELAY
implementations. Early in the boot the kernel will use an approximate,
however after the timer has been probed it will switch to a more accurate
implementation.

Reviewed by: manu
Sponsored by: ABT Systems Ltd
Differential Revision: https://reviews.freebsd.org/D5762

Move arm's devmap to some generic place, so it can be used
by other architectures.

Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D6091
Sponsored by: DARPA, AFRL
Sponsored by: HEIF5

ARM: Fix bug introduced in r297286.
- don't put command line without guard to kernel environment.
- kernel environment delivered from ubldr must have absolute precedence.

ARM: Parse command line delivered by U-Boot:
- in atags
- in DT blob (by using 'fdt chosen' U-Boot command)

The command line must start with guard's string 'FreeBSD:' and can contain
list of comma separated kenv strings. Also, boot modifier strings from
boot.h are recognised and parsed into boothowto.

The command line must be passed from U-Boot by setting of bootargs variable:
'setenv bootargs FreeBSD:boot_single=1,vfs.root.mountfrom=ufs:/dev/ada0s1a'
followed by 'fdt chosen' (only for DT based boot)

ARM: Fix ATAG handling in LINUX_BOOT_API:
- Don't convert atags address passed from U-Boot. It's real physical
address (and we have 1:1 mapping).
- Size of tags is encoded in words, not in bytes

ARM: Teach LINUX_BOOT_ABI to recognize DT blob.
This allow us to boot FreeBSD kernel (using uImage encapsulation) directly
from U-boot using 'bootm' command or by Android fastboot loader.
For now, kernel uImage must be marked as Linux, but we can add support for
FreeBSD into U-Boot later.

Make it an error to build an ARM kernel with COMPAT_FREEBSDn where n < 10.
We changed the ABI for ARM in 10, an removed support for the old ABI in 11,
as such binaries from these releases are unable to be run on a head kernel.

Reviewed by: bz, emast
Sponsored by: ABT Systems Ltd
Differential Revision: https://reviews.freebsd.org/D5652

Make the memory size returned from fdt_get_mem_regions a 64-bit type. This
is the physical memory size so may be larger than a u_long can hold, e.g.
on ARM with LPAE we could see an address space of up to 40 bits. On ARM
u_long is only 32 bits so the memory size will be truncated, possibly to
zero.

Reported by: bz
Sponsored by: ABT Systems Ltd

Stop setting the memory size in the arm EFI and FDT code, we don't use it.

Sponsored by: ABT Systems Ltd

Fix fdt_get_mem_regions() to work with 64-bit addresses

Use u_long instead of uint32_t variables to avoid overflow
in case of PA space bigger than 32-bit.

Obtained from: Semihalf
Submitted by: Michal Stanek <mst@semihalf.com>
Sponsored by: Annapurna Labs
Approved by: cognet (mentor)
Reviewed by: andrew, br, wma
Differential revision: https://reviews.freebsd.org/D5393

ARM: Use new ARMv6 naming conventions for cache and TLB functions
in all but ARMv4 specific files.
Expand ARMv6 compatibility stubs in cpu-v4.h. Use physical address
in L2 cache functions if ARM_L2_PIPT is defined.

ARM: Introduce new cpu-v4.h header and move all ARMv4 specific code
from cpu-v6.h to it.
Remove unneeded cpu-v6.h includes.

ARM: Consistently use cpu_setttb() instead of setttb().
Remove unused #define for drain_writebuf.

ARM: Don't misuse ARM_TP_ADDRESS as ARMv4 / ARMv6 selector.

Use kernel_pmap directly instead of pmap_kernel(). The kernel_pmap is
already used for __ARM_ARCH >= 6 and so even for __ARM_ARCH < 6 on some
common places.

ARM: remove old pmap-v6 code. The new pmap-v6 is mature enough, and
dual implementation is showstopper for major cleanup.

This patch only removes old code from tree. Cleanups will follow asap.

Convert ss_sp in stack_t and sigstack to void *.

POSIX requires these members to be of type void * rather than the
char * inherited from 4BSD. NetBSD and OpenBSD both changed their
fields to void * back in 1998. No new build failures were reported
via an exp-run.

PR: 206503 (exp-run)
Reviewed by: kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D5092

Introduce support for HW watchpoints and single stepping for ARMv6/v7

Allows for using hardware watchpoints for 1, 2, 4, 8 byte long addresses.
The default configuration of watchpoint is RW but code allows to select
RO or WO and X.
Since debugging registers are per-CPU (CP14) the watchpoint is set on
the CPU that was lucky (or not) to enter DDB.

HW breakpoints are used to perform single step in KDB.
When HW breakpoint is enabled all watchpoints are temporary disabled
to avoid recursive abort on both watchpoint and breakpoint.
In case of branch, the breakpoint is set to both - next instruction
and possible branch address. This requires at least 2 breakpoints
supported in the CPU however this is a must for ARMv6/v7 CPUs.

Reviewed by: imp
Submitted by: Zbigniew Bodek <zbb@semihalf.com>
Obtained from: Semihalf
Sponsored by: Juniper Networks Inc.
Differential Revision: https://reviews.freebsd.org/D4037

Store the pointer to the bootloader-provided env data in a static var
for use in debug printing.

Make the 'env' directive described in config(5) work on all architectures,
providing compiled-in static environment data that is used instead of any
data passed in from a boot loader.

Previously 'env' worked only on i386 and arm xscale systems, because it
required the MD startup code to examine the global envmode variable and
decide whether to use static_env or an environment obtained from the boot
loader, and set the global kern_envp accordingly. Most startup code wasn't
doing so. Making things even more complex, some mips startup code uses an
alternate scheme that involves calling init_static_kenv() to pass an empty
buffer and its size, then uses a series of kern_setenv() calls to populate
that buffer.

Now all MD startup code calls init_static_kenv(), and that routine provides
a single point where envmode is checked and the decision is made whether to
use the compiled-in static_kenv or the values provided by the MD code.

The routine also continues to serve its original purpose for mips; if a
non-zero buffer size is passed the routine installs the empty buffer ready
to accept kern_setenv() values. Now if the size is zero, the provided buffer
full of existing env data is installed. A NULL pointer can be passed if the
boot loader provides no env data; this allows the static env to be installed
if envmode is set to do so.

Most of the work here is a near-mechanical change to call the init function
instead of directly setting kern_envp. A notable exception is in xen/pv.c;
that code was originally installing a buffer full of preformatted env data
along with its non-zero size (like mips code does), which would have allowed
kern_setenv() calls to wipe out the preformatted data. Now it passes a zero
for the size so that the buffer of data it installs is treated as
non-writeable.

Add helper functions proc_readmem() and proc_writemem().

These helper functions can be used to read in or write a buffer from or to
an arbitrary process' address space. Without them, this can only be done
using proc_rwmem(), which requires the caller to fill out a uio. This is
onerous and results in code duplication; the new functions provide a simpler
interface which is sufficient for most existing callers of proc_rwmem().

This change also adds a manual page for proc_rwmem() and the new functions.

Reviewed by: jhb, kib
Differential Revision: https://reviews.freebsd.org/D4245

Add support for usermode (vdso-like) gettimeofday(2) and
clock_gettime(2) on ARMv7 and ARMv8 systems which have architectural
generic timer hardware. It is similar how the RDTSC timer is used in
userspace on x86.

Fix a permission problem where generic timer access from EL0 (or
userspace on v7) was not properly initialized on APs.

For ARMv7, mark the stack non-executable. The shared page is added for
all arms (including ARMv8 64bit), and the signal trampoline code is
moved to the page.

Reviewed by: andrew
Discussed with: emaste, mmel
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D4209

Add support for branch instruction on armv7 with ptrace single step

Previous code supported only "continuous" code without any kind of
branch instructions. To change that, new function was implemented
which parses current instruction and returns an addres where
the jump might happen (alternative addr).
mdthread structure was extended to support two breakpoints
(one directly below current instruction and the second placed
at the alternative location).
One of them must trigger regardless the instruction has or has not been
executed due to condition field.
Upon cleanup, both software breakpoints are removed.

This implementation parses only the most common instructions
that are present in the code (like 99.99% of all), but there
is a chance there are some left, not covered by the parsing routine.
Parsing is done only for 32-bit instruction, no Thumb nor Thumb-2
support is provided.

Reviewed by: kib
Submitted by: Wojciech Macek <wma@semihalf.com>
Obtained from: Semihalf
Sponsored by: Juniper Networks Inc.
Differential Revision: https://reviews.freebsd.org/D4021

Do not set 'flush to zero' VFPSCR_FZ bit by default. The correct
implementation of IEEE 754 arithmetic depends on denormals operating
correctly. Both perl test suite and paranoia tripped over the
setting.

Reported by: Stefan Parvu <sparvu@kronometrix.org>
Discussed with: andrew
Sponsored by: The FreeBSD Foundation
MFC after: 1 week

preload_search_info: make sure mod is set

Add a check to preload_search_info to make sure mod is set. Most of the
callers of preload_search_info don't check that the mod parameter is
set, which can cause page faults. While at it, remove some now unnecessary
checks before calling preload_search_info.

Sponsored by: Citrix Systems R&D
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D3440

Make kstack_pages a tunable on arm, x86, and powepc. On i386, the
initial thread stack is not adjusted by the tunable, the stack is
allocated too early to get access to the kernel environment. See
TD0_KSTACK_PAGES for the thread0 stack sizing on i386.

The tunable was tested on x86 only. From the visual inspection, it
seems that it might work on arm and powerpc. The arm
USPACE_SVC_STACK_TOP and powerpc USPACE macros seems to be already
incorrect for the threads with non-default kstack size. I only
changed the macros to use variable instead of constant, since I cannot
test.

On arm64, mips and sparc64, some static data structures are sized by
KSTACK_PAGES, so the tunable is disabled.

Sponsored by: The FreeBSD Foundation
MFC after: 2 week

Fix KSTACK_PAGES issue when the default value was changed in KERNCONF

If KSTACK_PAGES was changed to anything alse than the default,
the value from param.h was taken instead in some places and
the value from KENRCONF in some others. This resulted in
inconsistency which caused corruption in SMP envorinment.

Ensure all places where KSTACK_PAGES are used the opt_kstack_pages.h
is included.

The file opt_kstack_pages.h could not be included in param.h
because was breaking the toolchain compilation.

Reviewed by: kib
Obtained from: Semihalf
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D3094

Fix the spelling of __ARM_ARCH >= 6 in sys/arm/arm.

Remove pc_cpu, it was duplicating pc_cpuid so was unneeded.

Clear the C bit of the saved program state register when also clearing the
return value. We use this bit to signal when a syscall has failed, and
without this getcontext/setcontext may fail.

MFC after: 1 week

The kernel sends signals to the processes via ABI specific sv_sendsig method.
Native ABI do not need signal conversion, only emulators may want this. Usually
emulators implements its own sv_sendsig method. For now only ibcs2 emulator does
not have own sv_sendsig implementation and depends on native sendsig() method.
So, remove any extra attempts to convert signal numbers from native sendsig()
methods except from i386 where ibsc2 is living.

Add support for getting the memory map from EFI if it has been pased in
by loader.efi.

Remove trailing whitespace from sys/arm/arm

Do not set preload_addr_relocate for ARM. Apparently there was a time
when loader(8) passed physical addresses in loader metadata for arm, but
that is no longer true; all metadata has already been adjusted to vitual
addresses by loader.

I can't track down the exact revision in loader where a change from physical
to virtual metadata addresses happened. The code involved is very twisty
and complicated. I suspect the change was an unintended consequence of the
r247301, r247413, r248118 series of changes I made a couple years ago.

Add the kernel support for Thumb-2. It is only supported on ARMv7 as the
main ARMv6 target, the Raspberry Pi, doesn't support Thumb-2.

This as been tested with a Thumb-2 userland, however building one is
currently unsupported as there are known toolchain issues breaking some
binaries. Further work will also be needed to decide on the method of
selecting which instruction set to build for, and to benchmark both to
find how building everything as Thumb-2 will affect performance.

Relnotes: yes

Add new CP15 operations and DB_SHOW_COMMAND to print CP15 registers

Submitted by: Wojciech Macek <wma@semihalf.com>
Reviewed by: imp, Michal Meloun <meloun@miracle.cz>
Obtained from: Semihalf

Remove an unused variable.

Remove the bootconfig parsing. We never used it and always passed either an
empty string or NULL to the setup functions that called into it.

New pmap code for armv6. Disabled by default, option ARM_NEW_PMAP enables it.

This is pretty much a complete rewrite based on the existing i386 code. The
patches have been circulating for a couple years and have been looked at by
plenty of people, but I'm not putting anybody on the hook as having reviewed
this in any formal sense except myself.

After this has gotten wider testing from the user community, ARM_NEW_PMAP
will become the default and various dregs of the old pmap code will be
removed.

Submitted by: Svatopluk Kraus <onwahe@gmail.com>,
Michal Meloun <meloun@miracle.cz>

Do not qualify the mcontext_t *mcp argument for set_mcontext(9) as
const. On x86, even after the machine context is supposedly read into
the struct ucontext, lazy FPU state save code might only mark the FPU
data as hardware-owned. Later, set_fpcontext() needs to fetch the
state from hardware, modifying the *mcp.

The set_mcontext(9) is called from sigreturn(2) and setcontext(2)
implementations and old create_thread(2) interface, which throw the
*mcp out after the set_mcontext() call.

Reported by: dim
Discussed with: jhb
Sponsored by: The FreeBSD Foundation
MFC after: 1 week

Add new code to read and parse cpu identification data using the new CPUID
mechanism defined for armv7 (and also present on some armv6 chips including
the arm1176 used on rpi). The information is parsed into a global cpuinfo
structure, which will be used by (upcoming) new cache and tlb maintenance
code to handle cpu-specific variations of the maintence sequences.

Submitted by: Svatopluk Kraus <onwahe@gmail.com>,
Michal Meloun <meloun@miracle.cz

Cleanup up ARM *frame structures...

- Eliminate unused irqframe
- Eliminate unused saframe
- Instead of splitting r4-sp storage between the stack and switchframe,
just put all the registers in switchframe and eliminate the un_32 struct.

Submitted by: Svatopluk Kraus <onwahe@gmail.com>,
Michal Meloun <meloun@miracle.cz>

Fix usage of kern_getenv().

Follow up to r225617. In order to maximize the re-usability of kernel code
in userland rename in-kernel getenv()/setenv() to kern_setenv()/kern_getenv().
This fixes a namespace collision with libc symbols.

Submitted by: kmacy
Tested by: make universe

ddb: allow specifying the exact address of the symtab and strtab

When the FreeBSD kernel is loaded from Xen the symtab and strtab are
not loaded the same way as the native boot loader. This patch adds
three new global variables to ddb that can be used to specify the
exact position and size of those tables, so they can be directly used
as parameters to db_add_symbol_table. A new helper is introduced, so callers
that used to set ksym_start and ksym_end can use this helper to set the new
variables.

It also adds support for loading them from the Xen PVH port, that was
previously missing those tables.

Sponsored by: Citrix Systems R&D
Reviewed by: kib

ddb/db_main.c:
- Add three new global variables: ksymtab, kstrtab, ksymtab_size that
can be used to specify the position and size of the symtab and
strtab.
- Use those new variables in db_init in order to call db_add_symbol_table.
- Move the logic in db_init to db_fetch_symtab in order to set ksymtab,
kstrtab, ksymtab_size from ksym_start and ksym_end.

ddb/ddb.h:
- Add prototype for db_fetch_ksymtab.
- Declate the extern variables ksymtab, kstrtab and ksymtab_size.

x86/xen/pv.c:
- Add support for finding the symtab and strtab when booted as a Xen
PVH guest. Since Xen loads the symtab and strtab as NetBSD expects
to find them we have to adapt and use the same method.

amd64/amd64/machdep.c:
arm/arm/machdep.c:
i386/i386/machdep.c:
mips/mips/machdep.c:
pc98/pc98/machdep.c:
powerpc/aim/machdep.c:
powerpc/booke/machdep.c:
sparc64/sparc64/machdep.c:
- Use the newly introduced db_fetch_ksymtab in order to set ksymtab,
kstrtab and ksymtab_size.

Unify interrupts bit definition and usage. While here remove PSR_C_bit.

Submitted by: Svatopluk Kraus <onwahe at gmail.com>,
Michal Meloun <meloun at miracle.cz>
Differential Revision: https://reviews.freebsd.org/D754

Use a SYSINIT to init the array of interrupt names on arm. This was
called from initarm() in arm/machdep.c, but many legacy arm platforms
have their own private initarm(), so a SYSINIT fixes everyone.

Reported by: jmg

Add the start of the ARM platform code. This is based on the PowerPC
platform code, it is expected these will be merged in the future when the
ARM code is more complete.

Until more boards can be tested only use this with the Raspberry Pi and
rrename the functions on the other SoCs.

Reviewed by: ian@

Cleanup some style nits.

Interrupts need to be disabled on entry to cpu_sleep() for ARM. Given
that and the need to be in a critical section when switching to idleclock
mode for event timers, use spinlock_enter()/exit() to achieve both needs.

The ARM WFI (wait for interrupt) instruction blocks until an interrupt is
asserted, and it will unblock even if interrupts are masked, and it will
unblock immediately if an interrupt is already pending. It is necessary
to execute it with interrupts disabled, otherwise the interrupt that
should unblock it may occur and be serviced just prior to executing the
instruction. At that point the system is inappropriately asleep until
the next timer tick or some other random interrupt happens.

In general, interrupts need to be disabled continuously from the time the
decision is made that there is no work to be done and sleeping is needed
until actually going to sleep, to avoid a race where handling a new
interrupt changes the basis for deciding there is no work to be done.

Submitted by: hps@ (in slightly different form)

Initialise fpscr to a sane value when we create the pcb. This sets NaNs to
be the default NaN and for denormalised numbers to be flushed to zero.

Rename global cnt to vm_cnt to avoid shadowing.

To reduce the diff struct pcu.cnt field was not renamed, so
PCPU_OP(cnt.field) is still used. pc_cnt and pcpu are also used in
kvm(3) and vmstat(8). The goal was to not affect externally used KPI.

Bump __FreeBSD_version_ in case some out-of-tree module/code relies on the
the global cnt variable.

Exp-run revealed no ports using it directly.

No objection from: arch@
Sponsored by: EMC / Isilon Storage Division

The arm exception entry points currently vector through a function pointer
to the actual handler routine. All the pointers are static-intialized to
the only handlers available, and yet various platform-specific inits still
set those pointers (to the values they're already initialized to). Begin
to drain the swamp by removing all the redundant external declarations and
runtime setting of the pointers that's scattered around various places.

When a thread begins life it doesn't own the VFP hardware state on any cpu.

Remove all dregs of a per-thread undefined-exception-mode stack. This is
a leftover from the days when a low-level debugger had hooks in the
undefined exception vector and needed stack space to function. These days
it effectively isn't used because we switch immediately to the svc32 mode
stack on exception entry. For that, the single undef mode stack per core
that gets set up at init time works fine.

The stack wasn't necessary but it was harmful, because the space for it
was carved out of the normal per-thread svc32 stack, in effect cutting
that 8K stack in half. If svc32 mode used more than 4k of stack space it
wandered down into the undef mode stack, and then an undef exception would
overwrite a couple words on the stack while switching to svc32 mode,
corrupting the scv32 stack. Having another stack abut the bottom of the
svc32 stack also effectively mooted the guard page below the stack.

This work is based on analysis and patches submitted by Juergen Weiss.

Fix the arm sys_sigreturn(): its argument is a struct ucontext, not a
struct sigframe containing the struct ucontext.

The signal trampoline return code on the other hand DOES have just a
struct sigframe on the stack to work with, so have it get a pointer to
the ucontext out of there to pass along to sys_sigreturn.

In other words, make everything work right whether sys_sigreturn is
invoked from the trampoline or from userland code calling sigreturn(2).

Submitted by: Takashi Komatsu <komatsu.taka@jp.panasonic.com>
Reviewed by: cognet

Replace many pasted identical definitions of cpu_initclocks() with a common
implementation in arm/machdep.c. Most arm platforms either don't need to
do anything, or just need to call the standard eventtimer init routines.
A generic implementation that does that is now provided via weak linkage.
Any platform that needs to do something different can provide a its own
implementation to override the generic one.

If the L2 cache type is PIPT, pass a physical address for a flush.

While this is technically more correct, I don't think it much matters,
because the only thing in the tree that calls cpu_flush_dcache() is md(4)
and I'm > 99% sure it's bogus that it does so; md has no ability to do
anything that can perturb data cache coherency.

Remove bogus blank line.

Convert two while(1); statements into proper panics. Soon, kernels
with early printf support will print this info... For kernels without,
the observed behavior will be the same as it is now...

No need to set physmem in each initarm() instance anymore, it's handled
in common code now.

It turns out a global variable is the only straightforward way to
communicate the kernel's physical load address from where it's known in
initarm() into cpu_mp_start() which is called from non-arm code and
takes no parameters.

This adds the global variable and ensures that all the various copies
of initarm() set it. It uses the variable in cpu_mp_start(), eliminating
the last uses of KERNPHYSADDR outside of locore.S (where we can now
calculate it instead of relying on the constant).

Consolidate code related to setting up physical memory configuration into
a new physmem.c file. The new code provides helper routines that can be
used by legacy SoCs and newer FDT-based systems. There are routines to
add one or more regions of physically contiguous ram, and exclude one or
more physically contiguous regions of ram. Ram can be excluded from crash
dumps, from being given over to the vm system for allocation management,
or both. After all the included and excluded regions have been added,
arm_physmem_init_kernel_globals() processes the regions into the global
dump_avail and phys_avail arrays and realmem and physmem variables that
communicate memory configuration to the rest of the kernel.

Convert all existing SoCs to use the new helper code.

Remove the ARM_USE_SMALL_ALLOC option and code related to it.

This was an optimization used only by a few xscale platforms. Part of
the optimization was to create a direct map for all physical pages, and
that resulted in making multiple mappings of pages in a way that bypassed
the logic in pmap.c to handle VIVT cache aliasing. It also just generally
made the code more complex and hard to maintain for all SoCs.

Reviewed by: cognet

Use abp_physaddr for the physical address over KERNPHYSADDR. This helps us
remove the need to load the kernel at a fixed address.

Change the way pcpu and curthread are stored per-core:
the old way was to store pcpu in a register, and get curthread from pcpu,
which is not very atomic, and led to issues if the thread was migrated
to another core between the time we got the pcpu address and the time we
got curthread.
Instead, we now store curthread where pcpu used to be store, and we
calculate the pcpu address based on the cpu id.

Add a function to print the contents of the static device mapping table,
and invoke it for bootverbose logging, and also from a new DDB command,
"show devmap". Also tweak the format string for the bootverbose output
of physical memory chunks to get the leading zeros in the hex values.

Retire machine/fdt.h as a header used by MI code, as its function is now
obsolete. This involves the following pieces:
- Remove it entirely on PowerPC, where it is not used by MD code either
- Remove all references to machine/fdt.h in non-architecture-specific code
(aside from uart_cpu_fdt.c, shared by ARM and MIPS, and so is somewhat
non-arch-specific).
- Fix code relying on header pollution from machine/fdt.h includes
- Legacy fdtbus.c (still used on x86 FDT systems) now passes resource
requests to its parent (nexus). This allows x86 FDT devices to allocate
both memory and IO requests and removes the last notionally MI use of
fdtbus_bs_tag.
- On those architectures that retain a machine/fdt.h, unused bits like
FDT_MAP_IRQ and FDT_INTR_MAX have been removed.

Call cpu_setup() immediately after the page tables are installed. This
enables data cache and other chip-specific features. It was previously
done via an early SYSINIT, but it was being done after pmap and vm setup,
and those setups need to use mutexes. On some modern ARM platforms,
the ldrex/strex instructions that implement mutexes require the data cache
to be enabled.

A nice side effect of enabling caching earlier is that it eliminates the
multi-second pause that used to happen early in boot while physical memory
and pmap and vm were being set up. On boards with 1 GB or more of ram
this pause was very noticible, sometimes 5-6 seconds.

PR: arm/183740

Call initarm_lastaddr() later in the init sequence, after establishing
static device mappings, rather than as the first of the initializations
that a platform can hook into. This allows a platform to allocate KVA
from the top of the address space downwards for things like static device
mapping, and return the final "last usable address" result after that and
other early init work is done.

Because some platforms were doing work in initarm_lastaddr() that needs to
be done early, add a new initarm_early_init() routine and move the early
init code to that routine on those platforms.

Rename platform_devmap_init() to initarm_devmap_init() to match all the
other init routines called from initarm() that are designed to be
implemented by platform code.

Add a comment block that explains when these routines are called and the
type of work expected to be done in each of them.

Move remaining code and data related to static device mapping into the
new devmap.[ch] files. Emphasize the MD nature of these things by using
the prefix arm_devmap_ on the function and type names (already a few of
these things found their way into MI code, hopefully it will be harder to
do by accident in the future).

Begin reducing code duplication in arm pmap.c and pmap-v6.c by factoring
out common code related to mapping device memory into a new devmap.c file.

Remove the growing duplication of code that used pmap_devmap_find_pa() and
then did some math with the returned results to generate a virtual address,
and likewise in reverse to get a physical address. Now there are a pair
of functions, arm_devmap_vtop() and arm_devmap_ptov(), to do that. The
bus_space_map() implementations are rewritten in terms of these.

Remove #include <machine/frame.h> from all the arm code that doesn't
really need it. That would be almost everywhere it was included. Add
it in a couple files that really do need it and were previously getting
it by accident via another header.

Remove all #include <machine/pmap.h> from arm code. It's already
included by vm/pmap.h, which is a prerequisite for arm/machine/pmap.h
so there's no reason to ever include it directly.

Thanks to alc@ for pointing this out.

If we avoid to use the page at addr 0, we should adjust the size to reflect it.

Fix a typo in a comment.

Rename device vfp to option VFP and retire the ARM_VFP_SUPPORT option. This
simplifies enabling as previously both options were required to be enabled,
now we only need a single option.

While here enable VFP on the PandaBoard.

Add the hw.floatingpoint sysctl to ARM to tell us if we have vfp support
in the kernel and the hardware includes a vfp unit.

Switch the vm_object mutex to be a rwlock. This will enable in the
future further optimizations where the vm_object lock will be held
in read mode most of the time the page cache resident pool of pages
are accessed for reading purposes.

The change is mostly mechanical but few notes are reported:
* The KPI changes as follow:
- VM_OBJECT_LOCK() -> VM_OBJECT_WLOCK()
- VM_OBJECT_TRYLOCK() -> VM_OBJECT_TRYWLOCK()
- VM_OBJECT_UNLOCK() -> VM_OBJECT_WUNLOCK()
- VM_OBJECT_LOCK_ASSERT(MA_OWNED) -> VM_OBJECT_ASSERT_WLOCKED()
(in order to avoid visibility of implementation details)
- The read-mode operations are added:
VM_OBJECT_RLOCK(), VM_OBJECT_TRYRLOCK(), VM_OBJECT_RUNLOCK(),
VM_OBJECT_ASSERT_RLOCKED(), VM_OBJECT_ASSERT_LOCKED()
* The vm/vm_pager.h namespace pollution avoidance (forcing requiring
sys/mutex.h in consumers directly to cater its inlining functions
using VM_OBJECT_LOCK()) imposes that all the vm/vm_pager.h
consumers now must include also sys/rwlock.h.
* zfs requires a quite convoluted fix to include FreeBSD rwlocks into
the compat layer because the name clash between FreeBSD and solaris
versions must be avoided.
At this purpose zfs redefines the vm_object locking functions
directly, isolating the FreeBSD components in specific compat stubs.

The KPI results heavilly broken by this commit. Thirdy part ports must
be updated accordingly (I can think off-hand of VirtualBox, for example).

Sponsored by: EMC / Isilon storage division
Reviewed by: jeff
Reviewed by: pjd (ZFS specific review)
Discussed with: alc
Tested by: pho

Add basic and not very reliable protection against going to sleep with
thread scheduled by interrupt fired after we entered critical section.
None of cpu_sleep() implementations on ARM check sched_runnable() now, so
put the first line of defence here. This mostly fixes unexpectedly long
sleeps in synthetic tests of calloutng code and probably other situations.

Initialize vm_max_kernel_address on non-FDT platforms. (This should have
been included in r246926.)

The second parameter to pmap_bootstrap() is redundant. Eliminate it.

Reviewed by: andrew

On arm, like sparc64, the end of the kernel map varies from one type of
machine to another. Therefore, VM_MAX_KERNEL_ADDRESS can't be a constant.
Instead, #define it to be a variable, vm_max_kernel_address, just like we
do on sparc64.

Reviewed by: kib
Tested by: ian

Eliminate the need for an intermediate array of indices into the arrays of
interrupt counts and names, by making the names into an array of fixed-length
strings that can be directly indexed. This eliminates extra memory accesses
on every interrupt to increment the counts.

As a side effect, it also fixes a bug that would corrupt the names data
if a name was longer than MAXCOMLEN, which led to incorrect vmstat -i output.

Approved by: cognet (mentor)

Add hw.board.serial and hw.board.revision for exporting board-specific info

Get reserved memory regions and exclude them from available memory map

Remove print_kernel_section_addr(). All statements in that function
expand to uncompilable code when the kernel configuration contains
"options DEBUG", such as it is for LINT. The toolchain is often a
better approach to figure this out, as it doesn't require one to
boot the kernel.

Reduce differences between these two initarms a bit more.

Minor cosmetic changes to bring atmel's initarm and the default
initarm for FDT closer together. More to follow.

Merge the FDT versions of initarm.

The copies of initarm used on platforms with FDT support were almost
identical. The differences were pulled out into separate functions that
were called by initarm.

This change merges the, now identical, copies of initarm and a few of it's
support functions. This is a step towards a common kernel on ARMv6.

Create a common set_stackptrs in sys/arm/machdep.c.

On single core devices set_stackptrs is only ever called with cpu = 0 in
initarm and will be identical to the existing function. On SMP this needs
to be implemented for sys/arm/mp_machdep.c, but the implementations are
identical for each SoC.

Call set_pcpu for ARMv6 architecture too

Merging projects/armv6, part 1

Cummulative patch of changes that are not vendor-specific:
- ARMv6 and ARMv7 architecture support
- ARM SMP support
- VFP/Neon support
- ARM Generic Interrupt Controller driver
- Simplification of startup code for all platforms

Fix a global shadowing problem when LINUX_BOOT_ABI was defined.

More Linux boot support. Create arm_dump_avail_init() to initialize
this array either from Linux boot data, when enabled, or in the
typical way that most ports do it. arm_pyhs_avail_init is coming
soon since it must be a separate function.

Add support for parsing Linux ATAGs such as you'd see from uboot or
redboot. Support is very preiminary and likely needs some work. Also,
do some minor code shuffling of the FreeBSD /boot/loader metadata
parsing code. This code is preliminary and should be used with
caution.

Create default_parse_boot_param which, if FreeBSD /boot/loader support
is enabled, sets values based on the metadata passed in. Otherwise
fake_preload_metadata is called. Change the default parse_boot_param
to default_parse_boot_param. Enable this functionality only on the mv
platform, which is where most of the code is from.

Reviewed by: cognet, Ian Lapore

Modify all the arm platform files to call parse_boot_param passing in
the boot parameters from initarm first thing. parse_boot_param parses
the boot arguments and converts them to the /boot/loader metadata the
rest of the kernel uses. parse_boot_param is a weak alias to
fake_preload_metadata, which all the platforms use now, but may become
more extensive in the future.

Since it is a weak symbol, specific boards may define their own
parse_boot_param to interface to custom boot loaders.

Reviewed by: cognet@, Ian Lapore

Final whitespace trim.

Pull out the common code to initialise proc0 & thread0 from initarm to a
common function.

Reviewed by: imp

Soft PMC support for ARM.
Callgraph is not captured, only current location.

Sample system wide profiling: "pmcstat -Sclock.hard -T"

TDF_* flags should be used with td_flags field and TDP_* flags should be used
with td_pflags field. Correct two places where it was not the case.

Discussed with: kib
MFC after: 1 week

Explicitely set ARM_RAS_START and ARM_RAS_END once the cacheline or the
page has been allocated, or we could end up using random values, and bad things
could happen.

PR: arm/161492
Submitted by: Ian Lepore <freebsd AT damnhippie dot dyndns DOT org>
MFC after: 1 week

In order to maximize the re-usability of kernel code in user space this
patch modifies makesyscalls.sh to prefix all of the non-compatibility
calls (e.g. not linux_, freebsd32_) with sys_ and updates the kernel
entry points and all places in the code that use them. It also
fixes an additional name space collision between the kernel function
psignal and the libc function of the same name by renaming the kernel
psignal kern_psignal(). By introducing this change now we will ease future
MFCs that change syscalls.

Reviewed by: rwatson
Approved by: re (bz)

Adjust the order of operations in spinlock_enter() and spinlock_exit() to
work properly with single-stepping in a kernel debugger. Specifically,
these routines have always disabled interrupts before increasing the nesting
count and restored the prior state of interrupts after decreasing the nesting
count to avoid problems with a nested interrupt not disabling interrupts
when acquiring a spin lock. However, trap interrupts for single-stepping
can still occur even when interrupts are disabled. Now the saved state of
interrupts is not saved in the thread until after interrupts have been
disabled and the nesting count has been increased. Similarly, the saved
state from the thread cannot be read once the nesting count has been
decreased to zero. To fix this, use temporary variables to store interrupt
state and shuffle it between the thread's MD area and the appropriate
registers.

In cooperation with: bde
MFC after: 1 month

Move prototypes for kern_sigtimedwait() and kern_sigprocmask() to
<sys/syscallsubr.h> where all other kern_<syscall> prototypes live.

Change the arguments of exec_setregs() so that it receives a pointer
to the image_params struct instead of several members of that struct
individually. This makes it easier to expand its arguments in the future
without touching all platforms.

Reviewed by: jhb

Eliminate an unnecessary vm include file.

In r197963, a race with thread being selected for signal delivery
while in kernel mode, and later changing signal mask to block the
signal, was fixed for sigprocmask(2) and ptread_exit(3). The same race
exists for sigreturn(2), setcontext(2) and swapcontext(2) syscalls.

Use kern_sigprocmask() instead of direct manipulation of td_sigmask to
reschedule newly blocked signals, closing the race.

Reviewed by: davidxu
Tested by: pho
MFC after: 1 month

Add cpu_flush_dcache() for use after non-DMA based I/O so that a
possible future I-cache coherency operation can succeed. On ARM
for example the L1 cache can be (is) virtually mapped, which
means that any I/O that uses temporary mappings will not see the
I-cache made coherent. On ia64 a similar behaviour has been
observed. By flushing the D-cache, execution of binaries backed
by md(4) and/or NFS work reliably.
For Book-E (powerpc), execution over NFS exhibits SIGILL once in
a while as well, though cpu_flush_dcache() hasn't been implemented
yet.

Doing an explicit D-cache flush as part of the non-DMA based I/O
read operation eliminates the need to do it as part of the
I-cache coherency operation itself and as such avoids pessimizing
the DMA-based I/O read operations for which D-cache are already
flushed/invalidated. It also allows future optimizations whereby
the bcopy() followed by the D-cache flush can be integrated in a
single operation, which could be implemented using on-chips DMA
engines, by-passing the D-cache altogether.

Do not set thread0.td_frame to a bogus value, as it's going to overwrite the
thread0 pcb, while the board-dependant code already set a good trapframe.

Reported by: Mark Tinguely <tinguely at casselton d0t net>

MFC after: 1 week

- Add an integer argument to idle to indicate how likely we are to wake
from idle over the next tick.
- Add a new MD routine, cpu_wake_idle() to wakeup idle threads who are
suspended in cpu specific states. This function can fail and cause the
scheduler to fall back to another mechanism (ipi).
- Implement support for mwait in cpu_idle() on i386/amd64 machines that
support it. mwait is a higher performance way to synchronize cpus
as compared to hlt & ipis.
- Allow selecting the idle routine by name via sysctl machdep.idle. This
replaces machdep.cpu_idle_hlt. Only idle routines supported by the
current machine are permitted.

Sponsored by: Nokia

Take the first baby step towards unifying and cleaning up arminit():
- Pull all the code to deal with the trampoline stuff into one
centeralized place and use it from everywhere.
- Some minor style tidiness

Reviewed by: tinguely

In keeping with style(9)'s recommendations on macros, use a ';'
after each SYSINIT() macro invocation. This makes a number of
lightweight C parsers much happier with the FreeBSD kernel
source, including cflow's prcc and lxr.

MFC after: 1 month
Discussed with: imp, rink

Revert VMCNT_* operations introduction.
Probabilly, a general approach is not the better solution here, so we should
solve the sched_lock protection problems separately.

Requested by: alc
Approved by: jeff (mentor)

Constify to please gcc 4.2.

- define and use VMCNT_{GET,SET,ADD,SUB,PTR} macros for manipulating
vmcnts. This can be used to abstract away pcpu details but also changes
to use atomics for all counters now. This means sched lock is no longer
responsible for protecting counts in the switch routines.

Contributed by: Attilio Rao <attilio@FreeBSD.org>

Add KTR tracing

In sendsig:

- Add sigacts locking.
- Add a mutex to struct sigacts that protects all the members of the struct.
- Create and log events via the CTRx macros.

Reviewed by: cognet

Display real/avail memory as per other platforms.

Approved by: cognet

Move the call to cpu_setup() before the call to vm_ksubmap_init().
vm_ksubmap_init() calls pmap_copy_page(), which uses the mini data cache
to do the copy, but we're running uncaching before cpu_setup().
For some reason it hasn't been a problem so far, but it is for the
PXA255.

Spotted out by: benno

Close some races between procfs/ptrace and exit(2):
- Reorder the events in exit(2) slightly so that we trigger the S_EXIT
stop event earlier. After we have signalled that, we set P_WEXIT and
then wait for any processes with a hold on the vmspace via PHOLD to
release it. PHOLD now KASSERT()'s that P_WEXIT is clear when it is
invoked, and PRELE now does a wakeup if P_WEXIT is set and p_lock drops
to zero.
- Change proc_rwmem() to require that the processing read from has its
vmspace held via PHOLD by the caller and get rid of all the junk to
screw around with the vmspace reference count as we no longer need it.
- In ptrace() and pseudofs(), treat a process with P_WEXIT set as if it
doesn't exist.
- Only do one PHOLD in kern_ptrace() now, and do it earlier so it covers
FIX_SSTEP() (since on alpha at least this can end up calling proc_rwmem()
to clear an earlier single-step simualted via a breakpoint). We only
do one to avoid races. Also, by making the EINVAL error for unknown
requests be part of the default: case in the switch, the various
switch cases can now just break out to return which removes a _lot_ of
duplicated PRELE and proc unlocks, etc. Also, it fixes at least one bug
where a LWP ptrace command could return EINVAL with the proc lock still
held.
- Changed the locking for ptrace_single_step(), ptrace_set_pc(), and
ptrace_clear_single_step() to always be called with the proc lock
held (it was a mixed bag previously). Alpha and arm have to drop
the lock while the mess around with breakpoints, but other archs
avoid extra lock release/acquires in ptrace(). I did have to fix a
couple of other consumers in kern_kse and a few other places to
hold the proc lock and PHOLD.

Tested by: ps (1 mostly, but some bits of 2-4 as well)
MFC after: 1 week

Add missing "struct" in i386/i386/machdep.c,v 1.497 by deischen@.

MFi386 rev 1.536 (sort of)
Move what can be moved (UMA zones creation, pv_entry_* initialization) from
pmap_init2() to pmap_init().
Create a new function, pmap_postinit(), called from cpu_startup(), to do the
L1 tables allocation.
pmap_init2() is now empty for arm as well.

1. Change prototype of trapsignal and sendsig to use ksiginfo_t *, most
changes in MD code are trivial, before this change, trapsignal and
sendsig use discrete parameters, now they uses member fields of
ksiginfo_t structure. For sendsig, this change allows us to pass
POSIX realtime signal value to user code.

2. Remove cpu_thread_siginfo, it is no longer needed because we now always
generate ksiginfo_t data and feed it to libpthread.

3. Add p_sigqueue to proc structure to hold shared signals which were
blocked by all threads in the proc.

4. Add td_sigqueue to thread structure to hold all signals delivered to
thread.

5. i386 and amd64 now return POSIX standard si_code, other arches will
be fixed.

6. In this sigqueue implementation, pending signal set is kept as before,
an extra siginfo list holds additional siginfo_t data for signals.
kernel code uses psignal() still behavior as before, it won't be failed
even under memory pressure, only exception is when deleting a signal,
we should call sigqueue_delete to remove signal from sigqueue but
not SIGDELSET. Current there is no kernel code will deliver a signal
with additional data, so kernel should be as stable as before,
a ksiginfo can carry more information, for example, allow signal to
be delivered but throw away siginfo data if memory is not enough.
SIGKILL and SIGSTOP have fast path in sigqueue_add, because they can
not be caught or masked.
The sigqueue() syscall allows user code to queue a signal to target
process, if resource is unavailable, EAGAIN will be returned as
specification said.
Just before thread exits, signal queue memory will be freed by
sigqueue_flush.
Current, all signals are allowed to be queued, not only realtime signals.

Earlier patch reviewed by: jhb, deischen
Tested on: i386, amd64

Export the variables needed for the copy/zero API.

Divorce critical sections from spinlocks. Critical sections as denoted by
critical_enter() and critical_exit() are now solely a mechanism for
deferring kernel preemptions. They no longer have any affect on
interrupts. This means that standalone critical sections are now very
cheap as they are simply unlocked integer increments and decrements for the
common case.

Spin mutexes now use a separate KPI implemented in MD code: spinlock_enter()
and spinlock_exit(). This KPI is responsible for providing whatever MD
guarantees are needed to ensure that a thread holding a spin lock won't
be preempted by any other code that will try to lock the same lock. For
now all archs continue to block interrupts in a "spinlock section" as they
did formerly in all critical sections. Note that I've also taken this
opportunity to push a few things into MD code rather than MI. For example,
critical_fork_exit() no longer exists. Instead, MD code ensures that new
threads have the correct state when they are created. Also, we no longer
try to fixup the idlethreads for APs in MI code. Instead, each arch sets
the initial curthread and adjusts the state of the idle thread it borrows
in order to perform the initial context switch.

This change is largely a big NOP, but the cleaner separation it provides
will allow for more efficient alternative locking schemes in other parts
of the kernel (bare critical sections rather than per-CPU spin mutexes
for per-CPU data for example).

Reviewed by: grehan, cognet, arch@, others
Tested on: i386, alpha, sparc64, powerpc, arm, possibly more

Introduce realmem.

Instead of using sysarch() to store-retrieve the tp, add a magic address,
ARM_TP_ADDRESS, where the tp will be stored. On CPUs that support it, a cache
line will be allocated and locked for this address, so that it will never go
to RAM. On CPUs that does not, a page is allocated for it (it will be a bit
slower, and is wrong for SMP, but should be fine for UP).
The tp is still stored in the mdthread struct, and at each context switch,
ARM_TP_ADDRESS gets updated.

Suggested by: davidxu

move pmap.h after vm.h include... some of the headers from pmap.h depend
upon vm.h

Finish the job of sorting all includes and fix the build by including
malloc.h before proc.h on sparc64. Noticed by das@

Compiled on: alpha, amd64, i386, pc98, sparc64

Sort includes a little so that bus.h comes before cpu.h (for device_t).

Add an implementation of cpu_est_clockrate(9). This function estimates the
current clock frequency for the given CPU id in units of Hz.

Add support for ptrace() and gdb breakpoints.

Start all license statements with /*-

Implement cpu_thread_siginfo() and set_mcontext().
Nuke getframe(), and choose which stack to use directly in sendsig().

Implement sigreturn().

Don't use cast as lvalue.

Implement ptrace_set_pc().
Add a stub for ptrace_clear_single_step().

Remove astpending, it has not been used for a long time.

Implement makectx().

Import FreeBSD/arm kernel bits.
It only supports sa1110 (on simics) right now, but xscale support should come
soon.
Some of the initial work has been provided by :
Stephane Potvin <sepotvin at videotron.ca>
Most of this comes from NetBSD.